Spatiotemporal Multimedia Emission Inventory For Polycyclic Aromatic Hydrocarbons Near Petroleum Production Plants In China Based On A 10’×10’ Grid

Polycyclic aromatic substances(PAHs),a kind of important persistent organic pollutants(POPs),have the long-term persistent,bioconcentration,volatile and highly toxic.Once emitted into the environment system,PAHs could bring a great threat to human health and ecological environment.Research about PAHs have attracted the attention of scientific community and governmental decision-making departments in recent years.The main sources of PAHs are the various combustion processes,such as energy consumption,waste incineration,etc.,and various industrial processes,such as coking,electrolytic aluminum,oil refining,etc.PAHs are also one of the major components of petroleum,and large-scale,high-intensity,long-duration oil exploitation is also the main way for PAHs to enter the environmental system.Therefore,it is instant and necessary to investigate the emission of PAHs in multimedia environment(including time trends and spatial distribution)and the contribution of different emission sources,especially in petroleum production plants,which would be helpful for the region to develop effective PAHs emission reduction measures to reduce the ecological risk of PAHs in environmental media.PAHs emission data and emission factors of Daqing,a typical oil exploration area in China,were collected to build a spatiotemporal model of PAHs emissions to various environmental media.Daqing was divided into 169 10’×10’ grids and these grids were assigned to different land use types to ensure the high spatial resolution of the model.On this basis,the PAHs emission inventory of atmosphere,soil and surface water media in Daqing were built from 1998 to 2013,and the spatiotemporal distribution of PAHs emission in multimedia environment were calculated.The previous results show that most of the PAH emissions in 1998-2013 were to the soil and the atmosphere,at 1.3×106 kg and 1.1×106kg total,respectively.PAH emissions to surface water were 4.5×104 kg in total.Burning biomass,such as straw and wood,was the main source of PAH emissions to the atmosphere even though Daqing is a major center for the petroleum industry.The main source of soil and surface water was the point source of industrial enterprises.PAHs emitted into multimedia environment were dominated by low rings(2 and 3 rings),accounting for more than 70%of total emission.PAH emissions to the atmosphere increased over the 15 years study period,but PAH emissions to soil and surface water decreased in the later part of the study period,especially after 2010.PAH emissions to the atmosphere varied seasonally,and the peak of PAHs emissions occurred in January and then began to decline after spring,when the lowest value occurred between May and August,with a gap about 2.3 times between the highest and the lowest.As for spatial distribution,atmospheric PAH emissions were concentrated in urban areas and around petroleum production plants,but atmospheric PAH emissions were also high in farmland and woodland because of wood and straw combustion.PAH emissions were lowest in wetlands.The spatial distribution of surface water and soil were similar,the highest emission density occurred in downtown lakes and reservoirs.The second high PAH emission densities for emissions to soil and surface water were found in and near urban areas and petroleum production plants.The PAH emission densities was lower in Durbert due to less extensive exploitation activities occur at No.9 plant than at the other production plants.