Based On The Theory Of Steady State Gas/Particle Partitioning In ? Level Multimedia Fugacity Model Study

Multimedia fugacity models address the problems of chemical pollution by comprising a completely quantitative account of the sources,transport processes,fate and sinks of organic chemicals.In this paper,two level III fugacity models are developed and applied in an environmental system containing six compartment,including air,aerosols,soil,water,suspended particulate matters(SPMs),and sediments.The first one is assuming equilibrium between compartments air and aerosols and between water and SPMs.Under this treatment,the fugacities of chemicals in air and aerosol in the atmosphere are assumed identical,and same for those in water and SPMs in the water body,which leads to a six-compartment and four-fugacity model(the four-fugacity model).In the second model,those two assumptions are removed,and all six compartment are treated the same way,leading to a six-compartment and six-fugacity model(the six-fugacity model).After construction of the four-fugacity and six-fugacity models,the simulation accuracy was verified.In this part of the study,polybrominated diphenyl ethers(PBDEs)were selected as target substances of two models,and seven typical congeners were selected: BDE-28,-47,-99,-100,-153,-154 and-209.Taking the entire city of Harbin as a research area,the emission inventory of PBDEs in Harbin was established to account for emissions of seven PBDEs congeners.The predicted results of gas,particle and soil phase from two models compares and verifies the measured results,it is found that six-fugacity model can accurately simulate the concentration of each phase,and there is no difference between the concentration of particle phase and soil phase of four-fugacity model and the measured value.However,the air phase concentration of four-fugacity model is much lower than measured results,and this deviation increases with the increase of bromine generation of PBDEs congeners.The verification results of gas/particle partitioning of two models show that four-fugacity model and six-fugacity model are consistent with the theoretical results of the equilibrium and the steady-state,respectively.For the investigation of influence of ambient temperature and TSP content on prediction results of two models,we solved the fugacity,concentration value and gas/particle and solid/dissolved partitioning parameter of four PBDEs congeners undertemperature range between-40? to 40? by using four-fugacity and six-fugacity models respectively.The results show that gas phase fugacity value and concentration value of six-fugacity model gradually decrease as the temperature decreases,until temperature reaches its second threshold t TH2 in MP threshold,the result of this model remains constant and the particle phase result always decreases with decreasing temperature.But for four-fugacity model,both gas phase and particle phase decrease monotonically as the temperature decreases,and under low temperature conditions,this prediction results are far from actual values.Similarly,we also calculates the fugacity,concentration value and gas/particle and solid/dissolved partitioning parameter of two models in the range of 10?g/m~3 to-500?g/m~3.The results show that the factor TSP have little effect to gas/particle and solid/dissolved partitioning simulated by two models.For the study of four-fugacity and six-fugacity models to simulate environmental behavior of the target compounds,we selected BDE-99 as target substance,and calculated the migration rate of this substance in six-compartment and four-compartment environment system and described its migration behavior completely.By comparing the migration rate between two models,it was found that the migration rate from gas phase to aerosol particle phase,to water phase or to soil phase calculated by four-fugacity model under low temperature conditions is extremely small,which is completely incompatible with truth,so the model cannot accurately describe the migration process between gas and aerosol particles.The migration process simulated by six-fugacity model completely avoids these drawbacks,and this model can accurately simulate migration between each two phase,especially the gas phase and particle phase are described clearly.What's more,it is found that the migration process of gas phase to particle phase is main way that the compound leaving the gas phase.