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Seasonal and diurnal patterns in the dispersion of SO2 from Mt. Nyiragongo

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... The dominant natural source is the volcanic activity at Mt. Nyiragongo, located near the border separating the Democratic Republic of Congo and Rwanda. It is an active volcano that has the largest constant lava lake in the world located at its summit, and SO 2 is continuously degassed from it throughout the year (Dingwell et al., 2016;Pouclet and Bram, 2021). Consequently, the region around this mountain suffers the highest SO 2 pollution than any other region within East and Central Africa as shown in Fig. 1a. ...
... Their evaluation was made against OMI SO 2 observations. On a local scale, Landgren (2011) andDingwell et al. (2016) used the FLEXPART-WRF model to study the dispersion of SO 2 from this mountain. Both of them compared their simulations to observations taken by ground based Differential Optical Absorption Spectroscopy (DOAS) instruments. ...
... The results show that WRF-Chem overestimates the amount of SO 2 close to the volcano's vent. An earlier study by Dingwell et al. (2016) also found a similar overestimation bias. However, much further away from the volcano, WRF-Chem underestimates the SO 2 amount. ...
Article
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Mount Nyiragongo, an active volcano, is the most dominant natural source of sulfur dioxide (SO2) in Africa. While a number of studies have employed atmospheric models to simulate the dispersion of SO2 from this mountain, prior to this study, no attempt has been made to use deep learning to bias correct the model's estimates. Here, the Weather Research and Forecasting model coupled with chemistry (WRF-Chem) was used to simulate massive SO2 plumes degassed from this mountain between September 2014 and August 2015. Satellite observations by the Ozone Monitoring Instrument (OMI) showed that the SO2 spread to over 500 km from the volcano site. A deep convolutional autoencoder algorithm (WRF-DCA) was then applied to reduce the bias that WRF-Chem showed against the OMI observations. Finally, the correction performance of WRF-DCA was compared with a conventional bias correction method, linear scaling (WRF-LS). The performance of WRF-Chem, WRF-DCA, and WRF-LS was analyzed using three metrics, that is, the normalized mean bias (NMB), the root mean square error (RMSE), and Pearson's correlation coefficient (R). The results showed that WRF-Chem overestimated SO2 at locations near the volcano site and underestimated SO2 at locations further away from the volcano site. It generated an overall average NMB of −0.61 against the OMI observations. Respectively, WRF-DCA and WRF-LS reduced this bias by an average of 0.25 (40.9%) and 0.21 (34.4%). Furthermore, although both methods also reduced the RMSE and improved the correlation, WRF-DCA consistently performed better than WRF-LS. This study demonstrates the advantage that deep learning can provide in estimating volcanic SO2 emissions.
... This is primarily because of the existence of an active volcano at Mt. Nyiragongo which is about 15 km from Goma. It is an open-vent volcano with a lava lake at the top and it continuously emits SO2 [36,37]. Overall, TRO-POMI observed higher SO2 column amounts than OMI. ...
... Nyiragongo is the dominant SO2 hotspot in the region, the overall decreasing trend is most likely associated with the processes going on within it. Arellano et al. [36] reported a decreasing trend in SO2 at this volcano and attributed it to degassed magma sinking down into the volcano's conduit. A further analysis of the CO vertical profile revealed significant trends at specific heights ( Figure 6 and Table 2). ...
Article
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The atmospheric chemistry constituents of nitrogen dioxide (NO2), sulphur dioxide (SO2) and carbon monoxide (CO) are associated with air pollution and climate change. In sub-Saharan Africa, a lack of sufficient ground-based and aircraft observations has, for a long time, limited the study of these species. This study thus utilized satellite observations as an alternative source of data to study the abundance of these species over the East African region. The instruments used included the Ozone Monitoring Instrument (OMI), the Atmospheric InfraRed Sounder (AIRS), and the TROPOspheric Monitoring Instrument (TROPOMI). An investigation of trends in the data series from 2005 to 2020 was carried out using the sequential Mann-Kendall test while the Pearson correlation coefficient was used to compare the data records of the instruments. The analysis revealed no trend in NO2 (p > 0.05), a decreasing trend in SO2 (p < 0.05), a decreasing trend (p < 0.05) in CO closer to the surface (850 hPa to 500 hPa) and an increasing trend (p < 0.05) in CO higher up in the atmosphere (400 hPa to 1 hPa). There is likely a vertical ascent of CO. The correlation between the instrument records was 0.54 and 0.77 for NO2 and CO, respectively. Furthermore, seasonal fires in the savanna woodlands were identified as the major source of NO2 and CO over the region, while cities such as Kampala, Nairobi, and Bujumbura and towns such as Dar es Salaam and Mombasa were identified as important NO2 hotspots. Similarly, the active volcano at Mt. Nyiragongo near Goma was identified as the most important SO2 hotspot.
... During the period April 2010eMarch 2011, a more detailed study of the local meteorology was conducted (Dingwell et al., 2016). Meteorological data with 0.75 deg resolution from the ERA reanalysis product was used as an input for the Weather Research and Forecasting (WRF) model. ...
... From the reported values of emission rate, and knowledge of the meteorological conditions, it is possible to estimate ground-level concentrations of the emitted gases at different distances downwind the crater. This study has been recently done by (Dingwell et al., 2016) for the SO 2 groundlevel concentration at the most important villages around Nyiragongo. It is also interesting to compare the record of long-term with past measurements of the bulk gas emission. ...
Article
The activity of open-vent volcanoes with an active lava-lake, such as Nyiragongo, is characterized by persistent degassing, thus continuous monitoring of the rate, volume and fate of their gas emissions is of great importance to understand their geophysical state and their potential impact. We report results of SO2 emission measurements from Nyiragongo conducted between 2004 and 2012 with a network of ground-based scanning-DOAS (Differential Optical Absorption Spectroscopy) remote sensors. The mean SO2 emission rate is found to be 13 ± 9 kg s⁻¹, similar to that observed in 1959. Daily emission rate has a distribution close to log-normal and presents large inter-day variability, reflecting the dynamics of percolation of magma batches of heterogeneous size distribution and changes in the effective permeability of the lava lake. The degassed S content is found to be between 1000 and 2000 ppm from these measurements and the reported magma flow rates sustaining the lava lake. The inter-annual trend and plume height statistics indicate stability of a quiescently degassing lava lake during the period of study.
... During the period April 2010eMarch 2011, a more detailed study of the local meteorology was conducted ( Dingwell et al., 2016). Meteorological data with 0.75 deg resolution from the ERA reanalysis product was used as an input for the Weather Research and Forecasting (WRF) model. ...
... From the reported values of emission rate, and knowledge of the meteorological conditions, it is possible to estimate ground-level concentrations of the emitted gases at different distances downwind the crater. This study has been recently done by (Dingwell et al., 2016) for the SO 2 groundlevel concentration at the most important villages around Nyiragongo. It is also interesting to compare the record of long-term with past measurements of the bulk gas emission. ...
Article
Mount Nyiragongo (3470 m a.s.l.) is an active stratovolcano of mafic composition located in the Virunga Mountains in the Democratic Republic of the Congo. It is considered as one of the most dangerous volcanoes in the world due to generation of voluminous and highly fluidized lava flows during historical eruptions and the proximity to densely inhabited areas. Nyiragongo volcano is also a source of prodigious gaseous emissions to the atmosphere during periods of both eruptive and non-eruptive activity. Documented records of the style, speciation, and magnitude of degassing from this volcano exist in the literature since three decades ago. These studies are mostly based on observations made during sporadic field campaigns or by satellite-borne sensors, owing to logistical constraints imposed by volcanic and political unrest. With the aim of strengthen the gas monitoring capabilities of Nyiragongo volcano, an automatic scanning spectroscopic (DOAS) system was installed in March 2004 in the Rusayo seismic station, 10 km from the volcano crater. This instrument is powered by solar panels and linked by radio telemetry to the Goma Volcanological Observatory. Combined with plume velocity data, this instrument provides near-to-real-time SO2 fluxes with a typical temporal resolution of 10 minutes during sunlight hours. In 2005 the instrument was upgraded and incorporated as part of the Network for Observation of Volcanic and Atmospheric Change (NOVAC). Since 2005 three additional instruments has been installed, at 10 - 14 km distance W - SW of the crater, as part of the NOVAC project. We present the results of the measurements performed at Nyiragongo during the period March 2004-October 2009. Wind data has been obtained from the Weather Research and Forecasting (WRF) model based on data from the U.S. National Oceanic and Atmospheric Administration (NOAA) to account for the effect of local topography. A statistical analysis of the results and its relation with other volcanological observations is presented. This study emphasizes the importance of long-term and continuous gas monitoring to better understand the human and environmental effects of the persistent activity of this volcano.
... In concordance with our earlier vindication of the capacity of the PiSpec to accurately constrain cell SO 2 column amounts, via comparison with a USB2000 spectrometer (Wilkes et al., 2017), we suggest that the comparisons with NOVAC and DROAS data demonstrate the capability of the PiSpec to accurately retrieve volcanic SO 2 emission rates. Following the substantial contribution to volcano monitoring and research made by the NOVAC project in recent years (e.g., Galle et al., 2010;Lübcke et al., 2014;Granieri et al., 2015;Hidalgo et al., 2015;Dingwell et al., 2016;Aiuppa et al., 2018), we suggest that the low-cost self-built PiSpec could augment efforts to assess and mitigate volcanic hazards globally, by enabling further dissemination of DOAS measurement systems on active volcanoes. ...
Article
Full-text available
Spectroscopy has been used to quantify volcanic gas emission rates, most commonly SO2, for a number of decades. Typically, commercial spectrometers costing 1000s USD are employed for this purpose. The PiSpec is a new, custom-designed, 3D-printed spectrometer based on smartphone sensor technology. This unit has ≈1 nm spectral resolution and a spectral range in the ultraviolet of ≈280–340 nm, and is specifically configured for the remote sensing of SO2 using Differential Optical Absorption Spectroscopy (DOAS). Here we report on the first field deployment of the PiSpec on a volcano, to demonstrate the proof of concept of the device’s functionality in this application area. The study was performed on Masaya Volcano, Nicaragua, which is one of the largest emitters of SO2 on the planet, during a period of elevated activity where a lava lake was present in the crater. Both scans and traverses were performed, with resulting emission rates ranging from 3.2 to 45.6 kg s−1 across two measurement days; these values are commensurate with those reported elsewhere in the literature during this activity phase (Aiuppa et al., 2018; Stix et al., 2018). Furthermore, we tested the PiSpec’s thermal stability, finding a wavelength shift of 0.046 nm/°C between 2.5 and 45°C, which is very similar to that of some commercial spectrometers. Given the low build cost of these units (≈500 USD for a one-off build, with prospects for further price reduction with volume manufacture), we suggest these units hold considerable potential for volcano monitoring operations in resource limited environments.
... Average monthly concentrations of SO 2 and SPM show markedly different characteristics. Consistent to research carried out for other volcanoes (Dingwell et al., 2016), SO 2 concentrations show seasonal changes. Proximal to the vent, SO 2 concentrations exhibit strong seasonality which is heavily dependent on the bearing from the volcano. ...
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With the eruption of Eyjafjallajökull (Iceland) in 2010, interest in the transport of volcanic ash after moderate to major eruptions has increased with regards to both the physical and the emergency hazard management aspects. However, there remain significant gaps in the understanding of the long-term behaviour of emissions from volcanoes with long periods of activity. Mt. Sakurajima (Japan) provides us with a rare opportunity to study such activity, due to its eruptive behaviour and dense observation network. In the 6-year period from 2009 to 2015, the volcano was erupting at an almost constant rate introducing approximately 500 kt of ash per month to the atmosphere. The long-term characteristics of the transport and deposition of ash and SO2 in the area surrounding the volcano are studied here using daily surface observations of suspended particulate matter (SPM) and SO2 and monthly ashfall values. Results reveal different dispersal patterns for SO2 and volcanic ash, suggesting volcanic emissions’ separation in the long-term. Peak SO2 concentrations at different locations on the volcano vary up to 2 orders of magnitude and decrease steeply with distance. Airborne volcanic ash increases SPM concentrations uniformly across the area surrounding the volcano, with distance from the vent having a secondary effect. During the period studied here, the influence of volcanic emissions was identifiable both in SO2 and SPM concentrations which were, at times, over the recommended exposure limits defined by the Japanese government, European Union and the World Health Organisation. Depositional patterns of volcanic ash exhibit elements of seasonality, consistent with previous studies. Climatological and topographic effects are suspected to impact the deposition of volcanic ash away from the vent: for sampling stations located close to complex topographical elements, sharp changes in the deposition patterns were observed, with ash deposits for neighbouring stations as close as 5 km differing as much as an order of magnitude. Despite these effects, deposition was sufficiently approximated by an inverse power law relationship, the fidelity of which depended on the distance from the vent: for proximal to intermediate areas (<20 km), errors decrease with longer accumulation periods (tested here for 1–72 months), while the opposite was seen for deposition in distal areas (>20 km).
... The map in Fig. 9 is a qualitative estimation of the total area potentially impacted by phreatomagmatic ash deposits in the past and should hence not be interpreted as a probabilistic hazard map. Spatial extent of the deposits depends on the vent location, eruption intensity and duration, and wind direction which varies dominantly between NW and SSW in the area (Dingwell et al. 2016). These parameters will also control the emplacement of future deposits. ...
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[1] Existing studies of the composition of volcanic plumes generally interpret the presence of sulfate aerosol as the result of comparatively slow oxidation of gaseous SO2. We report here new observations from Masaya Volcano, Nicaragua, which demonstrate that sulfate aerosol may also be emitted directly from volcanic vents. Simultaneous aerosol and gaseous S, Cl, and F compounds were collected at the rim of the passively degassing crater in May 2001. Mean concentrations of SO42−, Cl−, and F− within the plume were 83, 1.2, and 0.37 μg m−3, respectively (fine aerosol fraction 2.5 μm). The aerosols were highly acidic, with estimated pH of
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Numerous modifications to the Kain-Fritsch convective parameterization have been implemented over the last decade. These modifications are described, and the motivating factors for the changes are discussed. Most changes were inspired by feedback from users of the scheme (primarily numerical modelers) and interpreters of the model output (mainly operational forecasters). The specific formulation of the modifications evolved from an effort to produce desired effects in numerical weather prediction while also rendering the scheme more faithful to observations and cloud-resolving modeling studies.
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Petroleum and dairy operations are prominent sources of gas-phase organic compounds in California's San Joaquin Valley. Ground site measurements in Bakersfield and aircraft measurements of reactive gas-phase organic compounds were made in this region as part of the CalNex (California Research at the Nexus of Air Quality and Climate Change) project to determine the sources contributing to regional gas-phase organic carbon emissions. Using a combination of near-source and downwind data, we assess the composition and magnitude of emissions from these prominent sources that are relatively understudied compared to motor vehicles We also developed a statistical modeling method with the FLEXPART-WRF transport and meteorological model using ground-based data to assess the spatial distribution of emissions in the San Joaquin Valley. We present evidence for large sources of paraffinic hydrocarbons from petroleum extraction/processing operations and oxygenated compounds from dairy (and other cattle) operations. In addition to the small straight-chain alkanes typically associated with petroleum operations, we observed a wide range of branched and cyclic alkanes that have limited previous in situ measurements or characterization in emissions from petroleum operations. Observed dairy emissions were dominated by ethanol, methanol, and acetic acid, and methane. Dairy operations were responsible for the vast majority of methane emissions in the San Joaquin Valley; observations of methane were well-correlated with non-vehicular ethanol, and multiple assessments of the spatial distribution of emissions in the San Joaquin Valley highlight the dominance of dairy operations for methane emissions. The good agreement of the observed petroleum operations source profile with the measured composition of non-methane hydrocarbons in unrefined natural gas associated with crude oil suggests a fugitive emissions pathway during petroleum extraction, storage, or processing with negligible coincident methane emissions Aircraft observations of emission hotspots from operations at oil wells and dairies are consistent with the statistical source footprint determined via transport modeling and ground-based data. At Bakersfield, petroleum and dairy operations each comprised 22-23% of anthropogenic non-methane organic carbon and were each responsible for ~12% of potential precursors to ozone, but their direct impacts as potential SOA precursors were estimated to be minor. A comparison with the California Air Resources Board emission inventory supports the current relative emission rates of reactive organic gases from these sources in the region.
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The step-mountain eta model has shown a surprising skill in forecasting severe storms. Much of the credit for this should be given to the Betts and Miller (hereafter referred to as BM) convection scheme and the Mellor-Yamada (hereafter referred to as MY) planetary boundary layer (PBL) formulation. However, the eta model was occasionally producing heavy spurious precipitation over warm water, as well as widely spread light precipitation over oceans. In addition, the convective forcing, particularly the shallow one, could lead to negative entropy changes. As the possible causes of the problems, the convection scheme, the processes at the air-water interface, and the MY level 2 and level 2.5 PBL schemes were reexamined. A major revision of the BM scheme was made, a new marine viscous sublayer scheme was designed, and the MY schemes were retuned. The deep convective regimes are postulated to be characterized by a parameter called “cloud efficiency.” The relaxation time is extended for low cloud effic...
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Airborne measurements of gases and aerosols from the recently activated volcanic vents on Mt. Baker were made on March 27 and June 30, 1975. The total rates of emission of gaseous sulfur on these two days were estimated to be 0.35 and 1.3 kg s⁻¹, respectively. The latter rate is comparable to the largest single, industrial source of sulfur in the Pacific Northwest. A significant increase in the emission of sub-micron aerosols was also observed between March 27 and June 30. Small aerosol particles are produced in the plume of effluents, probably by gas-to-particle conversion, at a rate of about 2 x 10¹⁷ s⁻¹. However, the concentrations of cloud condensation nuclei and ice nuclei in the plume are comparatively small. Aerosols in the plume, greater than about 1 ..mu..m in diameter, consist predominantly of Al, Si, S, K and Ca. Some of the aerosols which were collected in the plume on June 30 might have been Pele's hairs, which are a sign of new magmatic activity.
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Chemical composition of rainwater is strictly related to atmosphere scavenging. Active degassing volcanoes release acid gases and solid particulate in the surrounding environment. Nyiragongo Volcano (DRC) is characterized by a high degassing activity from an active lava lake hosted within the crater. Chemistry of rainwater in the area is clearly dependent on the influence of the volcanic plume, especially at the rim of the Nyiragongo summit crater. Rainwater collected from this zone has pH values as low as 2, high salinity (EC 28–1800 μS/cm), and high contents of F− and Cl− (up to 193 and 270 ppm, respectively), NH4+ (up to 146 ppm) and SO42 − ions (up to 340 ppm) relative to worldwide rainwater. The chemical composition of rainwater after interaction with the volcanic plume tends to shift towards the condensable fraction of fumarolic fluids discharged from the summit crater. Rainwater acidified by the volcanic plume also removes metals from particulate suspended in the atmosphere, thus undergoing metal enrichment. Displacement of the Nyiragongo volcanic plume by predominantly westward-directed wind causes “natural” contamination of rainwater collected for drinking purposes in villages located on the western flank of the volcano. Rainwater falling in urban centers located S–SE of the Nyiragongo Volcano is not usually affected by the rain–plume interactions which strictly depends on wind directions. However, areas of possible contamination by the volcanic plume might create a further emergency and critical situations on top of an already existing severe humanitarian crisis. Rainwater is the principal drinking water supply in the Nyiragongo area, thus the geochemical monitoring of rainwater quality is of great importance to mitigate the hazard of natural contamination of this fundamental resource for the local communities.
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Numerous modifications to the Kain Fritsch convective parameterization have been implemented over the last decade. These modifications are described, and the motivating factors for the changes are discussed. Most changes were inspired by feedback from users of the scheme (primarily numerical modelers) and interpreters of the model output (mainly operational forecasters). The specific formulation of the modifications evolved from an effort to produce desired effects in numerical weather prediction while also rendering the scheme more faithful to observations and cloud-resolving modeling studies.
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The step-mountain eta model has shown a surprising skill in forecasting severe storms. Much of the credit for this should be given to the Betts and Miller (hereafter referred to as BM) convection scheme and the Mellor-Yamada (hereafter referred to as MY) planetary boundary layer (PBL) formulation. However, the eta model was occasionally producing heavy spurious precipitation over warm water, as well as widely spread light precipitation over oceans. In addition, the convective forcing, particularly the shallow one, could lead to negative entropy changes. As the possible causes of the problems, the convection scheme, the processes at the air-water interface, and the MY level 2 and level 2.5 PBL schemes were reexamined. A major revision of the BM scheme was made, a new marine viscous sublayer scheme was designed, and the MY schemes were returned. The MY level 2.5 turbulent kinetic energy (TKE) is initialized from above in the PBL, so that excessive TKE is dissipated at most places during the PBL spinup. The method for calculating the MY level 2.5 master length scale was rectified. To demonstrate the effects of the new schemes for the deep convection and the viscous sublayer, tests were made using two summer cases: one with heavy spurious precipitation, and another with a successful 36-h forecast of a tropical storm. The new schemes had dramatic positive impacts on the case with the spurious precipitation. The results were also favorable in the tropical storm case. The developments presented here were incorporated into the eta model in 1990. The details of further research will be reported elsewhere. The eta model became operational at the National Meteorological Center, Washington, D.C., in June 1993. 60 refs., 8 figs.
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This paper presents the global project Network for Observation of Volcanic and Atmospheric Change (NOVAC), the aim of which is automatic gas emission monitoring at active volcanoes worldwide. Data from the network will be used primarily for volcanic risk assessment but also for geophysical research, studies of atmospheric change, and ground validation of satellite instruments. A novel type of instrument, the scanning miniaturized differential optical absorption spectroscopy (Mini-DOAS) instrument, is applied in the network to measure volcanic gas emissions by UV absorption spectroscopy. The instrument is set up 5-10 km downwind of the volcano under study, and typically two to four instruments are deployed at each volcano in order to cover different wind directions and to facilitate measurements of plume height and plume direction. Two different versions of the instrument have been developed. Version I was designed to be a robust and simple instrument for measurement of volcanic SO2 emissions at high time resolution with minimal power consumption. Version II was designed to allow the best possible spectroscopy and enhanced flexibility in regard to measurement geometry at the cost of larger complexity, power consumption, and price. In this paper the project is described, as well as the developed software, the hardware of the two instrument versions, measurement strategies, data communication, and archiving routines. As of April 2009 a total of 46 instruments have been installed at 18 volcanoes worldwide. As a typical example, the installation at Tungurahua volcano in Ecuador is described, together with some results from the first 21 months of operation at this volcano. Bibtex entry for this abstract Preferred format for this abstract (see Preferences) Find Similar Abstracts: Use: Authors Title Keywords (in text query field) Abstract Text Return: Query Results Return items starting with number Query Form Database: Astronomy Physics arXiv e-prints
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On January 2, 2010 the Nyamuragira volcano erupted lava fountains extending up to 300m vertically along an ∼1.5km segment of its southern flank cascading ash and gas on nearby villages and cities along the western side of the rift valley. Because rain water is the only available potable water resource within this region, volcanic impacts on drinking water constitutes a major potential hazard to public health within the region. During the 2010 eruption, concerns were expressed by local inhabitants about water quality and feelings of physical discomfort (e.g. nausea, bloating, indigestion, etc.) after consuming rain water collected after the eruption began. We present the elemental and ionic chemistry of drinking water samples collected within the region on the third day of the eruption (January 5, 2010). We identify a significant impact on water quality associated with the eruption including lower pH (i.e. acidification) and increases in acidic halogens (e.g. F(-) and Cl(-)), major ions (e.g. SO(4)(2-), NH(4)(+), Na(+), Ca(2+)), potentially toxic metals (e.g. Al(3+), Mn(2+), Cd(2+), Pb(2+), Hf(4+)), and particulate load. In many cases, the water's composition significantly exceeds World Health Organization (WHO) drinking water standards. The degree of pollution depends upon: (1) ash plume direction and (2) ash plume density. The potential negative health impacts are a function of the water's pH, which regulates the elements and their chemical form that are released into drinking water.
Article
We present the first application of a multi-stage impactor to study volcanic particle emissions to the troposphere from Masaya volcano, Nicaragua. Concentrations of soluble SO4 2–,Cl–, F–, NO3 –, K+, Na+,NH4 +, Ca2+ and Mg2+ were determined in 11 size bins from 0.07 m to >25.5 m. The near-source size distributions showed major modes at 0.5m (SO4 2–, H+,NH4 +); 0.2 m and 5.0 m (Cl–) and 2.0–5.0 m(F–). K+ and Na+ mirrored the SO4 2– size-resolvedconcentrations closely, suggesting that these were transported primarily asK2SO4 and Na2SO4 in acidic solution, while Mg2+ andCa2+ presented modes in both m and >1 m particles. Changes in relative humidity were studied by comparing daytime (transparent plume) and night-time (condensed plume) results. Enhanced particle growth rates were observed in the night-time plume as well as preferential scavenging of soluble gases, such as HCl, by condensed water. Neutralisation of the acidic aerosol by background ammonia was observed at the crater rim and to a greater extent approximately 15 km downwind of the active crater. We report measurements of re-suspended near-source volcanic dust, which may form a component of the plume downwind. Elevated levels ofSO4 2–, Cl–, F–,H+, Na+, K+ and Mg2+ were observed around the 10 m particle diameter in this dust. The volcanic SO4 2– flux leaving the craterwas 0.07 kg s–1.
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Methods for estimating the dry deposition velocities of atmospheric gases in the U.S. and surrounding areas have been improved and incorporated into a revised computer code module for use in numerical models of atmospheric transport and deposition of pollutants over regional scales. The key improvement is the computation of bulk surface resistances along three distinct pathways of mass transfer to sites of deposition at the upper portions of vegetative canopies or structures, the lower portions, and the ground (or water surface). This approach replaces the previous technique of providing simple look-up tables of bulk surface resistances. With the surface resistances divided explicitly into distinct pathways, the bulk surface resistances for a large number of gases in addition to those usually addressed in acid deposition models (SO2,O3, NOx and HNO3) can be computed, if estimates of the effective Henry's Law constants and appropriate measures of the chemical reactivity of the various substances are known. This has been accomplished successfully for H2O2, HCHO, CH3CHO (to represent other aldehydes), CH3O2H (to represent organic peroxides), CH3C(O)O2H, HCOOH (to represent organic acids), NH3, CH3C(O)O2NO2 and HNO2. Other factors considered include surface temperature, stomatal response to environmental parameters, the wetting of surfaces by dew and rain, and the covering of surfaces by snow. Surface emission of gases and variations of uptake characteristics by individual plant species within the landuse types are not considered explicitly.
Article
Nicaragua comprises seven historically active volcanoes (Cosigüina, San Cristobal, Telica, Cerro Negro, Momotombo, Masaya, and Concepcion), five of which are in a state of continuous degassing. Published measurements of the atmospheric dispersion of continuous emissions from Nicaraguan volcanoes, the chemical and aerosol microphysical modifications of the released gases and aerosols, and related acid deposition and impacts on the environment cover only short periods of time. We applied a three-dimensional atmosphere-chemistry/aerosol numerical model over Central America focussing on Nicaraguan volcanic emissions for month long simulation periods during the dry and wet seasons of 2003. The model is able to reproduce observed monthly precipitation and wind speed throughout the year 2003. Model results for near surface SO2 concentrations and SO2 dry deposition fluxes around Masaya volcano are in very good agreement with field measurements. During the dry season, oxidation of SO2 to sulphate plays only a minor role downwind of the Nicaraguan volcanoes and over the Pacific Ocean, whereas SO2 released from Arenal and Poas in Costa Rica is oxidised to sulphate much faster and closer to the volcanoes due to higher humidity and cloud water availability. During the wet season, more variable wind conditions lead to reduced dispersion of SO2 over the Pacific Ocean and increased dispersion inland. The availability of liquid water in the atmosphere favours sulphate formation close to the Nicaraguan volcanoes via aqueous phase oxidation and represents another limitation for the dispersion of SO2. Strong precipitation removes sulphate quickly from the atmosphere by wet deposition. Atmospheric SO2 concentrations and in particular dry deposition close to the volcanoes show a pronounced diurnal cycle.
  • A G Allen
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Allen, A. G., Oppenheimer, C., Ferm, M., Baxter, P. J., Horrocks, L. A., Galle, B., McGonigle, A. J. S., Duffell, H. J., 2002. Primary sulfate aerosol and associated emissions from Masaya volcano, Nicaragua. Journal of Geophysical Research: Atmospheres 107 (D23), ACH 5 1–8.
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Nyamuragira eruptive event: Implications for essential potable water resources
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Cuoco, E., Tedesco, D., Poreda, R. J., Williams, J. C., Francesco, S. D., Balagizi, C., Darrah, T. H., 2013b. Im-710 pact of volcanic plume emissions on rain water chemistry during the January 2010 Nyamuragira eruptive event: Implications for essential potable water resources. Journal of Hazardous Materials 244-245, 570-581.
Investigation into magma degassing at Nyiragongo volcano, Democratic Republic of the Congo
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