Study On Combined Pollution Of Heavy Metals And Organic Pollutants In River Sediments

A variety of anthropogenic emissions of pollutants are present in natural water environment. Pesticides become a common class of important pollutants in water environment because of their heavy toxicity, high environmental release rate, and wide influence range. In the past20years, the types and use of pesticides are increasing. In northeast China, atrazine and malathion are widely applied pesticides for corns and vegetables. Pesticides applied to soil could enter rivers, lakes and other water bodies through rainfall, runoff and other means, causing surface water pollution. Heavy metals are also a kind of pollutants which are widely present in natural water and surficial sediments. They will combine with pesticides and affect the adsorption, desorption and degradation behaviors of pesticides in sediments. Therefore, it is important to study the adsorption, desorption and degradation behaviors of heavy metals and pesticides in sediments. This study will be benefit for understanding the transport and transformation, toxicity, and ecological restoration of complex pollutants in natural water environment.In this paper, various environmental behaviors of pesticides (atrazine, malathion etc), including adsorption, desorption and toxicity, were investigated in the presence of toxic heavy metals (lead, cadmium, copper, zinc etc) in river sediments-water system. Combined effects of two types of pollutants were studied from different angles, including:(1) various types of sediment samples were collected to study the thermodynamic adsorption characteristics of different types of pesticides on them. Influence of the active components and physical and chemical properties of sediments samples on pesticides adsorption process were analyzed, and the regression models of the six pesticides and main factors in sediments were also established;(2) typical pesticides and heavy metals were selected, and then adsorption of pullutans in sediments were investigated in different complex systems, including differents heavy metals, pesticides or heavy metals and pesticides co-exsited. The strengh of the adsorption capacity of each pollutant and types of interaction among pollutants are obtained in the different complex systems;(3) we selected luminescent bacteria as a typical aquatic micro-organisms, joint toxic effects of luminescence bacteria from pesticides and heavy metals were observed and the mechanism of the roles was discussed to obtain the relationship between the combined toxicity and pollutants concentrations via analysis of variance and multiple linear regression;(4) artificial neural networks, factorial experimental design and multiple linear regression and other mathematical means were used to simulate the process that the single adsorption of atrazine on the sediments, the adsorption of atrazine in the presence of heavy metals Cu2+and Cd2+. A certain models of the adsorption mechanism were established for forecasting, and we have also used the establied model of atrazine under different conditions to discuss the adsorption mechanism in the different complex systems, in order to clear the strength and types of effect on adsorption of atrazine from different coexisting heavy metals.