The distribution and transport of sulfate “species” in the New York metropolitan area during the 1977 Summer Aerosol Study

Abstract

The atmospheric distribution of sulfate was analyzed at four sites operated by various cooperating laboratories for the period of 18 July–29 August 1977 in the New York metropolitan subregion. The sulfate concentrations measured in NYC were categorized according to wind trajectory and values ≥ 15 μg m −3 were normally associated with a strong westerly component. SO 2 − 4 values ≤ 5 μg m −3 were associated with other wind trajectories, that had not passed over the Ohio Valley. Comparison of the 1977 study with the New York Summer Aerosol Study (1976) indicated that on the average the SO 2 − 4 concentrations were slightly lower in 1977. The highest concentrations (> 20 μg m −3) occurred simultaneously with the return flow of ozone-laden high pressure systems. The results of a SO 2 − 4 episode which affected the region from 3–9 August 1977 were analyzed using trajectory analyses, satellite imagery and measurements of the chemical species H +, NH + 4, and SO 2 − 4. Transport of SO 2 − 4 was observed and the presence of a strong acid distribution in the rural areas was denonstrated. The aerosol in New York City appeared to be more nearly neutral, probably a result of reaction with ammonia.