Pyrethroids Pesticides Residues And Thier Behavior In A Multimedium Environment Of Liangtan River Basin

With the wide use of pyrethroids pesticides, in recent years, there were manyresearches about pyrethroids such as their reproductive and nerve toxicity and foundthat they can interfere body’s endocrine function. Pyrethroids were considered by manyresearchers as a kind of environmental endocrine disruptors(EDCs).The study ofpyrethroids residues level in a multimedia environment and the environmental behaviorsuch as migration, transformation and advection can provide the basis to understandtheir final destination in the environment leading to environment safety evaluation. Thestudy also has an important theoretical significance for pesticide pollution preventionand environmental management countermeasuresLiangtan river basin is the important production base for food, vegetables, oilsandsilkworm cocoon of Chongqing. Farming, forestry, animal husbandry and the thirdindustry was developed. Basin belongs to the shallow hill landscape, has a largefarmland. The total area was491.27km2and the agriculturalarea was207.54km2.Determination of pyrethroids residues level of Liangtan river watershed,simulation of its environmental behavior and risk assessment have a certain practicalsignificance to evaluate the toxicity and pollution conditions of small watershed inThree Gorges Reservoir and formulate corresponding countermeasures.In this thesis, on the basis of establishing the test method of pyrethroids, thepyrethroids residues characteristics in water, soil and sediment of Liangtan River,chemical behavior in a multimedia environment and the risk assessment for theirpollution were studied. Finally, the related countermeasures of pesticides environmentalmanagement in China were proposed.A liquid-liquid/oscillation extraction-gas chromatography detection method forpyrethroids was established in this thesis. Good linear relationships was found for sevenpyrethroids, the R2≥0.9990. The Method Detection Limit(MDL) for water samples was1.91-4.31ppt, the spiked recovery was95.62-99.0%; The MDL for soil(sediment)samples was0.1249-0.1715ppb, the spiked recovery was76.18-80.74%. The sensitivity,recovery, accuracy can meet the requirements for pyrethroids analysis in environmentalsamples.In water samples, Fenpropathrin and Permethrin, the detection rates (88.9%and77.8%) and mean concentrations (55.68ng/L and29.02ng/L) were the highest; for Cyfluthrin, the detection rates (22.2%) was the lowest and in some water samplespyrethroid were below the detection limit. The variation of pyrethroids in the watersamples was studied. The pesticide concentrations in October were sigificantly higherthan that in January of the next year. Spatial variation trend was in the following order:the right branch> left branch> after confluence, and the concentrations of pesticides inPJG, JF, TCWQ and TSQ were higher than other sampling sites.In agriculture soil samples, Lambda-cyhalothrin and Permethrin, the detection rates(all100%) and their mean concentrations (104.75ng/g and22.69ng/g) were highest. ForCyfluthrin, the detection rates (71.1%) and mean concentration (0.98ng/g) were thelowest. Time variation trend of pyrethroids in the soil samples was different from that ofwater samples: Their concentrations in January were slightly higher than in October.The changeability of pesticides composition ratios in right branch and TZ area was notsignificant while in left branch was significant. TCWQ site was seriously polluted bypyrethroids. Due to the urbanization, farmland into barren land, the concentration ofpyrethroids in ZJ site was the lowest.In sediment samples, the detection method was similar to that of soil samples. Theconcentrations in pyrethroids found to be as follow, Fenpropathrin got the first positionwith the mean value of44.59ng/g; the second was Permethrin with the mean value of15.68ng/g; the lowest was Fenvalerate with average value of2.78ng/g. The order wasdifferent from that of water and soil samples. The concentrations of pyrethroids insediment samples in October were higher than that in January, similar to the watersamples, but the changeability extent was smaller than that of water samples. Spatially,the pollution in TSQ, TCWQ and PJG sites were more serious, on the other hand TZ1site was slightly polluted.The pollution levels of pyrethroids in Liangtan river basin were compared withother regions’, found that pyrethroids residue level is higher, some measures should betakenThe behavior and fate of priority pyrethroid (Permethrin) in multimediaenvironment has been also modeled using EQC model. The results indicated that, themain repository of Permethrin in equilibrium state was the soil. In non equilibrium state,it was soil and sediment, and the proportion in the sediment phase was higher than it insoil phase. In the equilibrium state system, the main output mechanism of Permethrinwas degradation in soil; while in the nonequilibrium state system, the output was notonly by degradation in soil, also by degradation in sediment and advection migration. The total residence time of permethrin in the environment was controlled bydegradation reaction. The main intermedium transport process of Permethrin was thediffusion and deposition from water to sediment, the migration from air to soil.The risk to aquatic organisms of pyrethroids in Liangtan river water and sedimentwas also assessed. For water body, Cypermethrin was within the allowable limit, theover-limit ratio of Deltamethrin was61.11%related to the LC50of fish and fleas andEC50of molluscs. However, if related to NEC of mollusks, the over-limit ratio ofCypermethrin was11.11%. For sediment, all pyrethroids were excessive related to theLC50of Hyalella azteca; and the over-limit ratio of pyrethroids was less related to theLC50of Chironomidae, indicating that the Hyalella azteca was more sensitive topyrethroids than Chironomidae. These results showed that the pyrethroids pollution inLiangtan River was toxic to aquatic organisms.