The association of microbial activity with Fe, S and trace element distribution in sediment cores within a natural wetland polluted by acid mine drainage

Abstract

Natural recovery and remediation of acid mine drainage (AMD) reduces the generation of acidity and transport of trace elements in the runoff. A natural wetland that receives and remediates AMD from an abandoned copper mine at Parys Mountain (Anglesey, UK) was investigated for better understanding of the remediation mechanisms. Water column concentrations of dissolved Fe and S species, trace metal(loid)s and acidity decreased markedly as the mine drainage stream passed through the wetland. The metal(loid)s were removed from the water column by deposition into the sediment. Fe typically accumulated to higher concentrations in the surface layers of sediment while S and trace metal(loid)s were deposited at higher concentration within deeper (20-50 cm) sediments. High resolution X-ray fluorescence scans of sediment cores taken at three sites along the wetland indicates co-immobilization of Zn, Cu and S with sediment depth as each element showed a similar core profile. To examine the role of bacteria in sediment elemental deposition, marker genes for Fe and S metabolism were quantified. Increased expression of marker genes for S and Fe oxidation was detected at the same location within the middle of the wetland where significant decrease in SO 4 2and Fe 2+ was observed and where generation of particulate Fe occurs. This suggests that the distribution and speciation of Fe and S that mediates the immobilization and deposition of trace elements within the natural wetland sediments is mediated in part by bacterial activity.

Addition of organic acids to acid mine drainage polluted wetland sediment leads to microbial community structure and functional changes and improved water quality

“…Sediment samples containing natural microbial communities were obtained from the middle of a wetland in Anglesey, UK, through which a small river (southern Afon Goch) flows, and which receives AMD pollution from an abandoned Cu mine at Parys Mountain (Dean et al, 2013;Aguinaga et al, 2018). These surface sediments are rich in trace metals (0.2 -10 mg g -1 Al, 0.2 -0.6 mg g -1 As, 1 -5 mg g -1 Cu, 90 -140 mg g -1 Fe, 0.1 -2 mg g -1 Pb, 0.5 -3 mg g -1 Zn), and sulfur (3 -8 mg g -1 S), and with dissolved organic carbon (DOC) and nitrogen concentrations of approximately 0.5 mg g -1 and 0.01 mg g -1 , respectively (Aguinaga et al, 2019). They are composed of light brown, medium-to-fine sediment and contain larger soil particles and plant debris.…”

“…Total and inorganic C concentrations were obtained using a Shimadzu 5000 A TOC analyser (Shimadzu Limited, UK), as described previously (Aguinaga et al, 2019). DOC in the water was measured by subtracting inorganic C values from total C. Water samples for metal measurement were taken and filtered through a 0.45 µm cellulose acetate filter.…”

“…These microbial processes may be utilised for 'passive' AMD remediation methods that require minimal maintenance and rely on the use of natural processes (Johnson and Hallberg, 2005), such as within constructed wetlands and in bioreactor systems, where Fe oxidation drives formation of insoluble Fe precipitates such as ferrihydride, and sulfate reduction produces hydrogen sulfide (Neculita et al, 2007;Clyde et al, 2016). This in turn increases pH and generates particulate metal sulfides to reduce the dissolved metal concentration in the water column (Hedrich and Johnson, 2014;Aguinaga et al, 2019). In both natural and constructed wetlands this remediation is achieved in part through the interaction of plants with rhizosphere sediment bacterial, archaeal and fungal communities.…”

Reactores Bioquímicos Pasivos: Una alternativa biotecnológica para la remediación de drenajes ácidos de mina

“…Sugiriendo que el potencial metabólico involucrado en la degradación de la materia orgánica y de la biotransformación de metales es más diverso de lo conocido hasta ahora. Recientemente, se ha establecido que el metabolismo bacteriano influye sobre la especiación de los metales y sulfuros, conduciendo a una rápida atenuación de la contaminación por DAM (Aguinaga et al, 2019).…”

Microbial Diversity of a Disused Copper Mine Site (Parys Mountain, UK), Dominated by Intensive Eukaryotic Filamentous Growth

“…Combined, these aspects make Parys Mt a place of great scientific interest for geochemical and extremophile studies [3][4][5]. Investigations have been undertaken to examine the microbial communities, the chemical and physical characteristics of the watercourses draining the site (e.g., Afon Goch Dulas) and the impact of acid mine Microorganisms 2022, 10, 1694 2 of 17 drainage (AMD) on the surrounding wetlands [6][7][8][9]. Other microbial-based studies have focused on the biological communities present in an underground lake located at the site [10,11].…”