Relationship between Dieldrin Uptake in Cucumber and Solvent-Extractable Residue in Soil

Abstract

To prevent the distribution of cucumbers with dieldrin contamination exceeding the limit set by the Japanese Food Sanitation Law, the extraction solvent for dieldrin-contaminated soil was selected prior to cultivation so that the dieldrin residue level in cucumber could be predicted. The exhaustive extraction from soil could not explain the dieldrin uptake by cucumber plants. However, significant correlation (R(2) = 0.966, P < 0.001) was observed between dieldrin concentrations in cucumber and dieldrin concentrations extracted with 50% (v/v) methanol-water solution from soils. This was a result of the phytoavailability of dieldrin to the cucumber plants. The extractability of soil dieldrin with the methanol-water solution decreased as the organic carbon content in the soils increased. This suggested that a 50% (v/v) methanol-water solution is the optimal solution for predicting dieldrin concentrations in cucumbers by soil analysis.

Relationship between dieldrin uptake in cucumber fruits and methanol–water extractable residue in soil

“…1) in this study was similar to that reported by Sakai et al, 11) the coe cients of determination (R 2 ) of the regression lines for all cultivars of cucumbers were lower than those in the results obtained by Sakai et al 11) (Fig. 3).…”

“…In contrast, the latter technique has a time advantage because soil analysis allows prediction of the concentration before cultivation. However, results of Sakai et al 11) were not obtained from cucumber fruits, but from cucumber shoots in the early growth stage grown in a pot.…”

“…1-7) and greenhouse culture (Field Nos. [8][9][10][11][12]; therefore, the harvesting periods of the cucumber fruits varied between elds (Table 1). However, the fruit samples were collected from the same position (6th to 10th node on the 1st lateral branch) on all gra ed cucumbers grown in all plots, because White eld Åslund et al 13) indicated that the concentration of PCBs, which are also POPs, in pumpkin leaves and stems was negatively correlated with their distance from the root.…”

“…11) In brief, to determine the total dieldrin residue in the soil, 10 g of each airdried soil sample was Soxhlet-extracted with acetone for 16 hr. is method was de ned as "exhaustive extraction" in this study.…”

“…Murano et al 10) reported that the application of activated carbon to soil contaminated with heptachlor exo-epoxide (HEPX), one of the POPs, could decrease HEPX concentration in the soil solution and pumpkin shoots in the early growth stage. Furthermore, Sakai et al 11) found a signi cant correlation between dieldrin concentrations in early cucumber shoots grown in a pot in an environmentally (light and temperature) controlled cultivation room, and dieldrin concentrations in soil samples extracted with a 50% (v/v) methanol-water solution from soil. ey suggested that extraction by using a 50% (v/v) methanol-water solution is the optimal technique for predicting dieldrin concentrations in cucumbers.…”