Bioavailability Of DDT Residues In Soil

The present study was conducted to determine extractability of the aged DDT in soil with soxhlet extraction,n-butanol vibrating extraction,water vibrating extraction, and solid phase micro-extraction(SPME),and to measure the potential of the aged DDT absorbed by earthworm(Eisenia foetida),Chinese cabbage(Brassica campestris L.spp),white radish(Raphanus sativus L.),red radish(Raphnus sativus cv.)and cole (Brassica napus L.).The possible relativity between extractability and the potential absorbed by the organisms was analyzed to find a method predicting bioavailability of DDT in soil to earthworm and plants.The extractability of DDT in soil decreased with the increase in the time of aging. After aging for 60 days,the extractability of DDT in soil was 78.9%,74.8%,41.9%, 77.7%compared to those freshly amended in soil,respectively.The potential of DDT absorbed by earthworm from soil decreased also with the time of aging.After aging for 7,15,30,60 days,the amount of DDT absorbed by earthworm from soil were 76.7%,56.7%,52.9%,49.7%of those of freshly amended soil,respectively.The bioavailability of PP'-DDE,OP'-DDT,PP'-DDD,PP'-DDT to earthworm was linearly correlated with their extractability by n-butanol with R~2 values of 0.9605,0.8506,0.8504,0.9004,respectively.A similar linear correlation was also found between the bioavailability of PP'-DDE,OP'-DDT,PP'-DDD, PP'-DDT to earthworm and their extractability by soxhlet extraction with R~2 values of 0.9366,0.8016,0.9088,0.6998,respectively.Similarly,the R~2 values for 24-hour SPME were 0.9971,0.9026,0.8306 and 0.8593,respectively.However,the R~2 values for water vibrating extraction varied from 0.6140 to 0.8240,which were lower than those of butanol vibrating extraction and 24-hour SPME.The bioavailability of DDT to plants was also decreased with the time of aging. After aging for 60 days,the amounts of total DDTs bioavailable to Chinese cabbage, white radish,red radish and cole were 58.6%,39.0%,49.6%,44.3%of those of freshly amended soil,respectively.The amounts of total DDTs extracted by soxhlet extraction were correlated to the assimilated amounts by the Chinese cabbage,white radish,red radish and cole with the R~2 values of 0.9894,0.9889,0.9567 and 0.9929, respectively.The R~2 values for n-butanol extraction and water extraction varied from 0.9204 to 0.9993 and from 0.8326 to 0.9216,respectively.When the amount of 12-hour SPME was used,high correlations were obtained with the R~2 varied from 0.9579 to 0.9871.The results showed that soxhlet extraction,n-butanol vibrating extraction and SPME methods can all be used as predictors to predicting the bioavailability of DDTs to plants.