Melting of Antarctic lakes: seasonal influence on POPs and amino acids dynamics

Antarctica is almost entirely covered by an huge ice-sheet. In limited coastal areas, during only a short summer period, small and shallow seasonal lakes are fed by melted ice and snow. These have no or limited outlets and lose summer meltwater through evaporation or sublimation, accumulating solutes and particulate material from the catchment areas. The study of the effects of ice melting linked to the seasonal evolution of Antarctic lakes constitutes an experimental challenge. The waters of four lakes in Northern Victoria Land (Edmonson Point 14 and 15A, Inexpressible Island 10B and Tarn Flat 20) were sampled at the beginning and at the late/complete melting of ice, with the aim to highlight the seasonal evolution and amplification phenomena [1,2]. Both persistent organic pollutants (POPs, i.e. PCBs and PBDEs) and primary production indicators, such as L- and D- amino acids were determined in water samples. Combining the information deriving from the two classes of tracers allowed to obtain a more detailed indication of sources and processes. Samplings were carried out during the 2011-2012 austral summer. Pre-analytical steps were performed in the laboratories in Antarctica with particular attention to avoid contamination risks. PCBs and PBDEs were later analyzed by HRGC coupled to HRMS and LRMS (MAT95XP, Thermo Finnigan; 7890A-5975C, Agilent Technologies). The quantification of amino acids was performed using an HPLC with a chiral column coupled with an API 4000 triple quadrupole (AbSciex), achieving very low detection limits (4 - 200 ng L-1). PCBs showed a general slight increase during the melting season, while the behaviour of PBDEs resulted more complex, reflecting the influence of similar sources. The study of amino acids highlighted the role of local fauna, in particular in lake Edmonson Point 14, since the inputs of nutrients from seabirds greatly promoted the primary growth. Also the presence of bacteria was confirmed by relevant concentrations of D-alanine. An increase was observed also in lake 10B, probably due to marine inputs or evaporation linked to strong katabatic winds, while dilution phenomena were prevalent during the melting in the other lakes. Funds were provided by PNRA 2013/AZ2.05.