Distribution characteristics of heavy metals in columned sediments from the Wanquan River estuary and the relation with the development of Bo'ao district in Hainan Island

In this paper,columned sediments of Wanquan River estuary in Hainan Island were chosen for the case of study.Based on the 210Pb dating method,sedimentation rate was measured,and by the analysis of the contents of heavy metal elements(Mn,Cr,Co,Ni,Cd,Pb,Zn,Cu,As,Hg),as well as Si/Al ratio,the relations between estuary sedimentation and Bo' ao development were discussed.The results showed that sedimentation rate of columned sediments was 1.13 cm/a,which recorded the environmental information from 1991 to 2007 in Bo' ao district.Vertical distributions of heavy metals and grain size from the columned sediments were consistent with the phases of Bo' ao exploitation.During the elementary exploitation in Bo' ao area from 1991 to 1998,the contents of heavy metal elements in columned sediments changed gently;which indicated estuary environment was disturbed by natural processes.When Bo' ao began to develop energetically after 1999,the contents of heavy metal elements changed distinctly,and these profile types reflected the natural sedimentation and the human rebuilding activity.Contents of heavy metals were safe after all,and the environmental quality of Wanquan River estuary was favorable.