| Pesticide, plastic film mulch, chemical fertilizer and other agrochemicals have widely used in the agricultural production, resulting in the combined organic pollution on the soil. Pesticide has been extensively used as an agricultural means of production, and pesticide residual has been more and more serious in soil. Phthalate acid esters (PAEs) which have widely used in plastic film are a class of environmental endocrine disruptors. PAEs are easily able to migrate into the soil environment during use or disposal. Pesticide and PAEs combined pollution on the soil in our country has existed generally, and biological degradation is an important way to reduce organic pollutants in soil. The fungus which could degrade PAEs and pesticide was isolated from soil. The biodegradation of DBP and fenvalerate in liquid nutrient medium and soil was studied, and the dynamic changes of microorganisms in soil were also studied. The feasibility of the typical organic matter biodegradation in soil was discussed.(1) The fungus strains which could degrade PAEs and pesticide were isolated from the paddy soil by acclimation method with different concentration gradient of3kinds of PAEs and3kinds of pesticides. The PAEs and pesticide content, mycelium weight was detected and degradation effect was studied. The optimum degradation conditions were screened by using orthogonal experiment. The results showed that the degradation effect of PAEs and pesticide by strain DY4was the best, and DY4was identified as Geotrichum sp. The degradation rate of DBP and fenvalerate by strain DY4in liquid were47.97%and42.12%respectively. The optimum conditions determined by orthogonal test and extreme difference analysis were initial concentration of organic matter25mg·L-1, pH value7.5, and degradation without additional carbon source.(2) The degradation of DBP and fenvalerate in liquid and soil by DY4was studied. The results showed that the degradation rate of DBP and fenvalerate in liquid was highest at initial organics concentration of25mg·L-1, reached65.36%and55.77%, respectively, and OD value of fungus liquid was the highest too. The degradation of DBP and fenvalerate with the concentration of50mg·L-1in liquid by DY4conformed to the first-order kinetics model, and the half-life of DBP and fenvalerate was4.46and6.88d respectively. The degradation rate of DBP and fenvalerate was about50%-75%in soil during30days. Most degradation occurred in the first cultivation phase (0～15d). The count of colony was significantly decreased in15d, and recovered obviously in low concentration group but almost no recovered in100mg·L-1concentration group in30d. It is clearly that organic pollutants of high concentration are harmful to the microorganism.(3) The content changes of DBP and fenvalerate, the dynamic changes of fungi and soil basal respiration were studied with indoor simulation experiment. The results showed that the degradation rate of DBP and fenvalerate in inoculation treatment group was higher than that in uninoculated treatment group (the total degradation rate of DBP and fenvalerate with initial concentration of40and100mg·L-1in inoculation treatment group was higher than that in control group with27.01%and16.62%respectively). The ergosterol content and soil basal respiration in all treatment groups reached the lowest value in20d, which indicated the toxicity to the microorganism including fungi by DBP and fenvalerate.Soil basal respiration amount was gradually increased, but no recovery to the initial value after20days. Ergosterol content recovered obviously for adding fungus again in inoculation treatment group. The results indicated that the addition of DY4could enhance the biodegradation efficiency of DBP and fenvalerate in soil, and addition of fungus again in20d could maintain the stability of fungus community. |
PDF Full Text Request