Spatial and temporal trends of atmospheric organochlorine vapors in the central and upper Great Lakes

From November 1990 to October 1991, monthly air samples were collected from Saginaw Bay, Sault Ste. Marie (SSM), and Traverse City, Ml, to identify spatial and temporal variation in organochlorine (OC) vapors in the central and upper Great Lakes region. Average annual and maximum concentrations of Sigma PCB were highest at Traverse and lowest at SSM. PCB 8+5 dominated the congener mix, except at Traverse in the summer. Maxima of HCB, alpha- and gamma-HCH, DDT, and DDE were observed at Traverse or Saginaw, except one unusual event at SSM in May. All compound concentrations varied seasonally at all sites except alpha-HCH. Correlations measuring regression strength between air temperature and OC concentrations show Saginaw affected most by local sources, and SSM affected the least. Among compounds with high vapor pressure, correlations were low at Traverse indicating nonlocal sources. The spatial and temporal differences observed may limit prediction of regional atmospheric trends of these compounds.