The fate of a 1 kg/ha application of granular chlorine—36—labeled DDT made by helicopter on 10 June 1969 to a 4—ha old—field study are near Urbana, Ohio was traced and quantified in soil and biota through November 1974. Between 1970 and 1974, residues of DDT (DDTR, includes DDT plus metabolites) declined from 22.0 to 3.8 mg/kg tissue in earthworms (Lumbricus terrestris) and from 9.3 to 2.1 mg/kg in slugs (Decoceras laeve). Residues also declined from 12.1 to 4.7 mg/kg in firefly larvae (Photuris sp.), and from 32.3 mg/kg whole body in 1970 to 18.9 mg/kg in 1974 in short—tailed shrews (Blarina brevicauda), two predators of slugs and earthworms. The fact of moles (Scalopus aquaticus) and garter snakes (Thamnophis sirtalis), which fed primarily on earthworms, contained less DDTR (69.7 and 53.3 mg/kg, respectively) than did that of Blarina (308.5 mg/kg) but more than that of the other vertebrates. Levels of DDTR in foilage of grasses and forbs increased from 2—3 mg/kg in 1970 to 7.6 mg/kg in 1974, but remained relatively constant at 1.6 mg/kg in roots. Residues increased from 2.5 mg/kg in 1971 to 10.8 mg/kg in 1974 in isopods (Tracheoniscus rathkei); from 1.5 mg/kg in 1970 to 8.1 mg/kg in 1973 in crickets (Gryllus pennsylvanicus and Nemobius allardi); and from 1.4 mg/kg in 1970 to 5.4 mg/kg in 1973 in ground beetles (Carabidae), which were predators of isopods, crickets, and other herbivorous arthropods. Whole body residues increased in meadow voles (Microtus pennsylvanicus), which fed primarily on grasses, from 2.7 mg/kg in 1970 to 6.8 mg/kg in 1974; and in masked shrews (Sorex cinereus), which were predators of herbivorous arthropods, from 4.4 mg/kg in 1970 to 9.8 mg/kg in 1974. Cottontail rabbits (Sylvilagus floridanus), collected only in 1969 and 1970, contained DDTR levels similar to those of voles. Weasels (Mustela nivalis) contained about twice the residue levels of voles, their principal prey. Amounts of residues in samples of air collected at the surface of the soil were positively correlated with amounts in soil and with air temperature. The total quantity of DDTR in the top 12 cm of soil was estimated to be 1779 g in OCtober 1974, or 38% of the amount applied in 1969. Earthworms, which comprised the largest component of animal biomass, contained 5% of the total DDTR in the ecosystem in 1969, compared to 3% in the plants and other biota. As residues declined in earthworms and increased in plants over time, the total DDTR bound in the biota increased until it accounted for 22% of the total DDTR in the ecosystem in 1974. Losses of DDTR from the ecosystem eary year were attributed primarily to volatilization from soil, because losses in runoff and emigration insects and small mammals were negligible.
