%D %0 ARTICLE %T Distribution of organo-chlorine pesticides ( DDT and HCH ) between plant and soil system . %J %V 26 ( 2-3 ) %P 253-8 %A Feng K %A Yu BY %A Wang XL %A Ge DM %A Wang XZ %A Wong MH %A Cao ZH %M pub15499781 %X This paper reports a study of the distribution of organo-chlorine pesticides ( DDT and HCH ) between rice plants and the soil system by spraying before the heading stage at four different dosage levels--control , normal dosage ( 15 kg ha ( -1 ) of 6% HCH and 7 . 5 kg ha ( -1 ) of 25% DDT ) , double dosage and four times dosage . Soil and plant samples were taken respectively at the 1st h , 3rd , 10th , 20th , and 40th day after spraying and at the harvest time . The results indicate that less than 5% of HCH and 15% of DDT were absorbed by the surface of rice leaves for normal dosage . Most of both pesticides moved into the soil in solution after spraying . Compared with DDT , HCH was degraded and run off more easily . HCH residues in the surface soil layer ( 1-3 cm ) were already below 6 . 4 microg kg ( -1 ) at the mature stage , lower than Chinese Environmental Quality Standard for Agricultural Soils : HCH < 0 . 05 mg kg ( -1 ) . However DDT residues in the surface soil layer remained 172 microg kg ( -1 ) , higher than the national standard : DDT < 0 . 05 mg kg ( -1 ) . According to the test f OCP residues in rice seeds , it can be concluded that the OCP sprayed onto the surface of rice leaves can move into rice plants and accumulate in the seeds at the mature stage . HCH residues in rice seeds of the double and four times dosage treatments , and DDT residues in all treatments , exceeded the Chinese National Food Standard ( HCH < 0 . 10 mg kg ( -1 ) , DDT < 0 . 20 mg kg ( -1 ) ) .