Research On The Characteristics Of Bioavailable Form And The Occurrence State Of Heavy Metals In The Sedimentsof Mangrove Wetland In Bamenwan Areas,Hainan Island

Bamen Bay mangrove wetland which lie in the east areas of Hainan Island is an important mangrove nature reserve in China.In recent years,with the economic development of Hainan Island,human activities have become increasingly frequent,heavy metal pollutants with surface runoff into the Gulf estuary is also more and more.Due to the special physical and chemical properties of mangrove wetland sediments in estuarine areas,heavy metals are easily enriched and thus affect the surrounding ecological environment.In this paper,five main heavy metal elements(Cr,Cu,Pb,Zn,and Cb)in the sediments were studied in the study area of the Bamen Bay mangrove wetland.The main extraction and heavy-scale extraction were studied by single extraction and multi-step extraction.And then,the spatial distribution characteristics of mangrove wetland sediments are studied,also the biologically active state and its occurrence pattern,and the migration rule of heavy metal pollutants accumulated in mangrove wetlands are analyzed.through all these studies,the main findings are as follows:(1)The distribution of heavy metals in the mangrove wetland sediments of the study area shows that the contents of Cd and Cr in the heavy metal of the surface sediments of the Bayeux mangrove forest are relatively low,and the total contents of Pb and Zn are relatively low,There are significant differences between inside and outside.In terms of vertical distribution,various heavy metal elements are affected by the nature of the sediments in the study area,except for the individual elements of the individual regions,and are not concentrated in the surface,and the maximum appears in the sediment at depths of 5-10 cm.Because of the apparent leaching of surface sediments,the adsorption and flocculation of fine particulate matter in the middle sediments are favorable,leading to the concentration of heavy metal elements.(2)The study of the total amount of heavy metals in the sediments of the study area and the marine sediment standard and the environmental background values in the surface sediments of the South China Sea showed that the area did not exceed the national marine sediment standard I,indicating that the heavy metal enrichment in the study area Excessive,it is worth noting that,Zn elements in the surface of individual geological enrichment,showing a trend of pollution.(3)It was found that the effective contents of different heavy metal elements in the surface sediments were different in the horizontal distribution,and the bioavailability of the elements in the forest> forest edge> light beach,Zn and Cd were more than 50%,indicating that these two elements in the study area have a higher biological hazard.From the vertical distribution,the effective state of various heavy metal elements is not enriched in the sediments,and the maximum value appears at the depth of 10-20 cm and decreases with the depth.In different sediments,Cu,the results show that the total amount of heavy metals in the sediments is the total amount of heavy metals in the sediments of the study area,and the results are shown in Fig.The correlation coefficient between the element and the element is also high,which indicates that the heavy metal element in the study area is mainly composed of coexistence in the process of aggregation.(4)The occurrence forms of heavy metals in the surface sediments of the Bamen Bay mangrove wetland are mainly in the form of residual state,carbonate-bound state and iron-manganese oxidation state.The residual state is the most stable form,Acid-bound states and iron-manganese oxide-bound states as active forms,which can cause potential harm to the ecological environment.In the vertical direction,the change of the total amount of heavy metal elements is related to the change of non-residue concentration.In the study area,the five kinds of heavy metals in sediments are obviously enriched at 20-30 cm depth,which is consistent with the vertical distribution of heavy metal elements.In general,Zn,Cd and Pd are in red The activities of trees in the sediments are large and easy to be absorbed and utilized by passive plants,and attention should be paid to the future protection and restoration of the environment.