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Interaction of organic acids and pH on multi-heavy metal extraction from alkaline and acid mine soils
Ding, Y. Z.; Song, Z. G.; Feng, R. W. & Guo, J. K.
Abstract
Vegetation at mining sites can produce increased
heavy metal leaching by the organic acids and protons originating
from root secretion and litter degradation. Batch
experiments were conducted to investigate the effects of
organic acids and pH on the extraction of Pb, Cd, Zn and Cu
from an alkaline mine soil (sampled from a mining site of
Chenzhou City, Hunan Province) and an acid mine
soil (sampled from a mining site of Daxin county, Guangxi
Province). The results showed that in the presence of organic
acids (acetic, oxalic,malic, fumaric, tartaric and citric acids) at
pH 7, the extraction of Pb, Cd, Zn and Cu from the acid mine
soil was much higher than that from the alkaline mine soil, in
which only citric acid with higher concentration was capable
of extracting some heavy metals. Citric acid had the strongest
ability in extracting heavy metals, followed by oxalic acid.
Heavy metal extraction dramatically decreased with increasing
pH. Moreover, at low pH, oxalic acid promoted the risk of
Culeaching; at high pH, the leaching of Pb,Zn,Cd andCu was
enhanced by both oxalic and citric acids. This indicated that
those plants, which can produce substantial citric acid or
oxalic acid by root secretion and litter degradation, should not
be selected for the revegetation of mining sites.
Keywords
Chelating; Contamination; Leaching; Mining; Trace metals; Revegetation
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