1a. Objectives (from AD-416):
Cooperate in testing methods to reduce soil DDx (DDT, DDE, DDD and other breakdown products of DDT) and dieldrin by earthworms to see if addition of organic matter to contaminated soils, or growing crops on contaminated soils can reduce DDT and dieldrin uptake by earthworms and thus lower risk and raise clean-up cut-off limits and greatly reduce soil removal/replacement costs while protecting the environment.
1b. Approach (from AD-416):
1) Collect representative soils from DDx and dieldrin contaminated areas of the North Farm at BARC; 2) Identify earthworm species which occur in these soils; 3) Test the effect of organic matter amendments (manure compost; biosolids compost; biochar) on bioaccumulation of DDx by common soil earthworms; 4) Test the effect of growing crops in the earthworm bioaccumulation assay soil on the bioaccumulation of DDx and dieldrin by earthworms; 5) Examine the effect of treatments on nutrient and trace element accumulation by the earthworms; 6) Examine the effect of the soil amendments on changes in soil microflora which may affect earthworm activities; and 7) DDx and dieldrin and other halogenated hydrocarbon analyses to be provided by cooperators.
3. Progress Report:
The goal of this cooperative project is to test the reduction in bioavailability of soil dichlorodiphenyltrichloroethane (DDT) to earthworms using composts and plants. Old orchards and other land may contain excessive residues of DDT and dichlorodiphenyldichloroethane (DDE) from historic pesticide sprays. Because earthworms bioaccumulate DDE from soils, and some birds and small mammals ingest large amounts of earthworms, the most limiting risk pathway for soil DDE is earthworm bioaccumulation to harm wildlife. Old orchard soils at BARC contain sufficient DDE to require removal or other remediation at great expense, and an in situ remediation test was funded. Samples from a growth chamber microcosm test to evaluate varied organic amendments effect on DDX bioaccumulation by earthworms were analyzed and report is in preparation. Results were used to design a field validation test of using compost to reduce earthworm bioaccumulation of DDX on the field site at BARC. Based on variance in DDX accumulation, seven replications were installed comparing untilled contaminated soil, tilled contaminated soil, and tilled treatments with fresh and aged manure-green waste composts from the BARC composting site. Soils and earthworms were sampled before installation of the treatments and will be sampled again after earthworms exposures under environmental conditions which allow collection of worms from the surface soils. Manuscript on the microcosm study is in preparation. Manuscript prepared and submitted on associated test of laboratory method to measure mobile fraction of soil DDX correlated with earthworm DDX and dieldrin bioaccumulation.