Rate of Uptake of DDT from Soil by Earthworms

Abstract

SINCE 1958, when the occurrence of DDT and its metabolites in the tissues of earthworms was first reported, there have been more than twenty other reports of DDT residues being found in these animals^1,2. The amounts found have differed greatly, ranging from minute traces to concentrations of nearly 700 p.p.m., although concentrations of the order of 1 to 10 p.p.m. have been more commonly reported. Sometimes the concentrations of DDT residues found in the earthworms have been less than in the soil where they live, although the tissues of the worms have usually contained greater concentrations than the surrounding soil. When all the published data were considered, it was seen that there is a linear correlation between the concentration of DDT (and other organochlorine insecticides) in earthworms and that in the corresponding soil¹. Not all species concentrate insecticides in the same way or to the same degree³; Lumbricus terrestris and other species with permanent burrows take up DDT from the soil surface more readily than from residues that have been thoroughly mixed into the upper strata of soil. Conversely, some of the species without permanent burrows, that tunnel haphazardly through the upper 150 mm of soil, take up more residues from insecticides evenly distributed through the upper soil layers to plough depth.