Hydrogeochemistry of the deglaciated lacustrine systems in Antarctica: Potential impact of marine aerosols and rock-water interactions

摘要

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 majot 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~- > HCO_3~- > SO_4~(2-) > NO_3~- and Na~+ > Mg~(2+) > Ca~(2+) > K~+ respectively. Moreover, the lakes exhibit slightly alkaline condition due to dissolution of alkaline earth metals and atmospheric fallout. Na~+-Cl~--HCO_3~- 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.