Effects Of Dissolved Organic Matter And Soil Colloid On Napropamide Environmental Behavior In Soil System

The environmental behavior and bioavailability of napropamide affected by dissolved organic matter (DOM) and soil colloid were studied. The results showed that the sorption isotherms of napropamide on five kinds of soil can be described well with Freundlich Equation, the Kf values decreased as follow, huangnitu>black soil>yellow brown soil>red soil> calcareous soil. A strongly positive relationship was found between Kf and organic carbon content of soils (R2=0.997 p<0.05) . Organic matter content of soils was the decisive factor in affecting adsorption. Hydrogen bonding was found to be the common mechanism in the adsorption of napropamide.The study evaluated the potential of water-dispersible soil colloids to adsorb andmediated the transport of napropamide through macropores of aquifer sand columns.Freundlich coefficient Kf ranged from 3.98 Lkg-1 to 12.82 Lkg-1 for bulk soil and from 946Lkg-1 to 2679 Lkg-1 for the soil colloids.The presence of red soil and black soil colloidsenhanced the transport of napropamide by 9.82% and 10.63%, respectively. In spite of theincreased transportability of napropamide by the presence of soil colloids,the colloid-boundherbicide frction contributed <2% to the observed increase.This suggests thatmatrix-surface-site exclusion and blocking mechanisms induced by the presence of colloidsare more important than colloid sorption in promoting napropamide mobility.Batch adsorption and column experiments were conducted to measure the sorption andleaching of napropamide in soils in the presence of DOM derived from green manure (GM)and sewage sludge (SS). DOM reduced sorption of napropamide significantly onto thetested soils, which consequently facilitated the transport of napropamide exhibited by soilcolumn experiment.The sorption inhibition and the increased mobility of napropamidecaused by DOM of GM origin were more significant than that of SS origin for the samesoils. Within the selected concentration range of the napropamide and DOM napropamidesorption isotherm could be described well by the Freundlich equation. In comparison with...