Multimedia Environment Modeling Of Polychlorinated Organic Compounds (PCOCs) In Liao-he River Watershed

A dynamic multimedia environment mass balance fugacity model has been developed and applied to assess the fate and transport of the sixteen Polychlorinated Organic Compounds (PCOCs) in Liao-he River Watershed, including ten OrganoChlorine Pesticides (OCPs) and six Polychlorinated Biphenyls (PCBs). The multimedia environment of Liao-he River Watershed is comprised of "unit worlds", which are linearly connected. A unit world is comprised of five environmental compartments or cells (water, sediment, soil, air and vegetation) and a number of sub-cells. The vegetation compartment is divided into crops and forests. In the model, all transport and transformation processes are described using simple first-order kinetics. The rates of these processes are controlled by the physical-chemical properties of the contaminants. The properties, especially vapor pressures, Henry Law's Coefficients, transformation coefficients are profoundly affected by temperature, which are the function of temperature. Besides, the rates are also affected deeply by the environmental factors, such as wind rate, rain rate and river flux. In order to reduce the error with the model input, the environmental factors, notably temperature, wind rate, rain rate and river flux, are introduced into the model, which are dynamically in turn months. The model is solved using Runge-Kutta method.The model parameter results of γ-HCH are as follows. Firstly, the fugacity capacities of γ-HCH are Zq>Zb>Zso>Zsus=Zsed>Zagr>Zfor>Zw>Za in the environmental sub-cells and Z3>Z5>Z2>Z1>Z4 in the cells. Secondly, the fugacity capacities of y-HCH in the environmental media are the function of temperature, which are rising with the falling of temperature. The rising extent is, in turn, air particles, water and other condense phases, air. Finally, because the effect of temperature, river flux and rain to relative rate constants are contrast to that of temperature to fugacity capacities, the change of relative D parameters is in a disorder fashion.The background concentrations or initial values of PCOCs in soil, air and vegetation compartments are unknown. These values are roughly estimated by Level III model at the conditon of the fictitious pollution source. The estimated values of HCHs and DDTs in soil are successfully validated using the field data of adjacent area.The current dynamic Level IV fugacity model has been applied to assess the fate and transport of the sixteen PCOCs in Liao-he River Watershed during ten years. The results show that the field data in Liao-he River and sediment are appropriated in orders with simulated results for most PCOCs. The fugacity and concentrations curves of PCOCs are falling periodically per year when dynamic parameters are introduced. The fluctuation ranges are acutely, which can reach scores of times in one year. This is the effect of the periodical change of the temperature, river flux and rain. Besides, the concentrations of y-HCH in water, sediment, soil, air and vegetation of L01 are in turn decreasing 92.6%, 80.0%, 77.3%, 71.4%and 55.6%.The accumulation and transfer fluxes of environmental cells are as follows. Firstly, they are also falling periodically per year. Secondly, the soil is the greatest source and reservior for PCOCs in the multimedia environment. In the environmental system, the accumulations of y-HCH in soil are beyond 99%, which are the main source of other cells. Thirdly, the exterior import and main export of environmental system are advective input and output of air and water. Finally, the diffusive flux between air and vegetation and transpiration flux are greater than the diffusive flux between air and soil, therefore the mass transfer between soil and air is accelerated by the vegetation compartment.In order to identify influential variables, the sensitivity analysis of model parameters for y-HCH is carried out. The analysis results show that the temperature is the most influential variable to PCOCs concentrations in the environmental system, and other environmental factors, such as wind rate, river flux, compartment height, particles density and so on, are also important influential variables to the related compartments. Besides, the import concentrations of river and air are also essential influential variables in the water or air compartment, which are also affected the adjacent compartments. Finally, the physical-chemistry properties of y-HCH, such as Koc, Henry Law's coefficient etc., are also important influential variables.