Distribution and speciation of heavy metals and their sources in Kumho River sediment,Korea |
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| Authors: | Yeongkyoo Kim Byoung-Ki Kim Kangjoo Kim |
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| Institution: | (1) Department of Geology, Kyungpook National University, Daegu, 702-701, Korea;(2) Department of Environmental Engineering, Kunsan National University, Kunsan, 573-701, Korea; |
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| Abstract: | The interaction between heavy metals and river sediment is very important because river sediment is the sink for heavy metals
introduced into a river and it can be a potential source of pollutants when environmental conditions change. The Kumho River,
the main tributaries of the Nakdong River in Korea, can be one of the interesting research targets in this respect, because
it runs through different geologic terrains with different land use characteristics in spite of its short length. Various
approaches were used, including mineralogical, geochemical, and statistical analyses to investigate the distribution and behavior
of heavy metals in the sediments and their sources. The effect of geological factor on the distribution of these metals was
also studied. No noticeable changes in the species or relative amounts of minerals were observed by quantitative X-ray diffraction
in the sediments at different stations along the river. Only illite showed a significant correlation with concentrations of
heavy metals in the sediments. Based on an average heavy metal concentration (the average concentrations of Cd, Co, Cr, Cu,
Ni, Pb, and Zn were 1.67, 20.9, 99.7, 125, 97.6, 149, 298 ppm, respectively), the sediments of the Kumho River were classified
as heavily polluted according to EPA guidelines. The concentrations of heavy metals in the sediments were as follows: Zn > Pb > Cu > Ni > Cr > Co > Cd.
In contrast, contamination levels based on the average I
geo (index of geoaccumulation) values were as follows: Pb > Cd > Zn > Cu > Co = Cr > Ni. The concentrations of heavy metals increased
downstream (with the exception of Cd and Pb) and were highest near the industrial area, indicating that industrial activity
is the main factor in increasing the concentrations of most heavy metals at downstream stations. Sequential extraction results,
which showed increased heavy metal fractions bound to Fe/Mn oxides at the downstream stations, confirmed anthropogenic pollution.
The toxicity of heavy metals such as Ni, Cu, and Zn, represented by the exchangeable fraction and the fraction bound to carbonate,
also increased at the downstream stations near the industrial complexes. Statistical analysis showed that Pb and Cd, the concentrations
of which were relatively high at upstream stations, were not correlated with other heavy metals, indicating other possible
sources such as mining activity. |
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