[Effects of dissolved organic matter on napropamide adsorption and transport in soil system]

Dissolved organic matter (DOM) can affect the environmental behaviors of herbicides in soil. Batch adsorption and column experiments were conducted to measure the sorption and leaching 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 the tested soils, consequently which facilitated the transport of napropamide exhibited by soil column experiment. The sorption inhibition and the increased mobility of napropamide caused by DOM of GM origin were more significant than that of SS origin for the same soil. Within the selected concentration range of the napropamide and DOM in this study napropamide sorption isotherm could be described well by the Freundlich equation. In comparison with the control, DOM of GM and SS origins could reduce napropamide adsorption by 22.9% and 11.3% in the yellow-brown soil and 9.5% and 6.5% in the calcareous soil, respectively. Correspondingly, in the presence of DOM the leaching losses of napropamide in soil column increased by 73.42% and 26.87% in the yellow-brown soil and 43.54% and 28.29% in the calcareous soil, respectively.