No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
Dissolved major and trace geochemical dynamics in Antarctic lacustrine systems
... In consequence, those wind patterns could also explain the lower values of long distance transport pollutants. Roman et al. (2019) mentioned that the chemical composition of the lake water in Environ Monit Assess (2020) 192:246 CWM lakes is primarily influenced by marine aerosols, followed by weathering of the bedrock and precipitation; Lecomte et al. (2020) found that the lakes located on the west side of the CWM exhibited the greatest the Mg 2+ /Ca 2+ and Na + /(Na + +Ca 2+ ) meq L −1 ratios values as a consequence of sea spray. The Spearman correlation matrix (Table S3, Supplementary materials) shows the significant values among elements concentration with Croft Bay distance (CBD), runoff effect (RE), thallus size (TS), and thallus color (TC). ...
... All those were associated with GT from dry and wet deposition. The mobile elements like Sb, Na, K, Sr, and U were also linked in a roundabout way with GT from the marine source by its correlations to Ba, Ca, and Cs, in spite of the absence to CBD correlation (Arimoto et al. 1985;Lecomte et al. (2020). ...
Clearwater Mesa is a pristine area located SE of Croft Bay in James Ross Island, at the northeast of the Antarctic Peninsula. The closest anthropic construction is the summer Mendel station located 25 km to the NE. Clearwater is a remote basalt volcanic mesa, (64° 01′ S, 57° 42′ W) located at ~ 250 m a.s.l., with around 50 small shallow lakes, a well-developed lichens flora and scarce fauna. The mesa offers a good opportunity to use lichens, like Usnea antarctica, as a biomonitor species. The aim of this study was to determine the baseline levels of trace elements in Usnea antarctica and their relationships with geographical parameters and climatological aspects, to use them as reference levels in futures studies. Usnea antarctica was collected in 23 sites in two transects: perpendicular and parallel to the shore. We found high contents of the elements associated with long-distance transport like Sm, La, Sc, Fe, Co, Hg, and Ca. The elements linked to the marine biogenic cycle as Sr, Rb, Cs, K, Na, Sb, As, Se, and Br were less significant. The distance to the sea was the factor that related the element contents. Hg, Se, As, and Br content in Usnea antarctica increased from the inland towards the sea coast.
... For example, dissolved Fe in the Southern Ocean is known to be the key limiting factor for primary productivity (Lyons et al., 2015) leading to the formation of high nutrient low chlorophyll (HNLC) regions. However, only a few studies have investigated the coastal regions of Antarctica and the Southern Ocean to highlight the role of trace elements in controlling primary productivity (Lecomte et al., 2016;Lecomte et al., 2020;Lyons et al., 2015;Wadham et al., 2010). Satellite observation has identified 65,000 supraglacial lakes in the East Antarctic ice sheet (Stokes et al., 2019). ...
Coastal lakes in Antarctica receive an enormous amount of ions and trace elements (TEs) during the austral summer. Some of these TEs and ions are utilised as essential nutrients in primary productivity. In the present study, selected dissolved TEs (Ba, Mn, Cu, Co, Cd, Mo and U) along with dissolved organic carbon (DOC) and Chlorophyll-a were studied in ten coastal lakes of the Larsemann Hills, East Antarctica to decipher their (TEs) sources, understand geochemical behaviour and assess their role on nutrient dynamics. Dissolved concentrations of these TEs are in sub-nanomolar range; almost an order of magnitude lower than the average seawater and global river concentrations. Sea-salt spray and chemical weathering in the catchments of these lakes are dominant sources for these TEs and ions. Though most of the Antarctic lakes have been reported for their oligotrophic character, however, a significant amount of DOC and Chlorophyll-a, and occurrence of algal mats in some of the LH lakes indicate seasonal (austral summer) productivity with the availability of sunlight and nutrients. Our investigation reveals that phosphate (PO4³⁻) and Mo act as limiting nutrients because of their lower concentrations in the water column. Dissolved Cu plays an important role in bacterial-induced organic matter decompositions and release of organic carbon to lake water. We also found Ba excess (non-terrigenous) in the lake and catchment sediments varying from 26 to 63%. The higher Baexcess in the catchment sediments could be due to significant removal of dissolved Ba during the solute transport and later supplied to these lakes. The geochemical data sets presented in this study were found at a natural background level and therefore, would be useful for comparison with other global aquatic environments. Findings of the present study improve our understanding about the biogeochemical cycling of trace elements and their critical role in oligotrophic lakes of Antarctica.
The deglaciated lacustrine systems in Grovnes, Larsemann Hills, East Antarctica was assessed for its solute dynamics and hydrogeochemical interactions. These pristine high latitude lacustrine systems serve as a natural laboratory to understand the interaction between hydrosphere, lithosphere and atmosphere thus providing valuable insights on the functioning of major biogeochemical cycles. A total of 14 fresh water lakes were identified and the water samples were analysed for its physico-chemical characteristics. The abundance of anions and cations in the lake water samples were in the following order of Cl− > HCO3– > SO42− > NO3− and Na+ > Mg2+ > Ca2+ > K+ respectively. Moreover, the lakes exhibit slightly alkaline condition due to dissolution of alkaline earth metals and atmospheric fallout. Na+-Cl−–HCO3– and Na+-Cl− are the commonly noticed water type in the study area and higher concentration of Na+-Cl− were due to the effect of sea spray through marine aerosols. Reverse ion exchange is noticed in most of the lakes due to saline influence. Three major mechanisms such as rock dominance, precipitation/snow and evaporation/sea spray controls the lake water geochemistry in the study area. Silicate weathering and evaporite dissolution also contribute ionic load to the lake water. Significant positive correlations (p < .01) among major ions reveal sources from bedrock weathering along with marine aerosols. Trace element chemistry shows that rock-water interaction is the primary source for dissolved metals in the lake water followed by long range atmospheric transport in the form of aeolian dust. Mineral groups such as evaporites, sulphates, carbonates, metal oxides and hydroxides are responsible for the dissolution of metal complexes in the lake water. Furthermore, lakes falling within a micro basin have shown higher Na+-Cl− content which is due to the catchment effect where snow enriched with sea spray melts during the austral summer feeding these lakes.
This article presents analytical observations on physicochemical parameters and major and trace element concentrations of water, ice, and sediment samples from the lake systems of Clearwater Mesa (CWM), northeast Antarctic Peninsula. Geochemical analyses include inductively coupled plasma mass spectrometry (ICP-MS) for cations and trace elements and ion chromatography for anions. Some figures are included (i.e. Piper and Gibbs diagrams) which indicate water classification type and rock-water interactions in CWM, respectively. It also contains PHREEQC software output, listing the chemical speciation for dissolved elements, Saturation Indexes (SI), and modelling outputs. Each lake SI are also illustrated in a figure. Finally, total organic and inorganic carbon (TOC and TIC, respectively) were determined for bottom lake sediments and marginal salt samples. This information will be useful for future research assessing the impacts of anthropogenic pollution and the effects of climate change, providing insights into naturally occurring geochemical processes in a pristine environment, and evaluating geochemical behaviour of dissolved elements in high-latitude hydrological systems. These data correspond to the research article “Dissolved major and trace geochemical dynamics in Antarctic Lacustrine Systems” [1].
Diatoms are important ecological indicators in Antarctica, and paleolimnologists routinely apply transfer functions to fossil diatoms recovered from lake sediments to reconstruct past environments. However, living diatom communities may differ among the possible habitat types represented in sediment cores (both within lakes and their immediate proximity), hindering the full and accurate interpretation of fossil records. Therefore, an improved understanding of Antarctic diatom habitat preferences would substantially aid in interpreting regional paleo-material. To gain insights into habitat differences, we sampled epipelon, epilithon, Nostoc mats, lake-adjacent moss, and wet soil from > 30 lakes and ponds from Clearwater Mesa, James Ross Island, spanning a broad gradient in conductivity (a common basis for transfer functions). We found that diatom communities significantly differed between habitat types (although abundances were too low in Nostoc mats to characterize communities), with the clearest distinctions being between submerged (epipelon and epilithon) and exposed (moss and wet soil) groups. Submerged habitat types had greater abundances of attached aquatic taxa (i.e. Gomphonema spp.), while exposed habitats harboured more abundant aerophilic genera (e.g. Hantzschia, Luticola, and Pinnularia). Furthermore, only epilithon communities were significantly related to conductivity, and both epipelon and epilithon habitats showed conspicuous increases in Denticula jamesrossensis at greater conductivity values. Collectively, these results improve our knowledge of limno-terrestrial diatoms from the Maritime Antarctic Region, and further highlight the utility of incorporating knowledge of habitat preferences into (paleo)ecological research.
Lentic freshwater habitats are important centres of biodiversity within the infrequent ice-free oases across Antarctica. Given imminent climate changes, it is crucial to catalogue these habitats in order to provide baseline data for future monitoring and biological surveys. The lacustrine systems of Clearwater Mesa, a previously unexplored part of James Ross Island, north-eastern Antarctic Peninsula, are described here. We conducted basic geomorphological and limnological surveys over three Antarctic summers (2009–16) to characterize landscape evolution, infer the origin of lake basins and assess the variability in their water chemistry. Stable shallow lakes, formed in depressions between lava tumuli following the last deglaciation, were found to dominate the volcanic mesa, although several peripheral lakes in ice-proximal settings appear to have formed recently as a result of post-Neoglacial ice recession. We found large heterogeneity in conductivity (~10–7000 μS cm ⁻¹ ), despite the lithologically uniform substrate. This variability was shown to be related to lake type, basin type (open vs closed), meltwater source and proximity to the coast. Inter-annual differences were attributed to changes in sea spray influx and snow accumulation driven by variable weather conditions. Overall, the ion composition of lakes suggested that sea spray was the dominant source of ions, followed by the weathering of bedrock.
King George Island, situated in the South Shetland Islands archipelago, is one of the most visited sites in Antarctica. Antarctica attracts much attention because it is one of the most sensitive areas under the influence of global warming. To understand its hydrochemistry characteristics, we collected various types of water samples, including samples from streams, meltwaters, ground waters, snow and ice from around the Great Wall Station, Fildes Peninsula, King George Island, from January to February, 2015. Major ions, alkalinities, silicate, pH, dissolved oxygen, temperature, and electric conductivities were measured. Several approaches were applied to identify processes that affect the hydrochemistry on Fildes Peninsula, including ternary diagrams, principal components analysis and cluster analysis. Our data suggest that atmospheric seasalt deposition is the main factor controlling the hydrochemistry on Fildes Peninsula. After atmospheric influences were corrected for seasalt, we defined the weathering of local rocks to be another important factor on the Peninsula's hydrochemistry. Processes such as Ca dissolution from the Ca-bearing basalt, Si loss through secondary mineralization and biological uptake influence the chemical composition of runoffs on the peninsula. Cluster analysis identified 4 groups of streams based on their hydrochemical features, which reflect their original weathering characters under icecap and the combined effects with melt snow, biological activity and the anthropogenic input.
Hydrological systems of the ice-free areas of the James Ross archipelago (NE Antarctic Peninsula) provide a unique opportunity for studying recent environmental changes associated with the current Global Warming. Geochemical, hydrological, sedimentological, and magnetic studies were carried out on different lake systems and ephemeral ponds from post-Holocene periglacial environments to characterize their natural variability. Significant differences between the lakes were observed based on physicochemical analyses, and can be attributed to several characteristics and processes taking place (geochemical, diagenetic, biological, etc.) in individual lake catchments. Seymour-Marambio Island’s lakes exhibit high total dissolved solids (~3.300 mg L−1) due to the high rate of evaporation in the region, whereas trace elements show differences in the lithological source. Lakes from Vega and James Ross islands are comparatively diluted, with the highest pH values up to 10.2. Within Vega Island, trace elements discriminate lakes into sectors which show statistical differences due to variations in lithological sources. Dissolved sources can be divided according to their kinetics into: high-rate processes which occur during summer months (evaporation, salt precipitation, atmospheric precipitation, melting processes) and low-rate processes (mineral weathering, giving a long-term signature). The present multidisciplinary study contributes to a better understanding of Antarctic lake systems, and can be used as a baseline dataset for further studies investigating the impact of recent climate changes on the biological and geochemical characteristics of these pristine ecosystems in the future.
En esta contribución se describen las distintas técnicas y mediciones magnéticas utilizadas en Magnetismo Ambiental y Paleomagnetismo. Tales mediciones ofrecen útiles indicadores para realizar estudios relacionados con cambios climáticos y ambientales, así como herramientas de datación. Si bien es ampliamente conocida la utilidad de la susceptibilidad magnética, se discutirá el potencial y necesidad del uso de parámetros adicionales obtenidos a partir de mediciones de magnetizaciones remanentes (natural, anhistérica e isotérmica), histéresis magnética y estudios termomagnéticos.
Se presentan resultados magnéticos obtenidos en sedimentos lacustres del Archipiélago James Ross (NE de la Península Antártica). También se presentan estudios complementarios sedimentológicos, hidroquímicos, geoquímicos y de estadística multivariada, pero se pone énfasis en los parámetros magnéticos y su relación con los distintos procesos que ocurren en los sistemas lacustres antárticos. Se analiza además el uso de las paleointensidades relativas como herramienta de datación en lagunas antárticas.
Los rapidos cambios climaticos ocurridos en la peninsula Antartica han reactivado procesos hidrogeologicos que han sido limitados o han estado inactivos durante un relativamente largo periodo de tiempo. Estos procesos se evidencian en las zonas descubiertas de hielo del norte de la peninsula Antartica, como en cabo Lamb, donde se desarrolla el sistema hidrico superficial y subterraneo a lo largo de todo el verano antartico. El resultado es la movilizacion de grandes cantidades de agua, sedimentos y nutrientes hacia otros escenarios. Este estudio propone un modelo de comportamiento del agua superficial y subterranea que resulta validado para las zonas libres de hielo de la region basado en las observaciones de campo e interpretacion de la informacion tomada en cabo Lamb, que constituye la zona descubierta mas extensa de la Isla Vega. El modelo propuesto se basa en la interpretacion de 56 analisis quimicos que se consideran representativos del agua superficial, subterranea, el agua de la capa activa, el hielo glaciar y la nieve. La interpretacion hidroquimica esta determinada en principio por cuatro parametros (pH, conductividad electrica, relacion de D/18O y relacion SO4/Cl) demostrando que estas variables son las mas apropiadas para diferenciar el origen e interaccion de las aguas en las diferentes partes del sistema hidrogeologico.
Polar lakes respond quickly to climate-induced environmental changes. We studied the chemical limnological variability in 127 lakes and ponds from eight ice-free regions along the East Antarctic coastline, and compared repeat specific conductance measurements from lakes in the Larsemann Hills and Skarvsnes covering the periods 1987–2009 and 1997–2008, respectively. Specific conductance, the concentration of the major ions, pH and the concentration of the major nutrients underlie the variation in limnology between and within the regions. This limnological variability is probably related to differences in the time of deglaciation, lake origin and evolution, geology and geomorphology of the lake basins and their catchment areas, sub-regional climate patterns, the distance of the lakes and the lake districts to the ice sheet and the Southern Ocean, and the presence of particular biota in the lakes and their catchment areas. In regions where repeat surveys were available, inter-annual and inter-decadal variability in specific conductance was relatively large and most pronounced in the non-dilute lakes with a low lake depth to surface area ratio. We conclude that long-term specific conductance measurements in these lakes are complementary to snow accumulation data from ice cores, inexpensive, easy to obtain, and should thus be part of long-term limnological and biological monitoring programmes.
Background and aims – The Maritime Antarctic vegetation is a poorly developed tundra dominated by lichens and mosses, mostly present in moist environments, providing a favourable habitat for microorganisms. Although, diatoms represent one of the most common algal groups in the Antarctic region, moss-inhabiting diatoms are rarely studied. The moss vegetation on islands in the Maritime Antarctic region forms a favorable habitat for non-marine diatoms. These moss-inhabiting diatom communities are of particular interest as little is known about their species composition, ecological preferences and habitats. The present paper discusses the diversity of moss inhabiting diatoms from Byers Peninsula (Livingston Island) and Ulu Peninsula (James Ross Island), Maritime Antarctic region.
Methods – The composition of the moss inhabiting diatom flora of 84 samples collected from Byers Peninsula, Livingston Island and Lagoons Mesa area, James Ross Island has been studied using light microscopy.
Key results – A total of 130 taxa, belonging to 39 genera has been recorded. Detrended Correspondence Analysis using the entire sample set clearly separates the James Ross Island (JRI) communities from the Livingston Island (LI) communities showing mostly the dominance of taxa preferring terrestrial (JRI) instead of more moist and aquatic conditions (LI). A Principal Component Analysis of only the Livingston Island samples formed three groups clearly separated by their diatom species composition. Although some taxa seem to occur in high abundances in several assemblages, a number of taxa showed a distinct preference for a particular assemblage. Biotic stress caused by marine birds and mammals, expressed in higher nutrient and salinity levels, seems to play a key role in determining the species composition.
Conclusions – Our results showed clearly the presence of a well developed moss-inhabiting diatom flora on both studied localities. The composition of the studied communities is determined by the type of habitat, moisture and biotic influences (salinity and nutrients).
Virtually no information is available on the response of
land-terminating Antarctic Peninsula glaciers to climate change on a
centennial timescale. This paper analyses the topography, geomorphology
and sedimentology of prominent moraines on James Ross Island to
determine geometric changes and to interpret glacier behaviour. The
moraines are very likely due to a late Holocene phase of advance and
were formed by (1) shearing and thrusting within the snout, (2) shearing
and deformation of basal sediment, (3) more supraglacial debris than at
present and (4) short distances of sediment transport. Retreat of ~ 100
m and thinning of 15 - 20 m has produced a loss of 0.1 km3 of ice. The
pattern of surface lowering is asymmetric. These geometrical changes are
suggested most simply to be due to a net negative mass balance caused by
a drier climate. Comparisons of the moraines with the current
glaciological surface structure of the glaciers permits speculation of a
transition from a polythermal to a cold-based thermal regime. Small
land-terminating glaciers in the northern Antarctic Peninsula region
could be cooling despite a warming climate.
The diversity, ecology and biogeography of
diatoms in lakes, seepage areas and streams on the Ulu
Peninsula, a large ice-free area in the northern part of
James Ross Island (Weddell Sea), were studied. A diverse
diatom flora of 123 taxa was observed, dominated by
several Nitzschia taxa, Psammothidium papilio, Eolimna
jamesrossensis, Fragilaria capucina and Fistulifera saprophila.
The results from the similarity and diversity
analysis suggest James Ross Island to be biogeographically
positioned within the Maritime Antarctic region, yet with
some affinities with the flora of Continental Antarctica, as
shown by the presence of Luticola gaussii and Achnanthes
taylorensis. Based on our data, James Ross Island can thus
be located close to the boundary of the two main Antarctic
biogeographical regions. Diatom communities present in
streams and seepage areas could be clearly distinguished
from those in lakes, the latter being much more species
rich. Based on the multivariate analysis, conductivity and
nutrients were selected as the two main environmental
factors determining the diatom composition in the Ulu
Peninsula lakes. The revised taxonomy of the Antarctic
diatom flora induced the construction of a transfer function
for water conductivity in the studied lakes that can be
applied in further palaeoecological studies.
This study describes the origin, bedrock geology, geomorphology, hydrological stability and physical and chemical characteristics of a representative set of 29 lakes in the ice-free parts of the Ulu Peninsula, James Ross Island, located close to the northern tip of the Antarctic Peninsula. Based on these features, six different types of lakes were defined: stable shallow lakes on higher-altitude levelled surfaces, shallow coastal lakes, stable lakes in old moraines, small unstable lakes in young moraines, deep cirque lakes and kettle lakes. We observed a significant relationship between lake type and water chemistry. Bedrock, lake age and morphometry together with altitude were the most important factors underlying the observed limnological variability. Our results further suggested possible nitrogen limitation in the lake ecosystems. However, physical factors such as low temperature and light were also likely to be limiting.
The concentrations of major, minor and trace metals were measured in water samples collected from five shallow Antarctic lakes (Carezza, Edmonson Point (No 14 and 15a), Inexpressible Island and Tarn Flat) found in Terra Nova Bay (northern Victoria Land, Antarctica) during the Italian Expeditions of 1993-2001. The total concentrations of a large suite of elements (Al, As, Ba, Ca, Cd, Ce, Co, Cr, Cs, Cu, Fe, Ga, Gd, K, La, Li, Mg, Mn, Mo, Na, Nd, Ni, Pb, Pr, Rb, Sc, Si, Sr, Ta, Ti, U, V, Y, W, Zn and Zr) were determined using spectroscopic techniques (ICP-AES, GF-AAS and ICP-MS). The results are similar to those obtained for the freshwater lakes of the Larsemann Hills, East Antarctica, and for the McMurdo Dry Valleys. Principal Component Analysis (PCA) and Cluster Analysis (CA) were performed to identify groups of samples with similar characteristics and to find correlations between the variables. The variability observed within the water samples is closely connected to the sea spray input; hence, it is primarily a consequence of geographical and meteorological factors, such as distance from the ocean and time of year. The trace element levels, in particular those of heavy metals, are very low, suggesting an origin from natural sources rather than from anthropogenic contamination.
Major dissolved ions (Ca2+, Mg2+, Na+, K+, Cl-, SO42-, HCO3-, and CO32-) and dissolved silica (SiO2) in rivers have been studied for more than a hundred years for multiple reasons: (i) geochemists focus on the origins of elements and control processes, and on the partitioning between dissolved and particulate forms; (ii) physical geographers use river chemistry to determine chemical denudation rates and their spatial distribution; (iii) biogeochemists are concerned with the use of carbon, nitrogen, phosphorus, silica species, and other nutrients by terrestrial and aquatic biota; (iv) oceanographers need to know the dissolved inputs to the coastal zones, for which rivers play the dominant role; (v) hydrobiologists and ecologists are interested in the temporal and spatial distribution of ions, nutrients, organic carbon, and pH in various water bodies; (vi) water users need to know if waters comply with their standards for potable water, irrigation, and industrial uses.The concentrations of the major ions are commonly expressed in mg L-1; they are also reported in meq L-1 or mueq L-1, which permits a check of the ionic balance of an analysis: the sum of cations (Sigma+ in eq L-1) should equal the sum of anions (Sigma- in eq L-1). Dissolved silica is generally not ionized at pH values commonly found in rivers; its concentration is usually expressed in mg L-1 or in mumol L-1. Ionic contents can also be expressed as percent of Sigma+ or Sigma- (%Ci), which simplifies the determination of ionic types. Ionic ratios (Ci/Cj) in eq eq-1 are also often tabulated (Na+/Cl-, Ca2+/Mg2+, Cl-/SO42-, etc.). As a significant fraction of sodium can be derived from atmospheric sea salt and from sedimentary halite, a chloride-corrected sodium concentration is commonly reported (Na#=Na+-Cl- (in meq L-1)). The export rate of ions and silica, or the yield (YCa2+, YSiO2) at a given station is the average mass transported per year divided by the drainage area: it is expressed in units of t km-2 yr-1 (equal to g m-2 y-1) or in eq m-2 yr-1.This chapter covers the distribution of riverine major ions, carbon species, both organic and inorganic, and silica over the continents, including internal regions such as Central Asia, and also the major factors such as lithology and climate that control their distribution and yields.Based on an unpublished compilation of water analyses in 1,200 pristine and subpristine basins, I am presenting here an idealized model of global river chemistry. It is somewhat different from the model proposed by Gibbs (1970), in that it includes a dozen major ionic types. I also illustrate the enormous range of the chemical composition of rivers - over three orders of magnitude for concentrations and yields - and provide two global average river compositions: the median composition and the discharge-weighted composition for both internally and externally draining regions of the world.A final section draws attention to the human alteration of river chemistry during the past hundred years, particularly for Na+, K+, Cl-, and SO42-; it is important to differentiate anthropogenic from natural inputs. Trace element occurrence is covered by Gaillardet (see Chapter 5.09).
Saline lakes are important environmental features, with significant
geochemical impacts on ecology, water resources, and economic activity
around the world. Ancient sediments within saline lake basins also offer
important sedimentary archives of past climates and tectonics, because
such deposits can record significant hydrologic variations.Saline lake
geochemistry is the product of a complex system involving meteoric
precipitation, weathering, groundwater, evaporation,
precipitation-dissolution reactions, and biotic activity. Its study is
therefore an inherently interdisciplinary effort, and substantial
reviews of the subject have emphasized relevant aspects of the hydrology
(Rosen, 1994), mineralogy ( Spencer, 2000), sedimentology ( Hardie et
al., 1978; Smoot and Lowenstein, 1991), and evolutionary pathways taken
by progressively evaporated waters ( Eugster and Hardie, 1978).The
purpose of this paper is to summarize the geochemistry of saline lake
basins throughout the world, from dilute inflow to evaporated brine.
Following the general approach of Eugster and Hardie (1978), we will
review the theoretical background of the evolution of closed basin
waters, and then selected field examples that are representative of the
major water types. In this work, we have assigned an increased
importance to the effect of magnesium salts on brine evolution pathways,
and have incorporated this into new models of brine evolution and
evaporite precipitation. We follow Chapter 5.16 in referring to waters
with total dissolved solids greater than 3.5×104 mg L-1 as true
"brines," and those with from 1 mg L-1 to 104 mg L-1 as "brackish."
The Antarctic climate system varies on timescales from orbital, through millennial to sub-annual, and is closely coupled to other parts of the global climate system. We review these variations from the perspective of the geological and glaciological records and the recent historical period from which we have instrumental data (the last 50 years). We consider their consequences for the biosphere, and show how the latest numerical models project changes into the future, taking into account human actions in the form of the release of greenhouse gases and chlorofluorocarbons into the atmosphere. In doing so, we provide an essential Southern Hemisphere companion to the Arctic Climate Impact Assessment.
This overview examines available circum-Antarctic glacial history archives on land, related to developments after the Last Glacial Maximum (LGM). It considers the glacial-stratigraphic and morphologic records and also biostratigraphical information from moss banks, lake sediments and penguin rookeries, with some reference to relevant glacial marine records. It is concluded that Holocene environmental development in Antarctica differed from that in the Northern Hemisphere. The initial deglaciation of the shelf areas surrounding Antarctica took place before 10 000 14C yrs before present(BP), and was controlled by rising global sea level. This was followed by the deglaciation of some presently ice-free inner shelf and land areas between 10 000 and 8000 yr BP. Continued deglaciation occurred gradually between 8000 yr BP and 5000 yr BP. Mid-Holocene glacial readvances are recorded from various sites around Antarctica. There are strong indications of a circum-Antarctic climate warmer than today 4700–2000 yr BP. The best dated records from the Antarctic Peninsula and coastal Victoria Land suggest climatic optimums there from 4000–3000 yr BP and 3600–2600 yr BP, respectively. Thereafter Neoglacial readvances are recorded. Relatively limited glacial expansions in Antarctica during the past few hundred years correlate with the Little Ice Age in the Northern Hemisphere.
The geochemistry and vertical stratification of shallow meltwater ponds at 78°S near Bratina Island (McMurdo Ice Shelf) have been determined for late winter (October) and summer (January) conditions as part of the Latitudinal Gradient Project. Of the five frozen ponds investigated in October, all were stratified with respect to conductivity, and three had highly saline basal brines beneath the ice at temperatures of −16 to −20°C. In the ice column, inclusions of saline fluid were observed in channels between ice crystals; the abundance increasing with depth and decreasing ice crystal size. In January, seven of the ten ponds investigated (including ponds sampled in October) retained conductivity stratification, whereas significant thermal stratification was observed in only three ponds (maximum ΔT = 5.5°C). Basal brines, ice and meltwaters were Na-Cl or Na-SO4 dominated. FREZCHEM52 modelling, supported by changes in ion ratios, indicated that the precipitation of mirabilite (Na2SO4.10H2O) and gypsum (CaSO4.2H2O) during progressive freezing is an important determinant in chemical evolution of the basal brine. High pH (8.8–11.2) and over-saturation with respect to dissolved oxygen (> 20 mg L−1) in summer, and the presence of sulphide ions in basal brines in winter, occurred in those ponds which experienced high biological productivity during the summer months.
Background and aim - The non-marine diatom communities in the Antarctic Region are characterized by a typical species composition, in close relationship with their environment. Despite the growing interest, the diatom flora of James Ross Island is only poorly known. The present paper discusses the diversity of limnoterrestrial diatoms on this island: seepages and streams. Methods - The diatom flora of 53 samples taken on the eastern side of the Ulu peninsula on James Ross Island has been studied using light and scanning electron microscopy. Key results - A total of 69 diatom taxa belonging to 26 genera have been observed. The genera Luticola, Diadesmis, Muelleria and Pinnularia dominated the species composition. The flora shows an interesting mixture of cosmopolitan and Antarctic species containing several species reaching on James Ross Island their most northern distribution in the Antarctic Region. The taxonomical position of one widespread Antarctic species, Psammothidium papilio (D.E.Kellogg, Stuiver, T.B.Kellogg & Denton) Kopalová & Van de Vijver comb. nov., is corrected. Conclusions - The limnoterrestrial diatom flora of James Ross Island has a rather low number of species, of which a large proportion shows a restricted Antarctic distribution. © 2012 National Botanic Garden of Belgium and Royal Botanical Society of Belgium.
By means of PHREEQC inverse modeling, we have simulated the weathering reactions in Los Reartes River, a mountainous (2400–670 m a.s.l.) drainage basin from the Sierras Pampeanas of Crdoba, Argentina, analyzing the effect of lithology, relief, and climate. The steep upper half of the basin (slopes > 20) is occupied by exposed granite; the remaining area is mostly metamorphic, with cropping out gneisses and progressively decreasing slopes (< 6).="" climate="" is="" semihumid="" to="" semiarid;="" rainfall="" mainly="" occurs="" in="" summer="" and="" decreases="" with="" decreasing="" height.="" phreeqc="" inverse="" models="" developed="" using="" water="" chemical="" data="" showed="" that="" (a)="" oligoclase="" was="" the="" major="" supplier="" of="" solutes,="" while="" the="" main="" precipitated="" phase="" was="" kaolinite="" in="" the="" granite="" domain;="" (b)="" muscovite="" is="" the="" chief="" supplier="" of="" solutes="" and="" illite="" is="" the="" main="" precipitated="" phase="" in="" the="" gneissic="" realm;="" (c)="" the="" steeper="" portions="" of="" the="" metamorphic="" reach="" are="" less="" crucial="" in="" supplying="" solutes="" than="" the="" lower="" ones,="" thus="" highlighting="" the="" importance="" of="" the="" water="" residence="" time="" in="" the="" kinetics="" of="" dissolution;="" (d)="" in="" the="" driest="" time="" of="" the="" year="" (winter,="" 20="" mm/month)="" we="" registered="" the="" highest="" production="" of="" dissolved="" and="" precipitated="" phases;="" fluxes="" (mmol/month),="" however,="" are="" higher="" at="" the="" end="" of="" the="" rainy="" season;="" (e)="">2 consumption is important all along the Los Reartes drainage basin and, in terms of mmol/kg H2O, the lowermost portion of the basin is the most significant supplier; (f) CO2 accounts for over 50 of all the species involved in the weathering reactions occurring at the Los Reartes drainage basin.
A limnological survey of 15 lakes and 6 streams was carried out on Byers Peninsula (Livingston Island, South Shetland Islands, Antarctica) during austral summer 2001–2002. Most of the surface waters had low conductivities (20–105 �S cm¡1) and nutrients (total phosphorus 0.01–0.24 �M), but some coastal lakes were enriched by nutrient inputs from seal colonies and marine inputs. Plankton communities in the lakes contained picocyanobacteria (102–104 cells ml-1), diatoms, chrysophytes and chlorophytes, and a large
fraction of the total biomass was bacterioplankton. Zooplankton communities were dominated by Boeckella poppei and Branchinecta gainii; the benthic cladoceran Macrothrix ciliata was also recorded, for the first time in Antarctica. The chironomids Belgica antarctica and Parochlus steinenii, and the oligochaete Lumbricillus sp., occurred in stream and lake benthos. The phytobenthos included cyanobacterial mats, epilithic diatoms and the aquatic moss Drepanocladus longifolius. These observations underscore the limnological richness of this seasonally ice-free region in maritime Antarctica and its value as a long-term reference site for monitoring environmental change.
Five test runs were performed to assess possible bias when performing the loss on ignition (LOI) method to estimate organic matter and carbonate content of lake sediments. An accurate and stable weight loss was achieved after 2 h of burning pure CaCO₃ at 950 °C, whereas LOI of pure graphite at 530 °C showed a direct relation to sample size and exposure time, with only 40–70% of the possible weight loss reached after 2 h of exposure and smaller samples losing weight faster than larger ones. Experiments with a standardised lake sediment revealed a strong initial weight loss at 550 °C, but samples continued to lose weight at a slow rate at exposure of up to 64 h, which was likely the effect of loss of volatile salts, structural water of clay minerals or metal oxides, or of inorganic carbon after the initial burning of organic matter. A further test-run revealed that at 550 °C samples in the centre of the furnace lost more weight than marginal samples. At 950 °C this pattern was still apparent but the differences became negligible. Again, LOI was dependent on sample size. An analytical LOI quality control experiment including ten different laboratories was carried out using each laboratory’s own LOI procedure as well as a standardised LOI procedure to analyse three different sediments. The range of LOI values between laboratories measured at 550 °C was generally larger when each laboratory used its own method than when using the standard method. This was similar for 950 °C, although the range of values tended to be smaller. The within-laboratory range of LOI measurements for a given sediment was generally small. Comparisons of the results of the individual and the standardised method suggest that there is a laboratory-specific pattern in the results, probably due to differences in laboratory equipment and/or handling that could not be eliminated by standardising the LOI procedure. Factors such as sample size, exposure time, position of samples in the furnace and the laboratory measuring affected LOI results, with LOI at 550 °C being more susceptible to these factors than LOI at 950 °C. We, therefore, recommend analysts to be consistent in the LOI method used in relation to the ignition temperatures, exposure times, and the sample size and to include information on these three parameters when referring to the method.
Antarctic terrestrial biodiversity occurs almost exclusively in ice-free areas that cover less than 1% of the continent. Climate change will alter the extent and configuration of ice-free areas, yet the distribution and severity of these effects remain unclear. Here we quantify the impact of twenty-first century climate change on ice-free areas under two Intergovernmental Panel on Climate Change (IPCC) climate forcing scenarios using temperature-index melt modelling. Under the strongest forcing scenario, ice-free areas could expand by over 17,000 km(2) by the end of the century, close to a 25% increase. Most of this expansion will occur in the Antarctic Peninsula, where a threefold increase in ice-free area could drastically change the availability and connectivity of biodiversity habitat. Isolated ice-free areas will coalesce, and while the effects on biodiversity are uncertain, we hypothesize that they could eventually lead to increasing regional-scale biotic homogenization, the extinction of less-competitive species and the spread of invasive species.
The inland waters of the polar regions are diverse, including very dilute and very salty lakes, hot springs, deep lakes and shallow ponds, rivers and streams. Throughout, however, ice is very important, and there is both continuous light during a part of summer and continuous darkness during a part of winter. Attention is drawn to the origins of polar lakes and ponds; physical limnology (ice, water temperatures, light, circulation, hydrology); chemical limnology (inorganic ions, nutrients and trace metals, dissolved organic matter, dissolved gases); biological limnology (phytoplankton, benthic algae and macrophytes, zooplankton, fish, benthic animals, bacteria and decomposition, ecosystem analysis); and flowing water limnology. -P.J.Jarvis
The distribution of a series of elements in lacustrine environments from Terra Nova Bay, Northern Victoria Land, Antarctica, has been examined, in order to gain insight into the natural processes regulating species distribution, and to detect possible present or future local and/or global anthropogenic contamination. Attention was focused on freshwaters, algae, mosses, and lichens (one site only). Lake water composition was found to be influenced by marine spray, lake geographical position and meltwater input. Bioaccumulation of elements by algae was observed. Higher element concentrations in algae than in mosses have been interpreted taking into account this phenomenon. Data processing by chemometric techniques showed correlations between elements and similarities among samples. No evidence of a detectable metal contamination was found in the investigated area.
Concentrations of lead (Pb) have been measured by ultraclean Isotope Dilution Mass Spectrometry in six sections of the 2083 m Vostok deep Antarctic ice core which integrates some 155,000 years. Lead contamination of 15,000–32,000 pg Pb g−1 existed on the outside of the cores, but measured concentrations decreased abruptly along a radius from the outside to the center of the cores, establishing interior values in the 2–40 pg Pb g−1 range. These interior data show that natural concentrations of Pb have varied strongly in Antarctic ice during the last 155,000 years: Pb values were high during the end of the ice age (Illinois) which proceeded the last interglacial and during the Last Glacial Maximum; they were low during the last interglacial and most of the last ice age (Wisconsin). Soil dust appears to be the major source of natural Pb, but the volcanic contribution is found to be significant during low Pb time periods.
Estimates of the average composition of various Precambrian shields and
a variety of estimates of the average composition of upper continental
crust show considerable disagreement for a number of trace elements,
including Ti, Nb, Ta, Cs, Cr, Ni, V, and Co. For these elements and
others that are carried predominantly in terrigenous sediment, rather
than in solution (and ultimately into chemical sediment), during the
erosion of continents the La/element ratio is relatively uniform in
clastic sediments. Since the average rare earth element (REE) pattern of
terrigenous sediment is widely accepted to reflect the upper continental
crust, such correlations provide robust estimates of upper crustal
abundances for these trace elements directly from the sedimentary data.
Suggested revisions to the upper crustal abundances of Taylor and
McLennan [1985] are as follows (all in parts per million): Sc = 13.6, Ti
= 4100, V = 107, Cr = 83, Co = 17, Ni = 44, Nb = 12, Cs = 4.6, Ta = 1.0,
and Pb = 17. The upper crustal abundances of Rb, Zr, Ba, Hf, and Th were
also directly reevaluated and K, U, and Rb indirectly evaluated (by
assuming Th/U, K/U, and K/Rb ratios), and no revisions are warranted for
these elements. In the models of crustal composition proposed by Taylor
and McLennan [1985] the lower continental crust (75% of the entire
crust) is determined by subtraction of the upper crust (25%) from a
model composition for the bulk crust, and accordingly, these changes
also necessitate revisions to lower crustal abundances for these
elements.
1. The electron and the proton content (measured as electrode potential [Eh] and pH) of an environment characterize this environment in many ways. In this paper the electrode potential and the pH are used as empirical parameters rather than as electrochemical data capable of thermodynamic interpretation. From published and unpublished work by the authors and from the literature, more than 6,200 pairs of characteristics were gathered, covering most types of the aqueous environment as well as the potential milieu of the chief actors in these environments: algae and bacteria. 2. It appears that the Eh-pH limits of biological systems and of the naturally occurring aqueous environment almost coincide. This would indicate that there are few, if any, sterile terrestrial environments caused by limiting Eh-pH characteristics. 3. As it seems unlikely that environments will be found outside the limits outlined in this paper, physico-chemical speculations on the sedimentary environment should be limited by this outli...
The McMurdo Dry Valleys of Antarctica are the largest ice-free region on the continent. These valleys contain numerous water bodies that receive seasonal melt from glaciers. For forty years, research emphasis has been placed on the larger water bodies, the permanent ice-covered lakes. We present results from the first study describing the geochemistry of ponds in the higher elevations of Taylor Valley. Unlike the lakes at lower elevations, the landscape on which these ponds lie is among the oldest in Taylor Valley. These upland ponds wax and wane in size depending on the local climatic conditions, and their ionic concentrations and isotopic composition vary annually depending on the amount of meltwater generated and their hydrologic connectivity. This study evaluates the impact of changes in summer climate on the chemistry of these ponds. Although pond chemistry reflects the initial meltwater chemistry, dissolution and chemical weathering within the stream channels, and possibly permafrost fluid input, the primary control is the dilution effect of glacier melt during warmer summers. These processes lead to differences in solute concentrations and ionic ratios between ponds, despite their nearby proximity. The change in size of these ponds over time has important consequences on their geochemical behaviour and potential to provide water and solutes to the subsurface.
Meltwater ponds in the Victoria Valley and in the Labyrinth at the head of the Wright Valley of Victoria Land were sampled in January (summer) and October (late winter) of 2004 to establish their geochemistry and stratification, and to compare this with that of coastal meltwater ponds at a similar latitude near Bratina Island. In summer, vertical profiles were measured in 14 ponds; 10 were thermally stratified (maximum ΔT = 11.5°C) and 12 demonstrated a conductivity increase ([similar]25x) in the lowest 10–20 cm of the water column. When 11 of these ponds were resampled in October, the ice columns were stratified with respect to conductivity and five ponds had highly saline (up to 148 mS cm−1), oxygenated basal brines present under the ice. Basal brines and summer melt waters were Na-Cl dominated, and Victoria Valley pond meltwaters were enriched in Ca relative to the Labyrinth ponds. Early gypsum precipitation directs the chemical evolution of residual brine during freezing. These ponds were enriched in NO3 relative to the coastal ponds at Bratina Island, due to dissolution of nitrate-bearing soil salts, and the reduced influence of marine aerosols and biological productivity on pond chemistry.
When basalt lava flows from air into water it leaves a distinctive record of the waterlevel of the time in the form of lava sheets overlying and passing down into vitric breccia and/or pillow lava. Relative movements of waterlevel and a volcanic pile or terrain over a period of time may be readily deciphered from such records.
In this chapter, we have tried to review the recent literature on trace elements in rivers, in particular by incorporating the results derived from recent ICP-MS measurements. We have favored a "field approach" by focusing on studies of natural hydrosystems. The basic questions which we want to address are the following: What are the trace element levels in river waters? What controls their abundance in rivers and fractionation in the weathering. +. transport system? Are trace elements, like major elements in rivers, essentially controlled by source-rock abundances? What do we know about the chemical speciation of trace elements in water? To what extent do colloids and interaction with solids regulate processes of trace elements in river waters? Can we relate the geochemistry of trace elements in aquatic systems to the periodic table? And finally, are we able to satisfactorily model and predict the behavior of most of the trace elements in hydrosystems?
A 14 year integration with a regional atmospheric model has been used to determine the near-surface climatological wind field over the Antarctic ice sheet at a horizontal grid spacing of 55 km. Previous maps of the near-surface wind field were generally based on models ignoring the large-scale pressure-gradient forcing term in the momentum equation. Presently, state-of-the-art atmospheric models include all pressure-gradient forcing terms. Evaluation of our model output against in situ data shows that the model is able to represent realistically the observed increase in wind speed going from the interior to the coast, as well as the observed wind direction at South Pole and Dumont d'Urville and the bimodal wind distribution at Halley. Copyright © 2004 Royal Meteorological Society
V, Cr, Mn, Cu, Zn, Co, Ag, Cd, Ba, Pb, Bi and U have been measured in a series of dated snow samples, covering the period from 1834 to 1990, collected at remote, low accumulation sites in Coats Land, Antarctica. They were determined by ultrasensitive inductively coupled sector field mass spectrometry in ultraclean conditions. Concentrations are found to be extremely low, down to 3×10−15 g/g, for most metals, then confirming the high purity of Antarctic snow. The results show contrasting time trends for the different metals. For Mn, Co, Ba, and possibly V and Cd, no clear time trends are observed. For Cr, Cu, Zn, Ag, Pb, Bi and U, on the other hand, pronounced enhancements are observed during the recent decades. They are attributed to emissions of heavy metals to the atmosphere from human activities in Southern America, Southern Africa and Australia, especially non-ferrous metal mining and smelting in Chile, Peru, Zaire, Zambia and Australia. It shows that atmospheric pollution for heavy metals in the remote Antarctic continent is not limited to Pb and Cu, as previously thought, but also affects several other metals. It is a further indication that atmospheric pollution for heavy metals is really global.
In this study we report analyses of lead in annual ice layers from the interior of northern Greenland and in annual layers of ice from the interior of the Antarctic continent. We show that lead concentrations increase from <0.001γPb/kg ice at 800 BC to >0.200 γPb/kg ice today in north pole ice sheets, the sharpest rise occurring after 1940, and that the levels of lead in south polar ice sheets are generally below our detection limits before 1940 and rise only to about 0.020 γPb/kg ice after 1940 (in this paper the symbol gamma, γ, means microgram, 10−6 g). The increase of lead with time in north polar snows is ascribed mainly to lead smelteries before 1940 and to burned lead alkyls after 1940. The difference between the concentrations of lead in northern and southern polar snows is ascribed to barriers to north-south tropospheric mixing which originate from meridional circulating cells and which hinder the migration of aerosol pollutants from the northern hemisphere to the Antarctic.
We present a comprehensive geochemical data set for a suite of back-arc alkaline volcanic rocks from James Ross Island Volcanic Group (JRIVG), Antarctic Peninsula. The elemental and isotopic (Sr, Nd, Pb and Li) composition of these Cenozoic basalts emplaced east of the Antarctic Peninsula is different from the compositions of the fore-arc alkaline volcanic rocks in Southern Shetlands and nearby Bransfield Strait. The variability in elemental and isotopic composition is not consistent with the JRIVG derivation from a single mantle source but rather it suggests that the magma was mainly derived from a depleted mantle with subordinate OIB-like enriched mantle component (EM II). The isotopic data are consistent with mantle melting during extension and possible roll-back of the subducted lithosphere of the Antarctic plate. Magma contamination by Triassic–Early Tertiary clastic sediments deposited in the back-arc basin was only localized and affected Li isotopic composition in two of the samples, while most of the basalts show very little variation in δ7Li values, as anticipated for “mantle-driven” Li isotopic composition. These variations are difficult to resolve with radiogenic isotope systematics but Li isotopes may prove sensitive in tracking complex geochemical processes acting through the oceanic crust pile, including hydrothermal leaching and seawater equilibration.
Pb, Cd, Cu, and Zn have been measured using ultraclean procedures in eight sections taken from two well-dated ice cores from Law Dome, an independent small size ice cap with high accumulation rate situated in the coastal area of East Antarctica. Seven sections were dated from the 1830s to 1940s and one was dated from three millennia ago. The data show that there are strong seasonal variations in the concentrations of Pb and Cd, with values approximately tow-to fourfold higher in winter than in spring-summer. Evaluation of the contributions from the different sources suggests that contribution from sea salt spray is relatively important, especially for Cd. Contribution from marine biogenic emissions could also be very significant. The importance of marine contributions is consistent with strong intrusions of marine air masses at this coastal site, especially during wintertime.
We report data for maritime Antarctic lakes showing extremely fast physical ecosystem change, combined with the ecological responses to that change. Nutrient levels at some sites exhibit order of magnitude increases per decade.
Polar lakes are early detectors of environmental change because snow
Surface and Groundwater, Weathering and Soils, Treatise on Geochemistry
- D M Deocampo
- B F Jones
Deocampo, D.M., Jones, B.F., 2014. Geochemistry of saline lakes. In: Drever, J.I. (Ed.),
Surface and Groundwater, Weathering and Soils, Treatise on Geochemistry,,
second ed.vol. 7. Elsevier, Amsterdam, pp. 437e469.
Freshwater algae. National antarctic "discovery" expedition 1901e1904
- R L Folk
Folk, R.L., 1974. Petrology of Sedimentary Rocks. Hemphill, Austin, Texas, pp. 1e57.
Fritsch, F.E., 1912. Freshwater algae. National antarctic "discovery" expedition
1901e1904. British Museum of Natural History 6, 1e66.
Deserts and Desert Environments
- J Laity
Laity, J., 2008. Deserts and Desert Environments. Wiley-Blackwell, Chichester, UK.
User's guide to PHREEQC (versi on 2) e a computer code program for speciation, bathreaction, one-dimensional transport and inverse geochemical calculations
- D L Parkhurst
- C A Apello
Parkhurst, D.L., Apello, C.A., 1999. User's guide to PHREEQC (versi on 2) e a computer code program for speciation, bathreaction, one-dimensional transport
and inverse geochemical calculations. U.S. Geol. Surv. Water Res. Invest. Rep. 99,
4259.
Geological Map of James Ross Island. I. James Ross Island Volcanic Group (1:125 000 Scale)
- J L Smellie
- J S Johnson
- A E Nelson
Smellie, J.L., Johnson, J.S., Nelson, A.E., 2013. Geological Map of James Ross Island. I.
James Ross Island Volcanic Group (1:125 000 Scale). British Antarctic Survey,
Cambridge, UK. BAS GEOMAP 2 Series, Sheet 5.
Origen de elementos mayoritarios y caracterizaci on de sistemas lacustres prístinos en Clearwater Mesa
- P A Vignoni
- K L Lecomte
- J M Lirio
- S H Coria
Vignoni, P.A., Lecomte, K.L., Lirio, J.M., Coria, S.H., 2017. Origen de elementos mayoritarios y caracterizaci on de sistemas lacustres prístinos en Clearwater Mesa,
Isla James Ross, Península Ant artica. Artículo breve. XX Congreso Geol ogico
Argentino, 7-11 agosto Tucum an 18, 122e128. ST.