Wetland Receiving Acid Mine Drainage Research Articles

Impact of seasonal variation on the treatment response of constructed wetlands receiving acid mine drainage in a subtropical region

Acid mine drainage (AMD) emanating from coalfields is a severe form of water pollution with adverse ecological impacts. AMD from Makum Coalfield, Assam, India, is highly polluted and unregulated. The present study describes the influence of seasonality on the efficacy of constructed wetlands (CWs) applied for treating synthetic AMD, analogous to mine water characteristics from the Makum Coalfield. Rainfall is predominant in the northeast region of India. The effect of rainfall events on sheltered (SCW) and unsheltered (UCW) CWs was investigated under natural conditions from January to August. Acidic AMD containing Fe, Al, Mn, Zn, Co, Ni, Cr and sulfate concentrations as 100, 25, 6, 5, 1, 1, 1 and 1100 mg L−1 was continuously supplied to CWs at a hydraulic loading rate of 0.014 m3 m−2 d−1. SCW and UCW raised the pH (>5.5) and demonstrated comparable treatment performance in the dry season. Heavy rainfall imposed a highly sensitive and poor treatment response in UCW, resulting in significantly lower sulfate removal in UCW (51.34 %) than SCW (60.29 %). SCW demonstrated superior metal removal for Fe (90 %), Al (79 %), Zn (94 %), Co (92 %), Ni (91 %) and Cr (96 %), which significantly differed from UCW (85 % Fe, 70 % Al, 93 % Zn, 82 % Co, 83 % Ni and 90 % Cr), except Mn. These findings indicated possible shortening of hydraulic retention time in UCW with minimal or insignificant dilution. This experimental study underlines the limitations of wetland systems in the rainfall-affected region and recommends necessary design control measures to manage the effects of rainfall.

Assessing Alternative Supporting Organic Materials for the Enhancement of Water Reuse in Subsurface Constructed Wetlands Receiving Acid Mine Drainage

Acid mine drainage (AMD) is a global problem with severe consequences for the environment. South Africa’s abandoned mines are a legacy from the country’s economic dependence on the mining sector, with consequent negative impacts on ecosystems. AMD remediation includes active and passive techniques. Constructed wetlands (a passive technique) have lower operational costs but require larger spaces and longer timeframes to achieve the remediation of AMD, and are supported by anaerobic sulphate-reducing bacteria (SRB), which capable of remediating high-sulphate-laden AMD while precipitating dissolved metals from the AMD. Organic substrates supporting these activities are often the limiting factor. When enhancing existing passive AMD remediation technologies, alternative waste material research that may support SRB activity is required to support the circular economy through the reduction in waste products. Chicken feathers show potential as a substrate enhancer, boosting organic carbon availability to SRB, which sustains passive AMD treatment processes by achieving pH elevation, sulphate and metal reductions in AMD water for reuse. Microbial biodiversity is essential to ensure the longevity of passive treatment systems, and chicken feathers are proven to have an association with SRB microbial taxa. However, the longer-term associations between the AMD water parameters, microbial diversity and the selected substrates remain to be further investigated.

Trace metals in Phragmites australis and Phalaris arundinacea growing in constructed and natural wetlands

Constructed wetlands with horizontal subsurface flow (HF CWs) designed for treatment of municipal sewage have been monitored extensively with respect to removal of organics, suspended solids, nitrogen, phosphorus and bacteria. However, the information on the removal of various metals and metalloids in these systems is very limited. During the period 2002-2004 aboveground and belowground biomass of Phragmites australis (common reed) and Phalaris arundinacea (reed canarygrass) were sampled in three HF CWs in the Czech Republic. Concentrations of monitored elements in both aboveground and belowground plant tissues were similar to those found in plants growing in natural stands. The concentrations were much lower as compared to those found in plants growing in wetlands receiving acid mine drainage waters, waters from smelters or highway runoff. Concentrations decrease in the order of roots>rhizomes>leaves>stems. The leaf:stem concentration ratios were quite similar for all monitored elements ranging between 1.0 and 1.9. The root:leaf concentration ratio varied widely between 1.5 (Cu) and 54 (Cr) with a mean value of 20.0. Belowground/aboveground plant tissue concentration ratios varied from 2.2 (Cu) to 32 (Cr) with the average value of 9.9.

Microbial Populations Identified by Fluorescence In Situ Hybridization in a Constructed Wetland Treating Acid Coal Mine Drainage

Microorganisms are an integral part of the biogeochemical processes in wetlands, yet microbial communities in sediments within constructed wetlands receiving acid mine drainage (AMD) are only poorly understood. The purpose of this study was to characterize the microbial diversity and abundance in a wetland receiving AMD using fluorescence in situ hybridization (FISH) analysis. Seasonal samples of oxic surface sediments, comprised of Fe(III) precipitates, were collected from two treatment cells of the constructed wetland system. The pH of the bulk samples ranged between pH 2.1 and 3.9. Viable counts of acidophilic Fe and S oxidizers and heterotrophs were determined with a most probable number (MPN) method. The MPN counts were only a fraction of the corresponding FISH counts. The sediment samples contained microorganisms in the Bacteria (including the subgroups of acidophilic Fe- and S-oxidizing bacteria and Acidiphilium spp.) and Eukarya domains. Archaea were present in the sediment surface samples at < 0.01% of the total microbial community. The most numerous bacterial species in this wetland system was Acidithiobacillus ferrooxidans, comprising up to 37% of the bacterial population. Acidithiobacillus thiooxidans was also abundant. Heterotrophs in the Acidiphilium genus totaled 20% of the bacterial population. Leptospirillum ferrooxidans was below the level of detection in the bacterial community. The results from the FISH technique from this field study are consistent with results from other experiments involving enumeration by most probable number, dot-blot hybridization, and denaturing gradient gel electrophoresis analyses and with the geochemistry of the site.

The effect of vegetation on porewater composition in a natural wetland receiving acid mine drainage

The effect of plant growth on surface and porewater concentrations of Fe, Mn, Cu, and S within a natural wetland receiving acidic spoil heap drainage was determined over a period of one year. Comparisons were made between unvegetated sites and those colonized by either Phragmites australis or Eriophorum angustifolium. The presence of vegetation increased surface and porewater concentrations of Fe and Mn in spring and summer largely due to the effects of higher evapotranspiration rates in vegetated areas. Microbiological processes were also thought to be important in controlling iron and sulfur concentrations at depth due to bacterial sulfate reduction and metal sulfide precipitation and iron and manganese concentrations close to the sediment surface due to bacterially mediated oxidation. These processes varied in importance with season due to changes in the dominant chemical and biological processes, although the complexity of the system prevented isolation of the principal mechanism involved.

Characterization of Natural Wetland Soils Receiving Acid Mine Drainage

A proposed section of Appalachian Corridor H will pass through an area of the Beaver Creek watershed in Tucker County, WV previously mined for the acid-producing Upper Freeport coal. Presently, partially-reclaimed spoils from past mining activities are generating acid mine drainage. Wetlands adjacent to the spoils are supporting vegetative communities and they appear to be naturally treating the drainage. We characterized soils of the acid mine drainage- impacted wetlands and non-impacted wetlands to establish baseline soil status and to compare the acid mine drainage-impacted soils and non-impacted soils. We analyzed soil samples for pH, sulfate, acid volatile sulfides, chromium reducible sulfides, organic sulfur, total sulfur, total carbon, and total iron. Platinum redox electrodes were placed in some of the wetland soils to assess near surface redox chemistry. Wetlands receiving acid mine drainage generally contained higher levels of total sulfur, and the sulfur in these wetlands was more likely to be in the form of acid volatile sulfides, sulfate, and/or chromium reducible sulfides. Chromium reducible sulfides ranged from 0.0 to 103.4 umol g -1 and acid volatile sulfides ranged from 0.0 to 32.3 umol g -1 in all wetlands. The carbon content in wetlands receiving acid mine drainage was generally lower than the non-impacted wetlands and the iron content was generally higher in the acid mine drainage- impacted wetlands. Redox values indicated that conditions are present in impacted wetlands for iron and sulfur reduction to occur.

Field Study on Heavy Metal Accumulation in a Natural Wetland Receiving Acid Mine Drainage

The mechanism of surface water remediation in a natural wetland that is receiving heavy metal-rich acidic mine drainage was investigated. Selective sequential extraction was useful to derive the mechanisms of heavy metal removal in the wetland. In the upstream portion of the wetland, dissolved Fe was removed mainly as oxide-bounded mineral phases, such as hydroxides. These are important for the subsequent removal of other heavy metals. Other ion-exchangeable and carbonate-bounded heavy metals are also observed in the upstream, associated with Fe oxides. Organic matter and Fe–Mn oxides in the upstream remove Cu and Zn ions from the drainage, respectively. In the middle of portion of the wetland the removal of heavy metal ions in relatively low concentrations occurs by the emergent vegetation. Greater clay abundance and higher microbial activity of sulfate reducing bacteria in the downstream parts achieved low-level removal of metals. Multi-cell wetlands are recommended for the treatment of acidic metal bearing surface water drainage, if sufficient land area and expenses are available to construct.

Comparison of heavy metal accumulation in a natural wetland and constructed wetlands receiving acid mine drainage

Metal accumulations in sediments and plants of constructed and natural wetlands were compared in two wetlands constructed by the Tennessee Valley Authority (TVA) for the treatment of acid mine drainage and a natural wetland. Load rates and removal efficiencies of most metals were generally greater in the constructed wetlands than in the natural wetland. There were similar sediment and plant metal concentrations between one constructed wetland and the natural wetland and greater metal concentrations in the sediments and plants in the other constructed wetland compared to the natural wetland. Data indicate that Mn, Zn, Cu, Ni, B, and Cr are being accumulated in the plants at all three wetlands, although accumulation of metals by these plants accounts for only a small percentage of the removal of the annual metal load supplied to each wetland.

Field Study on Heavy Metal Accumulation in a Natural Wetland Receiving Acid Mine Drainage

Field Study on Heavy Metal Accumulation in a Natural Wetland Receiving Acid Mine Drainage

The Interaction of Natural Organic Matter with Iron in a Wetland (Tennessee Park, Colorado) Receiving Acid Mine Drainage

Pore water from a wetland receiving acid mine drainage was studied for its iron and natural organic matter (NOM) geochemistry on three different sampling dates during summer 1994. Samples were obtained using a new sampling technique that is based on screened pipes of varying length (several centimeters), into which dialysis vessels can be placed and that can be screwed together to allow for vertical pore-water sampling. The iron concentration increased with time (through the summer) and had distinct peaks in the subsurface. Iron was mainly in the ferrous form; however, close to the surface, significant amounts of ferric iron (up to 40% of 2 mmol L-1 total iron concentration) were observed. In all samples studied, iron was strongly associated with NOM. Results from laboratory experiments indicate that the NOM stabilizes the ferric iron as small iron oxide colloids (able to pass a 0.45μm dialysis membrane). We hypothesize that, in the pore water of the wetland, the high NOM concentrations (>100 mg C L-1) allow formation of such colloids at the redoxcline close to the surface and at the contact zone to the adjacent oxic aquifer. Therefore, particle transport along flow paths and resultant export of ferric iron from the wetland into ground water might be possible.

Plant Litter Decomposition in Wetlands Receiving Acid Mine Drainage

AbstractThe impact of acid mine drainage on the decomposition of wetland plant species of northern West Virginia was studied to determine if the potential exists for nutrient cycling to be altered in systems used to treat this drainage. There were two objectives of this study. First, decomposition of aboveground plant material was measured to determine species decomposition patterns as a function of pH. Second, decomposition of litter from various pH environments was compared to assess whether litter origin affects decomposition rates. Species differences were detected throughout the study. Decomposition rates of woolgrass [Scirpus cyperinus (L.) Kunth] and common rush (Juncus effusus L.) were significantly lower than those of calamus (Acorus calamus L.) and rice cutgrass (Leersia oryzoides L.). Differences among species explained a large proportion of the variation in percentage of biomass remaining. Thus, differences in litter quality among species was important in determining the rate of decomposition. In general, significantly more decomposition occurred for all species in high pH environments, indicating impeded decomposition at low pH. While decomposition of some species litter differed depending on its origin, other species showed no effect. Cattail (Typha latifolia L.), in particular, was found to have lower decomposition rates occurring with material grown at low pH. Lower decomposition rates could result in lower nutrient availability leading to further reduction of productivity under low pH conditions.

Determination of the Rate of Sulfide Production in a Constructed Wetland Receiving Acid Mine Drainage

Determination of the Rate of Sulfide Production in a Constructed Wetland Receiving Acid Mine Drainage

Diversity Patterns of Invertebrate Fauna in Cattail Wetlands Receiving Acid Mine Drainage

Diversity Patterns of Invertebrate Fauna in Cattail Wetlands Receiving Acid Mine Drainage