Fate Simulation of 2,4,4'-Trichlorobiphenyl in the Bohai Rim Using the Multimedia Model

Abstract

To study the multimedia transfer and fate of polychlorinated biphenyls (PCBs) in the Bohai Rim, we used the BETR-Urban-Rural model to simulate and calculate the concentration distribution, fate distribution, and transfer processes of 2,4,4'-trichlorobiphenyl (PCB28) in nine environmental compartments under a steady-state assumption. The input parameters and output results of the model underwent sensitivity analysis and uncertainty analysis, respectively. The results showed that the simulated concentrations of PCB28 in fresh water, rural soil, urban soil, and sediment could fit the measured concentrations well, thus verifying the reliability of the model. The concentration of PCB28 in urban soil was the highest, and the average concentration was 5.26×10-6 mol·m-3. In contrast, the concentration of PCB28 in rural air was the lowest, and the average concentration was 5.79×10-14 mol·m-3. When the environmental system reached equilibrium, the largest sink of PCB28 in the Bohai Rim was soil, accounting for approximately 96.45% of the total amount remaining in the system. The mutual transfer processes between air and other environmental compartments were the dominant pathways for PCB28 inter-media transport in the Bohai Rim. Most PCB28 entering the Bohai Sea was transferred by airflow, and the fluxes from rural air to coastal water accounted for approximately 97.22% of the total fluxes of PCB28 entering the sea. According to the result of sensitivity analysis, the emission rates, grid dimensions, and transport velocity were the key parameters affecting the model output. Uncertainty analysis showed that the distributions of PCB28 concentrations in rural air and urban air fitted well with lognormal distributions, and the coefficients of variances (CVs) were 0.44 and 0.41, respectively.