CHEMICAL-COMPOSITION OF FOG WATER AND INTERSTITIAL AEROSOL IN BERKELEY, CALIFORNIA

Fog water and interstitial particles were sampled at Berkeley, California, during foggy periods in the summer of 1986. The sampling site received marine fog advected from the San Francisco Bay, Samples of ambient particulate material (total aerosol) were collected using a filter sampler with a heated inlet. Concentrations of Na+, K+, NH4+, Cl-, NO3-, and SO42- were measured in the particles and Fog water, for which pH was also measured. Black carbon aerosol was determined on the filter samples using optical attenuation. The marine fog showed the influence of mixing and chemical reaction with anthropogenic pollutants. Twenty-six percent of the black carbon was present in fog droplets, indicating that incorporation of combustion particles into fog droplets had occurred. Anthropogenic particulate species were not scavenged by fog water as efficiently as sea-salt components. Non-sea-salt SO42- was enhanced in the total aerosol during fog compared to dry conditions, and this observation has been interpreted as evidence for heterogeneous production of SO42- in fog. The fog had elevated SO42- and NO3- levels compared to sites closer to the ocean, Sufficient NH3(g) was available to neutralize the increased acidity from anthropogenic H2SO3 and HNO3 so that the median pH was 4, as compared to pH 2.2 observed in Los Angeles fog water under more polluted conditions. Loss of Cl- from the fog or its precursor aerosol was enhanced compared to other measurements of San Francisco Bay Area fog at more remote locations.