Organochlorine Insecticide Residues in Soybean Plant Tops: Root vs. Vapor Sorption¹

Abstract

Soybeans were grown in specially constructed pots to determine the amount of residue contamination in plant tops from 20 ppm surface or subsurface soil‐applied 14C‐labeled p,p'‐DDT, dieldrin, endrin, or heptachlor. Regardless of the insecticide treatment, plant tops were contaminated by both root sorption and foliar sorption of vapors emanating from the soil. Root sorption was the major source of contamination by dieldrin, endrin, and heptachlor, though vapor sorption of dieldrin was nearly as great. Foliar contamination by vapor sorption of DDT residues was nearly seven times greater than for root sorption. Foliar contamination from vapor sorption of residues from all four insecticides was near the same order of magnitude, about 6.5 ppm plant dry weight, whereas contamination from root sorption from endrin was 38, heptachlor 21, dieldrin 11, and DDT 1 ppm. Plant parts were assayed by several methods. Although residue concentrations were different for each insecticide, both the apparent plant degradation and mobility of the insecticide, or degradation products, were: DDT ≥ heptachlor > endrin > dieldrin where root sorption was the source of residue. One heptachlor degradation product, in addition to heptachlor epoxide, two endrin degradation products, and p,p'‐DDE and p,p'‐DDD were found.

Beneficial effects of plants in the remediation of soil and groundwater contaminated with organic materials

“…In general, the deeper the soil horizon, the lower the organic matter concentration and the lower the porosity and soil aeration (see pp. [11][12][13][14][15][16][17][18]33 in Reference 51). It is in the surface A horizon where all the components required for microbial growth are present: humus acting as substrate, high soil porosity allowing for adequate oxygen diffusion, an aqueous environment coming from rainfall, and warming from solar radiation.…”

DDT residues in the environment—A review with a New Zealand perspective

“…Indeed, the sampling of plant tissues has been used as a method of measuring atmospheric contamination as discussed previously. Authors have usually not directly examined the source of plant-accumulated DDT residues, but the work of Beall & Nash (1971) suggests that the majority of foliar DDT is derived from the vapour phase, and similar results have been obtained from work on PCBs .…”

“…Nash et al (1970) were able to detect radiolabel in soybean and cotton tops of plants grown in soil containing l4 C-pp'DDT, but were unable to detect p,p'-DDT by gas chromatography. In a later paper where the contributions resulting from root uptake and foliar deposition were separated (Beall & Nash 1971), it was shown that the majority of the label volatilised from the soil was recovered as p,p '-DDT, p,p'-DDE, or p,p'-DDD, while less than 2% of the label translocated from the roots was present in these compounds. This result suggests that p,p'-DDT has been either degraded or chemically altered in some other way.…”

Organic Contaminants in Terrestrial Food Chains

“…[53][54][55][56][57] There is some evidence to suggest that there is some uptake and translocation of the more polar chlorinated hydrocarbon insecticides. 53 Volatilization from the soil surface and redeposition was an important mechanism in laboratory studies in which the experimental technique allowed comparison of uptake-translocation and volatilization-redeposition. Volatilization and redeposition of PCBs and DDT resulted in plant parts with concentrations as great as 20% of the concentration in surface soil.…”