Study On Environmental Behavior And Prediction Methods Of PCBs

Gas-particle partitioning ofPersistent Organic Pollutants (POPs) is an important process,which affects the deposition in water and soil, chemical reactions, long-range transport potential and overall persistence of POPs.This study mainly investigated the environmental behavior and prediction methods of Polychlorinated biphenyls(PCBs), which could provide the theoretical basis and methods for evaluating the fate of PCBs in atmosphere quickly and accurately, and provide methods and theoretical support for the removal of PCBs in water environment.Simulation experiment of partitioning process of PCB52 between the gas phase and simulation particles was studied.The effects of content of organic matter, size and moisture content of simulated particleson the distribution behavior of PCBs were also studied. Adsorption isotherm were builded based on the studyof partitioning process of PCB52 at the temperatures of 10, 30and 40℃, respectively.It was found that Freundlich adsorption isotherm was better to explain the gas-particle partitioning behavior of PCB52 than Langmuir adsorption isotherm.Considering that thetotal sorption of PCB52 was dominated by both absorption into organic matter and adsorption onto surface of particles, a newmodel was builded, which could help describe the gas-particle partitioning behavior of PCB52. PCB52's adsorption onto surface performed more evidently at low temperature than high temperature, and the concentration of PCB52 in particles decreased with the increase of the temperature.Based on the theoretical linear solvation energy relationship, quantum chemical parameters,such as average molecule polarizability(α),dipole(μ),the most positive formal charge on a hydrogen atom inorganic molecule(qH+),the highest occupied orbital energy(EHOMO),the lowest unoccupied orbital energy(ELUMO) and the maximum atom electron density(Qmax),were chosed as the descriptors of model.The QSPRpredicted models on gas-particle patitioning coefficients (1g103Kp)of PCBs in three regions inAthenswere builded according to the experimental concention of PCBs in gas and particles inAthens The estimated capacity, predictability, stability and reliability of three predicted models were examined. The result indicated that three models were reliable and robust.The predicted models of urban center and background area had had better estimated capacity, predictability and stability. Two models could accurately predicated gas-particle patitioning coefficients of PCBs in area whose environmental conditions similar as the experimental data source area.The estimated capacity, predictability and stability of predicted model of the coast area was worst of all. The predicted models were believed to be helpful toexplain the mechanism and influence factors of gas-particle partitioning of PCBs.The degradation behavior of PCB52 in aqueous solution by ultrasound/Fenton process was investigated. And the effects of ultrasonic power, ultrasonic frequency, initial pH values of the solution and dosage of hydrogen peroxide and ferrous ions on the degradation efficiency were studied. The results indicated that the degradation efficiency increased with the decrease of pH value, and the ultrasonic frequency, ultrasonic power, and dosage of hydrogen peroxide and ferrous ions existed optimal values. The degradation of PCB52 in aqueous solution was in conformity with pseudo-first order kinetics. The degradation efficiency of PCB52 in aqueous solution by ultrasound/Fenton process was higher than the degradation efficiency by ultrasound or Fenton reagent alone,92.8% of 70μg/L PCB52 was removed.