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Geochemistry of the Albano and Nemi crater lakes in the volcanic district of Alban Hills (Rome, Italy)
Abstract
Lake Albano, located 20 km to the SE of Rome, is hosted within the most recent crater of the quiescent Alban Hills volcanic complex that produced hydromagmatic eruptions in Holocene times. Stratigraphic, archaeological and historical evidence indicates that the lake level underwent important variations in the Bronze Age. Before the IV century B.C. several lahars were generated by water overflows from the lake and in the IV century B.C. Romans excavated a drainage tunnel. The lake is located above a buried carbonate horst that contains a pressurized medium-enthalpy geothermal reservoir from which fluids escape to the surface to produce many important gas manifestations of mostly CO2. Previous studies recognized the presence of gas emissions also from the crater bottom. In 1997 the possibility of a Nyos-type event triggered by a lake rollover was considered very low, because the CO2 water concentration at depth was found to be far from saturation. However, considering the high population density nearby, the Italian Civil Protection Department recommended that periodical monitoring be carried out. To this scope we initiated in 2001 a systematic geochemical study of the lake. Thirteen vertical profiles have been repeatedly carried out in 2001–2006, especially in the deepest part of the lake (167 m in 2006), measuring T, pH, dissolved O2 and electrical conductivity. Water samples were collected from various depths and chemically and isotopically analysed. Two similar profiles have been measured also in the nearby Nemi crater lake. Results indicate that in the 4.5 years of monitoring the pressure of gas dissolved in the Lake Albano deep waters remained much lower than the hydrostatic pressure. A CO2 soil survey carried out on the borders of the two lakes, indicates the presence of some zones of anomalous degassing of likely magmatic origin. A water overturn or a heavy mixing of deep and shallow waters likely occurred in winter 2003–2004, when cold rainfall cooled the surface water below 8.5 °C. Such overturns cause only a limited gas exsolution from the lake when the deep water is brought to a few meters depth but can explain the observed decrease with time of dissolved CO2 at depth and related water pH increase. A gas hazard could occur in the case of a sudden injection through the lake bottom of a huge quantity of CO2-rich fluids, which might be caused by earthquake induced fracturing of the rock pile beneath the lake. A limnic gas eruption might also occur should CO2 concentration build up within the lake for a long time.
... Cava dei Selci (Figure 2). Gas emissions also occur from the bottom of Albano Lake crater and on its eastern border (Carapezza et al., 2008). It is noteworthy that the most important and dangerous gas emissions of Albani Hills are located where stone quarrying (e.g. ...
... (described by Plutarcus and Titus Livius) when Romans excavated a drainage tunnel that kept the lake level 70 m below the crater rim (Funiciello et al., 2002 and2003). A significant CO 2 -rich gas emission occurs from the lake bottom (Cioni et al., 2003), having a magmatic signature as indicated by 3 He/ 4 He in dissolved gas (R/Ra= 1.30; Carapezza et al., 2008). A similar He isotopic composition (R/Ra= 1.28) was found in the Acqua Acetosa CO 2 -rich vent on the eastern border of the lake (Figure 3). ...
... The zone to the SE of Acqua Acetosa with the highest soil CO 2 flux (up to 500 g m -2 day -1 ) is marked with an asterisk. The inferred NE-SW faults nearby may extend to the deepest zone of the crater (modified afterCarapezza et al., 2008). ...
The area of Central Italy around Rome contains natural gas discharging zones and several others where quarrying or mining excavation removed the impervious superficial layers allowing a free hazardous discharge to the surface of endogenous gas. These gas manifestations are mostly located above buried structural highs of fractured Mesozoic limestones hosting the main regional aquifer and revealed by gravity anomalies. In the last decades, many gas blowouts occurred in this area, from wells whose depth ranged from 10–15 to 350 m. The main component of the emitted gas is CO2 with minor H2S; only in a blowout offshore of Fiumicino CH4 prevailed. Several animals even of large size and two persons were killed by the emitted gas (mostly by H2S), and nearby houses were evacuated because of dangerous indoor CO2 concentrations. He and CO2‐carbon isotopes suggest that gas has a deep mantle signature, as indicated for Fiumicino gas by N2 isotopic composition and N2/³⁶Ar ratios. Gas rising from depth first accumulates in the buried Mesozoic limestone reservoir, and from there it escapes along deep‐reaching faults. On its way to the surface, the gas dissolves into and pressurizes any encountered confined aquifer, which may then produce a gas blowout when reached by wells. The main direction of the gas feeding faults was estimated through the alignment of visible gas emissive points, the shape of the positive anomalies in soil CO2 flux maps, and new structural‐geological observations, finding that they correspond mostly to the main orientation of the underlying limestone structural high.
... The decrease, at a depth of 50 -87 m, of the concentration-depth gradient for these constituents, with respect to previous surveys, suggests a possible influence of the calcium bicarbonate-poor shallow water at that (Fig. 5) and the pH increase (Fig. 3). The lake waters down to a depth of 50 m are calcite-, dolomite-and magnesiteoversaturated, but they become carbonateundersaturated at higher depths (Cioni et al. 2003;Carapezza et al. 2008). ...
... The CO 2 and CH 4 concentrations increase with depth. CO 2 is the most abundant dissolved gas below 260 m (Fig. 5), but in the deepest waters P CH4 (0.3 bar) is higher than P CO2 (see Carapezza et al. 2008). ...
... The Albano crater lake is located in a zone with endogenous gas emissions, likely of magmatic or mantle origin Carapezza et al. 2008). However, episodic occurrence of lake water rollover prevents CO 2 accumulation in the deep water, because of gas release occurring once this water is brought to the surface. ...
Albano Lake is within the youngest polygenetie crater of Colli Albani, from which several lahar-generating water overflows occurred up to early Roman times. The area has anomalous gas emissions and is affected by seismicity and uplift. The geochemistry of the lake have been systematically investigated since 2003 by measuring physico-chemical parameters along vertical profiles with a multiparametrie probe and by collecting water samples for chemical and isotopic analyses. The lake is thermally and chemically stratified, with an anoxic hypolimnion from -70 m to the bottom (-167 m). The isotopic composition of dissolved helium and total carbon is similar to that of the main gas emissions of Colli Albani and of the phenocryst inclusions of the Alhan volcanics, suggesting that an endogenous gas of deep provenance is injected into the lake water. The dissolved CO2 content is, however, far from saturation, and no Nyos-type hazardous gas cloud emission may presently occur in the lake. Temperature and chemical time variations indicate lhal water rollover episodes occur in harsh rainy winters when the surface lake temperature cools below 8.5 °C. Such rollovers tend to homogenize the physico-chemistry of the lake water and reduce the dissolved CO2 content. They may cause an environmental hazard because of related toxic algal blooms.
... The origin of He in volcanic lakes is related to that of the primary fluid source(s), since the behavior of this chemically inert gas along the vertical water column only depends on physical processes, such as advection and diffusion. The occurrence of significant mantle He contribution, typically recognized in Nyos-type volcanic lakes (Sano et al., 1987;Igarashi et al., 1992;Kipfer et al., 1994;Aeschbach-Hertig et al., 1996;Caliro et al., 2008;Carapezza et al., 2008;Caracausi et al., 2009), testifies to the presence of sublacustrine springs (Fig. 2). ...
... 1993). In more recent times, contemporaneous measurements of different physical-chemical parameters, such as temperature, pH, electrical conductivity, and dissolved oxygen at depth intervals of a few cm, were carried out in different volcanic lakes by using multi-sensor probes (Aguilera et al., 2000;Cioni et al., 2003;Schmid et al., 2005;Caliro et al., 2008;Carapezza et al., 2008;Kusakabe et al., 2008;Sarmento et al., 2008;Caracausi et al., 2009;Pasche et al., 2009;Cabassi et al., 2013) (Fig. 4a-d). These instruments commonly have high accuracy and precision (e.g., temperature: 0.01ºC accuracy and 0.001ºC precision) and they are able to store huge amounts of data, allowing the construction of almost continuous vertical profiles of the measured parameters that can be used to identify extremely thin (a few cm) water layers. ...
... A previously evacuated sampling flask (e.g., Giggenbach bottle) is connected to the hose outlet, or a previously water filled bottle is overturned above the hose outlet (water replacement method). (Aguilera et al., 2000;Cioni et al., 2003, Tassi et al., 2004Caliro et al., 2008;Carapezza et al., 2008;Cabassi et al., 2013). To prevent the effects of the possible formation of micro-gas bubbles during sampling, the hose was connected, through a threeway valve, to an evacuated glass vial equipped with a Teflon stopcock (Fig. 10). ...
Limnic eruptions represent a natural hazard in meromictic lakes hosted in volcanoes releasing CO2-rich magmatic gases. Biogeochemical processes also contribute to dissolved gas reservoirs since they can produce significant amounts of gases, such as CH4 and N-2. Dissolved gases may have a strong influence of the density gradient and the total dissolved gas pressure along the vertical profile of a volcanic lake. An external triggering event, possibly related to uncommon weather conditions, volcanic-seismic activity, or landslides, or spontaneous formation of gas bubbles related to the progressive attainment of saturation conditions at depth, may cause a lake rollover and the consequent release of dissolved gases. This phenomenon may have dramatic consequences due to i) the release of a toxic CO2-rich cloud able to flow long distances before being diluted in air, or ii) the contamination of the shallow water layer with poisonous deep waters. The experience carried out over the past twelve years at Lake Nyos, where a pumping system discharges CO2-rich deep water to the surface, has shown that controlled degassing of deep water layers is the best solution to mitigate such a hazard. However, the application of this type of intervention in other lakes must be carefully evaluated, since it may cause severe contamination of shallow lake water or create dangerous density instabilities. Monitoring of physical and chemical parameters controlling lake stability and the evolution in time of dissolved gas reservoirs can provide essential information for evaluating the risk associated with possible rollover phenomena. Conceptual models for the description of limnological, biogeochemical and volcanic processes regulating water lake stability have been constructed by interpreting compositional data of lake water and dissolved gas compositions obtained by applying different sampling and analytical techniques. This study provides a critical overview of the existing methodological approaches and discusses how future investigations of Nyos-type lakes, aimed at mitigating the hazard for limnic eruptions, can benefit from i) the development of new technical and theoretical approaches aimed to constrain the physical-chemical mechanisms controlling this natural phenomenon, and ii) information from different scientific disciplines, such as microbiology, fluid dynamics and sedimentology.
... The deepest layers of the lake can potentially host large amounts of CO 2 and can trigger catastrophic events (limnic eruptions) similar to those that occurred at Monoun and Nyos lakes (Cameroon), in 1984 and 1986, respectively (Sigurdsson et al. 1987; Barberi et al. 1989; Giggenbach 1990; Evans et al. 1994; Rice 2000; Kusakabe 1996). Previous studies have shown that the CO 2 concentration at Lake Albano increases with depth, although the maximum measured CO 2 concentrations are much lower than gas saturation (Martini et al. 1994; Cioni et al. 2003; Anzidei et al. 2008; Carapezza et al. 2008). More dangerous conditions may have occurred in the past. ...
... More dangerous conditions may have occurred in the past. In the fourth century B.C., Roman historians reported an episode of sudden lake overflow that may have been caused by the injection of CO 2 -rich fluids into the lake (Funiciello et al. 2002; Carapezza et al. 2008). That event persuaded the Romans to keep the water level 70 m below the lowest crater rim by means of a drainage tunnel. ...
... The aim of this paper is to provide an assessment of whether this seismic crisis caused a detectable and quantifiable variation of the CO 2 content of the lake. A decrease of the CO 2 concentration was previously observed during the period 1997–2006 and was attributed to lake water overturn during the winter (Anzidei et al. 2008; Carapezza et al. 2008). In this work, we computed the time-dependent CO 2 variations for a longer period (1989–2010) in order to detail the eventual relationship of such a variation with the 1989–1990 earthquakes. ...
... Lake Albano is located along the western slopes of the Colli Albani volcano and elongated in the NW-SE direction in correspondence with a structural high of the carbonate basement ( Carapezza et al. 2008). This lake, showing a maximum depth of 167 m, is the deepest volcanic lake in Italy ( Anzidei et al. 2008). ...
... 2a, 3a, and 4a) show a thermocline at relatively shallow depth (from 10 to 20 m at Lake Albano and from 5 to 15 m at Lake Averno and Monticchio lakes). These temperature vs. depth patterns are basically consistent with those measured during previous studies ( Chondrogianni et al. 1996;Cioni et al. 2003Cioni et al. , 2006Caliro et al. 2008;Carapezza et al. 2008Carapezza et al. , 2010Caracausi et al. 2009;Chiodini et al. 2012), except those of the epilimnion that, by definition, is affected by seasonal changes. Lake Albano (Fig. 2b) shows two chemoclines at the depth of 110 and 150 m, respectively, although in both cases, the increase of the EC values is relatively low (cf. ...
... not detected of Lake Piccolo (Fig. 4c) show a strong decrease at 3-7 m depth (from 8.5 to 7.2) and 15 m (from 7.2 to 6.2), whereas the deeper water layers do not show significant pH changes, except at −30 m where it slightly increases up to 6.3. As also reported by previous authors (Chiodini et al. 2000(Chiodini et al. , 2012Cioni et al. 2006;Carapezza et al. 2008Carapezza et al. , 2010Caracausi et al. 2009), the investigated lakes are characterized by a permanent clinograde, with the occurrence of an anaerobic hypolimnion from the depths of 60, 7, 11, and 5 m at Lake Albano, Lake Averno, Lake Grande, and Lake Piccolo, respectively (Figs. 2d, 3d, and 4d), surmounted by an epilimnion, i.e., the only portion of the water body where dissolved O 2 is available. ...
This paper focuses on the chemical and isotopic features of dissolved gases (CH4 and CO2) from four meromictic lakes hosted in volcanic systems of Central–Southern Italy: Lake Albano (Alban Hills), Lake Averno (Phlegrean Fields), and Monticchio Grande and Piccolo lakes (Mt. Vulture). Deep waters in these lakes are characterized by the presence of a significant reservoir of extraatmospheric dissolved gases mainly consisting of CH4 and CO2. The δ13C-CH4 and δD-CH4 values of dissolved gas samples from the maximum depths of the investigated lakes (from −66.8 to −55.6‰ V-PDB and from −279 to −195‰ V-SMOW, respectively) suggest that CH4 is mainly produced by microbial activity. The δ13C-CO2 values of Lake Grande, Lake Piccolo, and Lake Albano (ranging from −5.8 to −0.4‰ V-PDB) indicate a significant CO2 contribution from sublacustrine vents originating from (1) mantle degassing and (2) thermometamorphic reactions involving limestone, i.e., the same CO2 source feeding the regional thermal and cold CO2-rich fluid emissions. In contrast, the relatively low δ13C-CO2 values (from −13.4 to −8.2‰ V-PDB) of Lake Averno indicate a prevalent organic CO2. Chemical and isotopic compositions of dissolved CO2 and CH4 at different depths are mainly depending on (1) CO2 inputs from external sources (hydrothermal and/or anthropogenic); (2) CO2–CH4 isotopic exchange; and (3) methanogenic and methanotrophic activity. In the epilimnion, vertical water mixing, free oxygen availability, and photosynthesis cause the dramatic decrease of both CO2 and CH4 concentrations. In the hypolimnion, where the δ13C-CO2 values progressively increase with depth and the δ13C-CH4 values show an opposite trend, biogenic CO2 production from CH4 using different electron donor species, such as sulfate, tend to counteract the methanogenesis process whose efficiency achieves its climax at the water–bottom sediment interface. Theoretical values, calculated on the basis of δ13C-CO2 values, and measured δ13CTDIC values are not consistent, indicating that CO2 and the main carbon-bearing ion species (HCO3−) are not in isotopic equilibrium, likely due to the fast kinetics of biochemical processes involving both CO2 and CH4. This study demonstrates that the vertical patterns of the CO2/CH4 ratio and of δ13C-CO2 and δ13C-CH4 are to be regarded as promising tools to detect perturbations, related to different causes, such as changes in the CO2 input from sublacustrine springs, that may affect aerobic and anaerobic layers of meromictic volcanic lakes.
... The deepest layers of the lake can potentially host large amounts of CO 2 and can trigger catastrophic events (limnic eruptions) similar to those that occurred at Monoun and Nyos lakes (Cameroon), in 1984 and 1986, respectively (Sigurdsson et al. 1987; Barberi et al. 1989; Giggenbach 1990; Evans et al. 1994; Rice 2000; Kusakabe 1996). Previous studies have shown that the CO 2 concentration at Lake Albano increases with depth, although the maximum measured CO 2 concentrations are much lower than gas saturation (Martini et al. 1994; Cioni et al. 2003; Anzidei et al. 2008; Carapezza et al. 2008). More dangerous conditions may have occurred in the past. ...
... More dangerous conditions may have occurred in the past. In the fourth century B.C., Roman historians reported an episode of sudden lake overflow that may have been caused by the injection of CO 2 -rich fluids into the lake (Funiciello et al. 2002; Carapezza et al. 2008). That event persuaded the Romans to keep the water level 70 m below the lowest crater rim by means of a drainage tunnel. ...
... The aim of this paper is to provide an assessment of whether this seismic crisis caused a detectable and quantifiable variation of the CO 2 content of the lake. A decrease of the CO 2 concentration was previously observed during the period 1997–2006 and was attributed to lake water overturn during the winter (Anzidei et al. 2008; Carapezza et al. 2008). In this work, we computed the time-dependent CO 2 variations for a longer period (1989–2010) in order to detail the eventual relationship of such a variation with the 1989–1990 earthquakes. ...
Lake Albano (Alban Hills volcanic complex,
Central Italy) is located in a densely populated area near
Rome. The deep lake waters have significant dissolved CO2
concentrations, probably related to sub-lacustrine fluid discharges
fed by a pressurized CO2-rich reservoir. The analytical
results of geochemical surveys carried out in 1989–2010 highlight the episodes of CO2 removal from the lake.
The total mass of dissolved CO2 decreased from ∼5.8×
107 kg in 1989 to ∼0.5×107 kg in 2010, following an
exponential decreasing trend. Calculated values of both dissolved
inorganic carbon and CO2 concentrations along the
vertical profile of the lake indicate that this decrease is
caused by CO2 release from the epilimnion, at depth <9 m,
combined with (1) water circulation at depth <95 m and (2)
CO2 diffusion from the deeper lake layers. According to this
model, Lake Albano was affected by a large CO2 input that
coincided with the last important seismic swarm at Alban
Hills in 1989, suggesting an intimate relationship between
the addition of deep-originated CO2 to the lake and seismic
activity. In the case of a CO2 degassing event of an order of
magnitude larger than the one that occurred in 1989, the
deepest part of Lake Albano would become CO2-saturated,
resulting in conditions compatible with the occurrence of a
gas outburst. These results reinforce the idea that a sudden
CO2 input into the lake may cause the release of a dense gas
cloud, presently representing the major volcanic threat for
this densely populated area.
... Seismic activity and gas emissions are considered the main risk source for the villages located in the Colli Albani area, whereas it is not yet clear which could be the level of hazard due to slow deformations . In fact, this area is characterized by recurrent seismic activity (Feuillet et al., 2004; Tertulliani and Riguzzi, 1995; Amato et al., 1994 and reference therein); temperature and water composition variations (Boni et al., 1995; Calcara et al., 1995; Carapezza et al., 2008); gas emissions, CO 2 and in minor part H 2 S (Carapezza et al., 2003Carapezza et al., , 2008 Carapezza and Tarchini, 2007; Tuccimei et al., 2006; Pizzino et al., 2002; Chiodini and Frondini, 2001 and reference therein) and by significant ground deformations detected by high precision leveling and PS-InSAR time series. The mean rate of uplift has been estimated from 3 to 7 mm/year, from PS-InSAR and leveling surveys, respectively, on very different time spans (Amato and Chiarabba, 1995; Salvi et al., 2004). ...
... Seismic activity and gas emissions are considered the main risk source for the villages located in the Colli Albani area, whereas it is not yet clear which could be the level of hazard due to slow deformations . In fact, this area is characterized by recurrent seismic activity (Feuillet et al., 2004; Tertulliani and Riguzzi, 1995; Amato et al., 1994 and reference therein); temperature and water composition variations (Boni et al., 1995; Calcara et al., 1995; Carapezza et al., 2008); gas emissions, CO 2 and in minor part H 2 S (Carapezza et al., 2003Carapezza et al., , 2008 Carapezza and Tarchini, 2007; Tuccimei et al., 2006; Pizzino et al., 2002; Chiodini and Frondini, 2001 and reference therein) and by significant ground deformations detected by high precision leveling and PS-InSAR time series. The mean rate of uplift has been estimated from 3 to 7 mm/year, from PS-InSAR and leveling surveys, respectively, on very different time spans (Amato and Chiarabba, 1995; Salvi et al., 2004). ...
... During the last few years, a series of papers on geochronology (Freda et al., 2006; Marra and Karner, 2005), stratigraphic and physical properties from down hole drilling (Mariucci et al., 2008), experiments on the magma composition (Freda et al., 2008) and eruption products (Sottili et al., 2009) have shed new light on the history and present physical state of the volcanic structure. Other works (Funiciello et al., 2003; Anzidei et al., 2008 ) highlighted the relevance of high water level variations and catastrophic withdrawal of the Albano maar lake since pre-historic age as possible indicators of sudden variation of CO 2 flow and upwelling of hydrothermal fluids (Carapezza et al., 2008). A comprehensive hazard assessment of active and quiescent volcanoes may strongly depend from the morphology of the edifice structure. ...
The Colli Albani volcanic complex, located in central Italy about 15 km SE of Rome, has been dominated by periodic eruptive histories started about 561 ka and ending with the most recent and voluminous activity of the Albano maar (<70 ka) phase. Earthquakes of moderate intensity, gas emissions and significant ground deformations are the recent evidences of a residual activity. We decided to start a monitoring test by installing as first step three GPS permanent stations on the volcanic structure, in sites easily accessible. The analysis of about 2 years of GPS observations has evidenced a peculiar velocity pattern of the Colli Albani stations with respect to those located nearby, but outside the volcano edifice. With respect to Eurasia, the horizontal velocities are NE directed with magnitudes of 2.2 ± 1.4 mm/year (RDPI), 3.0 ± 0.8 mm/year (RMPO) and 3.3 ± 1.2 mm/year (NEMI). The uplift rates are determined with minor accuracy and range from 3.3 and 6.0 mm/year. We used a non-linear inversion algorithm to determine the best-fit parameters for a Mogi spherical source based on the Levenberg–Marquardt least squares approach. The best-fit is obtained with a source at 4.6 km depth beneath the western flank of the volcano and a volume variation of 3.6 × 10−4 km3/year. This result is in agreement with the volume rate retrieved by PS-InSAR technique and rather different from the rate inferred from leveling surveys. Consequently, non-linear trends of the hydrothermal system charge cannot be excluded apriori and the continuous GPS monitoring should be considered a priority in assessing the hazard of the Colli Albani.
... Compositions of Air Saturated Water (ASW) and previously determined lake samples ) are also shown groundwater (600 m) are mainly enriched in CO 2 with respect to a normal air saturated water (ASW); minor amounts of methane are also present. The lake sample is perfectly inserted into the CO 2 enrichment trend with depth that characterizes Lake Albano ; the sample collected into the Roman emissary shows a high dissolved CO 2 content, comparable to that of the lake at 50 m depth reported by Carapezza et al. (2008). The dissolution of CO 2 and the availability of the Ca 2? ion from the leaching of volcanic rocks well explain the formation of calcitic speleothems inside the tunnel (Fig. 2), even in the absence of carbonate rocks. ...
... Dashed line is the Central Italy Meteoric Water Line(Longinelli and Selmo 2003). Literature data fromCarapezza et al. (2008) of lake at 10 m depth are ...
Many lakes have been object of hydraulic works in historical times, and the drainage
tunnel carved by Romans for regulating the level of Lake Albano (Central Italy) can be
considered as one of the most important historical hydraulic tunnels in the world. We
sampled and analysed lake and groundwater from lake Albano emissary and other
hydraulic works in the area, characterising their geochemical and isotopic composition
for extracting information useful for a possible reuse of the tunnel for anthropogenic
purposes. The collected water samples exhibit common chemical features, typical of
water-rock interaction processes in volcanic areas. Analyses of minor and trace
elements confirmed the abovementioned results, indicating the presence of an
atmospheric pollution source for heavy metals, although their concentrations are
mostly below the Maximum Admitted Concentrations for drinking water issued by the
World Health Organization.
The chemical composition of dissolved gases indicated that both lake and groundwater
are mainly enriched in CO2. Isotopic analyses suggested a clear volcanic origin for
CO2 dissolved in lake water, while carbon dioxide in groundwater from the Roman
emissary is produced by soil respiration. As further confirmed by Oxygen and
Deuterium isotopic composition, the Roman emissary drains local suspended aquifers
neither in contact with the lake water body nor influenced by volcanic activity,
suggesting the opportunity to use the tunnel as a "zero-condition" monitoring site for
individuating a possible future renewal of volcanic activity.
... The source strength of CO 2 , heat from magma, and other factors like water table depth or climate can change over time, and conditions may be right for gas buildup in a crater lake for only a small window of its existence. Several Italian crater lakes are located in areas of strong CO 2 emission (Chiodini and Frondini 2001), and magmatic gas components have been found in lake waters (Carapezza et al. 2008;Caracausi et al. 2009;Cabassi et al. 2013). The lakes currently pose no hazard of a catastrophic release, but unusual events that might have involved gas releases are recorded in ancient Roman writings (Cioni et al. 2003). ...
... Results of a multi-year study of Lake Albano indicate that an anomalous spike in CO 2 input accompanied a seismic swarm in 1989 (Chiodini et al. 2012). Carapezza et al. (2008) suggest that a prolonged warm spell without winter-time mixing might allow initiation of stable stratification and gas buildup in this lake, the reverse of a proposed weakening of stratification in Cameroonian lakes due to an unusually cool period in the mid-1980s (Kling 1987b). ...
Lakes Nyos and Monoun are known for the dangerous accumulation of CO2 dissolved in stagnant bottom water, but the shallow waters that conceal this hazard are dilute and undergo seasonal changes similar to other deep crater lakes in the tropics. Here we discuss these changes with reference to climatic and water-column data collected at both lakes during the years following the gas release disasters in the mid-1980s. The small annual range in mean daily air temperatures leads to an equally small annual range of surface water temperatures (ΔT ˜6-7 °C), reducing deep convective mixing of the water column. Weak mixing aids the establishment of meromixis, a requisite condition for the gradual buildup of CO2 in bottom waters and perhaps the unusual condition that most explains the rarity of such lakes. Within the mixolimnion, a seasonal thermocline forms each spring and shallow diel thermoclines may be sufficiently strong to isolate surface water and allow primary production to reduce PCO2 below 300 μatm, inducing a net influx of CO2 from the atmosphere. Surface water O2 and pH typically reach maxima at this time, with occasional O2 oversaturation. Mixing to the chemocline occurs in both lakes during the winter dry season, primarily due to low humidity and cool night time air temperature. An additional period of variable mixing, occasionally reaching the chemocline in Lake Monoun, occurs during the summer monsoon season in response to increased frequency of major storms. The mixolimnion encompassed the upper ˜40-50 m of Lake Nyos and upper ˜15-20 m of Lake Monoun prior to the installation of degassing pipes in 2001 and 2003, respectively. Degassing caused chemoclines to deepen rapidly. Piping of anoxic, high-TDS bottom water to the lake surface has had a complex effect on the mixolimnion. Algal growth stimulated by increased nutrients (N and P) initially stimulated photosynthesis and raised surface water O2 in Lake Nyos, but O2 removal through oxidation of iron was also enhanced and appeared to dominate at Lake Monoun. Depth-integrated O2 contents decreased in both lakes as did water transparency. No dangerous instabilities in water-column structure were detected over the course of degassing. While Nyos-type lakes are extremely rare, other crater lakes can pose dangers from gas releases and monitoring is warranted.
... Holocene phreatic activity in the Albano maar occurred 5-6 ka B.P. and probably in the fourth century before the Common Era. High lake levels and catastrophic withdrawal of the Albano maar lake since prehistoric age are possible indicators of sudden variation of CO 2 flow and upwelling of hydrothermal fluids [Funiciello et al., 2003;Carapezza et al., 2008]. Seismic tomography identifies a low-velocity region, perhaps still hot or partially molten, >6 km beneath the youngest craters, and a high-velocity region, probably a solidified magma body, beneath the older central volcanic construct [Chiarabba et al., 1997]. ...
... 10.1002/2015RG000492 magmatic origin and subordinately H 2 S) during Holocene and continuing to the present day [Tuccimei et al., 2006;Carapezza et al., 2008Carapezza et al., , 2010Carapezza et al., , 2012. In particular, Lake Albano, on the western flank, was affected by a large CO 2 input that coincided with the last important seismic swarm in 1989, suggesting an intimate relationship between the addition of deep-originated CO 2 to the lake and seismic activity. ...
Calderas are among the most active and dangerous volcanoes. Caldera unrest is defined by enhanced seismicity, gravity changes, surface deformation and degassing. Although much caldera unrest does not lead to an eruption, every eruption is preceded by an unrest episode. Therefore, the proper description of unrest and the forecast of its possible outcome is a timely and challenging task. Here we review the best known unrest at calderas from 1988 to 2014, building on previous work and propose an updated database. Where established, the root cause for unrest is always magmatic; none was purely hydrothermal or tectonic. An interpretive classification of unrest invokes two spectra – compositional (mafic to felsic) and the state of magma conduits feeding from the magma reservoir(s) to the surface (from fully plugged, through semi-plugged, to open). Magma and gas in open conduits can rise and erupt freely; magma in semi-plugged conduits erupts less frequently, yet still allows some gas to escape; plugged conduits allow neither magma nor gas to escape. Unrest in mafic calderas is subtler, less pronounced and repeated, especially with open systems, ensuring the continuous, aseismic and moderate release of magma. Plugged felsic calderas erupt infrequently, anticipated by isolated, short and seismically active unrest. Semi-plugged felsic calderas also erupt infrequently and are restless over decades or centuries, with uplift, seismicity and degassing and, on the longer-term, resurgence, suggesting repeated stalled intrusions. Finally, the expected advances in better understanding caldera unrest are discussed.
... Due to the instability of the area resulting from earth tremors and residual thermal activity the possibility of lake-rollover and CO 2 limnic eruption is thought to pose the highest threat of the volcano today (Funiciello et al. 2003). Underwater gas springs have been documented from direct observation through bathyscaphe methodologies (Capelli et al. 1998) and gas saturation of the bottom waters have been shown from isotopic studies (Carapezza et al. 2008). The processes involved in a limnic eruption could follow those of the tragic events that occurred in Lakes Nyos and Monoun in 1996 (Sigurdsson et al. 1987;Rice 2000), although CO 2 concentrations at Albano Lake are at much lower levels. ...
... Whilst in spring and summer the O 2 profile, indicated a full overturn with O 2 diffusion to deeper water layers down to 60 m and concentration about 5 mg L -1 (see Fig. 4). Similar O 2 profiles have been observed by Carapezza et al. (2008) and Cioni et al. (2003). ...
The crater lake Lake Albano is an increasingly diminishing water resource in terms of volume, the lake level has dropped more than four meters since the 1960s, and water quality resulting from elevated levels of nitrogen and phosphorus. The area of the lake, and the volcano as a whole, is also considered to be geologically hazardous due to continual shallow seismic activity, gaseous emissions and hydrothermal activity. Therefore, most research has been focussed on the geological aspects of the Albano lake system, whilst long-term limnological studies have been lacking. A meromictic classification was given to the lake, but this was based on one year studies of the surface water only. Presented and discussed are the results of a water chemistry and biological study of the full depth profile of Lake Albano from 2004 to 2008. During winter 2005-2006 the lake underwent a complete overturn, resulting in an influx of nutrient rich hypolimnetic water into the upper productive layers and oxygenated epilimnetic water into the deepest water layers. The effect of full overturn on the phytoplankton community is described and compared with those of meromictic years. The interplay between natural and anthropological processes on water quality and water usages is also discussed.
... This discussion is still ongoing and divides the scientific community in two "schools": the Lake Nyos event was triggered by a phreatic eruption, and thus volcano-related (Barberi et al., 1989;Tazieff, 1989) vs. the Lake Nyos event was a limnic event, releasing gas stored in bottom waters after lake overturn (Kling et al., 1987(Kling et al., , 1989Kanari, 1989;Kusakabe et al., 1989). Post-1986 monitoring of the evolution of water and dissolved gas chemistry of Lake Nyos strongly supports the latter theory (Evans et al., 1993(Evans et al., , 1994Kling et al., 2005;Kusakabe et al., 2008;Kusakabe, 2014), now also observed at other lakes worldwide (e.g., Lago Albano, the two Monticchio lakes, Italy; Laguna Hule and Río Cuarto, Costa Rica; Lac Pavin, France; and, of course, Lake Monoun, Cameroon) (Aeschbach-Hertig et al., 1999;Kusakabe et al., 2000;Carapezza et al., 2008;Chiodini et al., 2012;Cabassi et al., 2013a,b;Caracausi et al., 2013). The group of people attending the 1987 meeting were soon named the International Working Group on Crater Lakes (IWGCL). ...
... After the 1986 Lake Nyos gas burst concern gradually raised on the fact if other volcanic lakes are able to release a CO 2 cloud in a similar way. Especially in the 2000s, deep waters of meromictic (constantly stratified) volcanic lakes were sampled and gauged to detect CO 2 accumulation, e.g.: Albano, Monticchio and Averno lakes (Italy, Caliro et al., 2008;Carapezza et al., 2008;Chiodini et al., 2012;Cabassi et al., 2013a;Caracausi et al., 2013), Lake Kivu (DRC-Rwanda; Schmid et al., 2005;Tassi et al., 2009b), Río Cuarto and Laguna Hule (Costa Rica;Cabassi et al., 2013b). As residence time of lake water in Nyos-type lakes (high volume) is very long (yearsdecades), the monitoring frequency often seems to higher than needed. ...
Volcanic lake research boosted after lethal gas burst occurred at Lake Nyos (Cameroon) in 1986, a limnic rather than a volcanic event. This led to the foundation of the IAVCEI–Commission on Volcanic Lakes, which grew out into a multi–disciplinary scientific community since the 1990s. We here introduce the first data base of volcanic lakes VOLADA, containing 474 lakes, a number that, in our opinion, is surprisingly high. VOLADA could become an interactive, open-access working tool where our community can rely on in the future. Many of the compiled lakes were almost unknown, or at least unstudied to date, whereas there are acidic crater lakes topping active magmatic–hydrothermal systems that are continuously or discontinuously monitored, providing useful information for volcanic surveillance (e.g., Ruapehu, Yugama, Poás). Nyos–type lakes, i.e. those hosted in quiescent volcanoes and characterized by significant gas accumulation in bottom waters, are potentially hazardous. These lakes tend to remain stably stratified in tropical and sub-tropical climates (meromictic), leading to long-term build–up of gas, which can be released after a trigger. Some of the unstudied lakes are possibly in the latter situation. Acidic crater lakes are easily recognized as active, whereas Nyos–type lakes can only be recognized as potentially hazardous if bottom waters are investigated, a less obvious operation. In this review, research strategies are lined out, especially for the “active crater lakes”. We make suggestions for monitoring frequency based on the principle of the “residence time dependent monitoring time window”. A complementary, multi–disciplinary (geochemistry, geophysics, limnology, statistics) approach is considered to provide new ideas, which can be the base for future volcanic lake monitoring. More profound deterministic knowledge (e.g., precursory signals for phreatic eruptions, or lake roll–over events) should not only serve to enhance conceptual models of single lakes, but also serve as input parameters in probabilistic approaches. After more than 25 years of pioneering studies on rather few lakes (~ 20% of all), the scientific community should be challenged to study the many poorly studied volcanic lakes, in order to better constrain the related hazards.
... Holocene phreatic activity in the Albano maar occurred 5-6 ka B.P. and probably in the fourth century before the Common Era. High lake levels and catastrophic withdrawal of the Albano maar lake since prehistoric age are possible indicators of sudden variation of CO 2 flow and upwelling of hydrothermal fluids [Funiciello et al., 2003;Carapezza et al., 2008]. Seismic tomography identifies a low-velocity region, perhaps still hot or partially molten, >6 km beneath the youngest craters, and a high-velocity region, probably a solidified magma body, beneath the older central volcanic construct [Chiarabba et al., 1997]. ...
... 10.1002/2015RG000492 magmatic origin and subordinately H 2 S) during Holocene and continuing to the present day [Tuccimei et al., 2006;Carapezza et al., 2008Carapezza et al., , 2010Carapezza et al., , 2012. In particular, Lake Albano, on the western flank, was affected by a large CO 2 input that coincided with the last important seismic swarm in 1989, suggesting an intimate relationship between the addition of deep-originated CO 2 to the lake and seismic activity. ...
This is a remarkable reference for researchers interested in volcanic hazards and silicic volcanism. Because of long repose and often obscure shapes and large size calderas are a volcanic type less obvious and less well studied. Because they represent potentially highly dangerous and highly explosive volcanos which could have large-scale and even global impact when they erupt, it is very important to understand their behavior. This new volume represents an extensive effort at compiling real observations at earth's calderas. The authors manage to incorporate a very impressive list of original references that go far beyond standard volcanological literature and also often extend back many centuries to include the perspective of longer historic time at some calderas. If volcanologists are serious about eruption forecasting, they must be willing to dig out and absorb the lessons of historic observations as well as design instruments and make good measurements. There is an initial introductory chapter of 27 pages which attempts to lead the way to interpretation of various patterns of caldera unrest, based on synthesis of the various individual cases. The meat of the volumes is in sections on the individual calderas, enriched with many maps and figures documenting the caldera unrest. A valuable asset of the compilation is its broad scope, which incorporates the activity of related or possibly related cones, domes, solfataras, etc., with the parent ( ) caldera.
... A dramatic overflow of the lake towards the Roman plain ( Fig. 2) occurred in 398 BCE, and a drainage tunnel was excavated in 394 BCE by the Romans to prevent further overflows by keeping the lake level beneath the lowest crater rim. The present state of Lake Albano and the possible occurrence of a new lahar generating overflows are discussed in Carapezza et al. (2008Carapezza et al. ( , 2010. ...
... There is no evidence that these lahars occurred during volcanic eruptions and so they are considered as inter-eruptive phenomena. The lahars possibly originated from seismically induced sudden injections into the lake bottom of hot CO 2 -rich fluids (Funiciello et al. , 2003Carapezza et al. 2008) which caused water overflows toward the Campino plain from the lowermost point of the crater rim (Fig. 2). ...
Although controversy exists about the age of its most recent eruption (either 36 ka or <23 ka). Colli Albani volcano is unanimously considered to be quiescent and not exinct. During the Holocene. several lahars were generated by overflows from Albano crater lake up to the fourth century BCE. when the Romans excavated a drainage tunnel to keep the lake level below the crater rim. Such recent activity, together with the frequent occurrence of seismic swarms underneath the crater zone, the ongoing uplift of the volcanic edifice and the magmatic affinity of the emitted gas. indicate the presence of an active magma chamber. The most likely site for a new eruption is the deep crater hosted in the southern part of the Lake Albano. where the last eruptive events occurred. Any eruption would have a strong explosive character enhanced by the interaction of magma with the water of the lake and would endanger a densely inhabited area up to the outskirts of Rome. The hazard of a new overflow from Lake Albano is very low because of the present low level of the lake. There is instead a potential for CO2 release from the deep lake water following the occurrence of rollovers, which would threaten the lake shore, a site where thousands of people spend their vacations in the summer. However, the content of dissolved CO2 is presently far from saturation and no Nyos-type events will occur today. Presently, the main hazard is related to strong gas emissions (CO2· H2S and Rn) from fractured zones and gas blowouts from wells reaching shallow gas-pressurized aquifers.
... In Europe, many long-dormant volcanic provinces host lakes marked by gas emissions. Lake Albano, around 20 km south-east of Rome, Italy (Anzidei et al., 2008;Cabassi et al., 2013;Carapezza et al., 2008;Funiciello et al., 2003;Martini et al., 1994;Rouwet et al., 2019) contains CO 2 that is released each year due to thermal convection of the water (seasonal overturn) (Chiodini et al., 2012). Convection prevents the accumulation of CO 2 a depth, unlike at a permanently stratified lake (meromictic lake), such as lake Nyos. ...
Risk mitigation in long-dormant volcanic provinces is a challenge due to the absence of collective memory of past disasters as well as the scarcity, and subtlety, of unrest signals that can be monitored. In this study, the impact of a potential limnic eruption is assessed at the 92-m-deep lake Pavin (French Massif Central). The lake is hosted in a maar crater formed during the last eruptive event in metropolitan France (~7 ka) and contains dissolved CO2 in the deepest water layer, below 60 m. Carbon dioxide (CO2) emissions measured at the lake surface (0.44 km 2) reach up to 10.1 tons/day during the winter. Beyond this (limited) continuous degassing of the lake, the current CO2 budget in the monimolimnion layer (at a depth of 60 m to 92 m) was estimated at 1750 tons, of which about 450 tons are available for release in case of overturn of the lake. Scenarios for CO2 dispersion in the lower atmosphere were simulated with the DISGAS and TWODEE-2 models by varying (i) meteorological conditions, (ii) the amount of CO2 released, (iii) and the mechanisms of degassing during a potential limnic eruption. The simulations allowed identification and delimitation of areas potentially impacted by hazardous CO2 levels in the air down-valley from the lake and directly around the lake. The spatio-temporal evolution of the potential CO2 cloud raises issues regarding the impacts of such a hypothetical event in the close vicinity of the lake and, given the area is populated and highly visited, needs to be considered in future risk mitigation strategies.
... A better estimate of the amount of CO 2 released by diffuse degassing is important not only for volcano monitoring, but also for quantifying gas hazards, since CO 2 can reach high concentrations in weakly or poorly ventilated areas [28][29][30][31][32][33][34]. The accumulation of CO 2 presents potential hazards for humans, animals, and ecosystems at the local scale, while also having the capacity to influence global climate patterns. ...
The La Fossa volcano is near the inhabited zone of the island of Vulcano and is a suitable case for studying gas sources of different geological origins. Since the last eruption, fumarolic-solfataric activity has interested this area with fumarolic emissions, mainly at the top of the volcanic cone and at Vulcano Porto. In recent decades, the anomalous degassing zones on the island have not significantly changed their location. On the contrary, there have been several significant changes in the emission rate due to the addition of volcanic gas. In these zones, CO2 flux from the ground is responsible for a decrease in the indoor air quality. A recent increase in volcanic degassing led to an increase in the gas hazard in the inhabited area of Vulcano Island, and people were temporarily displaced from Vulcano Porto. The results of this study show that a monitoring system can be used for the early detection of transients in soil CO2 flux (φCO2) in the anomalous degassing zone of Vulcano. Synchronous monitoring of φCO2 and outdoor air CO2 concentration has shown variations in volcanic degassing that affect outdoor air CO2 concentration in the populated zone of Faraglione.
... Nevertheless, it is a fact that, especially, the 1986 Lake Nyos gas burst has increased the general awareness of the potential danger this type of volcanic lakes poses (e.g. Giggenbach et al., 1991;Martini et al., 1994;Aeschbach-Hertig et al., 1996Caliro et al., 2008;Carapezza et al., 2008;Chiodini et al., 2012;Cabassi et al., 2013Cabassi et al., , 2014Rouwet et al., 2019Rouwet et al., , 2020Rouwet, 2021). Rouwet et al. (2014) introduced the first, incomplete version of the community-based, interactive, and open-source (https:// vhub.org/resources/2437) ...
Volcanic lakes pose specific hazards inherent to the presence of water: phreatic and phreatomagmatic eruptions, lahars, limnic gas bursts and dispersion of brines in the hydrological network. Here we introduce the updated, interactive and open-access database for African volcanic lakes, country by country. The previous database VOLADA (VOlcanic LAke DAta Base, Rouwet et al., Journal of Volcanology and Geothermal Research, 2014, 272, 78–97) reported 96 volcanic lakes for Africa. This number is now revised and established at 220, converting VOLADA_Africa 2.0 in the most comprehensive resource for African volcanic lakes: 81 in Uganda, 37 in Kenya, 33 in Cameroon, 28 in Madagascar, 19 in Ethiopia, 6 in Tanzania, 2 in Rwanda, 2 in Sudan, 2 in D.R. Congo, 1 in Libya, and 9 on the minor islands around Africa. We present the current state-of-the-art of arguably all the African volcanic lakes that the global experts and regional research teams are aware of, and provide hints for future research directions, with a special focus on the volcanic hazard assessment. All lakes in the updated database are classified for their genetic origin and their physical and chemical characteristics, and level of study. The predominant rift-related volcanism in Africa favors basaltic eruptive products, leading to volcanoes with highly permeable edifices, and hence less-developed hydrothermal systems. Basal aquifers accumulate under large volcanoes and in rift depressions providing a potential scenario for phreatomagmatic volcanism. This hypothesis, based on a morphometric analysis and volcanological research from literature, conveys the predominance of maar lakes in large monogenetic fields in Africa (e.g. Uganda, Cameroon, Ethiopia), and the absence of peak-activity crater lakes, generally found at polygenetic arc-volcanoes. Considering the large number of maar lakes in Africa (172), within similar geotectonic settings and meteoric conditions as in Cameroon, it is somewhat surprising that “only” from Lake Monoun and Lake Nyos fatal CO2 bursts have been recorded. Explaining why other maars did not experience limnic gas bursts is a question that can only be answered by enhancing insights into physical limnology and fluid geochemistry of the so far poorly studied lakes. From a hazard perspective, there is an urgent need to tackle this task as a community.
... 50,000 years ago [25]. Lake Albano has a surface of 6 km 2 , a maximum depth of 175 m (which is the greatest of the Italian crater lakes), and is funnel-shaped [19,26,27], which would suggest fluids circulation related to residual anomalies associated with past volcanic activities [28] (further description of the study area is available in Supplementary Materials Section S1, Table S1). ...
Inland freshwaters are of great importance for human health and activities, but major stressors such as nutrient pollution, deforestation, and urbanization are compromising their status. Water quality degradation and freshwater ecosystem preservation are current issues worldwide requiring frequent and efficient monitoring protocols. The increasing need for large amounts of data to comply with national and international regulations on water quality monitoring highlights traditional procedures limits. Therefore, the purpose of the present study is to investigate the potential of alternative and rapid methods for chlorophyll concentration surveys in freshwaters. The Phyto-PAM (pulse amplitude-modulated) instrument and the Case-2 Regional Coast Colour (C2RCC) satellite image processor were selected to estimate chlorophyll concentration in the surface waters of Lake Albano (Central Italy), selected as a pilot area for the project BLOOWATER (Water JPI 2018 Joint Call Closing the Water Cycle Gap). The correlation tests’ results indicate significant relations with chlorophyll data measured spectrophotometrically, confirming the suitability of both methods for chlorophyll retrieval. However, the relatively low strength of the correlation between remotely sensed and spectrophotometric data (r = 0.57, p < 2.2 × 10⁻¹⁶) was not as satisfactory as with Phyto-PAM values (r = 0.97, p = 1.2 × 10⁻⁴). Even though the techniques in this study proved to be promising in the water body under investigation, their current limitations suggest the need for further calibration and integration with other systems (e.g., unmanned aerial vehicles).
... Lake Albano is ranked as meso-eutrophic [47,76], with progressive deterioration over time due to an increase of sewage discharge [77] and over-extraction of groundwater within the watershed. Cyanotoxic algal blooms regularly occur in Lake Albano, when the water column mixing brings hypolimnetic nutrients to the surface [76,78,79]. Even though its quality is gradually deteriorating, Lake Albano is designated SCI (IT6030038). ...
Prompt estimation of phytoplankton biomass is critical in determining the ecological quality of freshwaters. Remote Sensing (RS) may provide new opportunities to integrate with situ traditional monitoring techniques. Nonetheless, wide regional and temporal variability in freshwater optical constituents makes it difficult to design universally applicable RS protocols. Here, we assessed the potential of two neural networks-based models, namely the Case 2 Regional CoastColour (C2RCC) processor and the Mixture Density Network (MDN), applied to MSI Sentinel-2 data for monitoring Chlorophyll (Chl) content in three monomictic volcanic lakes while accounting for the effect of their specific water circulation pattern on the remotely-sensed and in situ data relation. Linear mixed models were used to test the relationship between the remote sensing indices calculated through C2RCC (INN) and MDN (IMDN), and in situ Chl concentration. Both indices proved to explain a large portion of the variability in the field data and exhibited a positive and significant relationship between Chl concentration and satellite data, but only during the mixing phase. The significant effect of the water circulation period can be explained by the low responsiveness of the RS approaches applied here to the low phytoplankton biomass, typical of the stratification phase. Sentinel-2 data proved their valuable potential for the remote sensing of phytoplankton in small inland water bodies, otherwise challenging with previous sensors. However, caution should be taken, since the applicability of such an approach on certain water bodies may depend on hydrological and ecological parameters (e.g., thermal stratification and seasonal nutrient availability) potentially altering RS chlorophyll detection by neural networks-based models, despite their alleged global validity.
... In some zones, these sources co-occur with anthropogenic sources. The investigation of the gas emissions from volcanoes (Jones and Cox, 2001;Brovkin et al., 2010;Frölicher et al., 2011;Burton et al., 2013;Cox et al., 2013;Wang et al., 2014;Flesia and Frezzotti, 2015), rift zones, and the active plate boundaries (Marini and Chiodini, 1994;Chiodini et al., 1995Chiodini et al., , 2004Minissale et al., 1997;Carapezza et al., 2003Carapezza et al., , 2008Carapezza et al., , 2012aCarapezza et al., , 2012bCarapezza et al., , 2019Gambardella et al., 2004Gambardella et al., , 2012aCamarda et al., 2016Camarda et al., , 2020Tamburello et al., 2018;Frondini et al., 2018) helps gain information on the effects the carbon cycle on the climate. The process of diffuse soil degassing from tectonic zones is anomalous and occurs over a long period of time. ...
Anthropogenic emissions of greenhouse gases (GHGs) co-occur with emissions of these gases from volcanic and urban environments. Therefore, it remains a challenge for the scientific community to identify the contamination sources and quantify the specific contributions. Stable isotopes have many applications in different fields under geosciences, including volcanology, environmental surveying, and climatology. Isotopic surveys allow identification of photosynthetic fractionation in tree forests and gas sources in urban zones, and tracking of volcanic degassing. Thus, the stable isotopic composition of the local GHGs allows the evaluation of the environmental impacts and assists in mitigating the emissions.
The present study aimed to distinguish the tropospheric sources of CO2 in the different ecosystems based on the stable isotopic composition of CO2. The study relies on field experiments performed in both volcanic and urban zones of the Mediterranean region. Experiments to identify the CO2 origins were designed and conducted in the field. The CO2 in the air in Palermo, the soil CO2 released at Vulcano (Aeolian Islands, Italy), and the CO2 emitted at Cava dei Selci (Rome, Italy) were selected for conducting case studies.
Isotope surveying of the CO2-containing air in Palermo revealed that the CO2 content was correlated to human activity. Mobile-based measurements of carbon isotope were conducted to distinguish the different sources of CO2 at the district scale. In particular, the isotopic surveying process distinguished landfill-related CO2 emissions from the fossil fuel burning ones. The underlying geological reservoir was identified as the main source of air CO2 at Cava dei Selci. Finally, partitioning of soil CO2 enabled estimation of the geological CO2 estimation in the Vulcano Porto settled zones.
The results of the present study revealed that detailed investigations on stable isotopes assist in tracking the CO2 sources and the fate of gas emissions. The fine-tuned experimental solutions assisted in broadening the research perspectives. In addition, deeper insights into the carbon cycle were obtained.
... The volcanic complex, that hosts a 175 m deep lake (e.g. Cioni et al., 2003;Carapezza et al., 2008;Barbieri et al., 2013;Cabassi et al., 2013), is at about 20 km SE of Rome (Latium, Central Italy; Fig. 1a) and is located in one of the most densely populated municipalities of Latium. Permanent gas (mainly consisting of CO 2 and H 2 S) emissions (e.g. ...
The Colli Albani volcanic complex (Lazio, Italy) hosts areas characterized by anomalously high emissions of CO2-rich gases (e.g. Tivoli, Cava dei Selci, Tor Caldara, Solforata). The source of these gases is a regional aquifer within the Mesozoic carbonate rock sequences. These degassing zones release significant concentrations of H2S and other toxic gases (e.g. GEM: Gaseous Elemental Mercury, and Rn) and represent a serious hazard for local inhabitants, especially for those living at Cava dei Selci (near Rome, Italy), where the emitting areas are nested inside residential neighborhoods. In April 2016, a comprehensive geochemical survey was carried out in an abandoned stone quarry nearby the urban settlement aimed to: (i) investigate the gas composition from both punctual discharges and anomalously high diffuse soil degassing sites, and (ii) evaluate their environmental impact on the local air quality. The spatial distribution of the soil CO2 fluxes was mainly dependent on the local geostructural setting, whereas shallow secondary processes (e.g. oxidation and gas-water interaction) likely represent the main controlling factor on reactive and/or water-soluble gas species, such as CH4 and H2S. The total output of CO2 from the abandoned stone quarry accounted for 0.53% of total CO2 discharged from the whole Colli Albani volcanic district. The naturally emitted toxic gases (e.g. CO2, H2S, CH4, GEM) largely affect the air quality and pose a serious threat for the health of the local residents. A mobile multi-instrumental station able to continuously and simultaneously acquire CO2, H2S, SO2, CH4, GEM and CO was deployed to verify the concentrations of both the main deep-originated gas compounds and potential secondary gaseous contaminants (i.e. SO2) around and inside the urban settlement most exposed to the lethal gases. Hydrogen sulfide was found to be the most impacting gas, occasionally exceeding the 24-h air quality guideline for ambient air and causing odor annoyance at a distance up to more than 250 m downwind from the emitting area. In poorly ventilated basements, toxic gas accumulations up to hazardous levels were measured, producing anomalous outdoor air concentrations at the street level in front of the descending vehicular access to private garages and relatively far from the main emitting area. The geochemical survey, carried out via mobile station and soil gas measurements, resulted to be particularly efficient for evaluating the potential effects caused by gas emissions in inhabited areas. The multi-measurement approach adopted in the present study is of paramount importance for managing future urban development plans.
... Meromictic volcanic lakes characterized by a relatively low input rate of volcanic-hydrothermal gases (CO 2 ) typically show dissolved CH 4 , produced by microbial activity occurring in the bottom sediments and within the water column, at concentrations comparable to those of CO 2 [24][25][26][27][28]. External gas (CO 2 ) inputs play as a trigger for prokaryotic activity [29][30][31], whose activity along the water column and in the bottom sediments likely represents the main controlling factor for the development and temporal evolution of a dissolved gas reservoir within these lakes. ...
Volcanic lakes are characterized by physicochemical favorable conditions for the development of reservoirs of C-bearing greenhouse gases that can be dispersed to air during occasional rollover events. By combining a microbiological and geochemical approach, we showed that the chemistry of the CO2- and CH4-rich gas reservoir hosted within the meromictic Lake Averno (Campi Flegrei, southern Italy) are related to the microbial niche differentiation along the vertical water column. The simultaneous occurrence of diverse functional groups of microbes operating under different conditions suggests that these habitats harbor complex microbial consortia that impact on the production and consumption of greenhouse gases. In the epilimnion, the activity of aerobic methanotrophic bacteria and photosynthetic biota, together with CO2 dissolution at relatively high pH, enhanced CO2- and CH4 consumption, which also occurred in the hypolimnion. Moreover, results from computations carried out to evaluate the dependence of the lake stability on the CO2/CH4 ratios, suggested that the water density vertical gradient was mainly controlled by salinity and temperature, whereas the effect of dissolved gases was minor, excepting if extremely high increases of CH4 are admitted. Therefore, biological processes, controlling the composition of CO2 and CH4, contributed to stabilize the lake stratification of the lake. Overall, Lake Averno, and supposedly the numerous worldwide distributed volcanic lakes having similar features (namely bio-activity lakes), acts as a sink for the CO2 supplied from the hydrothermal/magmatic system, displaying a significant influence on the local carbon budget.
... The two Newberry Volcano lakes are unique in their chemistries and gas contents, and have few analogues, although several Italian volcanic CO 2rich lakes may have strong similarities (Carapezza et al. 2008;Chiodini et al. 2012;Cabassi et al. 2013). At Newberry Volcano and the Italian lakes, sudden intense CO 2 degassing is a possibility through seismic triggers or disrupted lake stratification, and presents a volcanic hazard that must be considered (Evans et al. 1993;Caudron et al. 2012;Chiodini et al. 2012). ...
Newberry Volcano in Oregon, USA, has two small crater lakes inside its caldera: East Lake and Paulina Lake. The 50-80 m deep lakes differ in morphology, water chemistry and sediment composition, although separated only by a narrow volcanic ridge. East Lake is a terminal lake with gaseous geothermal inputs, whereas Paulina Lake has an outlet (Paulina Creek) and subaqueous, high-alkalinity hot springs. The sediment in both lakes is organic-rich and mainly consists of diatom frustules (SiO2) with some volcanic ash, accumulating at sedimentation rates of 1.5-2 mm a⁻¹ (²¹⁰Pb dated). In Paulina Lake the sediment has up to 14% Fe2O3 of hydrothermal origin and 250 ppm As. Sediment in East Lake is Fe-poor but has up to 4 ppm Hg, and fish are also Hg-rich. Both lakes host productive ecosystems, with primary producers using geothermal CO2, P and Si, and nitrogen fixed by cyanobacteria (Nostoc sp.). Water budgets and water residence times were calculated from stable isotope budgets. East Lake has a steep vertical δ¹³C (dissolved inorganic carbon, DIC) gradient, with surface δ¹³C values of up to 5.5‰, largely due to diffusional CO2 losses and photosynthetic carbon withdrawal. Paulina Lake is better mixed, has a lower organic productivity and limited surface CO2 evasion; its δ¹³C (DIC) gradient is small. We theorize that the lakes are fed by different geothermal components as a result of phase separation below East Lake. The gas component (CO2, H2S, Hg) enters East Lake, as indicated by the rising bubble trains in the lake. A residual fluid, depleted in Hg but rich in Si, Fe, carbonate, P and As, enters Paulina Lake. The presence of highly toxic components and the gas-charging of East Lake present natural hazards, which may change when new volcanic activity is initiated, and thus should be monitored.
... Many volcanic lakes with a geothermal/volcanic CO 2 input (Chiodini et al. 2000(Chiodini et al. , 2012Carapezza et al. 2008) have δ 13 C compositions that deviate from atmosphere-derived carbon. The bulk δ 13 C of dissolved carbonate in volcanic lakes is a function of the bulk δ 13 C of the input term, and the fractionations that may occur in the lake as a result of photosynthetic activity. ...
Volcanic lakes carry fluids that range from ultra acid, high TDS brines to largely meteoric fluids. Their water compositions are governed by volcanic fluid inputs, which range from almost raw, cooled volcanic gases (largely S-Cl-F-CO2 rich fluid) to more mature solutions that result from interaction of these acid fluids with volcanic rocks. Volcanic inputs can have reacted with mature protoliths (low degrees of neutralization) or with freshly intruded magma (high degrees of water rock interaction), the latter often resulting in the precipitation of secondary minerals such as alunite. The detailed chemical lake water composition is a reflection of mineral precipitation, fractionation of trace elements in the precipitated phases (such as the rare earThelements and metals in sulfides) and element vapor phase transport by the volcanic gases. Variations in lake composition result from a changing volcanic input composition or magnitude and thus are important in volcano monitoring. The lake water dynamics also impact the lake water composition over time, and variations in evaporation rate, meteoric water input and dramatic changes in input may cause changes in element concentrations and ratios related to non steady state effects. The recovery time to steady state differs strongly between open and closed lake systems. The stable isotope compositions of volcanic lake waters reflect W/R interaction (higher δ18O), degree of volcanic gas input (higher δ18O and δD), and evaporation at elevated temperatures (flat evaporation lines). Isotope ratios of other elements usually reflect the nature of the volcanic inputs or dissolved rock. Volcanic lakes can be charged with toxic elements that upon release may impact local ecosystems and agricultural land or drinking water downstream. Volcanic lakes charged with poorly soluble gases such as CO2 and methane may represent hazards of limnic eruptions. Failure of retaining walls or dams of acid lakes may cause acid floods with damage to land and livestock downstream.
... For modern spring waters in the area, d 18 O is about À 7.4% (Giggenbach et al., 1988; Duchi et al., 1991; Minissale et al., 2002; Mariucci et al., 2008), the d 18 O of modern precipitation in the region lies between À 6% and À 7% (Longinelli and Selmo, 2003). On the other hand, the d 18 O composition of modern waters from the nearby Lake Albano is between À 0.8% and 1%, and the dD-d 18 O variations are compatible with a simple evaporation process of local meteoric water (Carapezza et al., 2008 For normalized d 18 O values we have used the following offset (fractionation) values of enrichment to isotopic equilibrium calcite. C. neglecta +2.4% (Filippi et al.,1999). ...
Sediments from Valle di Castiglione in Italy provide a reference sequence for Middle Pleistocene to Holocene palaeoclimate reconstruction of the Mediterranean area. Stable isotope and trace element signals from ostracod valves, as well as palaeoenvironmental analyses (autoecology, community analysis and mutual ostracod temperature range), provided results that cannot be correlated with those derived from pollen and other proxy records. The lack of correlation is attributed to the peculiar geological, hydrogeological and hydrochemical setting of the Valle di Castiglione maar lake. The main trigger for the hydrochemical changes in the waterbody and, therefore, in the ostracod isotopic and trace element signatures, is likely the volcano-tectonic activity in the area. This illustrates how ostracod trace element and isotopic analyses are not the most appropriate tools for palaeoclimate reconstructions from lakes with complex hydrological features, such as some crater lakes, and demonstrates the need for care in selecting lacustrine sequences for such studies.
... Many of these lakes have a substantial diffusive CO 2 flux to the ambient atmosphere (Pérez et al. 2011;Mazot and Bernard, this issue) and some have direct bubble transport of CO 2 to the surface (Caudron et al. 2012). Examples are the African lakes Monoun, Nyos and Kivu, the carbonate lakes in Italy (Carapezza et al. 2008;Chiodini et al. 2012), Kelut lake on Java (Bernard and Mazot 2004;Caudron et al. 2012;Mazot and Bernard, this issue) and Quilotoa and Cuicocha lakes in Ecuador (Fig. 9, Aguilera et al. 2000;Gunkel et al. 2008;Gunkel and Beulker 2009). ...
This book aims to give an overview on the present state of volcanic lake research, covering topics such as volcano monitoring, the chemistry, dynamics and degassing of acidic crater lakes, mass-energy-chemical-isotopic balance approaches, limnology and degassing of Nyos-type lakes, the impact on the human and natural environment, the eruption products and impact of crater lake breaching eruptions, numerical modeling of gas clouds and lake eruptions, thermo-hydro-mechanical and deformation modeling, CO2 fluxes from lakes, volcanic lakes observed from space, biological activity, continuous monitoring techniques, and some aspects more. We hope to offer an updated manual on volcanic lake research, providing classic research methods, and point towards a more high-tech approach of future volcanic lake research and continuous monitoring.
... Many of these lakes have a substantial diffusive CO 2 flux to the ambient atmosphere (Pérez et al. 2011; Bernard, this issue) and some have direct bubble transport of CO 2 to the surface (Caudron et al. 2012). Examples are the African lakes Monoun, Nyos and Kivu, the carbonate lakes in Italy (Carapezza et al. 2008; Chiodini et al. 2012), Kelut lake on Java (Bernard and Mazot 2004; Caudron et al. 2012; Bernard, this issue) and Quilotoa and Cuicocha lakes in Ecuador (Fig. 9, Aguilera et al. 2000; Gunkel et al. 2008; Gunkel and Beulker 2009). The last class of lakes are dominated by meteoric fluids, either as a result of their sheer size (Toba lake, Indonesia; Bolsena lake, Italy; Crater Lake, Oregon) or because the volcanic/ geothermal inputs are indeed very small (maarRouwet et al. 2008; Taran and Rouwet 2008) lakes in the Eifel, FRG, Hertig et al. 1996). ...
Volcanic lakes are amongst the most spectacular natural features on the planet. These intersections of magmatic-hydrothermal systems and the Earth’s surface are, poetically speaking, “blue windows” into the depth of a volcano (Fig. 1). The changing water compositions and colors of these lakes over time provide insights into the volcanic, hydrothermal and degassing processes of the underlying volcano.
... This term can be extended to several other volcanic lakes which show similar compositional features of water and dissolved gases, e.g. Kivu (D.R.C.-Rwanda) [34,144], Monticchio, Albano and Averno (Italy) [37,86,[145][146][147], Pavin (France) [121,148]. ...
Hule and Río Cuarto are maar lakes located 11 and 18 km N of Poás volcano along a 27 km long fracture zone, in the Central Volcanic Range of Costa Rica. Both lakes are characterized by a stable thermic and chemical stratification and recently they were affected by fish killing events likely related to the uprising of deep anoxic waters to the surface caused by rollover phenomena. The vertical profiles of temperature, pH, redox potential, chemical and isotopic compositions of water and dissolved gases, as well as prokaryotic diversity estimated by DNA fingerprinting and massive 16S rRNA pyrosequencing along the water column of the two lakes, have highlighted that different bio-geochemical processes occur in these meromictic lakes. Although the two lakes host different bacterial and archaeal phylogenetic groups, water and gas chemistry in both lakes is controlled by the same prokaryotic functions, especially regarding the CO2-CH4 cycle. Addition of hydrothermal CO2 through the bottom of the lakes plays a fundamental priming role in developing a stable water stratification and fuelling anoxic bacterial and archaeal populations. Methanogens and methane oxidizers as well as autotrophic and heterotrophic aerobic bacteria responsible of organic carbon recycling resulted to be stratified with depth and strictly related to the chemical-physical conditions and availability of free oxygen, affecting both the CO2 and CH4 chemical concentrations and their isotopic compositions along the water column. Hule and Río Cuarto lakes were demonstrated to contain a CO2 (CH4, N2)-rich gas reservoir mainly controlled by the interactions occurring between geosphere and biosphere. Thus, we introduced the term of bio-activity volcanic lakes to distinguish these lakes, which have analogues worldwide (e.g. Kivu: D.R.C.-Rwanda; Albano, Monticchio and Averno: Italy; Pavin: France) from volcanic lakes only characterized by geogenic CO2 reservoir such as Nyos and Monoun (Cameroon).
... 화산지진의 분류 및 특성 화산활동은 지진(McNutt, 1996), 지형변형 (Dzurisin, 2003), 위성위치추적 시스템 (Fernndez et al., 2003), 경사계 (Battaglia and Bachlery, 2003), 공중음파 (Fee et al., 2013), 지화학적 (Carapezza et al., 2008) 방법 등을 이용하여 감시할 수 있다. 이 중에서 마그마나 화산가스가 지하에서 지표면으로 이동하 면서 발생되는 화산지진은 가장 핵심적이며 보편적으로 실행 되고 있는 감시 방법 중의 하나이며, Omori (1911), Sassa (1936, Imbo (1954) 등의 선구적 연구에 의해 화산지진의 신 호 특성이 많이 밝혀진 바 있다. ...
Continuous seismic observation of volcanic earthquakes related to migration of magma or gas, is one of the most important methods used to monitor active volcanoes. In this review paper, we introduce the characteristics of volcanic earthquakes and their classification based on locations of foci, waveforms, frequencies, lithology, and source mechanisms. We also present some examples of successful warnings of volcanic eruptions and the present status of some observations of volcanic earthquakes in Japan, the United States, Italy, and New Zealand.
... For the Campoverde core, the situation is less clear, as travertine abounds in the hinterland and the discharge feeding the former lake consisted largely of groundwater originating from the Colli Albani, noted for its high fluxes of CO 2 (e.g. Funiciello et al., 2003;Tuccimei et al., 2006;Carapezza et al., 2008). ...
In the past decade (2000-2010), research within the scope of the 'Hidden Landscapes' project by RUG archaeologists provided important information on the Holocene history of the Agro Pontino graben. This information complemented earlier studies by Dutch Universities (UvA, RUG and UL). The graben was found to hold important tephrochronological, palaeoecological and archaeological archives, which deserve to be studied in more detail. This is demonstrated by the recent robust dating of the Avellino pumice layer at 3945 +/- 10 cal BP obtained from this archive (Sevink et al., 2011) and by the complex denudation record resulting from early land use in its hinterland. An overview is given of the recent knowledge on the Bronze Age to recent landscape that existed in the graben and of the major Early Bronze Age sites, of which most were associated with a large lake. Doubts have grown about the reliability of the existing chronological framework derived from earlier pollen cores by conventional radiocarbon dating. These doubts are discussed in the context of results from recent research, with emphasis on the 'hard water effect' that has been largely neglected in the earlier studies. The main current research topics are indicated.
... Recently, the Colli Albani volcano has been studied using seismological (Bianchi et al. 2008;Feuillet et al. 2004;Tertulliani and Riguzzi 1995;Chiarabba et al. 1994;Amato et al. 1994 and reference therein), geodetic (Riguzzi et al. , 2009Salvi et al. 2004;Amato and Chiarabba 1995) and geochemical (Carapezza et al. 2003(Carapezza et al. , 2008Carapezza and Tarchini 2007;Tuccimei et al. 2006;Pizzino et al. 2002;Chiodini and Frondini 2001 and reference therein) data. Moreover, several studies have shed new light on the historic and present physical state of this volcanic structure: researches on geochronology Freda et al. 2006;Marra and Karner 2005), stratigraphic and physical properties from borehole studies (Mariucci et al. 2008;Vinciguerra et al. 2009), experiments on the magma composition (Freda et al. 2008), eruption products (Sottili et al. 2009) and petrographic and crystal-chemical investigations (Laurora et al. 2009). ...
The Colli Albani volcanic complex (Rome, Italy) has been dominated by episodic eruptions commencing around 561 ka and ending with the most recent activity of the Albano maar phase (<70 ka). Earthquakes of moderate intensity, gas emissions and significant ground deformations are the recent evidences of a residual activity. Former geodetic data from leveling surveys, GPS stations and InSAR observations tracked ongoing significant uplift of the order of few mm/year near the Colli Albani western flank. Different uplift rates were detected by each technique in different time spans, suggesting also the possibility of sporadic recharge of the hydrothermal system. The renewed high precision leveling data from IGMI survey carried out in 1997/1999 and the last leveling survey carried out in 2006 show that the uplift along the route is currently significant at an average rate of ~3 mm/year. Radar interferograms from ALOS satellite show uplift rate of ~6 mm/year, southwest of the central sector of the leveling route. We have undertaken a joint inversion of the various geodetic data (vertical rates from leveling surveys, GPS site velocities and InSAR observations acquired by ALOS satellite) using a nonlinear inversion technique to estimate the parameters of a point-pressure source, possibly capable of explaining the ongoing deformation at Colli Albani volcano.
... Several vertical profiles have been carried out since 1997 in the deepest part of Albano Lake measuring temperature (T), pH, dissolved O 2 and electrical conductivity by a multiparametric probe (Cioni et al., 2003; Carapezza et al., 2005b; Carapezza et al., in press). Dissolved gases were analysed in water samples from several depths. ...
The Albano Lake is the deepest volcanic lake in Italy (− 167 m) and fills the youngest maar of the quiescent Colli Albani volcano. The lake has undergone significant level changes and lahar generating overflows occurred about 5800 yrs B.P. and likely in 398 b.C., when Romans excavated a tunnel drain through the maar wall. Hazardous lake rollovers and CO2 release are still possible because the Albano volcano shows active ground deformation, gas emission and periodic seismic swarms. On November 2005, the first high resolution bathymetric survey of the Albano Lake was performed. Here we present the results provided by a Digital Elevation Model and 2-D and 3-D images of the crater lake floor, which is made by coalescent and partly overlapping craters and wide flat surfaces separated by some evident scarps. Submerged shorelines are identified at depths between − 20 m and − 41 m and indicate the occurrence of significant lake level changes, likely between 7.1 and 4.1 ka. The current lake volume is ~ 447.5 × 106 m3 and the total quantity of dissolved CO2 is 6850 t estimated by chemical analyses of samples collected on May 2006. A decrease of nearly one order of magnitude of the CO2 dissolved in the lake water below − 120 m, observed from December 1997 to May 2006 (from 4190 to 465 t respectively), has been attributed to lake water overturn. The observed oscillations of the dissolved CO2 concentrations justify the efforts of monitoring the chemical and physical characteristics of the lake. At present the quantity of dissolved CO2 is very far from saturation and Nyos-type events cannot presently occur.
Carbon dioxide (CO2) accumulation and emission are well-known features of deep lakes, making them a significant unavoidable carbon source to the atmosphere. In the case of meromictic lakes, degassing devices are installed to controllably release through a pipe the CO2 trapped in the bottom waters. Otherwise, the gas is emitted diffusely at the air-water surface or accidentally through a limnic eruption when the saturation limit is reached. This controlled degassing operation gives rise to an end-of-pipe carbon capture opportunity that has yet to be explored. In the perspective of promoting negative emission technologies, as this is required to reach the near-term global carbon neutrality objective, this study outlines an end-of-pipe solid sorbent-based carbon capture technique that targets the CO2 released through controlled degassing of deep meromictic lakes. A direct air capture (DAC) system astutely dimensioned and optimised by the vacuuming of air enriched with CO2 from the controlled degassing of the lake is therefore proposed and its technical, economic, and environmental feasibility discussed based on the cases of lakes Nyos and Monoun in Cameroon. It resulted that, even on a small scale, capturing CO2 from lake degassing at 8 vol% (80,000 ppm) can achieve a life cycle cost of 15 bar-compressed CO2 between 350 tCO2−1, two to three times less than that of conventional DAC depending on the energy source used, with potentially attractive marginal abatement costs of CO2, especially if natural gas, hydro or solar PV are considered.
Since geogenic carbon dioxide fluxes can sometimes be very large in mofette areas, such areas pose a potential hazard to humans and wildlife.
Within this chapter, not completely explainable or only partly understood phenomena around acid springs and mofettes are presented. It might even be, that some phenomena are not tangible or can finally be explained by natural sciences. Geyser-like splashing stones, soap bubbles through which pointed branch ends pierce without the bubbles bursting quickly, sinking meadow islands, a somewhat unappetizing goulash soup or coots and wild boars playing with carbonic acid are presented.
The presence of water in volcano craters implies a higher susceptibility to specific, potentially hazardous volcanic events, such as phreatic and phreatomagmatic eruptions, lahars, and limnic gas bursts. The driving process behind these hazards is magmatic degassing, inhibited to be released freely into the atmosphere due to a variable degree of the physical and chemical decelerating capacity of the lake itself (e.g., selective scrubbing of gases, condensation of vapor, CO2 storage due to hydrostatic loading, and bubble absorption along with gas rise). This review chapter (1) presents new ideas on hazardous events related to volcanic lakes, (2) shows how volcanic lakes are perceived by the local populations and cultures (risk perception), (3) revises and proposes mitigation strategies, (4) provides tips on how to ideally interpret precursory signals of such events in a suited, multidisciplinary monitoring setup, and (5) can become a road map for future volcanic lake research, by posing unanswered questions and proposing working hypotheses.
CO2 flux measurements are often used to monitor volcanic systems, understand the cause of volcanic unrest, and map sub-surface structures. Currently, such measurements are incomplete at Tarawera (New Zealand), which erupted with little warning in 1886 and produced a ∼17 km long fissure. We combine new soil CO2 flux and C isotope measurements of Tarawera with previous data from Rotomahana and Waimangu (regions also along the 1886 fissure) to fingerprint the CO2 source, understand the current pathways for degassing, quantify the CO2 released along the entire fissure, and provide a baseline survey. The total CO2 emissions from the fissure are 1227 t⋅d–1 (742–3398 t⋅d–1 90 % confidence interval), similar to other regions in the Taupō Volcanic Zone. The CO2 flux from Waimangu and Rotomahana is far higher than from Tarawera (>549 vs. ∼4 t⋅d–1 CO2), likely influenced by a shallow silicic body at depth and Okataina caldera rim faults increasing permeability at the southern end of the fissure. Highly localized regions of elevated CO2 flux occur along the fissure and are likely caused by cross-cutting faults that focus the flow. One of these areas occurs on Tarawera, which is emitting ∼1 t⋅d–1 CO2 with a δ¹³CO2 of −5.5 ± 0.5 ‰, and comparison with previous observations shows that activity is declining over time. This region highlights the spatial and temporal complexity of degassing pathways at volcanoes and that sub-surface structures exert a primary control on the magnitude of CO2 flux in comparison to the surface mechanism (i.e., CO2 released through the soil or lake surface).
The physical-environmental characterization of the coastal territories of Lazio is undoubtedly very complex both from the physical and the evolutionary-environmental point of view. These are, in fact, areas of complex land-sea interaction. In particular, the recent evolution of the coastal zone is tied to the impact due to the modern human settlement, a question strongly linked to the history of the so-called unhealthy areas drainages, marsh and lagoon, or surfaces however not suited or unsuitable to the settlement, especially if understood with poorly and careless sensibility to the delicate urban planning. These places have been too often object, even in a recent or very recent past, of speculations related to the conquest of the territory, which resulted early in a change to agricultural lands with intensive exploitation and new cities of the regime's propaganda, and subsequently in further territories to force in vocation of the uncontrolled touristic seaside business. Their history and the sequences of the occurred evolution induce to highlight those geomorphological characteristics mainly related to the geological dynamics and their subsequent and subordinate hydrogeological arrangement, focusing on the present elements of Hazard, undoubtedly underestimated. We present a first exploration on the current state of the areal knowledge regarding the evolutionary dynamics, providing a diachronic framework of change of the geographical coastal areas correlating them to both historic and archeological information. These last evidences lead to the hypothesis of an evolution historically quite rapid, as example the plain of Fondi, the ancient Sinus Amiclanus. We propose elements of interdisciplinary and multidisciplinary methodology for a careful geoenvironmental analysis which can be, without any doubt and because of the appearing elements of areal hazard, extended to other coastal Tyrrhenian fronts both north and south, going so far as to coasts ancient Volturno rivernot excluding the role played by the Roman comagmatic Province and by the Colli Albani and Roccamonfina volcanic systems.
On 21 August 1986 almost 1800 people were asphyxiated by a CO2 cloud violently released by Lake Nyos, Cameroon. Post-1986 monitoring of Lake Nyos revealed that CO2 steadily accumulates in bottom waters through recharge from soda-rich aquifers. The 1986 lake roll-over event triggered scientific research on volcanic lakes, creating “Nyos biased” interpretations: the search for dissolved CO2 in other lakes might have led to over-interpretations regarding hazard assessment. In this study, a thorough review of the historical literature on Lago Albano over the past approx. 2800 years shows no clear evidence of Nyos-type bursts, contrary to previous ideas. In 1989 Lago Albano was affected by a large CO2 pulse, concomitant with a seismic swarm below Colli Albani volcano. Tracing back in historical literature, at least two similar anomalous degassing episodes occurred out of five seismic crises between 1829 and 1927. Partial temperature- and density-driven roll-over of the top-9 m of Lago Albano commonly releases accumulated CO2 each winter (Chiodini et al., 2012). This degassing dynamics avoids long-term CO2 accumulation in bottom waters, as is the case at permanently stratified lakes in the tropics, such as Lake Nyos. Here we show that Lago Albano is an “anti-Nyos-type" lake: sudden recharge and regularly periodic release of CO2 (Lago Albano) vs. steady recharge and sudden release of CO2 (Lake Nyos). Despite past evidence of hazardous events, (1) the intensive well pumping from the Albano aquifer might lower lake level, and hence decrease the CO2 saturation pressure threshold, and (2) the absence of cold winters, hence avoiding yearly lake roll-over favoring CO2 accumulation at bottom layers, are modern factors that rise the need to revise hazard assessment and future monitoring strategies. Despite the fact that CO2 concentration in bottom waters was far from saturation conditions during the last survey (May 2010; Chiodini et al., 2012), making a limnic eruption highly unlikely, it is necessary to know the saturation state of CO2 in bottom waters and physical lake stability at any time, in order to be prepared for a next anomalous co-seismic CO2 degassing event of unknown quantity near Lago Albano.
This is a review paper on the Lakes Nyos and Monoun gas disasters that took place in the mid-1980s in Cameroon, and on their related geochemistry. The paper describes: (i) the gas disasters (the event and testimonies); (ii) the unusual geochemical characters of the lakes, i.e., strong stratification with high concentrations of dissolved CO2; (iii) the evolution of the CO2 content in the lakes during pre- and syn-degassing; (iv) the noble gas signatures and their implications; (v) a review of models of a limnic eruption; (vi) a revision of a spontaneous eruption hypothesis that explains the cyclic nature of a limnic eruption (Kusakabe 2015); (vii) a brief review of the origin of the Cameroon Volcanic Line (CVL) and the geochemistry of CVL magmas; (viii) a brief review of other CO2-rich lakes in the world; and (ix) concluding remarks.
Degassing of the two lakes has been successful. Most of the
dissolved CO2 has been removed from Lake Monoun, resulting in the stoppage of the degassing system. However, the CO2 content in the lake started to increase in recent years due to the continuing supply of gas from the underlying magma, indicating the necessity of the continuous removal of gas from the lake. Lake Nyos will attain the same situation in several years when degassing will stop. Thus, a continuation of scientific monitoring of the lakes is essential. Since the transfer to Cameroonian scientists of monitoring techniques, including analytical equipment necessary for the monitoring, has been effected through the SATREPS project (Japan’s Official Development Aid), the responsibility is now theirs, and it is strongly hoped that the lake monitoring, the rehabilitation of displaced people, and the setting up of an infrastructure for them, etc., will be carried out by the Cameroonian Government and local scientists.
Lake Pavin is located in the Auvergne Mountains, central France, at 1300 m a.s.l. This small lake (0.44 km2), partially fills an explosive volcanic crater in the Cezallier, a young volcanic area south of the Mont Dore. Its deepest part, from 65 to 92 m, is permanently anoxic, a very rare limnic phenomenon termed meromixis. Pavin is the cradle of French limnology, having been first surveyed in 1770, and then regularly studied since 1880 by local botanists and zoologists from Clermont-Ferrand, along other pristine lakes of the Cezallier. Pavin scientists, such as Delebecque the founder of French limnology and his friend Martel the founder of speleology, visiting the area in 1892, always used up-to-date sampling techniques and methodologies, often borrowed from other disciplines. Meromixis at Pavin was described for the first time in the 1950s and after 1970, its deep waters attracted new teams of isotope geochemists, water chemists, microbiologists and sedimentologists, often from foreign origin. After the unexpected and deadly limnic explosion of Nyos Lake (Cameroun) in 1986, the possibility of Pavin degassing was investigated and concluded to a lack of risk under present conditions. Pavin exceptional history and corpus of legends, referring to its repeated misbehavior and latent fear, perceived locally and in the greater area (Chaps. 2 and 3), remained unknown to contemporary scientists until now. To allow for the re-interpretation of these complex sources, a sensory grid of maar-lakes degassing is proposed here, based on scientists’ observations or reports at other maar- lakes very similar to Pavin, Nyos (1986) and Monoun (1984) in Cameroun, Albano (398 BC) and Monticchio (1770s–1820s) in Italy.
In the past, variations in the chemical contents (SO 4 2− , Cl − , cations) of crater lake water have not systematically demonstrated any relationships with eruptive activity. Intensive parameters (i.e., concentrations, temperature, pH, salinity) should be converted into extensive parameters (i.e., fluxes, changes with time of mass and solutes), taking into account all the internal and external chemical–physical factors that affect the crater lake system. This study presents a generalized box model approach that can be useful for geochemical monitoring of active crater lakes, as highly dynamic natural systems. The mass budget of a lake is based on observations of physical variations over a certain period of time: lake volume (level, surface area), lake water temperature, meteorological precipitation, air humidity, wind velocity, input of spring water, and overflow of the lake. This first approach leads to quantification of the input and output fluxes that contribute to the actual crater lake volume. Estimating the input flux of the "volcanic" fluid (Q f -kg/s) –– an unmeasurable subsurface parameter –– and tracing its variations with time is the major focus during crater lake monitoring. Through expanding the mass budget into an isotope and chemical budget of the lake, the box model helps to qualitatively characterize the fluids involved. The (calculated) Cl − content and dD ratio of the rising "volcanic" fluid defines its origin. With reference to continuous monitoring of crater lakes, the present study provides tips that allow better calculation of Q f in the future. At present, this study offers the most comprehensive and up-to-date literature review on active crater lakes.
Recent studies suggested that Alban Hills (Rome) is a quiescent and not an extinct volcano, as it produced Holocene eruptions and several lahars until Roman times by water overflow from the Albano crater lake. Alban Hills are presently characterized by high PCO2 in groundwaters and by several cold gas emissions usually in sites where excavations removed the superficial impervious cover. Gas consists mostly of CO2 with minor H2S and the diffuse CO2 soil flux is locally very high. Accidental gas blowouts, occurred during shallow well drillings (tens to hundreds m depth) in zones with no surface gas manifestations, indicate the presence of gas pressurized aquifers confined underneath impermeable layers, within both the volcanic rock pile and the underlying Pleistocene loose sediments. Degassing mostly occurs in correspondence of bordering faults of buried horsts cut in the Mesozoic carbonate basement, hosting the main aquifer. Carbon isotopic composition (δ13CCO2) suggests that CO2 is at least partly originated by thermal decarbonation of these limestones. 3He/4He isotopic ratio of the gas (up to 1.9 Ra) is the same or even slightly higher than that of olivine and clinopyroxene fluid inclusions of the Alban Hills volcanic products, indicating a possible magmatic source for the gas. Low R/Ra values, compared to MORB and island arc magmas, are characteristic of the potassic Roman Comagmatic Province and reflect a deep involvement of crustal material in the magma genesis. The lack of high temperature fumaroles can be explained by an efficient meteoric cold water penetration and circulation in the volcano permeable terrains.
Systematic CO2 soil flux surveys at Cava dei Selci on the Colli Albani volcano (28 seasonal surveys since the year 2000) have shown a significant variation of diffuse CO2 release, with a marked decrease, from 25 to 4 tonnes/day, from May 2000 to August 2004, followed by a new increase. Over the same period, CO2 flux halved at S. Maria delle Mole (16.8 tonnes/day in 2000 and 8.3 tonnes/day in 2006). Also the quantity of CO2 dissolved in the deep waters of the Albano crater lake decreased by one order of magnitude in the period 1997-2006. The high CO2 flux values in 2000 could represent the “tail” of a strong degassing episode recorded at Colli Albani in 1995 and related to local earthquakes. The following decrease of CO2 flux could reflect a permeability decrease caused by hydrothermal calcite precipitation favored by PCO2 reduction in the deep source Published Kunming, China 4.5. Degassamento naturale
L’area vulcanica dei Colli Albani è caratterizzata dalla presenza di manifestazioni
gassose associate ad alti strutturali del basamento carbonatico rivelati da anomalie
gravimetriche positive (Di Filippo e Toro, 1980). Si tratta di emissioni di gas freddi,
composti prevalentemente di CO2, con minori quantità di H2S, N2 e CH4 (Giggenbach et al.,
1988; Chiodini e Frondini 2002; Funiciello et al., 2002; Carapezza et al., 2003). Localmente il
flusso di gas dal suolo è rilevante e, nelle zone morfologicamente depresse, negli scavi e
scantinati, l’accumulo di CO2, gas inodoro ed incoloro più pesante dell’aria, crea
condizioni pericolose per persone ed animali. La zona più pericolosa è quella di Cava dei
Selci (Comune di Marino) dove sono avvenuti nel passato ripetuti incidenti mortali e dove
le case sono molto vicine all’emissione di gas (Carapezza et al., 2003). Di seguito vengono
presentati i risultati ottenuti da campagne di misura per la stima del flusso di CO2 dal
suolo nelle aree indicate in fig. 1 e, a Cava dei Selci, anche delle variazioni temporali
registrate nell’emissione gassosa dal suolo e nella concentrazione di CO2 e H2S nell’aria. Le
misure sono state eseguite all’interfaccia suolo-aria utilizzando una camera d’accumulo.
La concentrazione di CO2 all’interno della camera viene misurata in continuo da uno
spettrometro IR ed il suo aumento è proporzionale al flusso (Chiodini et al., 1998). Si
rimanda a Carapezza e Granieri (2004) per un confronto delle tecniche più comunemente
impiegate per la misura del flusso di CO2 dal suolo e per la descrizione dei principali
meccanismi di trasporto del gas nei terreni porosi, conduttivo e viscoso, cui faremo
riferimento nel seguito.
The Italian peninsula shows high complexity of the mantle-crust system and of the Plio-Quaternary magmatism. The lithospheric thickness has remarkable lateral variations from about 110 km to about 30 km. Intermediate and deep-focus earthquakes indicate the presence of a lithospheric slab under the Aeolian-Calabrian area and at the southern end of Campania. Much less extensive intermediate-depth seismicity characterizes the Roman-Tuscany region, where the existence of a relic slab has been hypothesized. The deep seismicity in the southern Tyrrhenian Sea is associated with active calcalkaline to shoshonitic volcanism in the Aeolian arc. Alkaline potassic volcanism occurs in central Italy, and potassic lamproitic magmatism coexists with crustal anatectic and various types of hybrid rocks in the Tuscany area. The parallelism between changing magmatism and variation of the structure of the crust-mantle system makes central-southern Italy a key place where petrological and geophysical data can be used to work out an integrated model of the structure and composition of the upper mantle. Beneath Tuscany the upper mantle has been affected by intensive subduction-related metasomatism. This caused the formation of phlogopite-rich veins that cut through residual spinel-harzburgite and dunite. These veins, possibly partially molten, may explain the unusually soft mechanical properties that are detected just below the Moho. In the Roman Province, the upper mantle is formed by a relatively thin lid (the mantle part of the lithosphere) and by metasomatic fertile peridotite, probably connected with the upraise of an asthenospheric mantle wedge above the Apennines subduction zone. Geochemical data indicate that metasomatism, though still related to subduction, had different characteristics and age than in Tuscany. In the eastern sector of the Aeolian arc and in the Neapolitan area, the upper mantle appears to be distinct from the Roman and Tuscany areas and is probably formed by fertile peridotite contaminated by the presently active subduction of the Ionian Sea floor. The overall picture is that of a mosaic of various mantle domains that have undergone different evolutionary history in terms of both metasomatism and pre-metasomatic events. The coexistence side by side of these sectors is a key factor that has to be considered by models of the geodynamic evolution of the Central Mediterranean area.
Among the physical-chemical characters taken into account, the increases of temperature, ammonium and dissolved carbon dioxide with depth are interpreted as providing information about the contribution of endogene fluids to the lake water budgets. The greater extent of such evidence at Lakes Monoun and Nyos (Cameroon) appears associated with the disasters that occurred there during the last decade; some similarities observed at Lake Albano (Italy) suggest a potential instability also for this crater lake. -from Authors
Groundwater surveys were performed by detailed(around 300 sites) grid-analysis of water temperature, pH, redox potential, electrical conductivity, 222Rn, alkalinity and by calculating the pCO2, throughout the Ciampino and Marino towns in the Alban Hills quiescent volcano (Central Italy). Following several episodes of dangerous CO2 exhalation from soils during the last 20 years and earlier ashistorically recorded, the work aimed at assessing the Natural Gas Hazard (NGH) including the indoor-Rn hazard. The NGH was defined as the probability of an area to become a site of poisonous peri-volcanic gas exhalations from soils to the lower atmosphere (comprising buildings). CO2 was found to be a ``carrier'' for the other poisonous minor and in trace components (HsS, CH4, 222Rn, etc.). This assessment was performed by extrapolating in the aquifer CO2 and 222Rn conditions, and discriminating sectors where future CO2 flux in soils as well as indoor-Rn measurements have to be noted. A preliminary indoor-Rn survey was performed at about 200 sites. The highest values were found in the highest pCO2 and high 222Rn values in groundwater. This indicates convection and enhanced permeability in certain sectors of the main aquifer, i.e., along the bordering faults and inside the gas-trap of the Ciampino Horst., where ``continuous gas-phase micro-macro seepage mechanism'' is invoked to explain the high peri-volcanic gases flux.
Lake Albano is a complex maar that fed the last phases of Colli Albani volcanic activity. The study of several new stratigraphic sections opened by archeological excavations and civil works has revealed the existence of two previously unknown, primary explosive volcanic deposits, and of several lahar deposits, distributed mainly in the Ciampino plain. Morphological analysis, radiometric dating, the distribution of the early human settlements in the area and the revision of the ancient history and myths of Roma, are coherent in indicating that the activity of lake Albano is much younger than previously believed and extends into Holocene. Until the 4th century B.C. catastrophic exondations have occurred from the lowest rim of the lake, with lahar emplacement on the northern slope. The repetition of these phenomena was prevented by a drain-tunnel dug by the Romans. The overflows were possibly triggered by sudden injections, in the lake bottom, of hot and CO2-rich fluids that are certainly present underneath the volcano. The presence of several gas emission sites, the high CO2 flux in zones corresponding to structural highs of the carbonate basement, the existence of pressurised aquifers also at shallow depth and the reported sudden increase of water temperature and gas release in relation to earthquakes, indicate that a similar hazard persists nowadays.
Carbon dioxide soil flux has been used for many years to monitor Italian active volcanoes and both the active Dynamic Concentration (DCM) and the passive Accumulation Chamber (ACM) methods are employed. These two methods have been compared by means of 218 simultaneous flux measurements carried out in the La Fossa area of Vulcano Island, where a large variation of CO2 soil release occurs. Results indicate that DCM overestimates CO2 flux and is proportional to it only in high flux zones (flux higher than 100 gm−2 day−1). Using ACM fluxes and the Stefan–Maxwell equation, the measured CO2/depth curves in the soil could be reproduced. In high flux points CO2 is transported mostly by viscous flow up to a very shallow depth and then by diffusive flow, which is the dominant gas transport mechanism in low flux points. Carbon dioxide soil flux values are controlled by proximity to active gas releasing fractures, by changes in the barometric pressure and by variations in soil permeability.
A method of choosing threshold values between anomalous and background geochemical data, based on partitioning a cumulative probability plot of the data is described. The procedure is somewhat arbitrary but provides a fundamental grouping of data values. Several practical examples of real data sets that range in complexity from a single population to four populations are discussed in detail to illustrate the procedure.The method is not restricted to the choice of thresholds between anomalous and background populations but is much more general in nature. It can be applied to any polymodal distribution containing adequate values and populations with appropriate density distribution. As a rule such distributions for geochemical data closely approach a lognormal model. Two examples of the more general application of the method are described.
The Albano Lake is the deepest volcanic lake among the volcanoes located in the Italian peninsula. It belongs to the Colli Albani volcanic complex whose last largest eruptions are dated back to about ~30 Kyr, although minor events likely occurred during historical times at 7000 yr B.P. or earlier. After the end of the volcanic activity the Crater of Albano became a lake whose level changes are known since historical times. On November 2005, was performed the first very high resolution bathymetric survey of the Albano lake by means of a multibeam echo sounder, integrated with the GPS/RTK positioning technique A particular effort was devoted to produce a high resolution morphobathimetric map, which aims to provide a Digital Terrain Model of the lake floor for wide applications. The surveys did not revealed significant gas exhalative centres, which should indicate a current active gas release from the lake floor. Here we show the technical details of the bathymetric surveys, the very high resolution bathymetric map and the main morphological features of the Albano Lake bottom.
The accumulation chamber methodology allows one to obtain reliable values of the soil CO2 flux, ϕsoil CO2, in the range 0.2 to over 10 000 g m−2 d−1, as proven by both laboratory tests and field surveys in geothermal and volcanic areas. A strong negative correlation is observed between Δϕsoil CO2/Δt and ΔPatm/Δt. Maps of classes of log ϕsoil CO2 for the northern sector of Vulcano Island, Solfatara of Pozzuoli, Nea Kameni Islet and Yanbajain geothermal field evidence that active faults and fractures act as uprising channels of deep, CO2-rich geothermal or magmatic gases. The total diffuse CO2 output was evaluated for each surveyed area.
The present synthesis of the results of the PALICLAS project is partial and provisional. No individual can do full justice to all the data now gathered together by participants work- ing across such a wide range of disciplines. Moreover, too little time has elapsed to allow full intercomparison and integration. The present account first sets out the rationale underlying the attempt at synthesis, stressing the importance of harmonizing chronologies as well as of identifying calibrated and potentially quantifiable proxies for climate change. Subsequent treatment of the data is along chronological lines, with, in so far as possible, all the lines of evidence for climate change and ecosystem response considered, first for the Pleistocene, then subsequently the Holocene parts of the record. The final section attempts to summarise some of the conclusions and main achievements of the PALICLAS project.
A long seismic swarm has been recorded by a digital microseismic network that the Istituto Nazionale di Geofisica (ING) deployed from April 1989 to March 1990 in the Alban Hills Quaternary volcanic region, about 20 km southeast of Rome. The network consisted of thirteen digital stations equipped with four six-component (weak motion and strong motion sensors), three three-component and six vertical weak motion seismometers, including both broad-band and short-period sensors. More than 3000 earthquakes were detected during about one year of operation. The data recorded during the sequence provided an unprecedented opportunity to resolve details of the seismogenic features of this area that has experienced earthquakes since the Roman age. Although the temporal distribution of seismicity reveals a volcanic-type swarm activity, the recorded seismic signals show medium-high frequency waveforms and clear S-wave arrivals typical of `'tectonic" earthquakes. About 1100 earthquakes in a magnitude range between M(D) approximately 1.5 and M(D) approximately 4.0 have been located. The seismicity delineates a approximately 6x12km2NW-SE-elongated region that corresponds to the area where the most recent (0.027 Ma) phreato-magmatic activity took place. Almost no earthquakes occurred beneath the central cone and the eastern side of the caldera. The seismicity is shallow and is mostly concentrated in two clusters that are offset laterally and are at slightly different depths (3-5 and 4-6 km). The fault plane solutions of the strongest earthquakes reveal a approximately NE-SW extension, consistent with the regional orientation of the stress field along the Apenninic chain as obtained by other seismological data.
Composite monthly samples of atmospheric precipitation were collected over different periods of time ranging from one to seven years at 77 different locations throughout Italy. These samples were measured for their oxygen and hydrogen isotopic composition to obtain basic information for hydrological and meteorological studies in this area. On the basis of the results obtained a first map of the isotopic composition of precipitations in Italy has been drawn up. The main features of this map are the following: (1) no isotopic latitudinal gradient has been found along the Tyrrhenian coast from Sicily to the Italian–French border, despite the considerable range of latitude; (2) a minor latitudinal gradient is found in the southeasternmost section of the country (Apulia), partially favored by the local morphology; (3) a marked ‘shadow effect’ of the Apennines is apparent along the southern section of the Po valley and along the central section of the Adriatic coast; (4) the contribution of water vapor from the northernmost section of the Adriatic sea affects the eastern and central sections of the Po plain; (5) the shadow effect of the Alps is considerably smaller than expected; (6) the isotopic vertical gradients calculated in nine different areas and based on groups of two to five different stations vary but are essentially close to about −0.2‰/100m; (7) when mean monthly temperature values were available, their relationship with the isotopic composition of precipitation was found to be, on average, very poor; (8) the relationship between mean δ18O and mean δD calculated for the collection locations shows shifts of both the slope and the deuterium excess when compared to the global meteoric water line. These shifts are different for northern, central, and southern Italy; (9) in a few cases anomalously low monthly δ values suggest the existence of pronounced ‘amount effects’.
The Alban Hills, a Quaternary volcanic center lying west of the central Apennines, 15–25 km southeast of Rome, last erupted
19 ka and has produced approximately 290 km3 of eruptive deposits since the inception of volcanism at 580 ka. Earthquakes of moderate intensity have been generated there
at least since the Roman age. Modern observations show that intermittent periods of swarm activity originate primarily beneath
the youngest features, the phreatomagmatic craters on the west side of the volcano. Results from seismic tomography allow
identification of a low-velocity region, perhaps still hot or partially molten, more than 6 km beneath the youngest craters
and a high-velocity region, probably a solidified magma body, beneath the older central volcanic construct. Thirty centimeters
of uplift measured by releveling supports the contention that high levels of seismicity during the 1980s and 1990s resulted
from accumulation of magma beneath these craters. The volume of magma accumulation and the amount of maximum uplift was probably
at least 40×106 m3 and 40 cm, respectively. Comparison of newer levelings with those completed in 1891 and 1927 suggests earlier episodes of
uplift. The magma chamber beneath the western Alban Hills is probably responsible for much of the past 200 ka of eruptive
activity, is still receiving intermittent batches of magma, and is, therefore, continuing to generate modest levels of volcanic
unrest. Bending of overburden is the most likely cause of the persistent earthquakes, which generally have hypocenters above
the 6-km-deep top of the magma reservoir. In this view, the most recent uplift and seismicity are probably characteristic
and not precursors of more intense activity.
Recent studies suggested that Alban Hills (Rome) is a quiescent and not an extinct volcano, as it produced Holocene eruptions and several lahars until Roman times by water overflow from the Albano crater lake. Alban Hills are presently characterized by high PCO2 in groundwaters and by several cold gas emissions usually in sites where excavations removed the superficial impervious cover. Gas consists mostly of CO2 with minor H2S and the diffuse CO2 soil flux is locally very high. Accidental gas blowouts, occurred during shallow well drillings (tens to hundreds m depth) in zones with no surface gas manifestations, indicate the presence of gas pressurized aquifers confined underneath impermeable layers, within both the volcanic rock pile and the underlying Pleistocene loose sediments. Degassing mostly occurs in correspondence of bordering faults of buried horsts cut in the Mesozoic carbonate basement, hosting the main aquifer. Carbon isotopic composition (δ13CCO2) suggests that CO2 is at least partly originated by thermal decarbonation of these limestones. 3He/4He isotopic ratio of the gas (up to 1.9 Ra) is the same or even slightly higher than that of olivine and clinopyroxene fluid inclusions of the Alban Hills volcanic products, indicating a possible magmatic source for the gas. Low R/Ra values, compared to MORB and island arc magmas, are characteristic of the potassic Roman Comagmatic Province and reflect a deep involvement of crustal material in the magma genesis. The lack of high temperature fumaroles can be explained by an efficient meteoric cold water penetration and circulation in the volcano permeable terrains.
The sudden and catastrophic, or slow and continuous, release at surface of naturally occurring toxic gases like CO2, H2S and Rn poses a serious health risk to people living in geologically active regions. In general this problem receives little attention from local governments, although public concern is raised periodically when anomalous toxic-gas concentrations suddenly kill humans or livestock. For example, elevated CO2 concentrations have been linked to the death of at least 10 people in the central Italian region of Lazio over the last 20 years, while it was the CO2 asphyxiation of 30 cows in a heavily populated area near Rome in 1999 which prompted the present soil-gas study into the distribution of the local health risk. A detailed geochemical survey was carried out in an area of about 4 km2 in the Ciampino and Marino districts, whereby a total of 274 soil-gas samples were collected and analysed for more than 10 major and trace gas species. Data were then processed using both statistical and geostatistical methods, and the resulting maps were examined in order to highlight areas of elevated risk. General trends of elevated CO2 and Rn concentrations imply the presence of preferential pathways (i.e. faults and fractures) along which deep gases are able to migrate towards the surface. The CO2 and Rn anomalous trends often correspond to and are usually elongated parallel to the Apennine mountain range, the controlling structural feature in central Italy. Because of this fundamental anisotropy in the factors controlling the soil-gas distribution, it was found that a geostatistical approach using variogram analysis allowed for a better interpretation of the data. With regard to the health risk to local inhabitants, it was found that although some high risk areas had been zoned as parkland, others had been heavily developed for residential purposes. For example, many new houses were found to have been built on ground which has soil-gas CO2 concentrations of more than 70% and radon values of more than 250 kBq m−3. It is recommended that land-use planners incorporate soil-gas and/or gas flux measurements in environmental assessments in areas of possible risk (i.e. volcanic or structurally active areas).
The northwestern flank of the Colli Albani, a Quaternary volcanic complex near Rome, is characterised by high pCO2 values and Rn activities in the groundwater and by the presence of zones with strong emission of gas from the soil. The most significant of these zones is Cava dei Selci where many houses are located very near to the gas emission site. The emitted gas consists mainly of CO2 (up to 98 vol%) with an appreciable content of H2S (0.8–2%). The He and C isotopic composition indicates, as for all fluids associated with the Quaternary Roman and Tuscany volcanic provinces, the presence of an upper mantle component contaminated by crustal fluids associated with subducted sediments and carbonates. An advective CO2 flux of 37 tons/day has been estimated from the gas bubbles rising to the surface in a small drainage ditch and through a stagnant water pool, present in the rainy season in a topographically low central part of the area. A CO2 soil flux survey with an accumulation chamber, carried out in February–March 2000 over a 12 000 m2 surface with 242 measurement points, gave a total (mostly conductive) flux of 61 tons/day. CO2 soil flux values vary by four orders of magnitude over a 160-m distance and by one order of magnitude over several metres. A fixed network of 114 points over 6350 m2 has been installed in order to investigate temporal flux variations. Six surveys carried out from May 2000 to June 2001 have shown large variations of the total CO2 soil flux (8–25 tons/day). The strong emission of CO2 and H2S, which are gases denser than air, produces dangerous accumulations in low areas which have caused a series of lethal accidents to animals and one to a man. The gas hazard near the houses has been assessed by continuously monitoring the CO2 and H2S concentration in the air at 75 cm from the ground by means of two automatic stations. Certain environmental parameters (wind direction and speed; atm P, T, humidity and rainfall) were also continuously recorded. At both stations, H2S and CO2 exceeded by several times the recommended concentration thresholds. The highest CO2 and H2S values were recorded always with wind speeds less than 1.5 m/s, mostly in the night hours. Our results indicate that there is a severe gas hazard for people living near the gas emission site of Cava dei Selci, and appropriate precautionary and prevention measures have been recommended both to residents and local authorities.
On 15 August, 1984, a lethal gas burst issued from a submerged 96-m-deep crater in Lake Monoun in Cameroun, western Africa, killing 37 people. The event was associated with a landslide from the eastern crater rim, which slumped into deep water. Waters below 50 m are anoxic, dominated by high Fe2+ (∼600 mg/l) and HCO3− (≥ 1900 mg/l), anoxic and supersaturated with siderite, which is a major component of the crater floor sediments. The unusually high Fe2+ levels are attributed to reduction of laterite-derived ferric iron gradually brought into the lake as loess and in river input. Sulfur compounds are below detection limits in both water and gas. Gases effervescing from depressurized deep waters are dominantly CO2 with minor CH4, having δ13C of −7.18 and −54.8 per mil, respectively. Bacterial decomposition of organic matter may account for the methane, but 14C of lake water indicates that only 10% of the carbon is modern, giving an apparent age of 18,000 years. The dominant source of carbon is therefore attributed to long-term emission of CO2 as volcanic exhalation from vents within the crater, which led to gradual build-up of HCO3− in the lake. The density stratification of the lake may have been upset by an earthquake and underwater landslide on 15 August, which triggered overturn of the lake and caused nucleation of CO2 in the deep water. The resultant ebullition of CO2 from deep lake waters led to a gas burst at the surface and locally generated a water wave up to 5 m high. People travelling through the gas cloud were asphyxiated, presumably from CO2, and suffered skin discoloration from unidentified components.
The evaluation of volcanic hazard in the Roman hinterland related to the quiescent Colli Albani Volcano has recently been the subject of renewed attention and several interpretations by many authors. However, very little was known of the recent history of the volcano, making such interpretations rather speculative. The most recent activity of Colli Albani Volcano originated from the Albano polygenetic maar lake, which erupted several phreatomagmatic units, the most recent of which, the Peperino Albano ignimbrite, has been dated at around 25 ka. An area of several square kilometers centered around Albano Lake is presently the site of shallow and frequent seismic activity and gaseous emission as well as hydrothermal activity and is therefore considered the most prone to geologic hazards. This paper presents new stratigraphic and geomorphologic data as well as age determinations that allow rejuvenation of the most recent activity of the Colli Albani Volcano, and particularly the Albano maar lake, to the Holocene. This study allows for the first time to identify a potential hazard related to the Albano maar lake withdrawal interpreted to be related to endogenous causes, namely CO2 emission. The main results of the study are: (1) the Peperino Albano is not, as is generally believed, the last phreatomagmatic eruption from the Colli Albani Volcano; a previously unrecognized phreatomagmatic surge deposit has been identified overlying the paleosol at the top of the Peperino Albano and related lahar deposits; (2) two lahar deposits separated by paleosols top the stratigraphic succession and are dispersed only to the NW, corresponding to the lowest point of the maar rim, indicating that catastrophic hydrologic events occurred at the Albano Lake in recent times; rapid and substantial lake-level variations and lake withdrawal are reported by Roman historians and recorded by the stratigraphy of the Albano Lake lacustrine sediments; (3) microfracturing related to seismic energy release is linked to sudden variation of CO2 flow and upwelling of hydrothermal fluids. These occurrences across the lake are the likely causes that triggered during Holocene several episodes of lake withdrawal, rising the water table and probably triggering convective rollover of the lake water.
Colli Albani is a volcanic complex located in central Italy, very close to the city of Rome. Its last eruption is dated at 0.03-0.02 Ma. Now it displays a recurrent seismicity, sporadic gas emissions from soils, wells and springs, and post volcanic hydrothermal circulation. Moreover an uplift of about 30 cm over the last 43 years was recently detected by comparing the height differences between some vertices of repeated leveling surveys, thus suggesting a recent active magmatic process beneath the volcano. In 1995 a first-epoch GPS campaign was carried out with last generation receivers, the repetition campaign was performed in 1996. Data coming from the two repeated surveys were carefully processed and analyzed. A statistical analysis rigorously applied between the 1995 and 1996 adjusted coordinates shows significant coordinate differences. Some sites of the network, in particular, the sites of Vivaro (VVR), Cava di Ciampino (CVA) and Istituto Nazionale di Geofisica (INGR) display a significant subsidence of 2.6 ± 0.7, 2.7 ± 0.8 and 2.0 ± 0.8 cm, respectively, with a confidence interval at 95 percent level. This subsidence seems to be induced by a water table level lowering in Vivaro, while in the area where the sites of Cava di Ciampino and INGR are located, this motion is also confirmed by historical levelling data that show a subsidence of ~ 2 cm/yr during the last 45 years and could be due to local tectonics. Moreover, significant planimetric deformations are exhibited by the site of Castel Romano (CSR). It is remarkable that the stations of CVA, INGR and CSR are located in the area that was struck by the June 12, 1995, Md = 3.8 earthquake, although the displacement vectors are quite small. The motion of the Capranica Prenestina (CPR) station, which shows an uplift of 2.7 ± 0.7 cm, must be considered separately, being located outside the volcanic structure and placed over the carbonatic outcrops of the Prenestini Mts. Furthermore, the accuracy obtained in height determinations does not allow us to confirm if the central part of the GPS network corresponding to the area investigated by Amato and Chiarabba is uplifting within the analyzed time span.
Lake Albano was stratified at the time of our survey, in December 1997, in agreement with previous observations [Martini et al., Geochem. J. 28 (1994) 173–184; Cioni et al., Report for the Civil Protection Department (1995); Pedreschi, Accad. Lucch. Sci. Lett. Arti (1995) 39]. In the absence of phenomena induced by seismic activity, either local or regional, lake stratification may be perturbed by cooling of shallow waters below ∼8.5°C. Circulation is expected to homogenize lake waters and eventually to trigger gas exsolution when total gas pressure exceeds hydrostatic pressure. In December 1997, total gas pressure in lake water was very close to atmospheric pressure (0.9–1.3 bar) at all depths, possibly due to the occurrence of a recent episode of circulation and presumed gas exsolution. The state of saturation of Lake Albano waters and the similarity of the relative concentrations of Na, K, Mg, and Ca in lake waters, local groundwaters, and local volcanic rocks indicate that Na, K, Mg, and Ca concentrations in Lake Albano waters are mainly governed by incongruent dissolution of local volcanic rocks, coupled with minor calcite precipitation at shallow depths.
On August 21, 1986, a gas cloud issued from Lake Nyos in Cameroon killed over 1700 people. An Italian technical mission reached the area seven days later and obtained the first field evidences of the catastrophe. On the basis of observations and measurements in the field and of samples collected, the origin of the gas outburst is attributed to a phreatic explosion from beneath the bed of the lake. This interpretation appears to fit well the observed and reported phenomena, and seems perfectly consistent with the geological-geothermal conditions of the area.
The Albani Hills are affected by strong CO2 degassing processes. The amount of CO2, which rises from the depths and subsequently dissolves into shallow groundwater, has been estimated to be more than 4.2×109 mol year−1. Most of the gas is released in localised anomalous spots (Lavinio, Solforata, and Ciampino–Albano–Nemi areas), generated by fluid leakage processes from buried pressurized reservoirs hosted by structural highs of the calcareous–siliceous marly basement. The groundwater circulating in the anomalous areas becomes CO2 oversaturated, generating observable gas manifestations whose composition is mainly controlled by gas–liquid separation processes. A gas flow rate of 6.1×108 mol year−1 has been measured from the two larger manifestations using the accumulation chamber technique. The presence at shallow level of CO2 oversaturated groundwater can explain several episodes of sudden release of gas which was documented by historical chronicles from Roman times, until now.
Seemingly stably stratified fluids, that is a heavier layer of fluid underlying an upper layer of lighter fluid, can overturn if there is a heat flux through the system. Such events are termed “rollover” in the engineering literature (occurring for instance in liquid natural gas tanks). They take place as well in lakes and ponds. In all such cases, the stratification starts off with the heavier, more dense fluid underlying lighter. Convection driven mixing at the stratification interface (due to the heat flux) as well as other processes serves to minimize with time the stabilizing density differences, which may eventually cause the stratification to invert. If gas has been contained under pressure in the lower layer, this gas may explosively vent from the fluid as it suddenly rises to the top such as occurs in liquid natural gas tanks where rollover is a hazard. These processes are quantifiable and are applied here to various scenarios that might refer to volcanic crater lakes whose lower layers are charged with volatiles. Provided herein are some examples of calculated conditions and calculated time of evolution leading to rollover with attendant release of gases from supersaturated ascending fluids. These calculations suggest rollover could occur in volcanic lakes. The August 1986 gas release at Lake Nyos is employed as an example. These estimates were made taking note that water is commonly supersaturated in CO2
A study of the He isotopic ratios of fluid inclusions in olivine and pyroxene from the Roman Comagmatic Province (RCP), Italy, is presented together with 87Sr/86Sr isotope compositions of the whole rock or pyroxene phenocrysts. A clear covariation in He and Sr isotopes is apparent, with a strong northward increase in radiogenic He and Sr being evident. He and Sr isotopes ratios range from 3He/4He=5.2 R a and 87Sr/86Sr=0.7056 in south Campania, to 3He/4He=0.44 R a and 87Sr/86Sr=0.715905 in the northernmost Latium. Helium isotope ratios are significantly lower than MORB values and are among the lowest yet measured in subduction zone volcanism. The 3He/4He of olivine and pyroxene phenocryst-hosted volatiles appear to be little influenced by posteruptive processes and magma-crust interaction. The 3He/4He–87Sr/86Sr covariation is consistent with binary mixing between an asthenospheric mantle similar to HIMU ocean island basalts, and an enriched (radiogenic) mantle end member generated from subduction of the Ionian/Adriatic plate. The contribution of radiogenic He from metasomatic fluids and postmetasomatism radiogenic ingrowth in the wedge is strongly dependent on the initial He concentration of the mantle. Only when asthenosphere He concentrations are substantially lower than the MORB source mantle, and metasomatism, occurred at the beginning of the subduction (~30 Ma), can ingrowth in the mantle wedge account for the 3He/4He of most radiogenic basalts.
Nuovi dati sull'attività recente del cratere del lago Albano e sul degassamento dei Colli Albani
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Palaeoenvironmental analysis of Italian crater lakes and Adriatic sediments (Paliclas)
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III: I centri dei laghi vulcanici di Castel Gandolfo e di Nemi e quelli dei bacini artificiali
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A seasonal survey of the water quality and phytoplankton dynamics of Lake Albano
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- Carapezza
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Palaeoenvironmental analysis of Italian crater lakes and Adriatic sediments
- F Oldfield
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Indagini climatiche, geomorfologiche e sedimentologiche
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