Pollution Of Heavy Metals And Pb-Sr Isotopic Implication In The Offshore Sediments From Xiamen Western Bay

The content, distribution and speciation of heavy metals in the sediment fromXiamen western Bay were studied. The pollution source and contribution of heavymetals in the sediment were revealed by using Pb-Sr isotope tracing technique. Theconclusions were summarized as follows,The content of heavy metals in the surface sediment of each site from XiamenWestern Bay was as follows, Fe＞Ti＞Mn (major elements), Zn＞Ba＞Cr＞Cu＞V＞Ni＞Li＞Pb＞Sr＞Co (trace metals). The content level differences of heavy metalswere large. Most elements had different degree of pollution. Fe, Ti, Ba, Co, V and Limainly existed in the residual fractions. Pb mainly existed in the residual fraction,followed by extractable fraction. The residual fractions of Zn, Sr, Cr, Cu, Mn and Niwere not dominant.Assessment results of heavy metal pollution in the surface sediments using severalevaluation methods were basically accordant. The pollution degree of Cu, Zn, Co, Cr,Pb and Ni were severe. Sampling site S7was the most polluted. Ratios of secondaryphase to primary phase (RSP, for short) of Fe, Ba, Co, V and Li were less than1.0ateach sampling site. The maximum RSP values of Zn, Cr, Cu and Ni in S7showedsevere pollution. The RSP values of Zn, Cr, Cu and Ni in S8and S13showed minorpollution.Modified BCR-sequential extraction showed the residual fractions of Fe, Zn, Ba, Ti,Co, Cr, Ni, Pb and V were dominant in core sediments. Low levels of other threefractions showed a weak migration of the above heavy metals. In the core sedimentsof H1and H2, Zn, Cu, Co and Ni showed high levels in non-residual factions, whileresidual factions in regolith and parent material were dominant. The human input ofZn, Cu, Co and Ni were obvious. Direct emission was the main pathways of heavymetal pollution in H1and H2core sediments. Atmospheric deposition and industrial discharge were the main pathways of heavy metal pollution in H3core sediment.Pb isotopic composition had greater differences in surface sediments. Pb pollutionat sites S1, S2, S3, S4and S5was mainly from industrial emissions and Pb-Zndeposit. Pb pollution at other sampling sites was mainly from marine paints andelectroplating sewage. Pb isotope ratios in surface sediments were different fromthose in vehicle exhaust and coal combustion. Pb-Zn deposit was main pollutionsources in some H2core sediements. Most H2core sediments were subjected toindustrial emission and Pb-Zn doposit.The contributions of Pb-Zn deposit, industry emission and parent material in totalLead isotopes were considerably stable. The highest contribution of parent materialshowed the interference for tracing anthropogenic sources. The tracing ofacid-extractable Pb isotopes could avoid the interference of natural sources. Pb-Zndeposit and industry emission were the main anthropogenic sources from bottom tosurface in core sediments. The contributions of Pb-Zn deposit, industry emission andvehicle exhaust were52.39%,32.65%and14.96%, respectively. Pb-Zn deposit wasthe main Pb source. After the ban of leaded gasoline, vehicle exhaust was not themain anthropogenic Pb source. Pb-Sr isotopes in H2core sediments were differentfrom those of the potential sources. The source of Sr in H2core sediments wascomplicatied, influenced by variety of potential sources.