The Residual Dynamics In Potato And Soil And Absorption Study Of Pendimethalin

In present paper the residue kinetic of pendimethalin in potato and soil as well as the adsorption character of soil were studied ,the samples were extracted with acid-methanol and cleaned up with florisil and were presented by GC-ECD and GC-MS analytic technique.The minimal dose of checkout and the concentration limit were 5×10^-12g and 0.001mg.kg^-1 in GC-ECD analytic technique and 1×10^-11g and 0.001mg.kg^-1 in GC-MS analytic technique. In this paper the addition concentration were 0.01mg.kg^-1,0.1mg.kg^-1 and 1.0mg.kg^-1 . The results showed that the recovery ratio of GC-ECD were 79%¹25.5%(tuber), 78%¹03.5%(plant), 80%⁹2.8%(soil) in 2002 and 71%¹05%(tuber), 75%¹03%(plant), 91.3%¹06%(soil) in 2003 respectively. Well in GC/MS analytic technique, the recovery ratio were 81%⁸7% (tuber), 90%⁹9% (plant), 89.3%⁹8% (soil) in2002 and 76.7%⁹7.7% (tuber), 72%⁹3.7% (plant), 83.7%¹09.3 % (soil) in 2003.The two-year and two-place test results of high dosage 2475g.hm^-2(a.i.) water solution of 33% pendimethalin EC applied pre-emergence in potato soil indicated that pendimethalin had a low residual quantity in potato plant and degraded fast. The residues of pendimethalin in potato plants were 0.024mg.kg^-1 after applied 14d in Changchun and 0.01mg.kg^-1 in Jinan 2002 year, and 0.035mg.kg^-1 after applied 21d in Changchun and 0.09mg.kg^-1 in Jinan 2003 year. There were a great difference of the original deposition between the two places. In Changchun the original deposition were 11.22mg . kg^-1 2002 and 2.98mg . kg^-1 2003, while it is 2.12mg . kg^-1 2002 and 6.96 mg . kg^-1 2003 in Jinan.The dynamic state equation of the pendimethalin degradation of two places in 2002 and2003 were as followed. In the year of 2002 in Changchun, the dynamic state equation is Ct =4.252t^-0.4467, r=-0.9052, and the half-life of pendimethalin T₁/2 is 1.6d, while in Jinan, the equation is C,=1.547t^-0.2041, r=-0.8052, T₁/2 is 3d.In the year of 2003 the dynamic state equation of the two places are Ct =1.7227 t^-0.2318 , r =-0.9495, T₁/2=3.0d and Ct =3.2707t^-0.3734, r=-0.9238, T₁/2=1.8d respectively. the degradation rate were 84% after 90d in changchun 2003 year and 94 % after 75 d in jinan 2003 year.The results showed that pendimethalin is easy to be degraded in potato plants and soil.The authors also determined the final residual concentration of pendimethalin in potato plants, potato tuber and soil. Because the potato tuber is edible before harvest, the assessed of edible test was added in 2003 year. From the results of two years it showed that whatever thehigh dosage and the low dosage water solution of pendimethalin EC applied pre-emergence in soil, the final residual were both under the lowest dosage of the minimal dose of checkout. While there were 0.15mg -kg "'-O^mg ?kg"] 2002 year and 0.15mg -kg ^-O.^mg "kg'] 2003 year in soil. Though the final residual data had two abnormal sections, it was permitted by the measurement error. The results showed that the residual concentration in soil was high, and the degradation rate in soil was slow; but there was no accumulation of pendimethalin residues in soil.According to the research results of the residual dynamics of pendimethalin, the authors suggest that 33% pendimethalin EC applied pre-emergence in potato should be below 1237.5g ? hm ²(a.i.) and be applied only once, and the interval from applying to harvesting is more than 30d.Compwered with the MRL of pendimethalin in potato were O.lmg ? kg '' in American EPA, 0.2mg ? kg"* in Japanese and 0.2mg ? kg A in Korea, in China, the MRL will be O.lmg ? kg "\Comparing these experiment data tested by the GC-ECD and GC-MS analytical technologies it was found that these data were all consistent with each other and the concentration limit were all under the MRLs.The absorption of pendimethalin in different soil was also studied in this paper. The results showed that the absorption of pendimethalin was higher in the high organic substance soil than that in the low organic substance soil. While whatever the pendimethalin will belong to the being easily absorpted herbicides and has a lower risk to the ground water.