Spatial and temporal variation of polychlorinated biphenyl (PCB) in precipitation in southern Sweden.

Spatial and temporal variations in polychlorinated biphenyl (PCB) concentrations were studied in precipitation at 11 sampling-sites over a period of 1 year and compared with PCB concentrations in the air. The study was carried out in a region of southern Sweden approximately 11 000 km2 in area. The PCB concentration in precipitation ranged between 1.18 and 81.4 ng l(-1). Two of the sampling sites showed concentrations that were approximately 30 times higher than at the rest of the sites. The variation in concentration between sites may be explained by location as well as by differences in weather conditions and particle content in the air. Wind direction played an important role for PCB concentration in precipitation in coastal areas, while at the inland sites this variable seemed to have a minor influence. We found no seasonal trends in PCB concentration in precipitation or any dependence on air temperature. To examine the intensity of precipitation scavenging, the total washout ratios (Wt) were calculated. There was a large variation in Wt over time, and the highest ratios were observed at the two sites where PCB concentration in the air was high. Furthermore, high concentrations of PCB in precipitation correlated with a high-chlorinated pattern, as shown by principal component analysis. For most of the sites there was a significantly negative relationship between PCB concentration and rain volume.