Trends of chlordane and toxaphene in ambient air of Columbia, South Carolina

A long-term record of chlordane and toxaphene (chlorobornanes, CHBs) measurements in Columbia, South Carolina is presented. Chlordane was used as a termiticide in the city and toxaphene was applied to cotton, soybeans and other crops in the region. Ratios among chlordane compounds in ambient air agreed well with those in technical chlordane when weighted for differences in volatility. Atmospheric concentrations (Ca, pg m-3) in pre-ban years (1988 for chlordane, 1986 for toxaphene) are compared to those made more recently by normalizing concentrations for the effect of varying ambient temperature. Plots of log Ca vs 1/T suggest that chlordane concentrations at 20°C declined by about 40% between pre-ban years and 1994–1995, but no change is apparent at 5°C. Recent concentrations of CHBs are lower than those measured when toxaphene was in use. Temperature slopes are flatter in post-ban years, possibly because of retarded evaporation of old residues as compared to freshly applied pesticide. The 1994–1995 concentrations of chlordanes and CHBs in Columbia air were several times higher than those found in the Great Lakes region. No distinct trend in CHB levels with air transport direction was noted, suggesting that volatilization from local or regional soils is supplying CHBs to Columbia air.