Study On The Behavior Of Complex Pollution System And Bioavailability Of Chlorotoluron In Soils

Impact of atrazine and nitrogen fertilizers on fate of chlorotoluron was studied in soil multimedia environment in this paper.The following experimental studies were conducted in this paper. (1) Research on the sorption isotherms of chlorotoluron in single and multimedia system. Adsorption of chlorotoluron followed a rapid adsorption phase in which the amount of adsorbed herbicide increased rapidly (rapid sorption), then it became slowly with the increasing of time (slow sorption). Concentration of chlorotoluron was higher in sterilized treatments than that of in insterilizered treatments. This indicated a part of chlorotoluron was degraded by microorganism during the process of adsorption. (2) Impact of atrazine and nitrogen fertilizers on the sorption of chlorotoluron in soil. The sorption of chlorotoluron was fitted by Freundlich. The sorption of chlorotoluron decreased enormously with the amount of atrazine in solution increased. The sorption of chlorotoluron increased with an increase of nitrogen fertilizers concentration as chlorotoluron and nitrogen fertilizers were applied into soil at the same time. After the soil was pre-incubated with deionized water, ammonium sulfate or urea for 6 days, chlorotoluron adsorption decreased. Chlorotoluron desorption increased with increasing of nitrogen concentration when nitrogen fertilizers and chlorotoluron were applied into soil at the same time. Furthermore, desorption of chlorotoluron was of no significant difference from 6-day incubation with nitrogen fertilizers compared to control. Desorption capability of chlorotoluron in incubated soils was greater than that of in un-incubated soil. The sorption of chlorotoluron in tri-solution was different from in single and bi-solution, which indicated the environmental behaviors of pollutants were more complicated in multi-media system. (3) Impact of atrazine on the sorption of chlorotoluron in model sorbents. The results suggested the sorption of chlorotoluron was stronger on"glass"organic matter than that of in cellulose and silica, indicating the sorption of chlorotoluron included distribution and competition in soil. (4) Impact of atrazine and nitrogen fertilizers on the degradation of chlorotoluron in different depth. The results showed the degradation rate of chlorotoluron increased with an increase of soil depths in single and mixture systems, indicating texture and organic matter of soil that were important on the degradation progress of chlorotoulron in soil. The degradation of chlorotoluron was accelerated when concentration of atrazine was 0~10mg/kg. However, degradation of chlorotoluron decreased when concentration of atrazine was 10~20mg/kg and half-life increased with increasing of atrazine concentration. After ammonium sulfate and urea were applied into soil, the degradation rate of chlorotoluron from these soils was slower than that of in untreated the soils with fertilizers. Moreover, degradation rate of chlorotoluron was faster in urea-treated soils than ammonium sulfate-treated soils in different soil depth. (5) Effect of atrazine and nitrogen fertilizers on the leaching of chlorotoluron in soil. The mobility of chlorotoluron increased when chlorotoluron and atrazine were applied into soil at the same time. However, the amount of chlorotoluron increased in soil column after the atrazine was applied into soil including aged chlorotoluron. Ammonium sulfate and urea reduced chlorotoluron leaching losses of chlorotoluron when fertilizers and chlorotoluron were applied into soil. More chlorotoluron remained in the soil columns were observed in urea treatments than in ammonium sulfate treatments. On the other hand, more chlorotoluron remained in the aged soil columns than that of in non-aged soil columns. (6) Toxicity of single and binary herbicide system combined with chlorotoluron and atrazine to earthworm Eisenia foetida was investigated. The results showed atrazine and chlorotoluron were toxic to earthworm, and that atrazine was more toxic to earthworm than chlorotoluron, the synergistic toxic effect of combined herbicides system to the earthworm. SOD activity of earthworms was greater in combined system than in single system, and that increased with an increase of atrazine concentration. The pathological section showed that the herbicides executed their effects on different parts. After chlorotoluron entering into earthworms, epidermis and intestines of earthworms were ruined. While atrazine ruined alimentary tract of earthworms and resulted death of earthworms. (7) The extractability of organic solvents was significantly different, with extractability decreasing in the order: methanol > methanol: water > ethanol > butanol. The extraction capacity of organic solvents was decreased for chlorotoluron after ageing 108 days. The extractability of ethanol was decreased by 38.61%~44.97% more than that of others; the extraction capacity of butanol was decreased by 25.45%~34.63%; it was same to methanol and methanol: water.