Polycyclic Aromatic Hydrocarbons In Soils Of Yancheng Coastal Wetland:Distribution,Sources And Their Relationship With Environmental Factors

Polycyclic aromatic hydrocarbons（PAHs）are environmental pollutants with carcinogenic,teratogenic,and mutagenic effects.They are commonly found in various environments such as water,atmosphere,and soil.As a transition zone between marine and terrestrial ecosystems,coastal wetlands have a unique geographical location and ecological environment,which makes the sources of PAHs widely available and easy to pass through the food chain,resulting in potential ecological risks.Exploring the distribution characteristics and sources of PAHs in the soil of Yancheng coastal wetland and the influence of environmental factors on PAHs help to reveal the pollution status of Yancheng coastal wetland.This research aims to provide a theoretical basis for the restoration of PAHs contaminated area,thereby providing scientific reference for the ecological restoration and protection of coastal wetlands.Yancheng coastal wetland is selected as the research site,which is divided into a core area and a buffer area according to the intensity of human disturbance.Then the buffer area and the core area were further divided into the buffer mudflat（HCQ-GT）,buffer area-Spartina alterniflora（HCQ-MC）,core area-mudflat（HXQ-GT）,core area-Spartina alterniflora（HXQ-MC）and core area-Scirpus×mariqueter and Phragmites australis（Cav.）Trin.ex Steud（HXQ-BC）according to the dominant vegetation community.A total of 48 sampling point were set up in the five areas.At the same time,each sampling point was divided into 3 soil layers by their depth,respectively 0～20 cm,20～50 cm and 50～100 cm.On this basis,the horizontal and vertical distribution characteristics of soil PAHs in Yancheng coastal wetland were analyzed.Besides,the sources of soil PAHs under different intensity of human disturbance were identified.Meanwhile,the ways of environmental factors affecting the distribution of PAHs were explored.The results were showed as following:（1）The total concentration of 16 PAHs(∑₁₆PAHs)in the surface soil of the coastal wetland in Yancheng ranged from 6.39 to 80.64 ng/g,with an average value of 35.88 ng/g.The concentration of 7 PAHs（∑₇PAHs）which were identified by the International Agency for Research on Cancer（IARC）as having clear carcinogenicity ranged from 0.81 to 30.92 ng/g,with an average of 12.74 ng/g.The average percentage of∑₁₆PAHs was 35.51%.（2）The results of variance analysis indicated that,in terms of horizontal distribution,surface soil PAHs and PAHs with different ring numbers showed significant differences in different areas of the core area,but didn’t show significant differences between the two areas of the buffer area.In the vertical distribution,the concentration of low-ring PAHs was higher in the 0～20 cm soil layer,while the high-ring PAHs tended to be enriched in 50～100 cm in the core area light beach and the Spartina alterniflora area in the core area;the high-ring PAHs tended to be enriched in the 0～20 cm soil layer in the mixed growth area of Scirpus×mariqueter and Phragmites australis（Cav.）Trin.ex Steud.（3）Three source analysis methods,qualitative（eigenratio method）and quantitative（principal component analysis method,positive definite matrix factorization method）were used to analyze the sources of soil PAHs in Yancheng coastal wetland under different intensity of human interference.The result of characteristic ratio analysis showed that the PAHs of the soil in the buffer zone mainly come from the combustion process and oil source,and those of the soil in the core area mainly come from the combustion process.The analysis results of the main composition analysis showed that the main sources of the soil PAHs in the buffer zone are mixed sources,petroleum sources and coal combustion sources;the core area soil PAHs mainly come from automobile exhaust emissions,coal combustion and mixed sources.The results of the positive definite matrix factorization method showed that the PAHs of the soil in the buffer zone mainly come from coal combustion,petroleum sources,industrial production,biomass combustion and automobile exhaust emissions;the soil PAHs in the core area mainly come from coal combustion,automobile exhaust emissions,industrial production and production.Material combustion,including automobile exhaust emissions,was the largest contributor to soil PAHs in the two areas.（4）The results of Pearson correlation analysis,redundancy analysis and multiple linear stepwise regression analysis showed that the buffer zone PAHs had a weak correlation with environmental factors.The soil layers of different depths in the core area Chr,Bb F,Bk F,Ba P,Dah A,Icd P,Bghi P,or 5-ring PAHs,6-ring PAHs,∑₇PAHs generally had relatively strong correlation with environmental factors.Soil organic matter（SOM）,soil particle size（SGS）and soil water content（SWC）regulated each other in the process of affecting the distribution of soil∑₇PAHs in the core area.The results of structural equation modeling showed that the environmental factors had different effects on the distribution of 4-ring PAHs,5-ring PAHs,6-ring PAHs and∑₇PAHs.