Long-term changes in the polychlorinated biphenyl content of United Kingdom soils.

Archived soils collected from five different long-term agricultural experiments in southern England have been analyzed retrospectively for a range of polychlorinated biphenyl (PCB) congeners. The change in soil PCB concentration over time has been similar in each field experiment, namely, that soil samples exhibited a sharp rise in soil PCB concentrations between about 1940 and the early 1960s, reaching a maximum (ca. 140-560 μg of ΣPCB/kg of soil) during the late 1960s/early 1970s. Since then there has been a dramatic reduction in ΣPCB concentrations, such that contemporary concentrations (ca. 20-30 rg/kg) are now similar to those of the early 1940s soils