The Residual Dynamics In Oilseed And Soil And Adsorption Study Of Clopyralid

Clopyralid is a selective post-emergence herbicide controlling broad-leaved weeds. The determination and degradation of clopyralid in soil and oilseed were studied. The soil samples were macerated with aqueous sodium hydrogen. The slurry was tumbled and centrifuged. The solution phase containing clopyralid was clean up with ethyl acetate. Then an aliquot(15ml) of the ethyl acetate collected was evaporated just to dryness by rotary evaporation at 40 ℃. The HPLC analysis was performed with Zorbax C₁₈ column. Clopyralid was elute with methanol-glacis acetic acid solution mixtures. The plant samples and seeds of oilseed were extracted with aqueous sodium hydrogen to attain clopyralid. And tumbled, centrifuged, finally clean up with silica. The HPLC analysis is the same as the soil. The method was simple. On the level of 0.10-1.0μg/ml,the average recovery of clopyralid in soil ,plant and seed were 77.3%-92.0% , 81.0%-92.0%, 73.0%-75.6%, respectively. The minimum detectable concentration of clopyralid in soil, plant and seeds of oilseed were 0.01mg/kg.The degradation of clopyralid in soil and plant of oilseed were studied by HPLC method and a 2-year field experiment in Jilin province. The soil and plant were treated with clopyralid at 338g(a.i)/hm². Sample the soil and plant at different time to do degradation dynamics analysis. The degradation procedure of clopyralid was correspond to the mathematic pattern, C=C₀e^-kt. In soil, the dynamic equation in 2004 was c=0.3676e^-0.1464t and the half-life was 4.74d, and the dynamic equation in 2005 was c=0.2974e^-0.1841t and half-life was 3.76d. In the plant of oilseed, the dynamic equation in 2004 was c=2.5899e^-0.06852t and the half-life was 10.11d, and the dynamic equation in 2005 was c=1.3292e^-0.08169t and half-life was 8.49d Clopyralid was not detected in soil , plant and seeds of oilseed at harvest. The result showed that clopyralid was dissipated in soil rapidly and the degradation of clopyralid in plant was slowly than in soil.The adsorption and desorption of clopyralid by soil was studied by equilibrium method. Three different soil types were used in the study. Clopyralid solutions(25ml) of different density were added to soil (5g) and were shaker at 25℃,A HPLC method was carried out to detect the clopyralid amount in water after 24 hours. The result showed that the adsorption and desorption of clopyralid were mainly influenced by organic carbon content.