Study On Mechanism Model Of Combined Pollution Among Heavy Metals And Pesticides In River Sediments

In recent years, emissions and volume of heavy metals and organic pesticides in the environment are increasing along with the rapid development of agriculture and industry. Because of pesticides’s characteristics of high toxicity, emissions from large, wide influence range, they have become an important pollutants in water environment. The pollution of heavy metals to the environment catches people’s eyes widely, their pollution prevention and control has been included in the "12th Five-Year" special planning. Copper and cadmium are two different types of typical heavy metal pollutants. In recent years, many public events about contaminated soil or sediment occurred in our country are associated with heavy metals. Atrazine and malathionis widely used in corn and vegetables in northeast China, and the pesticides can be applied to the soil by rainfall, runoff, and other ways to enter the rivers, lakes and other water bodies, resulting in the contamination of surface water. The harm of these two types of pollutants on the environment and human health has become prominent day by day. They always co-exist in the environment and produce a composite effect, and could significantly alter the physiological activity or toxic of one or some of the pollutants. They will cause serious damage to human health and aquatic ecosystems. As sources and sinks of many pollutants in the water environment, sediments play a significant role in the release and migration behavior of pollutants in the water environment. The composite pollution process in sediment is usually influenced by many factors, including external factors (such as environmental conditions) and internal factors (adsorbate such as sediment components, and adsorbents such as coexisted pollutants). The impact of various factors affecting the composite pollution is a process of comprehensive roles. It might presents increasingly influent relationship among the factors. Therefore, it is important to study the composite adsorption mechanism of heavy metals and organic pollutants in sediment, to clear contribution and mutual relations of each factor in the process of combined pollution. This study will be benefit for understanding the theoretical significance of composite ecological restoration in polluted rivers contaminanted by heavy metals and pesticides.In this paper, mechanism of combined pollution among heavy metals (cadmium, copper) and pesticides (atrazine, malathion) in river sediments-water system were investigated. Effect of different types of influencing factors on the process of combined pollution and their relationship were studied from different angles, mainly including:(1) artificial neural networks, multiple nonlinear regression and central composite experimental design were used to simulate the adsorption process of pollutants. The established BP models have been proven to have good predictive ability and accuracy, and the regression models have all passed the test of significance and goodness of fit test. This paper established an adsorption mechanism for prediction model, we also use a complex system to clear on the adsorption of atrazine adsorption mechanism of the establishment of the model discussed in atrazine under different conditionsthe strength and type of interaction effects of heavy metals from different coexisting;(2) Effect of different environmental factors (including temperature, pH, ion strength and aeration intensity) on combined pollution among pesticides and heavy metals were investigated. Artificial neural networks, multiple nonlinear regression and factorial experimental design were used to build a model to describe the relationship among environmental factors and atrazine adsorption. Interaction among co-exsited pollutants and environmental factors was also described by this model;(3) Interval programming was introduced into the adsorption process model. It is assumed that the cases were the subject for examination of the sediment components content as well as environmental factors, and the adsorption process model was established based on conditions of uncertainty. Relationship between sediment major components and the adsorption amount of pollutants was determined derived by the model and scope of atrazine maximum adsorption capacity in the two cases were educed by optimizing the models so that the ecological risk of atrazine could be evaluated, and the evaluated results showed that ecological risk of atrazine to aquatic organisms was not signifisant;(4) Considering effect of different types of influencing factors on combined pollution, the structural equation model which could reflect the interaction among various factors was established, and the role of factors were obtained. Comprehensive model can examine the combined pollution process, the role of external factors (environmental factors) and internal factors (adsorbent sediment (components) and adsorbate (coexistence pollutants) combined pollution process. The main role on atrazine adsorption of coexisted pollutants lies in sediments compounds, and environmental conditions on atrazine is much larger than the direct effect of the sediment fractions. This paper surposed corresponding constructive comments and countermeasures on combined pollution repair, weakening the impact of the combined pollution.