Studies On The Persistence Of Hexaflumuron In Haleyard Environment And Its Effects On Several Biological Indicators In Soil

Pesticide hexaflumuron is being popularized to use all over the world today, but availableinformation about its residual analysis and effects on biological indicators are rarely. Thedegradation and residual behavior of hexaflumuron in cabbage garden were investigated inChangsha and Tianjin. In order to comprehensively evaluate environmental security ofhexaflumuron and for its reasonable application and ecological environmental restoration, thedegradation dynamics of hexaflumuron in soil and its effects on urease, polyphendoxidase,catalase in soil and soil respiration were studied under various controlled conditions bystimulating methods in lab. The main conclusions obtained were listed as follows.The analysis methods of hexaflumuron in cabbage and soil were investigated. The resultsshowed: (1)A new analytical method for determining residues of hexaflumuron in cabbage andsoil was established. The quantification of the pesticide was measured by HPLC with a C₁₈column, a mixture of methanol plus water(73/27) as mobile phase, detection of UV wave length at215 nm.(2)The results showed that the average recoveries of the method in soil and cabbageranged from 80.05%～105.16% and 80.63%～98.34%, coefficient of variation was rangedfrom 1.17%～7.98 %.The minimum detectable limits in cabbage and soil were 2.36×10^-9 g. Theparameters such as accuracy, sensitivity, precision for the method were good to satisfy theessential rules of pesticide residue determination. (3)A series experiments to choose extract, theelution liquid and the sorbent in preceding process to establish clean-up method. Methanol as soilextraction, dichloromethane(with a little acetone) as cabbage extraction, dichloromethane andwater as the elution liquid, florisil as the sorbent were determined finally.In order to make up the standards for safe using of hexaflumuron on cabbage, an experimentwas conducted to study the residual dynamics of hexaflumuron in cabbage and soil in Changshaand Tianjin, doses 2400～3600 g·hm^-2 hexaflumuron 5% EC, respectively. The results showedthat the half-life of hexaflumuron in cabbage and soil at Changsha and Tianjin were 5.00 d, 4.48 dand 6.10 d, 5.47 d; The cabbage was sprayed three times with hexaflumuron 5% EC using thedoses 3600 g·hm², it was found that the final residues in cabbage and soil at Changsha andTianjin was 0.178 mg·kg^-1, 0.246 mg·kg^-1 and 0.218 mg·kg^-1, 0.254 mg·kg^-1, at 7 days lastapplication, respectively. Residues of effective components stated above were lower than MRL,which can be ensured edible safety of cabbages.Effects of environmental conditions and microbes on degradation of hexaflumuron alsostudied by simulation in laboratory. Results show that biodegradation of hexaflumuron played aleading role, with its rate positively related to temperature and moisture content but inversecor-relation with initial concentration of hexaflumuron.Effects of hexaflumuron on the activity of urease, polyphendoxidase and catalase was measured. Under controlled condition, the soil sample was incubated in laboratory for 1, 3, 5, 7, 14,21, 28 days, then testing their activity of soil enzyme. In the experiment, hexaflumuron treatingconcentration with four levels. The results as follows(1)Effects of hexaflumuron on urease in soildisplayed that 10.080 mg/kg treatment was inhibited during the incubation period, 5.040 mg/kgtreatment was inhibited at first then stimulated, while 0.504 mg/kg treatment was stimulated atfirst, then went similary with CK.(2) The effects of hexaflumuron on polyphendoxidase activitywas complicating. In generally, with the increasing concentration of hexaflumuron, the inhibitionrate of polyphendoxidase was increased. The polyphendoxidase activity in low concentrationtreatment was inhibited until 14 days, after that day come similarity with CK. While the highconcentration was inhibited from the first to 21st day, stimulated from the 21st day to 28th day.(3)Effects of hexaflumuron on catalase activity in soil displayed an character of"inhibition→activation→re-inhibition→returning to check", while 10.080 mg/kg treatmentdisplayed an character of"inhibition→activation→re-inhibition".Hexaflumuron also had some effects on soil respiration, the higher concentration, thegreater influence in the early days. But as time goes by, restrain turns to stimulate gradually, andafter 11 days the respiration of using hexaflumuron treatment and CK soil came consistent.Through statistical analysis, the result showed that hexaflumuron is a low toxicity or non-realharm pesticide.