Studies On The Translocation And Degradation Of Clomazone In Paddy Soils In Hunan Province

2001 Studies on the Translocation and Degradation of Clomazone in Paddy Soils of Hunan Province Abstracts The adsorption.. translocation and degradation of clomazone in paddy soils of Hunan province were studied in this thesis. Factors controlling the processes and the interaction mechanism were also investigated. The main results were as follows: 1 .The absorption of clomazone in paddy soils gave an approximate fit to the Freundlich empirical equation, the range of R values is from 0.9630 to 0.9990, which indicate the most distinct correlation. Absorption is not proportional to solution concentration with a constant partitioning of clomazone between the solution phase and the sorbent. In the isotherm equation CS~扖eq?~ the range 1/n values, from 0.668 to 0.798, also showed the degree of isotherm nonlinearity. The absorption was mainly influenced by organic matter and clay content, which is positively correlated with Kd values, the R values are 0.7656 and 0.8450.The calculated mean Koc value for four paddy soils was 590. According to classification of mobility of pesticides in soils, we describe clomazone to weak mobility but close to average level. ? 2.Under the control of 208mm rainfall through the four represented unsaturated paddy soil columns during 24h, the soil that had. the maximum amount of clomazone leached out was alluvial sandy paddy soil, than reddish yellow paddy soil, than yellow clayey paddy soil and than purple sandy clayey paddy soil, clomazone was leached, in turn, in quantities of 4.22%, 3.55%, 3.10%, 2.57% of the applied clomazone out of the 20cm cultivated soil layer. Meanwhile, rainfall had a direct effect on the vertical dissipation of clomazone, more rainfall led to more clomazone loss by leaching out of the soil columns. 3.On the basis of a comparison of clomazone fate in sterilized soil and reinoculated soil, results suggest that clomazone degraded more rapidly in nonsterilization soil. The half-lives of clomazone in sterilized soil and reinoculated soil were 25.2d and 5.7d, which indicated that cloniazone degradation was biologically dependent. 4.Various ingredients affected Clomazone degradation. The result showed that temperature.. soil moister content and pH values are the main factors. The degradation became more active to a certain extent with the temperature rising. At 25 centigrade, clomazone was degraded most rapidly. Too high (350C) or too low temperature (5 0C) slowed clomazone degrading. The more soil moisture content, the more rapidly clomazone was degraded. When lime was added to the paddy soil, the pH values was higher and the degradating process was quicken up, which resulted in the less residue of clomazone remained in the soil than the controlled ones. 5.The degradation of clomazone in different soils was not the sante. In this study under stimulated field conditions, the half-life of clomazone in four soils was obtained, ranging from 4 ~iir&~i~ 1:~4~Yi,~3~, 200! ? 5.7 to 22.Odays.Of the soils, purple sandy clayed...