Effects Of Cypermethrin On Toxicity And Microbial Degradation Of Chlorella Pyrenoidosa

Pyrethroid insecticides are important to replace the high toxic pcsticide, andapply in agricultural production more and more common. However, the toxicity ofpyrethroid pesticides on non target organisms and residual environmental pollutionproblems caused has received extensive attention at home and abroad in reccnt years.Beta-cypermcthrin, which as the most representative pyrethroid pesticide, plays animportant role in pest control. Several studies have found that, beta-cypermethrin hashigh toxicity to some beneficial insects and fish and other aquatic organisms, but alsohas the immune toxicity, neurotoxicity and developmental toxicity to mammals andhuman. Therefore, the scientific evaluation of hazard degree of beta-cypermethrin onenvironment and seeking solutions to the problem of pesticide residues has becomeparticularly important.Chlorella as the base of food chain and energy flow of water environment, candirectly influence the structure and function of aquatic ecosystem, which has theunique superiority in monitoring and evaluating the water environment. Underlaboratory cultivation, six different concentrations of beta-cypermethrin (0.8mg/L、2.0mg/L、5.0mg/L、12.0mg/L、30.0mg/L) are selected for experimental research.In the pesticide stress, cell growth is inhibited, and the high concentration groupoccurs ’zero growth’ phenomenon after24h culture. In addition, the96h medianeffect concentration (EC50) is4.304mg/L, which belongs to low toxicity.Physiological and biochemical indexes of the algal cell in response to beta-cypcrniet-hrin quickly. At high concentration group, chlorophyll content decrease rapidly atfer12h culture, the ratio of chlorophyll a and b imbalance, and algal cell membranepermeability increase obviously. At the same time, the content of soluble protein andmalondialdehyde of each treatment group ifrst increase and then decrease, show as abell-shaped curve. The results show that, the mechanism of toxicity may be caused bymetabolic enzymes and membrane lipid peroxidation.Paramecium as the base of food chain in aquatic ecosystem, is extremelysensitive to the reaction of toxic substances in water environment, has been the mainexperimental materials of ecotoxicology and environmental quality evaluation ofbiological ideal. The Paramecium was cultured by beta-cypermethrin with differentconcentration gradient, then the mortality, population growth and individual lengthand width were detected. The results showed that, the median lethal concentration(LC50) of beta-cypermethrin to Paramecium was27.536mg/L in1h,95%confidenceinterval was26.290?28.841mg/L. The chronic toxicity experiment indicated that lowconcentration promote population growth, high concentration inhibit. The lowconcentration beta-cypermethrin may have a role of endocrine disrupting chemicalson Paramecium. Paramecium body length and body width were significantly changedin the concentration group (12.0mg/L,20.0mg/L), and its form also become shortand thick. At high concentration group (20.0mg/L), Paramecium body became shortand thick phenomenon was more obvious, and formed a shape of cyst structure.Characteristics of bioremediation have many advantages, such as safety, highefficiency and no pollution, which is an ideal way to solve pesticide residues problem. In accordance with the gradually increasing the concentration of pesticide domesticat?ion method, a fungal strain named XC-01with high beta-cypcrmcthrin degradingcapability was isolated from activated sludge which carried from Longhua sewageplant. According to its morphological characteristic and the results of ITS sequencesanalysis, strain XC-01was identified as Aspergillus versicolor. Using orthogonaldesign method, found that the best level combination was temperature (30°C),inoculation amount (0.4g/L) and pH (7.0). Under the optimized condition, thedegradation rate of beta-cypermethrin run up to79.63%atfer240h treatment, whichas consistent with the orthogonal test variance analysis results (84.07%).