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Chlordane is a member of the persistent organic pollutants (POPs), a group of chemicals characterized by extremely long residence in the environment after application. Technical chlordane, composed of a large number of components, is a synthetic organochlorine substance that was used primarily as an insecticide. Uptake by root crops of persistent soil residues of chlordane was noted early in the chronology of the material. The present report is the first comprehensive study of the uptake of weathered soil residues of chlordane and its translocation throughout the tissues of food crops under both greenhouse and field conditions. The data show that for all 12 crops chlordane is not limited to root tissue but is translocated from the root to some of the aerial tissues. Chlordane accumulation in edible aerial tissue appears to be dependent on plant physiology. As expected, chlordane was detected in the edible root tissue of the three root crops examined, carrots, beets, and potatoes. In the remaining crops chlordane was detected in the edible aerial tissue of spinach, lettuce, dandelion, and zucchini, whereas it was not detected in edible aerial tissue of tomatoes, peppers, and corn; trace amounts of chlordane were detected in the edible aerial tissue of bush beans and eggplant. Under the conditions of the field trial the data indicate that for weathered chlordane residues, the soil-to-plant uptake route dominates over the air-to-plant uptake route. This is the case even when the soil concentration of the recalcitrant, weathered residues, for which volatilization is expected to be minimal, is as high as it would be directly following application. Greenhouse trials confirm this observation for zucchini, a member of the Cucurbitaceae family, which bioaccumulates weathered chlordane very efficiently in its edible fruits.

The use of technical chlordane, a mixture of 147 separate components, and chlordane-containing products has been illegal in the United States since 1988. Technical chlordane is a member of the persistent organic pollutants (POPs), all of which exhibit remarkably long half-lives in the environment. Due to its persistence, its former use at extremely high application rates, and its toxicity, technical chlordane in soil may be present at levels of concern to public health. Concentrations at a site for which the date and rate of application of technical chlordane were recorded permit an accurate description of its weathering and an assessment of its vertical and horizontal movement during the past several decades. This site also allows computation of half-life as an average across the 147 components in soil 38 years after application using explicitly stated assumptions. Levels of technical chlordane in soils spanning a variety of land uses including agricultural sites, residential lawns and gardens, and foundation sites are also presented.

In 1997 this laboratory initiated a research program with the objective of examining the effect that rinsing of produce with tap water would have on pesticide residues. Samples were obtained from local markets and/or grown at our experimental farm. Because approximately 35% of produce from retail sources contains pesticide residues, growing and treating produce at an experimental farm had the advantage that all such samples contain pesticide residues. Pesticides were applied under normal field conditions to a variety of food crops and the vegetation was allowed to undergo natural weathering prior to harvest. The resulting samples contained field-incurred or "field-fortified" residues. This experimental design was employed to mimic as closely as possible real world samples. Crops were treated, harvested, and divided into equal subsamples. One subsample was processed unwashed, whereas the other was rinsed under tap water. The extraction and analysis method used was a multi-residue method developed in our laboratory. Twelve pesticides were included in this study: the fungicides captan, chlorothalonil, iprodione, and vinclozolin; and the insecticides endosulfan, permethrin, methoxychlor, malathion, diazinon, chlorpyrifos, bifenthrin, and DDE (a soil metabolite of DDT). Statistical analysis of the data using the Wilcoxon signed-rank test showed that rinsing removed residues for nine of the twelve pesticides studied. Residues of vinclozolin, bifenthrin, and chlorpyrifos were not reduced. The rinsability of a pesticide is not correlated with its water solubility.

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We tested whether predator odors could reduce winter browsing of woody plants by white-tailed deer (Odocoileus virginianus). Urine from bobcats (Lyra rufus) and coyotes (Canis latrans) significantly reduced browsing of Japanese yews (Taxus cuspidata), and repellency was enhanced when urine was reapplied weekly as a topical spray. Urine of cottontail rabbits (Sylvilagus floridanus) and humans did not reduce damage, suggesting that deer do not respond aversively to odors of nonpredatory mammals or occasional predators with which they lack a long evolutionary association. Bobcat and coyote urine were more effective in tests conducted with eastern hemlock (Tsuga canadensis), which is less palatable to white-tailed deer than Japanese yew. A dichloromethane extract of bobcat urine was as effective as unextracted urine in reducing damage to hemlocks. Testing of the organic components of bobcat urine, particularly the volatile components, may enable identification of the compounds responsible for the repellency we observed.

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