Long-term residue of DDT compounds in forest soils in Maine.

Soils in forests sprayed aerially with DDT in 1958-1967 have been sampled for persistence of residues at intervals since then and most recently in 1993. Results of all the samples are presented and show persistence through 30 years, with evidence of decline of residue only in the third decade. The metabolites of DDT--DDE and DDD--increased over time, each comprising about a third of total residue in 1993. Residue continues to be held in the organic mat with little evidence of movement downward to the inorganic soil horizons.