Competitive adsorption,release and speciation of heavy metals in the Yellow River sediments,China |
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Authors: | Qingyun Fan Jiang He Hongxi Xue Changwei LÜ Ying Liang Saruli Ying Sun Lili Shen |
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Institution: | (1) Department of Ecology and Environment Science, Inner Mongolia University, Huhhot, 010021, Inner Mongolia, China |
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Abstract: | The competitive adsorption and the release of selected heavy metals and their speciation distribution before and after adsorption
in the Yellow River sediments are discussed. The adsorption of metals onto sediments increases with increasing pH value and
decreases with increasing ionic strength. The competitive coefficient K
c and the distribution coefficient K
d are obtained to analyze the competitive abilities of selected heavy metals, which are ranked as Pb > Cu >> Zn > Cd. The competition
among selected heavy metals becomes more impetuous with increasing ion concentration in water. Speciation analysis was done
by an improved analytical procedure involving five steps of sequential extraction. Cu, Pb and Zn were mainly transformed into
the carbonate-bound form (50.8–87.7%) in adsorption. Most of (60.7–77.3%) Cd was transformed into the exchangeable form, and
the percentage of carbonate-bound Cd was 19.7–30.4%. The release reaction was so quick that the release capacity of selected
heavy metals from sediments to aqueous solution reached half of the maximum value only in 30 s. As opposed to adsorption,
the release capacities of selected heavy metals were ranked as Cd > Zn >> Cu > Pb. In this study, Cd produces the most severe
environmental hazards, because its concentration in the release solution is 85.8 times more than the human health criteria
of US EPA. |
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Keywords: | Competitive adsorption Heavy metals Speciation analysis The Yellow River |
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