Plant uptake and translocation of highly weathered, soil‐bound technical chlordane residues: Data from field and rhizotron studies

Abstract

It has been observed that plants are susceptible to uptake from soil and in planta transport of technical chlordane, in spite of its hydrophobicity and sequestration within the soil matrix due to weathering. Field and rhizotron studies were conducted with Cucurbitaceae planted in highly weathered, chlordane-contaminated soil to investigate details of soil-to-plant contaminant uptake. In the field-work, Cucurbita pepo L. (zucchini) was grown in soil at four levels of chlordane contamination: Clean (<limits of quantitation, 5 ng/g), low (average, 370 ng/g), medium (average, 1,951 ng/g), and high (average, 4,572 ng/g). The analysis of plant tissues (root, stem, leaf, and fruit) resulted in the detection of chlordane consistently at the highest concentration in the root tissue at each level of soil contamination. As the soil chlordane concentration increased, the average chlordane concentration in the root tissue increased as follows: Clean, 370 ng/g; low, 8,130 ng/g; medium, 21,800 ng/g; high, 29,400 ng/g. Further analysis of the field-grown plants showed distinct differences in both the proportional distribution of chlordane among the plant tissues and the pattern of the chlordane residues in each tissue type. These differences are attributed to plant uptake from soil versus uptake from air. In the rhizotron studies, uptake of chlordane residues by C. pepo L. was compared with that of another Cucurbitaceae, Cucumis sativus L. (cucumber). Xylem sap from the rhizotron-grown plants was collected and analyzed for chlordane, in addition to determination of chlordane residues in soil, roots, and aerial plant tissue. Component fractions and enantiomer fractions of both chiral and achiral chlordanes were followed through soil, root, xylem sap, and aerial tissue compartments. They indicate that the xenobiotic residues translocate enantioselectively from the soil matrix into and through the plant environment with genera-specific patterns. The determination of chlordanes at ng/g concentration explicitly for the first time in the xylem sap of plants grown in contaminated soil confirms the presence of a soil-sequestered and highly hydrophobic organic contaminant within the aqueous plant environment.