Effects Of Herbicides On The Environmental Water System In The Sugarcane Fields In GuangXi

Sugarcane industry was considered as one of the pillar industries in Guangxi, with the planting areas of1.06million hectares each year. However, the expanding use of herbicides in the sugarcane production has increasingly exerted negative effects on the environmental water system, and the problem of pesticide residue was supposed to draw more attention on. To investigate the influence of herbicides on the environmental water system in Guangxi sugarcane planting areas, evaluate the adsorption and leaching behavior of herbicides in soil and understand their harm to the environmental water system, we developed a multi-residue analytical method for determination of the11herbicides in water and soil, and studied the adsorption and mobility behaviour of Ametryne and Metolaehlor in soil, and also investigated and monitored the water pollution caused by the herbicides used in Guangxi sugarcane growing areas.1、A multi-residue analytical method using gas-chromatography (GC) with nitrogen-phosphorus detector (NPD) for determination of11herbicides in water and soil was developed. This method applied C18solid-phase extraction (SPE) to extract and enrich the herbicides in water samples. A simplified quick, easy, cheap, effective, rugged and safe (QuEChERS) method was optimized toanalyze these11herbicides in soil. The results showed that these11herbicides had good separations within32min when using GC-NPD, and the MDQs for most herbicides were under0.5ng, except for Alachlor and Acetochlor (MDQ=1.5ng). The average recoveries for11herbicides in water were81～116%under the added concentrations of0.5μ.g/L,1μg/L and5μg/L except for the Metribuzin, RSD<6.7%(n=3). When in soil, the average recoveries were75～110.6%under the added concentrations of0.05mg/L,0.5mg/L and1mg/L except for the Hexazinone, RSD<7.3%(n=5).2、The adsorption and desorption behaviors of Ametryne and Metolaehlor on four typical soils were also investigated using the batch equilibration technique. The results showed that the adsorption isotherms for the two drugs in soil were "L" type and fitted well with the Freundlich equation, and the adsorption valve(Kf) for Ametryne and Metolaehlor ranged from2.54～7.58and0.77～4.85, and the time to reach the adsorption equilibrium were4-8h and8-12h, respectively, with the water-soil ratio of1:5. The adsorb capacities of Metolaehlor in the tested four soils followed the order of GuangXi Laibin> AnHui Xiaoxian> GuangXi Fusui> GuangXi Wuming. But for Ametryne, the order was GuangXi Laibin> GuangXi Fusui> GuangXi Wuming> AnHui Xiaoxian. There was a positive correlation between the adsorb capacity of Metolaehlor and the contents of organic matter in soil. For Ametryne, its adsorb capacity had a negative correlation with the contents of organic matter but negative correlation with the pH of the soil.3、Leaching ability is a parameter to evaluate the pesticide contamination to ground water. The leaching characters of Metolaehlor and Ametryne in four soils were examined using column leaching method in order to understand their harm to the environmental water. The mobility speed of Metolaehlor in soils followed the order of AnHui Xiaoxian> GuangXi Wuming> GuangXi Laibin> GuangXi Fusui. This drug belongs to "can be leached" in Anhui Xiao Xian sugarcane soil, belongs to "difficult to be leached" in GuangXi sugarcane soil. The mobility speed of Ametryne in soils followed the order of AnHui Xiaoxian> GuangXi Wuming> GuangXi Fusui> GuangXi Laibin. This drug belongs to "difficult to be leached" in the four types of soils.4、When investigated the environmental water pollution caused by the herbicides in Guangxi province, we found that Atrazine (0.091μg/L,29.2%)、Ametryne (0.018μg/L,8.3%)、Metolaehlor (0.188μg/L,8.3%) could be detected in well-water; Simazine(0.139μg/L,4%)、Atrazine(0.585μg/L,62.5%)、Acetochlor (0.311μg/L,33.3%)、Ametryne (0.341μg/L,58.3%)、Metolaehlor (1.312μg/L,29.2%) and Alachlor (0.088μg/L,4.2%) could be detected in surface water; atrazine (0.127μg/L,14.3%)、 Ametryne (0.037ug/L,7.1%) and Metolaehlor (0.453μg/L,7.1%) could be detected in drinking water.