Effect Of Environmental Behaviors Of Nanoscale Copper Oxide On Plants And Microbial Comunities

With the rapid development of nano metal materials,they get increasingly renovation causing its emergence in daily life.Nano CuO has extensive applications in catalysis,sensing and other industrial fields,in addition,it is used to be a kind of additive of pesticides or nutrients in the agricultural chemicals market.In the process of production,transportation and application,it will inevitably release into the soil climate.Its complicated chemical,physical and biological reactions with various components in soil make it migrate and transform in the environment causing a certain impact on the original soil ecosystem,producing toxic effects on microorganisms and plants and threatening environmental ecosystem and human health indirectly or directly.Therefore,it is quite meaningful to analyze the environmental behavior and toxicity mechanism of nano CuO particles,and to properly evaluate the harm to the environmental ecosystem and human health.In this study,nano CuO particles and CuSO4 were added into soil to simulate soil heavy metal pollution.Taking corn as a model plant and traditional heavy metal ion pollution as a comparison,this research explores the morphological distribution of nano CuO and its impact on soil p H,and clear the impact of environmental behavior of nano CuO in farmland soil on plant growth,physiological indexes and the heavy metals distribution in plant.Furthermore,in situ zymography was used to investigate temporal and spatial distribution of enzyme activity in rhizosphere under the addition of nano CuO.It can provide the basis for the release characteristics of nano CuO particles into the soil and plant stress.In order to understand the influence of nano CuO particles on soil ecoenvironment system comprehensively,we regard the soil microorganism as experimental object to investigate the change of soil enzyme activity and various microbial indexes under the stress of nano CuO particles and its influence on the structure and diversity of microbial community.The results were list as following:(1)The morphology of nano CuO particles in soil is different from traditional copper ions.With the addition of nano CuO,Cu mainly exist in reducible form which is twice than the soil with CuSO4.Then the oxidizable Cu is 5 times higher than that of CuSO4 treatment group,while the exchangeable Cu is one fifth.This is the main reason why nano CuO is low toxicity.The nano CuO gradually releases Cu ions in the soil,the soil p H is negatively correlated with exchangeable Cu,therefore,the p H decrease gradually after nano CuO addition.Nano CuO particles can inhibit the activities of Nacetyl-glucosaminidase and ?-glucosidase in rhizosphere,but it will be reflected in the later stage of plant growth.The resistance of ?-glucosidase activity to nano CuO is weaker compare with N-acetyl-glucosaminidase,however,nano CuO particles have no effect on phosphatase activity of Plant Rhizosphere.(2)The soil respiration rate and soil microbial biomass carbon under nano CuO treated were significantly higher than those of CuSO4 control group,and both of them have a significant negative correlation with available Cu.It shows that the toxic effect of CuO particles is less than CuSO4,which has little effect on the number and activity of microorganisms and has stable organic matter accumulation to support the growth and reproduction of microorganisms.The mineralization coefficient and soil microbial quotient of nano CuO group were higher than those of CuSO4 group,indicating that nano CuO had less inhibition on soil carbon mineralization and less disturbance on soil properties,composition structure and material content.(3)The activity of N-acetyl-glucosaminidase in soil was positively correlated with the content of Cu extracted by DTPA,and it was stimulated by copper ion.However,when the available copper in soil exceeds the limit of microbial tolerance,N-acetylglucosaminidase activity will decrease.?-glucosidase activity did not respond to nano CuO stress.Phosphatase activity has resistance to a moderate Cu concentration.Under the slow-release effect of nano CuO,the initial soil phosphatase has resistance to the stress in low Cu concentration and when the concentration increases,the activity of soil phosphatase activity will decrease.(4)Compared with CuSO4,CuO particles had less turbulence on soil microbial community structure and diversity.At the same total copper concentration,the toxicity of CuO towards plants and microorganisms is much smaller than that of CuSO4.Copper in soil treated by nano CuO mainly accumulates in plant roots rather than on the ground,indicating its poor transport capacity and less threat to human health via food chain.Compared with soluble copper salts Bactericide,the application of nano CuO in agriculture has potential advantages.