Pollution Characteristics Of Heavy Metals And Polycyclic Aromatic Hydrocarbons In The Surface Sediments Of Liaohe River Main Stream

Liaohe River is the mother river of Liaoning.Together with the Yangtze River,Yellow River,Huaihe River,Haihe River,Zhujiang River and Songhua River,Liaohe River is a part of the seven major water systems in China,that has a drainage area of201600 square kilometers and plays an important part in regulating the surrounding ecological environment.In 2010,Liaohe River Protection Area was established,and technical measures of natural closure,farmland abandonment and returning farmland to grass were implemented on both sides of the river,which effectively protected the river ecological environment.In this study,24 sediment sampling sections of Liaohe River’s surface sediment were taken as the research objects.After 8 years,the pollution level,spatial distribution characteristics and sources of heavy metals and PAHs of Liaohe River were analyzed,after that,the ecological risks were evaluated to clarify the pollution status and trend of Liaohe River.Our result will provide a strong evidence on water and ecological environment remediation.The results showed as follow:（1）The spatial distribution of 7 kinds of heavy metal（CD,Ni,Cu,as,Cr,Zn,Pb）in the sediment of the Liaohe River is significantly different.Compared with the initial stage of enclosure,the content of them is decreases.The average value is As-6.77 mg·kg^-1、Cd-0.087mg·kg^-1、Cr-35.88mg·kg^-1、Cu-12.48mg·kg^-1、Ni-15.29mg·kg^-1、Pb-17.05mg·kg^-1、Zn-31.725mg·kg^-1.Compared with the initial stage of closure,the pollution degree decreased.And then Through the enrichment coefficient analysis,we clear that the source of Pb is mainly affected by human activities,and the other six heavy metals are mainly organic sources.（2）In the surface sediments of Liaohe River,PAHs pollution level is higher than that of other rivers,which is mainly PAHs with high ring number（accounting for more than 60%）,the average content is 2786.44ng·g^-1,and the range is3058.38-2636.67ng·g^-1.The difference of low-rings PAHs was significant.The pollution sources of PAHs are complicated,and the sources of PAHs in each section mainly include oil,plant coal and fossil fuel.（3）Pearson correlation analysis showed that the correlation between heavy metals,clay and gravel was significant,PAHs and organic matter of river sediment were significant,which indicated that the two pollutants might be adsorbed separately,which provided the basis for the subsequent study of Liaohe River ecological remediation.（4）Using the Land Accumulation Index Method to evaluate the ecological risk of heavy metals,it is found that as and Cd in L20 section（Lengdong Bridge）are polluted;using the Ecological Risk Index Method to evaluate,it is found that Cr,Cu,Ni,Pb,Zn are low risks,while Cd and as contribute a lot to the potential risk of heavy metals,and the heavy metals in the surface sediments of the main stream of Liaohe River protection area are in the low risk level as a whole.（5）The ecological risk of PAH was evaluated by the method of Median Quotient and the Method of Middle and Low value of the effective interval.It was found that AnT,FLuA,Pyr,Chr,BKF in the surface sediment of Liaohe Nature Reserve were less likely to have biological harmful events,while ANA,DbA,BbF,BaP were more likely to have biological harmful events.We should follow closely the accumulation and accumulation of these four substances Potential risks.