| The famous Dongting Lake is one of the most important inland freshwater lakes in China.Xiangjiang River,Zijiang River,Yuanjiang River and Lishui River are the main drainage system in the Dongting Lake Basin.In this study,we drilled and sampled river bed sediments from the Four-river inlets of Dongting Lake,and obtained 125 sediment samples for study.Trace element and isotopic geochemical analyzes were performed using analytical techniques such as isotope mass spectrometry(ICP-MS)and multi-receiver inductively coupled plasma mass spectro-metry(MC-ICP-MS).Based on the above-mentioned sediment element and isotope geochemical analysis results,the degree of heavy metal pollution in sediments was evaluated,the characteristics of heavy metal pollution in sediments were analyzed,the Pb isotopic composition characteristics of sediments were explored,and the sources of heavy metal pollutants in sediments were revealed.In order to provide a scientific reference for the prevention and control of heavy metal pollution in sediments in the basin of Dongting Lake.The calculation results of heavy metal enrichment coefficient of sediments show that there is no obvious enrichment of Ba,Mo,Tl,Th and U in the Four-river inlets sediments of Dongting Lake,and Bi,Sc,V,Mn,Ni,Cu,Zn,Most sedimentary columns are medium-enriched,Among them,Bi,Cd and Pb are significantly enriched and highly enriched in inlet sediments of Xiangjiang River.The results of the geoaccumulation index(Igeo)and the comprehensive enrichment index(EI)show that the Xiangjiang River has the highest degree of pollution to sediments,and the most polluted heavy metal elements(Bi,Cd,Pb,Zn,Mn,Cu,V,etc.)On the other hand,the sediments from the Yuanjiang River are the least polluted,with the least of the heavy metal elements(Cd,V)being polluted;the overall pollution levels of the sediments from the Zijiang River and the Lishui River and the heavy metal pollutants are between the two.The lead isotope composition of sediments from the Four-river inlets sediments of Dongting Lake are enriched antimony-lead(Th-Pb).The lead isotope ratio of the whole rock sample is closer to the ratio of the dissolved sample,and the lead in the sediment may mainly occur in the soluble phase.The ratio of 206Pb/207Pb in sediments from the Four-river inlets sediments of Dongting Lake has similar trends in the interval from 0 to 64 cm.Traces of lead pollution from sediment sources indicate that lead in sediments from the Xiangjiang River is mainly comes from the lead-zinc ores(Pb of anthropogenic sources),coals(Pb of anthropogenic sources),and granite(Pb of natural source).It is composed of a natural source lead and two artificial lead components.The lead in sediments from the Zijiang River is mainly comes from the lead-zinc ores,coals,granitic rocks,and feldspar.It is a multi-component mixed lead consisting of two artificial lead and two natural lead.The lead in the upper sediments of the Yuanjiang River is mainly comes from the traffic emissions and coals.The lead in the lower sediments mainly comes from natural lead in slate,granitic rocks and feldspar.The lead in the upper sediments of Lishui River is mainly Pb of anthropogenic sources(coals),and the lead in the middle and lower layer sediments mainly comes from natural lead in feldspar and granitic rocks.The heavy metals such as Ba,Sc,V,Mn,Co,Cu,Zn and other elements in the sediments from the Four-river inlets sediments of Dongting Lake are similar to those of Pb.The correlation between these heavy metals and Pb and 206Pb/207Pb ratios is significant and can be reflected,the amount of anthropogenic heavy metals in sediments.When the heavy metals in sediments were dominated by anthropogenic sources,the ratio of Zn to 206Pb/207Pb was significantly correlated,indicating that the correlation of Zn-206Pb/207Pb has certain significance for the heavy metal pollution in sediments. |
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