Purification Function Of Herbicides In Xingkai Lake Wetland

Wetland ecosystem could remove excess nutrients and pollutants in the agriculturaldrainage because of its special structural and functional properties, however, these canbe influenced by excessive pesticide input. Acetochlor and butachlor are being usedwidely as herbicide for paddy field and dryland at Xingkai Lake Wetland. consideringthe effect of the wind dispersal and hydraulic connection, the application of pesticideshas risk to xingkai lake wetland ecological environment This thesis has used samplesfrom different points of Xingkai lake area to analyze the two kinds of herbicidescontent and distribution in water and soil in this area, meanwhile, used the method ofsediment capture to quantitatively analyze the purification efficiency for pesticides.Two kinds of herbicide residues were being investigated at different sampling sitesof soil and water in Xingkai Lake are. The results show that the sequence of averageacteochlor residue in the surface soil of different land use types in the xingkai lakearea as following: the dryland> grassland> Calamagrostis angustifolia Kom wetlands(lnlet)> Calamagrostis angustifolia Kom wetlands (outlet)> paddy field> woodland,which shows that acetochlor mainly distributed in the Calamagrostis angustifolia Komwetlands and the dryland, grassland, paddy fields and woodland near its, the mainsource of acetochlor is from the herbicide applicating directly. This result of butaehloris as following: the paddy field> Calamagrostis angustifolia Kom wetlands (lnlet)>Calamagrostis angustifolia Kom wetlands (outlet)> Glyceria spiculosa wetlands>dryland> sand Lake hillock, which shows that butachlor mainly distributed in theCalamagrostis angustifolia Kom wetlands and the dryland, grassland and paddy fieldsnear its, the main source of butaehlor is from the herbicide applicating directly. theaverage acetochlor residue in water in the xingkai lake area is as following: theCalamagrostis angustifolia Kom wetland (lnlet)dryland> large lake> Calamagrostisangustifolia Kom wetland> Glyceria spiculosa wetland> small lake, which showsthat acetochlor is widely distributed in the Calamagrostis angustifolia Kom wetlands,the main source of acetochlor is coming along with the drainage of farmlands runoffinto the Xingkai Lake area.Purification efficiency of two kinds of herbicides was studied though wetland.The result shows that the purification efficiency of Calamagrostis angustifolia Komwetland for butachlor was30%, but for acetochlor was only5%, almost no effect. These showed that the purification efficiency of butachlor is much better than that ofacetochlor to wetland, hence we can use wetlandsto tread butachlor in the drainagefrom farmlands, but not suitable for acetochlor. It analyses the reasons of thepurification efficiency differences between them: theadsorbing power of soil is themain reason. The higher Water-solubility of the pesticide, thestronger mobility inthe soil, howeve, the water-solublity of acetochlor is much higher than that ofbutachlor. So It could be conclused that the mobility of acetochlor is betterr than thatof butachlor, which means butachlor is easier to accumulate in the soil thanacetochlor. This is the main reason for the purification efficiency differences betweenthem. Acetochlor and butachlor are belong to the compound which is not easy tohydrolyze, and non-volatile in the water. These two herbicides are difficult to havephotolysis reaction in water and soil under the sunlight, hence hydrolysis andphotolysis are not the main reason leading to the purification efficiency differencesbetween them.