Occurrence,Source Apportionment And Fate Of Suspended Polycyclic Aromatic Hydrocarbons In Surface Water Of Typical Watershed

Polycyclic aromatic hydrocarbons（PAHs）are a kind of persistent organic pollutants widely existing in environmental media.They are carcinogenic,toxic and mutagenic.PAHs have seriously affected the survival of wild animals and threatened human health through the food chain.With the rapid development of industrialization and urbanization,a large amount of energy consumption such as steel,coke,pesticides and chemical industry has led to a significant increase in the concentration of polycyclic aromatic hydrocarbons in surface water.Polycyclic aromatic hydrocarbons have an incalculable negative impact on the ecological environment,and the problem of surface water pollution has become increasingly prominent.Understanding the occurrence characteristics,temporal and spatial variation trend of PAHs,quantitatively identifying its pollution sources,and clarifying its environmental fate are important guarantees to promote the steady improvement of governance work,which is of great significance to improve the scientificity and effectiveness of regional surface water PAHs pollution control and prevention.Taking a typical river in Europe as the research object,this paper analyzes the temporal and spatial variation characteristics of PAHs from 2002 to2016 through Mann-Kendall（M-K）trend test,wavelet analysis and one-way analysis of variance.The diagnostic ratios method and PMF model are used to explore the variation trend of main input sources,and the fugacity model is used to explore the mass distribution characteristics,concentration distribution characteristics,output characteristics and migration characteristics of PAHs in various environmental phases under different scenarios.The influence of parameters on the model results is determined through sensitivity analysis,in order to provide methodological reference for the study of PAHs occurrence,temporal and spatial variation law,input source response mechanism and environmental fate,so as to put forward policy suggestions on PAHs pollution control of regional surface water.The main conclusions are as follows:（1）The pollution characteristics of PAHs in suspended particulate matter in surface water were explored by M-K trend test,wavelet analysis and one-way analysis of variance.The results show that the content of∑₁₆PAHs fluctuated and decreased slowly since 2002.The results of M-K trend test shows that the content of∑₁₆PAHs observed obvious mutation in2010.The temporal variation of PAHs content in suspended particulate matter in surface water in the study area from 2002 to 2016 is mainly controlled by two characteristic time scales:10a（the first main cycle）and 5a（the second main cycle）.One-way analysis of variance showed that the distribution of∑₁₆PAHs was significantly higher in the upstream and midstream than in the downstream（P<0.05）,and the monomer variation coefficients of PAHs were greater than 0.1 and less than 1,belonging to medium variation.（2）The source of PAHs is analyzed by diagnostic ratios method and PMF model,and the uncertainty of the source analysis results of PMF model is analyzed.The source analysis results show that the main input sources of PAHs in suspended particulate matter in surface water are traffic source,biomass combustion source and coal-fired source,and the contribution rates were 40.9%,25.4%and 33.7%,respectively.From 2002 to 2009,the contribution rates of traffic source,biomass combustion source and coal-fired source were53.9%,14.8%and 31.3%,respectively.From 2010 to 2016,the contribution rates of coal-fired source,biomass combustion source and traffic source were 36.1%,35.9%and 28.0%,respectively.Compared with 2002 to 2009,from 2010 to 2016,the contribution rate of traffic source decreased by 25.9%,and the contribution rates of biomass combustion source and coal-fired source increased by 21.1%and 4.8%,respectively.The uncertainty analysis results show that the model results are robust and reliable.（3）The mass distribution characteristics,concentration distribution characteristics,output characteristics and migration characteristics between media of 16 kinds of PAHs in air phase,water phase,soil phase and sediment phase were simulated and analyzed by establishing Level I,II and III fugacity models of environmental multi-media,and the sensitivity of model parameters was explored.The results show that when the monomer PAHs reach a stable equilibrium state in the environmental system,their mass distribution rate in each phase of the environment will maintain a constant,which is independent of whether there is a chemical reaction in the environmental system and the inflow and outflow of substances.When monomer PAHs are directly discharged into the air phase,water phase and soil phase to reach a stable state,the mass fraction,concentration distribution,output characteristics and migration law of each phase in the non-equilibrium environment are quite different.The sensitivity analysis results show that the model input parameters have different effects on the model output results under different emission scenarios of different monomer PAHs.Accurately determining the values of these parameters is beneficial to improve the accuracy of the model results.