Determination of common anions in wet precipitation from southeastern Michigan by capillary electrophoresis

Snow and rainwater samples were collected in southeastern Michigan from January to June of 2004. Common inorganic and organic anions (chloride, sulfate, nitrate, formate, oxalate) were determined using capillary electrophoresis. About 66% of the samples exhibited a pH value < 5.6, which is natural acidity of uncontaminated wet precipitation due to the presence of CO₂ in the atmosphere. Chloride, sulfate, and nitrate were major chemical species found in the samples. The high levels of chloride in the winter samples were likely due to the salts (NaCl and MgCl₂) spread on roadways and sidewalks to reduce the build up of ice during the winter season. Both sulfate and nitrate might primarily come from local anthropogenic activities, e.g., burning fossil fuels and automobile emission. The high levels of hydrogen ions in the samples might be correlated to the relatively high concentrations of sulfate and nitrate that are likely formed from anthropogenic emission of SO₂ and NO_x in the region. This is an abstract of a paper presented at the 229th ACS National Meeting (San Diego, CA 3/13-17/2005).