Tracking chlordane compositional and chiral profiles in soil and vegetation

The cycling of chlordane and other persistent organic pollutants through the environment must be comprehensively elucidated to assess adequately the human health risks posed from such contaminants. In this study the compositional and chiral profiles of weathered chlordane residues in the soil and vegetative compartments were investigated in order to provide details of the fate and transport of this persistent pesticide. Zucchini was planted in a greenhouse in three bays containing chlordane-contaminated soil. At harvest the vegetation and soil were extracted and analyzed for chlordane content using chiral gas chromatography/ion trap mass spectrometry. Both achiral and chiral chlordane components were quantified. The chlordane concentration in the rhizosphere (soil attached to roots) was significantly less than that in the bulk soil. However, the enantiomeric ratio of the chiral components and overall component ratios had changed little in the rhizosphere relative to the bulk soil. Significant levels of chlordane were detected in the vegetation, the amount varying in different plant tissues from a maximum in roots to a minimum in fruit. In addition to the chlordane concentration gradient in plant tissues, significant shifts in compositional profile, as indicated by the component ratios, and in chiral profile, as indicated by the enantiomeric ratio, of the contaminant were observed in the plant tissues. The data indicate that abiotic processes dominate the transport of the chlordane components through the soil to the plant. This is the first report of the effect of rapid biotic processes within the plant compartment on chlordane compositional and chiral profiles.