| Coastal zone is a transitional zone between land and sea,reflecting the effect of land and sea.Heavy metals can not be degraded,which can enter the ecosystem through the food chain,posing a serious threat to ecological security and human health.Sediment is the source and sink of pollutants in waters.Heavy metals accumulate in sediments(sinks),which can be released under certain conditions to harm to the ecosystem(source).Therefore,the key point of ecological risk of heavy metals in water is sediment.Heavy metals have sulfur affinity,which can be combined with sulfide to form stable metal sulfides to reduce ecological risk.Therefore,sulfide plays an important role in the ecological toxicity of heavy metals in water.AVS(Acid-Volatile Sulfide)is the most reactive forms of sedimentary sulfides,being a hot spot in the study of the ecological risk of heavy metals.Hainan is the most important tropical coastal tourist area in China.In recent years,the development of tourism,aquaculture and industry have brought a certain degree of pollution to the marine environment,so far there is no systematic research on ecological risk about coastal waters of Hainan.Based on the field investigation,474 surface sediments and 4 columnar stations were located in Hainan coastal area.The distribution of AVS,SEM(Simultaneously Extracted Metals)and organic carbon in sediments of Hainan were studied.This paper analyzed the characteristics of inorganic sulfur species in the typical areas(Danzhou Bay and Changhua River),and discussed the ecological toxicity of sedimentary environment to the benthos.Lastly,based on the SEM-AVS model and(SEM-AVS)/foc model,the ecological risk assessment of Hainan coastal environment was carried out,which provided an important basic data and decision basis for Hainan coastal water environment protection.The research conclusions are as follows:(1)Hainan coastal sediment SEM content is in the range of 0.001~4.153?mol·g-1,all stations are within the third class standard of Marine Sediment Quality Standard of People's Republic of China(GB18668-2002),which means the concentrations of heavy metals are at a low level.In addition,the results show that the main sources of heavy metals are respectively degradation of organic matter,shipping pollution and industrial pollution.(2)The contents of AVS,CRS and ES in the sediments of typical areas are CRS > AVS > ES.The content of CRS is 50%~80% of RIS,which is the main reducing inorganic sulfide in sediments.The CRS/AVS in most stations are more than 3,indicating that AVS can be transformed into CRS efficiently,and the sediment environment is stable,which ecological toxicity of sediment environment is low.AVS in all stations of Hainan coastal sediments are at a low level,with the range of 0.0002~46.881?mol·g-1,most of them are less than the first class standard of Marine Sediment Quality Standard of People's Republic of China(GB18668-2002),the highest station is located in Nandu River estuary.The contents of AVS in columnar sampling stations are less than the first class standard.(3)Based on ISQC,heavy metals in sediments of Hainan coastal area will not produce toxic effects.(SEM-AVS)/foc model results show that 2.32% of all stations in Hainan have potential ecological risks,37.76% of the stations may have potential ecological risks,while 59.92% of the stations currently have no ecological risk.Among them,there is 1 station(located at the port)of the 25 stations in the Dongzhai Port Mangrove Wetland has potential ecological risks,3 stations may have potential ecological risks;while 10 stations near Sanya City of the Sanya Bay area may have potential ecological risks.Overall,most of the coastal areas of Hainan currently have no ecological risk,but more than 1/3 of the region may have potential ecological risks.Remarkably,most areas of Dongzhai Port Mangrove Wetland,a national nature reserve,have no ecological risk,but the area near the port has potential ecological risk;while there may be potential ecological risks near Sanya City. |
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