The Emission Characterization Of PAHs In Urban Atmosphere And Multimedia Fate Simulation In Shanghai

As a set of POPs(Persistent Organic Pollutants),PAHs(Polycyclic Aromatic Hydrocarbons) widely exist in the environment.They can lead to cancer,abnormality and genic mutation,so they are of great concern.Their main human sources are fussil fuel and biomass incompletely combustion.At first,PAHs was emitted into atmosphere,then transfer to water,soil and other medium by wet/dry deposition and diffusion,finally harm for human directly or indirectly.Taking shanghai city as an example,PAHs emission amount in atmosphere have been estimated,then the urban multimedia model has been used to simulate the fate of PAHs in urban multimedia environment and analyze behavior characterization of transfer,transformation and distribution.The PAHs fate in future has been forecasted,which indicate the effect to PAHs fate by the change of urban environmental condition.At last,PAHs ecological risk assessment has been given,providing science bases for urban development and environmental protection.The results have shown that annual emission amount from main source achieved 580.47t in 2000 and 528.659t in 2007,which present a decline trend.Nap and Phe emission amount are the biggest in 16 kinds of PAHs compounds,while high molecular weight compounds emission are smaller.By using MUM,it shown that the organic film achieved very high concentration but held minimal chemical mass,in contrast to soil and sediment,and high persistence were present in sediment,soil and water.The mainly input approach into environment system was emission,while flow output as the main loss.With the ring increasing,the percentage of reaction loss in water,vegetation and soil raise gradually.From atmosphere to vegetation and impervious surface transfer flux was the biggest and transfer flux from impervious surface to water increased with the ring.The results have shown that the concentration of PAHs in TSP ranged from 119.85 to 237.84 ng/m~3,with a mean value of 175.65ng/m~3,which lower than other domestic city,higher than overseas city.The PAHs concentration invarious function areas were closed to each other,and high contents in campus related to around environment.The results of various methods of source identification suggested that,PAHs were predominated by pyrogenic compound and incomplete combustion in campus and resident area,while by wood,coal and biomass incomplete combustion in traffic, industry and business area.The simulation results shown PAHs concentration in atmosphere was157.42 ng/m~3,consistent with the real value.Based on this,PAHs multimedia fate in 2020 has been modeled and the estimated values were lower than that in 2008.The accumulation mass in sediment and soil achieved 80.4t and 64.5t,respectively. Compared with values in 2008,PAHs mass in sediment declined obviously.The transfer behavior comparison between 2008 and 2020 suggested that the film increased the PAHs mobility in system,and the process of surface- or film-air exchange elevated concentration of PAHs in urban surface water,while air-vegetation -soil transfer is one of the most important mechanisms with respect to reducing PAHs mobility in multimedia system.Vegetation played an important role in amelioration the effect of air pollution.Estimated concentration of BaP and BaPE in 2005,2008 and 2020 were all lower than domestic standards,higher than WHO standards.The detected concentration of BaP in TSP was closed to domestic standards in outer cycle and industry area,but concentration of BaPE has exceeded the standards.Concentration of PAHs compounds in soil wsa all lower than soil repair standards,but concentration in film was 10-20 times higher than the standards,with very high ecological risk.For avoiding the pollution of PAHs serious,the main emission reduce approach for coking and oil refining was introducing advanced equipment,improving product technology and harmless working on waste gas.For reducing civil coke combustion emission,decrease the civil coke consumption would be useful.Controlling the number increase of mobile,making reasonable traffic policy and reducing waste gas emission by advanced technology were the useful methods to debase traffic emission of PAHs.Microorganism decomposition,physical-chemical technology and plant restoration can used to remove the PAHs accumulated in soil and sediment.