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Average electrical conductivity, pH, and elemental concentrations from solutions of dilute nitric acid shaking experiments for each of the 41 overburden samples at the end of the 72-hr shaking period
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The Appalachian coal industry has been successful in developing technologies to identify, handle, treat and isolate potentially acid-forming overburden materials at coal mines in the region. Modern coal mining permits have stringent guidelines for reclamation and water discharge limits. Total dissolved solids (TDS) is a new water quality parameter...
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Coal mining, the first step in the filthy lifecycle of coal causes deforestation and releases toxic amounts of minerals and heavy metals into the soil and water environment. Coal mining's environmental effects persist for years after coal is removed.Based on the latest technologies on coal mining practices are better than what was done earlier days...
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... For example, total digestion and chemical analysis can identify the presence of a COI, but release rates are not necessarily proportional to these concentrations (Querol et al., 2008;Zhang and Ouyang, 2014). Similarly, assuming absence of a source based on undersaturation estimated from geochemical modelling can be misleading (e.g., demonstrated for siderite in Biswas et al. (2017)), as can the assumption of a source without direct analysis (e.g., plagioclase feldspar (Clark et al., 2018) vs carbonates (Clark et al., 2017;Daniels et al., 2016;Odenheimer et al., 2015;Orndorff et al., 2015) as the short and long-term source of neutralisation). Source identification can also be affected by: 1) the scale of measurement, e.g., uranium sources identified by batch leaching tests (Kříbek et al., 2017) compared to field lysimeters ; and 2) the number of analyses, e.g., for NO 3 − Mahmood et al. ...
Coal has been a major global resource for at least the past 250 years. The major waste product of coal mining is waste rock, which is stored in dumps of various sizes. Although the adverse effects of coal waste rock dumps on ecosystems and human health are widely recognised, there is little information on their internal hydrological and geochemical processes in the peer-reviewed literature. Coal and conventional waste rock dumps share many similarities, but coal waste rock dumps differ in structure, organic matter content, and size, which can affect the timing and rate of aqueous chemical release. In this global systematic review, we identify limited links to climate setting and dump construction, and inconsistent reporting of sampling and monitoring approaches, as limitations to the generalisation of findings. Furthermore, sources of aqueous constituents of interest (COIs) are not routinely or adequately identified, which can lead to incorrect assumptions regarding COI availability and geochemical mobility. Water flow regimes within dumps are dominated by matrix and/or preferential flow, depending on dump texture; these flow mechanisms exert a primary control on patterns of aqueous COI release. The inability to successfully transfer COI release rates from laboratory or field scale trials to operational scale dumps is primarily due to limitations of testing methods and fundamental characteristics of scale. Prediction of future release rates is hampered by a lack of long-term studies that fully characterise geochemistry (e.g., source and COI production rates) as well as dump hydrology (e.g., water balance, water migration). Five critical elements to include in best practice investigations are climate setting, dump physical characteristics, geochemical processes, water regime, and environmental load over time, as aqueous release of COIs from coal waste rock dumps occurs over decades to centuries. Key considerations are identified for each of these elements to guide best practice.
... Because ABA parameters such as maximum potential acidity (MPA) and net neutralization potential (NNP) are used by coal companies to characterize overburden and are readily measured, their ability to be used to predict TDS release has been evaluated. Odenheimer et al. (2015) demonstrated that MPA and NNP may be useful to indicate general levels of low, moderate, and high TDS release; however, their semi-quantitative model was based on TDS computed from paste SC for a pulverized rock sample and did not consider upscaled or field-measured leachate characteristics. Modifying a method described by Barnhisel andHarrison (1976) andO'Shay et al. (1990), Orndorff et al. (2010) developed an alternative to the MPA method that used hydrogen peroxide (30% H 2 O 2 ) to oxidize sulfide minerals. ...
... Available information from previous column studies and water quality data from 10 field sites were compared with our batch extractions. Seventeen overburden samples and three weathered coal refuse samples (Table 1) were previously analyzed in column studies (Agouridis et al., 2012;Daniels et al., 2009Daniels et al., , 2014bDaniels et al., , 2016Hornberger and Brady, 2009;Odenheimer et al., 2015;Sena et al., 2014). In general, all column studies maintained unsaturated conditions with simulated rainfall (pH 4.6) leaching events. ...
A rapid batch extraction method was evaluated to estimate potential for total dissolved solids (TDS) release by 65 samples of rock from coal and gas-bearing strata of the Appalachian Basin in eastern USA. Three different extractant solutions were considered: deionized water (DI), DI equilibrated with 10% CO2 atmosphere (DI + CO2), or 30% H2O2 under 10% CO2 (H2O2+CO2). In all extractions, 10 g of pulverized rock (<0.5-mm) were mixed with 20 mL of extractant solution and shaken for 4 h at 50 rpm and 20–22 °C. The 65 rock samples were classified as coal (n=3), overburden (n = 17), coal refuse that had weathered in the field (n = 14), unleached coal refuse that had oxidized during indoor storage (n = 20), gas-bearing shale (n = 10), and pyrite (n = 1). Extracts were analyzed for specific conductance (SC), TDS, pH, and major and trace elements, and subsequently speciated to determine ionic contributions to SC. The pH of extractant blanks decreased in the order DI (6.0), DI + CO2 (5.1), and H2O2+CO2 (2.6). The DI extractant was effective for mobilizing soluble SO4 and Cl salts. The DI + CO2 extractant increased weathering of carbonates and resulted in equivalent or greater TDS than the DI leach of the same material. The H2O2+CO2 extractant increased weathering of sulfides (and carbonates) and resulted in the greatest TDS production and lowest pH values. Of the 65 samples, 19 had leachate chemistry data from previous column experiments and 35 were paired to 10 field sites with leachate chemistry data. When accounting for the water-to-rock ratio, TDS from DI and DI + CO2 extractions were correlated to TDS from column experiments while TDS from H2O2+CO2 extractions was not. In contrast to column experiments, field SC was better correlated to SC measured from H2O2+CO2 extractions than DI extractions. The field SC and SC from H2O2+CO2 extractions were statistically indistinguishable for 7 of 9 paired data sets while SC from DI extractions underestimated field SC in 5 of 9 cases. Upscaling comparisons suggest that (1) weathering reactions in the field are more aggressive than DI water or synthetic rainwater extractants used in batch or column tests, and (2) a batch extraction method utilizing 30% H2O2 (which is mildly acidic without CO2 enrichment) could be effective for identifying rocks that will release high amounts of TDS.
... Pyrite, bound up in coal residue and shales, produces sulfuric acid when exposed to oxygen and water [12]. In MTMVF spoils, this sulfuric acid is neutralized by carbonate materials, which are intentionally mixed with spoils to prevent acid-mine drainage [13,14]. The ready supply of sulfuric acid, carbonate bedrock, and high surface-area spoil materials creates ideal conditions for some of the highest weathering rates in the world. ...
Surface mining for coal has taken place in the Central Appalachian region of the United States for well over a century, with a notable increase since the 1970s. Researchers have quantified the ecosystem and health impacts stemming from mining, relying in part on a geospatial dataset defining surface mining’s extent at a decadal interval. This dataset, however, does not deliver the temporal resolution necessary to support research that could establish causal links between mining activity and environmental or public health and safety outcomes, nor has it been updated since 2005. Here we use Google Earth Engine and Landsat imagery to map the yearly extent of surface coal mining in Central Appalachia from 1985 through 2015, making our processing models and output data publicly available. We find that 2,900 km² of land has been newly mined over this 31-year period. Adding this more-recent mining to surface mines constructed prior to 1985, we calculate a cumulative mining footprint of 5,900 km². Over the study period, correlating active mine area with historical surface mine coal production shows that each metric ton of coal is associated with 12 m² of actively mined land. Our automated, open-source model can be regularly updated as new surface mining occurs in the region and can be refined to capture mining reclamation activity into the future. We freely and openly offer the data for use in a range of environmental, health, and economic studies; moreover, we demonstrate the capability of using tools like Earth Engine to analyze years of remotely sensed imagery over spatially large areas to quantify land use change.
... Postmining landscapes have lower slopes (Maxwell & Strager, 2013;Ross et al., 2016), increased water storage potential (Barbour et al., 2016;Ross et al., 2016;Wunsch et al., 1999), altered hydrologic flowpaths (Greer et al., 2017;Messinger & Paybins, 2003;Miller & Zégre, 2014;Nippgen et al., 2017;Zegre et al., 2014), and acid-generating pyrite in the particularly reactive form of small pyrite particles (Clark et al., 2018). Pyrite-bearing rocks are intentionally mixed with acid-neutralizing carbonate-bearing bedrock (Odenheimer et al., 2014) to prevent acid mine drainage. The physical fragmentation of bedrock alone likely leads to elevated weathering rates due to an increase in exposed surface area (equation (2)) as seen for rapidly weathering glacial till deposits (Calmels et al., 2007;Hilton et al., 2014;Lyons et al., 2005;Torres et al., 2017). ...
Weathering is the ultimate source of solutes for ecosystems, controls chemical denudation of landscapes, and drives the geologic carbon cycle. Mining and other land-moving operations enhance physical weathering by bringing large volumes of shattered bedrock to the surface. Yet, the relative influence of these activities on chemical weathering remains poorly constrained. Here we show that catchments impacted by mountaintop removal coal mining have among the highest rates of chemical weathering ever reported. Mined catchments deliver more than 7,600 kg·ha⁻¹·year⁻¹ of dissolved solids downstream. The chemical signatures of these exceptionally high weathering rates reflect the product of sulfuric acid weathering of carbonate-bearing rock, driven by the oxidation of pyritic materials. As this strong acid rapidly weathers surrounding carbonate materials, H⁺ ions are consumed and Ca²⁺, Mg²⁺, and HCO3⁻ ions are exported to balance the elevated SO4²⁻ exports, generating alkaline mine drainage. The sulfate exports from pyrite oxidation in mountaintop-mined catchments account for ~5–7% of global sulfate derived from pyrite, despite occupying less than 0.006% of total land area. Further, the suite of weathering reactions liberate 100–450 kg of rock-derived C·ha⁻¹·year⁻¹ as CO2, with an additional 90–150 kg C·ha⁻¹·year⁻¹ of C released when HCO3⁻ reaches the ocean. This rock C release contributes to the high carbon costs of coal combustion.
... Higher sulfur content in overburden (expressed as MPA) is related to higher TDS release Odenheimer et al. (2013). The %S measured in the core strata correlated well with TDS in column leachate for unmodified cores 1 and 2 (R = 0.982 and 0.996, respectively) ( Fig. 1a) but not as well (R = 0.770) in unmodified core 3; however, the correlation was lower (R = 0.504) when all outliers (%S > 0.2) were removed (Supplemental Table 2). ...
The exposure of readily soluble components of overburden materials from surface coal mining to air and water results in mineral oxidation and carbonate mineral dissolution, thus increasing coal mine water conductivity. A conductivity benchmark of 300 µS/cm for mine water discharges in the Appalachian region has been suggested to protect aquatic life and the environment. A USGS screening-level leach test was applied to individual strata from three cores collected from a surface mine site in the central Appalachian region to generate preliminary conductivity rankings, which were used to classify strata for two disposal scenarios: (1) unmodified scenario, which included all extracted strata and (2) modified scenario, which excluded 15% (by mass) of the overburden materials with the highest conductivities. We evaluated overburden leaching conductivity using EPA Method 1627 in 18 dry–wet cycles, generating conductivities of 1020–1150 µS/cm for the unmodified scenario and 624–979 µS/cm for the modified scenario. Hence, overburden segregation was successful in reducing the leachate conductivity, but did not reach the proposed benchmark. The leachate was dominated by sulfate in the first four cycles and by bicarbonates in cycles 5–18 in columns with higher sulfur content, while bicarbonates were dominant throughout experiments with overburden having lower sulfur content. The use of conductivity rankings, isolation of potentially problematic overburden strata, and appropriate materials management could reduce conductivity in central Appalachian streams and other surface mining areas.
... The overburden material, which covers the coal seam, is typically blasted and removed in order to reach the coal seam. This process allows exposure of these materials to physical and chemical weathering, which can release soluble constituents into surrounding water resources (Odenheimer et al., 2015). These samples were collected randomly within the radius of approximately 5 km from the open pit in all directions to find out the impact of coal mining in these areas. ...
The deterioration of environmental conditions is the major contributory factor to poor health and quality of life that hinders sustainable development in any region. Coal mining is one of the major industries that contribute to the economy of a country but it also impacts the environment. The chemical parameters of the coal, overburden, soil and sediments along with the coal mine drainage (CMD) were investigated in order to understand the overall environmental impact from high sulphur coal mining at North-eastern coalfield (India). It was found that the total sulphur content of the coal is noticeably high compared to the overburden (OB) and soil. The volatile matter of the coal is sufficiently high against the high ash content of the soil and overburden. The water samples have a High Electrical Conductivity (EC) and high Total Dissolve Solid (TDS). Lower values of pH, indicate the dissolution of minerals present in the coal as well as other minerals in the mine rejects/overburden. The chemical and nano-mineralogical composition of coal, soil and overburden samples was studied using a High Resolution-Transmission Electron microscopy (HR-TEM), Energy Dispersive Spectroscopy (EDS), Selected-Area Diffraction (SAED), Field Emission-Scanning Electron Microscopy (FE-SEM)/EDS, X-Ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Raman and Ion-Chromatographic analysis, and Mössbauer spectroscopy. From different geochemical analysis it has been found that the mine water sample from Ledo colliery has the lowest pH value of 3.30, Tirap colliery samples have the highest electrical conductivity value of 5.40 mscm⁻¹. Both Ledo and Tirap coals have total sulphur contents within the range 3–3.50%. The coal mine water from Tirap colliery (TW-15B) has high values of Mg⁺² (450 ppm), and Br⁻ (227.17 ppm). XRD analysis revealed the presence of minerals including quartz and hematite in the coals. Mineral analysis of coal mine overburden (OB) indicates the presence both of pyrite and marcasite which was also confirmed in XRD and Mossbauer spectral analysis. The presented data of the minerals and ultra/nano-particles present shows their ability to control the mobility of hazardous elements, suggesting possible use in environmental management technology, including restoration of the delicate Indian coal mine areas.
... Recent studies of TDS release from southwest Virginia spoils (n ¼ 15) in laboratory columns (Orndorff et al., 2015) and from eastern Kentucky spoils (n ¼ 3) in large field lysimeters (Agouridis et al., 2012; Sena et al., 2014) have indicated that (a) rock type and extent of pre-mine weathering have a strong influence on overall TDS release risk; (b) leachate SC levels are at their highest immediately after mine-spoil exposure and then drop relatively quickly over time; and (c) initial TDS release is dominated by SO 4 and Ca þ Mg, but HCO 3 increases with leaching as sulfate concentration declines over time. In a parallel study to the results reported here, Odenheimer et al. (2014) found that several ABA parameters such as maximum potential acidity (MPA; total-S Â 31.25) could reliably predict initial 1:2 spoil:water paste extract SC levels in a large set (n ¼ 41) of regional spoils and could therefore presumably be used to predict actual spoil discharge TDS risk. Historically, ABA has been the dominant set of laboratory static analyses utilized to predict coal mine drainage quality (Skousen et al., 2002). ...
... The combined variable MPA þ Sobek-NP did produce a relatively weak predictor for tail SC, however. In a parallel study to ours, Odenheimer et al. (2014) analyzed the same spoil sample set (along with two additional high SC samples from WV; total n ¼ 41) and found that MPA could reliably predict (R 2 ¼ 0.80) initial saturated paste TDS levels and therefore concluded that overall TDS risk (low, medium and high) Table 2Summary of simple correlation results (r values) for static lab predictors vs. initial peak and long-term tail specific conductance (SC). Analysis shown for complete data set (n ¼ 39) and with strong outliers (peak e 2; tail e 1; n ¼ 37) associated with black shale samples removed. ...
Appalachian USA surface coal mines face public and regulatory pressure to reduce total dissolved solids (TDS) in discharge waters, primarily due to effects on sensitive macroinvertebrates. Specific conductance (SC) is an accurate surrogate for TDS and relatively low levels of SC (300–500 μS cm−1) have been proposed as regulatory benchmarks for instream water quality. Discharge levels of TDS from regional coal mines are frequently >1000 μS cm−1. The primary objectives of this study were to (a) determine the effect of rock type and weathering status on SC leaching potentials for a wide range of regional mine spoils; (b) to relate leachate SC from laboratory columns to actual measured discharge SC from field sites; and (c) determine effective rapid lab analyses for SC prediction of overburden materials. We correlated laboratory unsaturated column leaching results for 39 overburden materials with a range of static lab parameters such as total-S, saturated paste SC, and neutralization potential. We also compared column data with available field leaching and valley fill discharge SC data. Leachate SC is strongly related to rock type and pre-disturbance weathering. Fine-textured and non-weathered strata generally produced higher SC and pose greater TDS risk. High-S black shales produced the highest leachate SC. Lab columns generated similar range and overall SC decay response to field observations within 5–10 leaching cycles, while actual reduction in SC in the field occurs over years to decades. Initial peak SC can be reliably predicted (R2 > 0.850; p < 0.001) by simple lab saturated paste or 1:2 spoil:water SC procedures, but predictions of longer-term SC levels are less reliable and deserve further study. Overall TDS release risk can be accurately predicted by a combination of rock type + S content, weathering extent, and simple rapid SC lab measurements.
