Distribution And Background Values Of Heavy Metals In Core Sediment In Xiamen Coastal Area

In order to investigate the distribution and background values of heavy metals in sediment of Xiamen coastal area,core sediment were taken as research object in this paper.The results will make contribution to heavy metal pollution prevention and measurement.In this paper,the vertical distribution of heavy metals in core sediments were studied,the sources of heavy matals were determined by multivariate statistical methods and lead isotope compositions.Based on the concentrations and fractions of heavy metals in surface and core sediment,17 heavy metals background values were determined by using mathematical statistics method?iteration 2??,reference method of heavy metals content in sediment,reference method of fraction in heavy metals.Geo-accumulation index(I_geo)and Enrichment factors?EF?were applied to evaluate the pollution degree of heavy metals in the core sediment.The main conclusions were summarized as follows:Sc,V,Cr,Co,Ni,Zn,Pb,Sr,Bi,Tl,Sb,Cd,Ba and Cu were stable in the H3 core sediment.Mo changed dramatically in the surface sediments,then turned stable from12 cm?1997 a?to the bottom of the core sediment.The contents of Fe and Mn decreased with depth in the whole core sediment.More than half of heavy metals in H3 core sediment had the highest concentration at 45 cm?1933a?,which may be related to the the highest human input of heavy metals at middle of 1930s in Xiamen.The correlation analysis and cluster analysis of heavy metals in H3 core sediment showed a good agreement.The sources of Mo,Mn and Fe were the same,and the sources of Sc,V,Cr,Ni,Tl,Sr,Ba,Co,Pb,Sb and Zn were similar.Cd and Bi sources were also similar,while Cu had the independent sources.According to the variation coefficient of heavy metal concentration,the concentrations of Sc,V,Cr,Ni,Tl,Sr,Ba,Co,Pb,Sb and Zn were close to the background value,mainly due to the weathering of rock in nature.In addition to natural sources,Mo had human input in the surface sediments.The specific sources of other heavy metals were not yet clear and need to be further studied.Pb isotope tracement in H3 core sediment showed that Pb was mainly derived from soil parent material and lead-zinc mine of Fujian province.The contribution of the Pb in soil parent material was 69.19%⁷7.32%,while Fujian lead-zinc mine had contribution of 22.68³0.81%.Pb sources in P107,P110 and P112 core sediments were mainly related to soil parent material,indicating that the core sediments above had little influence on human activities and the sedimentary environment was stable.The background values of heavy metals determined by different method had great accordance with each other.The background values of heavy metals were Sc 13.70mg/kg,V 77.75 mg/kg,62.00 mg/kg,Co,Cr,14.40 mg/kg,30.8 mg/kg Ni,Cu 24.88mg/kg,with recent 128.3 mg/kg,41.30 mg/kg Pb,Sr,94.90 mg/kg,Mo 1.123 mg/kg,Sb 0.555 mg/kg,Ba 406 mg/kg,Tl 0.903 mg/kg,Bi 0.729 mg/kg,Fe 31205 mg/kg,Mn374 mg/kg,and Cd 0.068 mg/kg.The background value of Zn was higher than the reference values,because of special regional characteristics in Xiamen coastal area.The background value of Pb isotope ²⁰⁶Pb/²⁰⁷Pb in sediments was 1.2040,and²⁰⁸Pb/²⁰⁶Pb was 2.4883.Geo-accumulation index(I_geo)and Enrichment factors?EF?showed that Mo was at moderate enrichment in the surface sediments.The other heavy metals showed less enrichment,suggesting they were mainly from natural source.