Study On Immobilized Atrazine Degradation Enzyme Properties And Soil Remediation Effect

Atrazine has been listed in the United Nations Environment Programme （UNEP） as one of28persistent toxic chemical pollutants. It has carcinogenicity, teratogenicity and sex hormoneimbalances biology and ecology toxicity. The harms caused by atrazine to the environment andmany kinds of organisms have attracted much more attentions. Therefore, the research chose theblack soil which had been contaminated by atrazine as the object of study, sodium alginate andPAC as carrier to immobobilize atrazine degrading enzymes. Under the condition of optimized freestate atrazine degrading enzymes to suit immobilized materials, the paper aimed at discussing thebasic degrading properties of immobilized enzymes and the repairing results of contaminated soil.Meanwhile, it also primary evaluated the zoology safety on the process of immobilized enzymesrepairing soil contaminated by atrazine. The main results were listed as follows:The study employed entrapping method to immobilize atrazine degrading enzymes, chosesingle factor analysis method to analyze the effect of concentration of sodium alginate,concentration of PAC, concentration of chitosan, concentration of nickel chloride, pH value, thetemperature of carrier, the volume of enzyme and the volume ratio of sodium alginate and PAC ondegrading results of immobilized degrading enzymes. The study also used principal componentanalysis to analyze the contribution rate of each factor to degradation rate. The results showed thatconcentration of sodium alginate, PAC and nickel chloride, pH, carrier temperature, enzymeconcentration and the ratio of the concentration of sodium alginate and PAC had greater impact ondegrading results of immobobilized atrazine degrading enzymes。The best scheme about the4factors after orthogonal test was A₃B₁C₁D₃: the concentration of sodium alginate was1.75%, theconcentration of PAC was1.4%, pH value was7.5and temperature was29℃. Considering theresults of variance and range analysis, the degrading capability of these4factors ordered assodium alginate> PAC> temperature>pH. The best composition of these materials not onlyshowed fine mechanical strength, but also good tenacity. After removing the weights for a while,the shape of these materials could recover. The results of scanning electron microscope proved thatthe best composition of these materials included mesoporous which benefitted immobilizingbiology molecule and macropore which played a certain role in restricting range.The immobilized enzymes under the condition of experimental simulation showed a greaterremediation effect on the soil polluted by atrazine (the initial atrazine concentration in soil was20 mg kg^-1). After28d’s remediation, the treatment which added immobilized enzymes was almostno atrazine detected. On the contrary, the atrazine concentration in the treatment withoutimmobilized enzymes was still10.13±0.77mg· kg^-1. The results showed that adding immobilizedenzymes into the soil could make the degradation rate of atrazine more faster.The test aimed at preliminary evaluation of zoology safety on the process of immobilizedenzymes repairing soil contaminated by atrazine by considering the three indexes: germ diversityin soil sample, respiratory intensity, active of key soil enzyme. The result showed that at the end ofthe test, soil microbe diversity index in atrazine contaminated treatment （AT） was2.01, lower thanthe index（2.27） of without contaminated treatments which were higher than the indexes ofenzymes＋AT and immobobilized enzymes+AT. The results indicated that degrading enzymes andimmobobilized atrazine degrading enzymes played a certain role in lowering the effect of atrazineon soil germ diversity. During the whole cultivation circle, respiratory intensity of immobobilizedatrazine degrading enzymes＋AT and enzymes＋AT treatment uncontaminated treatment wererising from5.68±0.43mg CO₂g^-1h^-1to6.50±0.11mg CO-2g1,5.41±0.24mg CO₂g^-1h^-1to7.39±0.49mg CO-12g1h-, respectively. Compared with it in uncontaminated treatment, increasingrange of respiratory intensity in these two treatments were lower. The results showed that atrazinehad a stimulating effect on soil microbe respiratory intensity and repairing treatment could ceasethe effect. The result of soil enzymes indicated that during the28days’ cultivation, soil ureaseactivity in uncontaminated treatment was0.4410.019mg g^-1, lower than enzymes+AT and inimmobobilized enzymes+AT. The results proved that free enzyme and immobobilized enzymescould promote soil urease activity. During the first three days, atrazine could activate soilphosphatase activity. With the passing time, atrazine had negative on phosphatase. Atrazine couldactivate soil sucrase activity at the first three days. From the7th day to28th day, all containingatrazine treatments showed the same trend on sucrase: first stimulating then restraining. To sum up,the immbobilized materials and atrazine degrading enzymes the research adopted had no negativeimpact on soil germ activity and soil diversty.