Plant Uptake of Chlorinated Insecticides from Soils
- R. G. Nash,
- M. L. Beall and
- E. A. Woolson2
Soybeans (Glycine max [L.] Merr., var. ‘Clark’) and cotton (Gossypium hirsutum L., var. ‘Acala 4-42’) were grown in Lakeland sandy loam and Hagerstown silty clay loam soils treated with 0.5 ppm 14C-DDT, -dieldrin, -endrin, and -heptachlor. Periodically, the top portion of one plant per pot was harvested and assayed for insecticide. At maturity, the seed and cotton lint were separated from the hay and assayed separately. Two methods of assay were used, i.e., gas-liquid chromatography and 14C counting by liquid scintillation.
Total 14C-residue concentrations in soybeans for all four insecticides increased linearly during active growth stages, whereas highest 14C-residues in cotton were found at the first harvest. No parent DDT or heptachlor was detected in any of the soybean or cotton samples by gas-liquid chromatographic determination, though small amounts of unidentified DDT residues were detected by liquid-scintillaton counting of plant extracts of both species. Heptachlor epoxide was present in soybeans at less than 0.1 ppm in hay and less than 0.04 ppm in seed. No heptachlor epoxide was detected in cotton, but unidentified 14C-heptachlor residues were present at an equivalent of less than 0.065 ppm. Dieldrin residues ranged as high as 0.3 ppm in soybean hay and 0.09 ppm in seed. Endrin residues ranged as high as 0.5 ppm in soybean hay and 0.1 ppm in seed, though actual endrin was less than these values. Dieldrin and endrin residues in cotton hay were below 0.03 ppm and none was detected in seed or lint. The use of 14C-labeled insecticides demonstrated that all 14C-residues were not removed from plants. Furthermore, discrepencies between gas-liquid chromatography and 14C determinations of plant extracts indicated endrin degradation products were present.
Soil type influenced the plant uptake of these insecticides, especially endrin. Plants grown in the Lakeland s1 soil concentrated greater insecticide amounts than the Hagerstown sicl, presumably because of the lower organic matter content of the Lakeland soil. Cotton removed considerably more insecticides from soils than soybeans because of their greater mass. Based on these results, cropping would not be an efficient method of removing chlorinated insecticides from contaminated soils.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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