Study on the Interaction between Humic Substances in Soil and Carbamate Pesticides Using Fluorescence Quenching Titration Method

To reveal the mechanisms of transport and conversion of carbamate pesticides in the presence of dissolved organic matters,the fluorescence quenching titration method was applied to investigate the interactions between carbamate pesticides and humic substances in soil.The results showed that the intrinsic fluorescence of carbofuran and carbaryl was quenched by the fulvic and humic acids to varying degrees.Static quenching was the primary mechanism during this process.The binding constants(K) of carbamate pesticides and humic substances were estimated using the fluorescence static quenching model.The order of lg K were: those of carbofuran and humic acid(4.96) those of carbaryl and humic acid(4.93) those of carbofuran and fulvic acid(4.72) those of carbaryl and fulvic acid(4.68).The values of lg K of carbamate pesticides and humic acids were clearly higher than those of carbamate pesticides and fulvic acids.This result indicated that the hydrophobic force is one of the main interactions between carbamate pesticides and humic substances,and further proved that hydrogen bonding could slightly affect the bonding of carbamate pesticides and humic substances.