Spatial and temporal regulation of the pesticide dieldrin within industrial catchments

The river catchments of south Yorkshire support a very high density of wool processing industries. Dieldrin was once used as a moth proofing agent, as a sheep dip, and as a pesticide to protect wool fleeces during storage and transport, all of which caused pollution of these catchments due to textil e processing. Weekly sampling of four of these rivers revealed two-classes of dieldrin contamination: the Aire and Calder (the rivers which support ve ry high concentrations of wool processing industries) had higher concentrat ions (averaging similar to 3 ng/l) than the Don and Trent (similar to 1 ng/ l). The average flux of dieldrin from these rivers into the Humber estuary was 9.8 g/day, with the Aire (of which the Calder is a tributary) and the T rent contributing almost equally, with a smaller contribution from the Don. The Trent has the highest average flow, explaining its large contribution to dieldrin flux. Less detailed sampling of rivers from the north Humber ca tchment which drain predominantly rural areas had dieldrin concentrations s imilar to the heavily industrialized southern catchment rivers. This sugges ts that dieldrin from agronomic and domestic usage may be more persistent t han the pollution caused by textile processing industries. Evidence is pres ented to suggest that the principle dieldrin sources to the Humber catchmen ts are sewage treatment plants, and that the dieldrin sources are in rapid equilibrium with the water column. (C) 2000 Elsevier Science B.V. All right s reserved.