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| Speciation Distribution and Ecological Risk Assessment of the Bio-available Heavy Metals in Lake Dalinouer, China |
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| KeyWord:heavy metals; bio-available fractions; ecological risk assessment; Lake Dalinouer |
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| Abstract: |
| In this work, the levels and distribution characteristics of bio-available fractions of Cu, Pb, Zn and Cd in sediments of Lake Dalinouer were analyzed using a sequential extraction method to study their geochemical behaviors in lake sediment and to find their controlling factors. The migration laws of heavy metals at water- sediment interface were also discussed on the basis of metals concentration in water. The results showed that environmental problem in the studied lake was Cu, Zn, and Pb related multi-metal pollution, Pb presented a remarkable migration trend from overlying water to the sediment, while Cu showed tenuous migration characteristic from pore water to overlying water. There was a different effect on the mainly bio-available fraction of heavy metals, because of the difference of their geochemical characteristics. Cu, Pb, Zn and Cd in the sediment core were dominated with bound to organic matter, carbonates, Fe-Mn oxides and carbonate, accounted for 61.6%, 60.7%, 71.5% and 53.6%, respectively. In horizontal direction, the bio-available fractions of Cu, Pb, Zn and Cd in surface sediments present an increasing trend from the southwest to northeast part of the lake; on the vertical dimension, the total levels of bio-available metal exhibit large fluctuation, but present an increased trend with depth increasing below 40 cm. The method of potential ecological risk index presented by Hakanson is used to assess heavy metals ecological risk. The results showed that the pollution index of the four metals ranged from 41.18 to 155.64 and present an increasing trend from southwest to northeast parts of the studied lake, indicated that the whole potential ecological risk of all heavy metals in Lake Dalinouer was low, and the pollution of southern lake should be taken into consideration seriously. |
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