Abstract:Spat ial variability of HCH (HCHS=α-HCH+β-HCH+γ-HCH+δ-HCH) and DDT (DDXS=4, 4'- DDE +4,4'-DDD+2, 4'-DDT+4, 4'-DDT) in typical agricultural soils of 7 counties located in the Huang-Huai-Hai Plain, China was examined, and vertical distribution pattern of the residues in 4 soil profiles investigated.Their distribution maps clearly indicated that the residues varied nearly randomly in distribution in these counties.DDT showed stronger variability than HCH.Soils with DDXS contents exceeding 50 μgkg-1, the upper limit specified by the Chinese government for the first-class soil quality, all distributed in the east part of Yucheng County.The study revealed the necessity of determining spatial variability in status of organochlorine pesticide for planning a correspondent management programme.The contents of HCHS at layers deeper than 30 cm were quite similar to what was found in the surface layer 0~30 cm in depth, with β-HCH dominating among its isomers.While, DDX S was concentrated in the surface layer, 0~30 cm in depth, but remained less than the detection limit or decreased markedly with depth.The results indicated that HCH and DDT residues in 0~100 cm soil profiles had declined down to safety level in most sites 20 years after the official ban.