Evaluating The Chemical Characteristics And Optical Properties Of Atmospheric Wet Deposition To An Alpine Lake And Snowpack
Kim, Hong S 1 ; Williams, Mark W. 2 ; Schmidt, Steven 3 ; Mladenov, Natalie 4
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There is an urgency to improve our understanding of how water quality in high-elevation catchments is responding to climate change. Clear, high elevation lakes and alpine snowpacks are environments most closely linked to the atmosphere and ecosystems that are particularly sensitive to atmospheric deposition of dust, bioaerosols, and pollutants. At Niwot Ridge, Colorado, measurements of dissolved organic carbon (DOC) concentrations in NADP wet deposition and dedicated Niwot Ridge Long Term Ecological Research (LTER) station atmospheric deposition collectors demonstrate that atmospheric deposition is an important source of carbon for this carbon-limited alpine environments. The average annual DOC loading from wet deposition (2002-2010) was 8.6 kg ha-1 yr-1 and spring and summer peak DOC concentrations often exceeded 5 mg C L-1. To evaluate the sources and chemical quality of atmospheric deposition and its influence on a clear, alpine lake, we examined NOAA airmass backward trajectories, estimates of DOC loading and concentration, and optical spectroscopic properties of organic matter in lake, snow, and wet deposition samples. We found that summer peaks in DOC concentration corresponded to higher amounts of tyrosine-like fluorescence and lower aromaticity, which suggest that summer wet deposition may represent an input of bioavailable organic carbon to these barren, carbon-limited ecosystems.