Seasonal variations in atmospheric SOx and NOy species in the adirondacks

Abstract

This paper reports the results of over 2 years of measurements of several of the species comprising atmospheric SO x (= SO 2+ SO 4 2−) and NO y (= NO+ NO 2 + PAN + HNO 3+ NO 3 −+ organic nitrates + HONO + 2 N 2 O 5 …) at Whiteface Mountain, New York. Continuous real-time measurements of SO 2 and total gaseous NO y provided data for about 50% and 65% of the period, respectively, and 122 filter pack samples were obtained for HNO 3, SO 2 and aerosol SO 4 2−, NO 3 −, H + and NH 4 +. Concentrations of SO 2 and NO y were greatest in winter, whereas concentrations of the reaction products SO 4 2− and HNO 3were greatest in summer. The seasonal variation in SO 4 2− was considerably more pronounced than that of HNO 3and the high concentrations of SO 4 2− aerosol present in summer were also relatively more acidic than SO 4 2− aerosol in other seasons. As a result, SO 4 2− aerosol was the predominant acidic species present in summer, HNO 3was predominant in other seasons. Aerosol NO 3 − concentrations were low in all seasons and appeared unrelated to simultaneous NO y and HNO 3concentrations. These data are consistent with seasonal variations in photochemical oxidation rates and with existing data on seasonal variations in precipitation composition. The results of this study suggest that emission reductions targeted at the summer season might be a cost-effective way to reduce deposition of S species, but would not be similarly cost-effective in reducing deposition of N species. kwAcid deposition, seasonal variation, sulfate, nitrate, nitric acid, sulfur dioxide, oxides of nitrogen, hydrogen peroxide, ozone, air pollution, Adirondack Mountains