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A comparison of dieldrin residues in various vegetable crops cultivated in a contaminated field

Saito, Takashi, Otani, Takashi, Seike, Nobuyasu, Okazaki, Masanori
Soil science and plant nutrition 2012 v.58 no.3 pp. 373-383
Brassica rapa subsp. campestris, Brassica rapa subsp. nipposinica var. perviridis, Cucumis sativus, Cucurbita maxima, Cucurbita pepo, Raphanus sativus, Solanum tuberosum, alternative crops, bioaccumulation factor, carrots, cucumbers, dieldrin, fruits, green leafy vegetables, leaves, pollutants, potatoes, pumpkins, radishes, roots, soil, tubers, vegetable crops, zucchini, Japan
Dieldrin, an insecticide that is considered a persistent organic pollutant, remains in the soil for a long time after application. In recent years, dieldrin has been detected in cucumber (Cucumis sativus L.) fruits produced in some areas at concentrations exceeding the tolerance limit in Japan. Thus, we compared dieldrin residues in 19 vegetable crops produced in a dieldrin-contaminated field. Since dieldrin concentrations in the soil of each crop plot differed about 2-fold, we used the bioconcentration factor to compare the degree of dieldrin residue contamination among crops. The bioconcentration factors of Cucurbitaceae crops were much higher than those of non-Cucurbitaceae crops. Among non-Cucurbitaceae crops, the bioconcentration factors of komatsunas (Brassica campestris var. perviridis), Japanese radishes (Raphanus sativus L.), carrots (Dancus carota L.), and potatoes (Solanum tuberosum L.) were relatively high. In these Cucurbitaceae plants, dieldrin was not accumulated in particular parts or organs. On the other hand, in carrot roots, Japanese radish roots, and potato tubers, higher amounts of dieldrin were detected in the skin, small amounts were found in the outer flesh, and none was detected in the inner flesh, core, or leaf. To select the alternative crops to grow in dieldrin-contaminated fields, we propose to use the “tolerance limit over factor”, which we calculated by dividing the bioconcentration factor by the tolerance limit of the crop. The tolerance limit over factor of Cucurbitaceae crops was higher than that of non-Cucurbitaceae crops. In Cucurbitaceae, the tolerance limit over factor of cucumbers was much higher than that of zucchini and pumpkins, though the bioconcentration factors of these cucurbits were nearly the same. In non-Cucurbitaceae crops, the tolerance limit over factors of komatsunas, Japanese radishes, and potatoes were similar in value to those of zucchini (Cucurbita pepo L.) and pumpkins (Cucurbita maxima Duch.). By considering the tolerance limit over factor values, we propose that Cucurbitaceae crops, root crops (especially Japanese radish), tubers (especially potato), and leafy vegetables (especially komatsuna), in which dieldrin tolerance limits are set at low concentrations, are not appropriate for cultivation in dieldrin-contaminated fields.