1995 integrated monitoring study: fog measurements in the southern san joaquin valley-preliminary results

摘要

Fogs were sampled at three ground-based stations in the southern portion of California's San Joaquin Valley as part of the winter component of the 1995 Integrated Monitoring Study (IMS95). The three sampling sites included two urban locations (Bakersfield and Fresno) and one rural location (near the Kern Wildlife Refuge). Both bulk and drop size-fractionated samples were collected at each site. Several gof events were sampled, with three periods of extensive fog coverage that included all three sampling sites. Results of preliminary data analysis are presented. Fog collected at the ites was generally quite basic. Most bulk fog samples had pH values above 6 reflecting strong inputs from ammonia. Occasional strong sulfur plumes at Bakersfield, hoever, tended to lower the fog pH. Aside from these periods, nitate was generally present at much higher concentrations in the fog than sulfate. Decreases in fogwater loadings of major species over the course of one extended fog episode at Fresno suggest s ignificant deposition was occurring to the surface, consistent with observations of substantial droplet fluxes to exposed surfaces during that period.