HIGHLY SOLUBLE ATMOSPHERIC TRACE GASES IN THE SOUTHWESTERN UNITED STATES - 1. INORGANIC SPECIES: NH3, HNO3, SO2.

Atmospheric concentrations of NH//3, HNO//3, and SO//2 have been measured at a variety of sites in the southwestern United States over the last few years. Sampling was by condensation collection. Over much of the region, NH//3 is associated primarily with agricultural activity, HNO//3 mostly with urban emissions, and SO//2 with industrial effluent. However, relatively high SO//2 concentrations (1 ppb) were observed at a remote coastal site, indicating substantial natural release of sulfur compounds in this area. Data from a relatively remote site in southern Arizona showed that copper smelting in the region increased SO//2 levels from 0. 3 to 2 ppb and probably caused a small increase in HNO//3 levels. There were large diurnal variations of both components. Urban concentrations of SO//2 and HNO//3 were unaffected by smelting. Levels of NH//3 varied with proximity to agricultural sources. Average values of 10 ppb were observed close to a recently fertilized field. The most frequent concentration observed at the more remote sites (taken to be background for the area) was 0. 9 ppb NH//3. Diurnal and seasonal variations of NH//3 were small.