Oxidized nitrogen chemistry and speciation in the Antarctic troposphere

Understanding the NOy budget at high latitudes is important for our knowled ge of present-day clean air chemistry and essential for reliable interpreta tion of existing ice core nitrate data. However, measurements of NOy compon ents at high latitudes have been limited, and no measurements have attempte d to address the budget of NOy. Here we report on a campaign conducted in t he austral summer of 1997 at the German Antarctic research station, Neumaye r, with first Antarctic measurements for NOy in addition to light alkyl nit rates, NO, HNO3 and p-NO3-. Inorganic nitrate has generally been assumed to be the dominant component of NOy in Antarctica, although this idea has not previously been tested. However, our results show that for this coastal st ation, methyl nitrate was present in much higher concentration than inorgan ic nitrate (median CH3ONO2 = 38 pptv, HNO3 = 5 pptv). It has been suggested earlier that some alkyl nitrates might have a marine source. If this sugge stion is correct, the implication arises that the oceans are an important s ource of NOy to the Antarctic troposphere and that their role in determinin g nitrate concentrations in ice must be considered.