Simulation Of The Transport And Deposition Of PCDD/Fs In The Atmospheric In Yangtze River Delta Region

Polychlorinated dibenzo-p-dioxins and polychlorinated dibenzo-furans (PCDD/Fs) are toxic persistent organic pollutants (POPs) which have the characteristics of persistent,semi volatile,accumulation and toxicity. They will be harmful to human and other mammals because of their endocrine toxicity,fertility toxicity,reproductive toxicity and carcinogenicity. So people paid more attention to the research of PCDD/Fs. Dioxins occur as by-products in the manufacture of organochlorides, in the incineration of chlorine-containing substances, metal smelting, in the bleaching of paper and other industries. It can be transported by local, regional or even global scales because of the long half-life period. Most of PCDD/Fs are semi-volatile organic compounds that partition between gas and particle phases in the atmosphere. Since the chemical transformation and removal of these POPs in the gas phase differ from that in the particle phase, the partitioning process is a key factor for simulating their fate in the atmosphere.The numerical model of air quality,included Mesoscale Modeling System(MM5),Sparse Matrix Operator Kernel Emissions Modeling System(SMOKE) and Community Multiscale Air Quality Modeling System(CMAQ), was widely used in the world. However, at present nobady had used it for the simulation of PCDD/Fs in domestic. In this work, we used MM5 to provide meteorological data and SMOKE to process the emissions of PCDD/Fs. Then, we used CMAQ regional air quality modeling system which has been modified for PCDD/Fs including the addition of the dual organic matter (OM) absorption and black carbon (BC) adsorption gas/particle partitioning model as well as chemical transformations to simulate the PCDD/Fs concentration distribution and deposition of Yangtze Delta Area for the four seasons(January. April,July and October) of 2006.The atmospheric fate of PCDD/Fs in Yangtze River Delta region was simulated for the four seasons of 2006. The modeling results showed the evidence of long range transport and the regional impacts because of the less depositions in local. The results indicate that the concentration of PCDD/Fs was completely different in four seasons,and in winter the concentration was significantly higher than that in summer in the atmosphere. Because it related to the emissions of PCDD/Fs and the meteorological conditions in local.The wet deposition is the primary deposition pathway of PCDD/Fs. It's four times as the dry deposition. The distribution of isomers of PCDD/Fs indicated the feature of "source". Preliminary comparison with limited measurements has also been conducted. It shows that the modeling results is acceptable in concentration and distribution of isomers, but need further improvement.