Effects of humic susbstances on adsorption of diledrin in soil

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Dieldrin is one of persistent organic pollutants (POPs) and organochlorine pesticides. Although the use of dieldrin has been restricted or banned for more than three decades, the chemical is still detected in some crops, especially in cucurbits. Organic chemicals with high hydrophobicity tightly adsorb on soil particles, and thus usually these chemicals are hardly taken up by plants from soil. Furthermore, the residual dieldrin in soil must have changed to bound residue, and most of it cannot be taken up by plants. However, some POPs including dieldrin, which have existed over three decades, are somehow taken up by cucurbits, which suggests that bioavailable POPs still exist in those soils. In the present study, the existence form of dieldrin in soil was examined.It has been suggested that the main adsorption sites of POPs on soil are soil organic matters. Therefore, both humic and fluvic acids and humin were extracted from soil, and the adsorptions of dieldrin on these humic substances were examined by batch method.The adsorption amounts of dieldrin on soil removed humic and fluvic acids were lower than those on the soil without treatment. These results suggest that humic acid and fulvic acids affected on the adsorption of dieldrin on soil.