Soluble acidic species in air and snow at Summit, Greenland

Simultaneous measurements of the concentrations of soluble acidic species in the gas, aerosol and snow phases at Summit, Greenland were made during summer 1993. Mean concentrations of gas phase HCOOH, CH{sub 3}COOH, and HNO{sub 3} (49{+-}28, 32{+-}17 and 0.9{+-}0.6 nmol m{sup {minus}3} STP, respectively) exceeded the concentrations of aerosol-associated HCOO, CH{sub 3}COO, and NO{sub 3}{sup {minus}} by 1-3 orders of magnitude. On average, SO{sub 2} concentrations (0.9{+-}0.6 nmol in m{sup {minus}3} STP) were approximately 1/3 those of aerosol SO{sub 4}{sup =}, but this ratio varied widely due largely to changes in the concentration of aerosol SO{sub 4}{sup =}. Concentrations of aerosol SO{sub 4}{sup =} plus SO{sub 2} consistently exceeded the sum of aerosol NO{sub 3}{sup {minus}} plus HNO{sub 3}, yet NO{sub 3}{sup {minus}} was 3-20 times as abundant as SO{sub 4}{sup =} in surface snow. Gas phase concentrations of HCOOH and CH{sub 3}COOH at Summit were unexpectedly as large as those previously reported for several high latitude continental sites. However, carboxylate concentrations in snow were lower than those of SO{sub 4}{sup =}. The authors observation of post-depositional loss of these carboxylic acids within hours after a snowfall must partially explain the low concentrations found in snow. The relative abundance ofmore » soluble acids in summer snow at Summit was opposite of that in the overlying atmosphere. These results highlight the need for improved understanding of the processes controlling transfer of soluble atmospheric species between air and snow. 19 refs., 2 figs., 1 tab.« less

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