Background Concentration of Sulfate in Precipitation along the West Coast of North America

摘要

The pH is not sufficient to characterize the acidity of precipitation, but rather its acid-base components must be described. The chemistry of natural emissions sources as well as the mechanisms of precipitation formation are key factors in determining the chemistry of precipitation along the west coast of North America. With the ocean biota as a source of atmospheric aerosol sulfate, it is expected that this 'background' chemistry will be dominated by sulfate. For the purpose of the study, 'background' was defined as a remote site generally upwind of urban areas, with the additional requirement that data with evidence of contamination by anthropogenic sources be excluded. Data from long term precipitation monitoring sites along the coasts of Oregon, Washington, and British Columbia were evaluated to estimate a background sulfate concentration in precipitation. In addition to screening the data for charge balance, collection efficiency, and anthropogenic influence, the data were corrected for sulfate associated with sea salt.