Abstract
To determine the role of organic matter in the attenuation of acid rock drainage (ARD), microcosm-based experiments were performed using ARD stimulated with plants and manures. Initial mineralogical, organic geochemical and microbial analyses indicated a predominance of goethite, a substantial amount of organic carbon originating from local sources, and a bacterial community comparable with those detected in a range of ARD sites worldwide. After 100 days of incubation, changes in the mineralogical, organic and microbiological composition of the ARD demonstrated that the plant additions stimulate microbes with the potential to degrade this organic matter but do not necessarily cause substantial Fe(III) reduction. Conversely, the greatest observed stimulation of Fe(III) reduction, associated with an increase in pH to near-neutral values, was observed using manure additions. These results demonstrate that the use of the optimal natural carbon source is important and can promote the metabolism of microorganisms potentially fuelling a range of geomicrobial processes, including iron and sulfate reduction.
Highlights
Acid mine drainage (AMD) is one of the most widespread forms of water pollution in the world characterised by surface waters with low pH and elevated concentrations of iron, other dissolved metals and sulfuric acid (Singer and Stumm 1970; Rimstidt and Vaughan 2003)
Reduction, associated with an increase in pH to nearneutral values, was observed using manure additions. These results demonstrate that the use of the optimal natural carbon source is important and can promote the metabolism of microorganisms potentially fuelling a range of geomicrobial processes, including iron and sulfate reduction
The mineralogy and geochemistry of the acid rock drainage (ARD) sediment and microcosm slurries were monitored using 57Fe Mössbauer spectroscopy, X-ray diffraction (XRD) and X-ray fluorescence (XRF) analyses and the total organic matter content was quantified using the sequential loss on ignition method (Heiri et al 2001, Beaudoin 2003; see supplemental material for details)
Summary
Acid mine drainage (AMD) is one of the most widespread forms of water pollution in the world characterised by surface waters with low pH and elevated concentrations of iron, other dissolved metals and sulfuric acid (Singer and Stumm 1970; Rimstidt and Vaughan 2003). This phenomenon is commonly associated with environmental disasters from mine spills but can arise from natural sources and is known as acid rock drainage, ARD (Liao et al 2016; Queiroz et al 2018; Moeng 2019). The mineralogical and geochemical transformations taking place, as well as the microbial communities present before and after 100 days of incubation, were determined to investigate the influence of natural carbon sources on the stimulation of Fe(III) reduction and the contribution to the ARD attenuation
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