A Study On Enrichment Of Heavy Metals In The Mangrove Wetland And Their Ecological Effects From Northern Hainan Island

Mangrove is a special kind of community types which is distributed in a tropical andsubtropical estuary intertidal,and it plays an important role in the protection of biodiversity.With the rapid development of urbanization and industrialization, heavy metals pollutionwere relatively serious because of the garbage and the using of pesticide and chemicalfertilizer.This paper selects mangrove wetland of Xin ying port, Dong zhai port and Qing lan porton northern Hainan Island as the research object,and study8kinds of heavy metalelements,such as Cr、Ni、Cu、Zn、As、Cd、Pb、Hg, etc,and study heavy metals distributionand pollution characteristics、risk evaluation of ecological harm and the absorption、accumulation and enrichment of heavy metals in mangrove.The main conclusions can be summed up as follows：1.The average value of Cr、Ni、Cu、Zn、As、Cd and Pb in study area were64.56mg/kg、31.09mg/kg、21.73mg/kg、60.71mg/kg、13.20mg/kg、0.11mg/kg、21.94mg/kgrespectively.Compared with the background value of Hainan Island,the content of As and Cdwere relatively high, especially the As.According to the analysis,the most importantenvironmental factor influencing the content of As were the using of pesticide and fertilizerand oily water of sea and the wastes of living.The most important factor influencing thecontent of Cd were the increasing of pollution of the waste water and industrial waste.2.The enrichment degree of heavy metal elements is as follows:As>Ni>Cu>Cr>Cd>Zn>Pb.Cr reached serious enrichment,Cd reached moderate pollution andZn reached light pollution,so should be close attention;Pb reached moderate elementslevel,and it did not appear pollution and poor phenomenon.3.Correlation analysis:Cr、Ni、Cu、Zn、Al、Fe was a significant negative correlation,itexplains that these elements have the same source,and the geochemical properties issimilar,and precipitated or accumulated jointly.As and Cd has no significant correlation,probably As and Cd with other heavy metal element is not obvious in the earth chemicalbehavior,and As and Cd has different sources with other elements.4.The thesis has adopted Nemerow index method, Potential ecological harm index method and Accumulation index method to evaluate the heavy metal’pollution from wet landin this researching area.the results showed that aii heavy metal elements had polluted theresearching area except Pb and Zn,and the most serious elements are As and Ni.In theresearch of heavy metals’ pollution of three researching area,we found that pollution in theQinlan Port ranked the first,followed by the pollution in the Xinyin Port,then the DongzhaiPort’pollution as the lightest.5.The ability of mangrove plants’to absorb and accumulate heavy metal elements wasdifferent,and the ability of absorption and accumulation of floristic component was alsodifferent.The accumulation ability of root and stalk of mangrove plants to Cr、Ni、Pb、As、Cd and Hg were relatively strong,it could be because of the heavy metal elements these hasno biological activity,so the plants can absorb a little;but the content of Zn and Cu in7mangrove plants are higher,especially in the root.6.The absorption ability of Scyphiphora Gaeren and Ceriops tagal to heavy metalelements were relatively strong,Xylocarpus granatum were inferior. The absorption ability ofScyphiphora hydrophyllacea to Cr、Ni、Cu、Zn、As and Cd were stronger,the accumulationability of Ceriops tagal to Pb were stronger. Scyphiphora Gaeren and Ceriops tagal would bevery useful in restoration of polluted area.The transfering ability of Ceriopstagal,Scyphiphora hydrophyllacea,Bruguiera sexangula,Aegiceras corniculatum,Bruguieragymnorrhiza,Xylocarpus granatum and Hernandia sonora to different heavy metals wereslightly better except to As,we should increase the plants which transfering ability to As werebetter in the restoration work.