Security Analysis of Residual Bifenthrin in Tea Plantation

To investigate the final residues and dynamic degradation of bifenthrin sprayed on Fuyun6,Jinguanyin,Tieguanyinand Shuixian(Camellia sinensis),a security analysis of residual bifenthrin in different tea plantation(Fu′an,Anxi and Wuyishan)was carried out after 1000-4000times of 2.5% bifenthrin was air-dried or 1,3,5,7,10,15days after spraying.Our results showed that the recovery rates of bifenthrin were over 93.9% and the original residues declined with diluted times of the pesticides.Meanwhile,higher residual contents was found in the Fu′an green teas in autumn of the year 2003,and there were no significant differences in the original residues in different tea varieties at different seasons.The average original residual amounts in the same tea varieties between different seasons was decreased with negative correlation to higher temperature after spraying with 1000-4000times of 2.5% bifenthrin.Dynamic degradation of bifenthrin was coincided with first-order kinetic equation.Furthermore,the average residue half life after treatment was 4.22days and there was no significant difference among the four kinds of tea varieties cultivated in Fu′an,Anxi and Wuyishan.There were significant differences among tea varities at the same seasons in different regions,and the the longest was 8.48days in Anxi autumn tea,However,the residue half life in the same climatic conditions of Fu′an were 2.19and 6.16days for oolong teas and green teas,suggesting that there were no significant differences between seasons but significant differences between two tea varieties.The average temperature,relative humidity and rainfall did not show a statistically significant correlation with the residue half life during the test period.The original residues resulted from 1000-4000times of 2.5% bifenthrin was less than 3.5mg/kg,which made a relatively low risk of exceeding criterion.