| Located in the north of the Luanhe River estuary,the Qilihai Lagoon,one of the most important modern wetlands,has extremely rich soil,biological and tourism resources.In areas where the ocean and land are connected,it is highly susceptible to unreasonable development and utilization by humans,which in turn leads to a decline in lagoon area,deterioration of water quality and degradation of ecosystem functions.In addition,heavy metal pollution caused by human activity is particularly worthy of attention.Once the heavy metal enters the environment in the form of a compound state,it is difficult to be degraded by natural organisms,and it is accompanied by the accumulation of the biological chain multiple times,causing the discomfort of the organism.Therefore,the study of the Qilihai Lagoon is of great significance.Based on the current environmental conditions,the contents of heavy metals,the speciation of various metals,particle size,nutrients and organic matterin in the sediments of Qilihai Lagoon were discussed in this paper by using a large amount of sampling data.And the pollution and risk of heavy metals in the study area were also understood simply.In addition,the data of heavy metals were used to carry out the correlation and cluster analysis about the sources by using SPSS19.0.And finally,in the Sufer10.0 and Origin8.0 software groups,the contents,spatial distribution and risk levels of heavy metals were simply illustrated by a variety of chart presentation methods.The main results are as follows:?1?In Qilihai surface sediments,the content mean of Cr,Ni,Cu,Zn,Pb and Cd were87.29,20.71,59.40,103.91,20.16 and 0.52 mg·kg-1,respectively.From the concentration point of view,the accumulation level of various metal elements,fixed in the sediment through a variety of paths,also shows differences,and their trend are in the descending order of Zn>Cr>Cu>Ni>Pb>Cd.From the spatial point of view,the four elements Cr,Cu,Zn and Cd show a relatively consistent trend,while,the distribution of the Ni and Pb have difference compared with other heavy metal.It was attributed the influence of organic matter and particle size.In addition,it plays an important ports that the discharge of land-based materials from domestic sewage an trash and the residual bait of fish and shrimp excreta during the breeding process.?2?The heavy metal of Cr,Ni,Cu,Zn,Pb and Cd in the surface sediments of the Qilihai were mainly present in the residual state,but the other forms occupied different proportions of the total gravity.In the secondary phase,Cr and Ni were dominated by the oxidizable fraction;Cu,Pb and Zn were dominated by the reducible fraction and Cd was dominated by the acid extractable fraction,respectively.Through the bioavailability of heavy metals,Six heavy metals were in the descending order of Pb>Cd>Ni>Cu>Zn>Cr.In the whole sampling site of the study area,11#sampling site has great potential ecological hazard,so it is necessary to strengthen the monitoring of the ecological environment quality in this site and the nearby area.?3?The correlation analysis showed that Cr,Cu,Zn,Pb,Ni and Cd elements are less affected by particle size and organic matter.Elements Cr,Ni,Cu,Zn and Cd come from the same source or have similar pollution pathways and transport processes.Pb may be closely related to atmospheric deposition.The cluster analusis suggested that the six heavy metals can be divided into two classes,in which Ni,Pb and Cd have similar rules,and Cr,Zn and Cu can be clustered into another type.?4?The results of the geoaccumulation index method showed that the pollution degree of the six heavy metals was Cd>Cu>Zn>Cr>Pb>Ni.Moreover,the most serious station was at the sampling sites of 2#and 6#,and the least station at the sampling sites of 1#and 9#.The results of the potential ecological hazard index method showed that the six heavy metals in the sediments of the Qilihai ranged from 178.77 to 347.21,showing a moderate to strongecological risk as a whole.The ratio of secondary phrase and primary phrase?RSP?shows that all six heavy metals were absence of contamination that it is closely related to rockdifferentiation.Human activity have little effect on the environment,and the quality ofecological environment is relatively clean to a certain extent.Six heavy metals were in the descending order of Pb>Cd>Ni>Cu>Zn>Cr.According to the risk assessment coding method?RAC?that Cd and Zn showed strong migration ability and biological activity compared with other elements,but the toxicity of Cd was higher than Zn.The greater the toxicity,the greater harm to the organism. |
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