Chemical-extraction methods to estimate bioavailability of DDT, DDE, and DDD in soil

A study was conducted to find a method to determine the bioavailability to earthworms of DDT, DDE, and DDD in soils. Measurements were made of the uptake by Eisenia foetida of the three compounds in seven soils in which they were freshly added or had persisted in the field for up to 49 yr. The worms assimilated 3.15-66.2% of the compounds in the test samples. Different amounts of the three compounds were sorbed by C18 membrane disks placed in suspensions of these soils, and different amounts also were extracted by solutions of tetrahydrofuran in water. The amounts of the compounds taken up by the C18 membrane disks and extracted by the tetrahydrofuran -water mixture correlated well with uptake by E. foetida from 10 samples of these soils. The correlation coefficients (r) were 0.921 or higher for the C18 membrane disk assay and 0.831-0.948 for the tetrahydrofuran-extraction assay in correlations of the chemical and biological assays. These methods thus offer promise as chemical assays to predict bioavailability of DDT and related compounds.