Mineralogical characteristics of sediments and heavy metal mobilization along a river watershed affected by acid mine drainage
January
Mineralogical characteristics of sediments and heavy metal mobilization along a river watershed affected by acid mine drainage
Yingying Xie 0 1
Guining Lu 0 1
Chengfang Yang 0 1
Lu Qu 0 1
Meiqin Chen 0 1
Chuling Guo 0 1
Zhi Dang 0 1
0 School of Environment and Energy, South China University of Technology , Guangzhou , China , 2 The Key Laboratory of Pollution Control and Ecosystem Restoration in Industry Clusters, Ministry of Education, South China University of Technology , Guangzhou , China , 3 Guangdong Provincial Engineering and Technology Research Center for Environmental Risk Prevention and Emergency Disposal, South China University of Technology , Guangzhou , China , 4 School of Environmental and Biological Engineering, Guangdong University of Petrochemical Technology , Maoming , China
1 National Natural Science Foundation of China (nos. 41330639 and 41720104004), the National Key Technology Support Program (no. 2015BAD05B05), the Guangdong Natural Science Funds for Distinguished Young Scholar (no. 2015A030306005), the Science and Technology Program of Guangdong Province (no
Trace-element concentrations in acid mine drainage (AMD) are primarily controlled by the mineralogy at the sediment-water interface. Results are presented for a combined geochemical and mineralogical survey of Dabaoshan Mine, South China. Developed sequential extraction experiments with the analysis of the main mineralogical phases by semi-quantitative XRD, differential X-ray diffraction (DXRD) and scanning electron microscopy (SEM) were conducted to identify the quantitative relationship between iron minerals and heavy metals. Results showed that schwertmannite, jarosite, goethite and ferrihydrite were the ment with the increasing pH from 2.50 to 6.93 along the Hengshi River. Decreasing contents of schwertmannite ranging from 35 wt % to 6.5 wt % were detected along the Hengshi River, which was corresponding to the decreasing metal contents. The easily reducible fractions exert higher affinity of metals while compared with reducible and relatively stable minerals. A qualitative analysis of heavy metals extracted from the sediments indicated that the reten-
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Data Availability Statement: All relevant data are
within the paper and its Supporting Information
files.
tion ability varied: Pb > Mn > Zn > As
Cu > Cr > Cd
Ni. Results in this study are avail for understanding the fate and transport of heavy metals associated with iron minerals and establishing the remediation strategies of AMD systems.
Introduction
Acid mine drainage (AMD), with elevated concentrations of SO42- and metal cations such as
Fe3+, is triggered by the exposure of atmospheric water and oxygen of sulfide minerals [1].
And it comprises a concatenated series of mineralogical and chemical reactions between
sediments and AMD water [
1
]. Researches on the ochreous precipitates from AMD have shown
that the deposits contain a diverse group of iron oxy-hydroxide minerals, in particular, the
dominant Fe-oxyhydroxide minerals which were detected alternately in the surface
sedi2014A020216004) and Fundamental Research
Funds for the Central Universities (no. 2015ZZ113).
poorly ordered hydroxysulfates (e.g., jarosite and schwertmannite) that are powerful sorbents
for trace metals and oxyanions [
2
]. Additionally, the release of heavy metals into the
groundwater is associated with Fe(III) oxyhydroxide minerals by dissolution or transformation [3±7].
Due to the potential ecological and human health risks [8±9] associated with such a release,
the growing awareness of the environmental protection calls for a better understanding of the
mineralogical characteristics and transport of metals under extremely acidic conditions of
AMD. Thus, a sound geochemical investigation is required at all stages to evolve the effective
remediation of AMD area [10±11].
Based on the previous reports [12±14], during or after formation of iron oxy-hydroxide
minerals, heavy metals can also be adsorbed onto minerals surfaces or trapped in structural
regions in minerals. In AMD contaminated rivers, sediments consist of a complex mixture of
secondary iron phases containing potentially toxic metal elements [
15
]. For example,
Regenspurg and Peiffer [
16
] reported that the high concentrations of Cr (up to 812 mg/kg) and As
(up to 6740 mg/kg) were detected in precipitates of the mineral schwertmannite in AMD
affected areas. As reported by Carlson et al. [
12
] in AMD system in Finland, ochreous
precipitates containing 5500±69800 mg/kg As were composed of schwertmannite, ferrihydrite, and
goethite. Mean concentrations of As, Cd, Cu, Pb and Zn were measured to be 1580, 9.0, 160,
710 and 1730 mg/kg in sediments collected along the Daduk creek, Korea [
17
]. Hence,
investigations on the mineralogy of precipitates which linked to critical environmental processes
including trace element cycling in AMD area were ugly needed [
5
].
According to the literature, attention has been (...truncated)