Two Termiticides Soil Behavior And Pollution Potential,

Chlorpyrifos and fenvalerate are among the 6 preventive termiticides recommended by Chinese Society of House Property. Furthermore, chlorpyrifos is the main termiticide within China, and fenvalerate is the most frequently used termiticide nowadays in Zhejiang province (including Ningbo). For this concern chlorpyrifos and fenvalerate were selected as test chemicals, and 3 kinds of regionally representative soil, namely Dongqianhu, Xiangshan, Qingling, were used as test media. Soil behavior, such as adsorption, degradation, mobility, and so on, of the two termiticides, was investigated. Purpose of present study is to predict efficacy of the two termiticide for termite control. The present study also head for predicting potential for ground water contamination results from field application of the two termiticides.Adsorption tests indicated that among the 3 soils, the Xiangshan showed the strongest adsorption towards the two termiticide, with adsorption rates of 94.8% and 86.4%, respectively, for chlorpyrifos and fenvalerate, while the Dongqianhu displayed a weak adsorption towards the two termiticides, with adsorption rates of 82.6% and 60.4%, respectively. Adsorption rates of Qingling were in middle of the 3 soil, i.e., 94.8% and 86.4%, respectively, for chlorpyrifos andfenvalerate. Compared with fenvalerate, chlorpyrifos had stronger affinity towards the 3 kinds of soil.The degradation experiments indicated that half life of chlorpyrifos was 494d, 260d, and 314d, representatively in sterilized Dongqianhu, Xiangshan, and Qingiing, while half life of fenvalerate was 831 d, 504d, and 825d, representatively in above 3 soils. In comparison with chlorpyrifos, fenvalerate had a longer half life in sterilized soils. Sterilization had obvious effects on half life of the two termiticides.The soil thin layer chromatograph indicated that remove factor (Rf) of chlorpyrifos was 0.277 s 0.217 > 0.149 for Dongqianhu, Qingiing, and Xiangshan, respectively, while Rf of fenvalerate was 0.164 > 0.124 > 0.108 for above 3 soils. From the point of view of Rf, chlorpyrifos and fenvalerate can be classified as low mobility. Compared with result of adsorption test, order of mobility of each termiticide in 3 soils reversely accorded with that of rate of adsorption, while it worthies notice that mobility of chlorpyrifos in all the 3 kinds of soil was higher than that in fenvalerate. This result was just the reversion of that predicted by the adsorption test.Taking organic matter content (X^, pH value (X2), percentage content of particles of <16.18um (X3), cation exchange capacity (X4)as independent variables, and taking Rfas dependent variable, a series of linear regressive equations were established. Comparing the calculated Rfwith the tested value, it is able to see that mobility of chlorpyrifos in natural soils can be better predicted by equation Y=0.197-0.034X1+10-4X4. As for fenvalerate equation Y=0.166-0.032X^10"% gives a better prediction.Soil water was collected at 40~45cm below the surface after a field application of chlorpyrifos and fenvalerate at practical rate. Residue of chlorpyrifos in soil water was measured in range of 0.00246~0.0147mg/L, while concentration of fenvalerate in soil water was detected from below test limit, i.e., =sO.OO7mg/L to 0.163mg/L...