DISTRIBUTION CHARACTERISTICS AND ECOLOGICAL RISK ASSESSMENT OF HEAVY METALS IN SURFACE SEDIMENTS IN SANYA BAY AND SURROUNDING WATERS

Based on the chemical analysis of Cu, Zn, Pb, Cr, As, Cd and Hg in 73 surface sediment samples in Sanya Bay and surrounding waters, the distribution characteristics of heavy metals were identified, the sources and influencing factors of heavy metals were discussed, and the ecological risk assessment was carried out by various means. The results show that the average contents of Cu, Zn, Pb, Cr, As, Cd and Hg in the study area were 12.77, 60.11, 21.11, 43.84, 7.05, 0.067 and 0.022 μg/g, respectively. The area with high content of As was the north of Xi Mao Zhou, while the content distribution of other heavy metals was generally low along the coast and gradually increased toward the sea. The contents of Cr and Hg were lossed compared with the background values, while the other heavy metals were slightly enriched. The content distribution of Zn, Pb and Cr conformed to the law of “grain size control effect”, and the material source was weathering and denudation of terrigenous detritus. Cu may be influenced by human activities in addition to terrestrial erosion. Cd and Hg were mainly from coastal sewage discharge. As was mainly from sewage discharge, agricultural application, cage aquaculture, etc. The total heavy metal pollution is in the low level standard, and the potential ecological risk of total heavy metals was also low, which reflected the overall fine sediment ecological environment of the study area, and the coastal area is better than the offshore sea area. The average pollution degree of single heavy metal was ranked as Cd>Pb>Zn>As=Cu>Cr>Hg, Cd and Pb were in the medium pollution level standard, while other heavy metals were in the low pollution level standard. The average degree of potential ecological risk of single heavy metals was in the low standard, ranking as Cd>Hg>As>Pb>Cu>Cr>Zn. Cd is the heavy metal element with the highest degree of pollution and potential ecological risk in the study area, so its prevention and control should be strengthened.