Comparison of Methods for Estimating Carbon Evasion and Export Associated with a Coal Mine Discharge

The evasion of CO2 from terrestrial waters plays a role in the global cycling of carbon but there are few datasets that have an accurate accounting of the flux. It has been shown that discharges from coal mines can have elevated concentrations of CO2 due to sulfuric acid-driven dissolution of carbonate rock. In this study, we compared three methods for calculating the export dissolved inorganic carbon (DIC) and the evaluation of CO2 from an abandoned-mine discharge in West Virginia. In Method #1, the source flux is calculated from the discharge and the concentrations at the portal. In Method #2, the stream flux is calculated over a stream reach and considers both upstream and downstream chemistries. In Method #3, the diffusive-flux model estimates evasion based on transport of CO2 through the water column. Methods #2 and 3 can be compared compared by knowing the area of the stream surface between the two measurement points. In general, the methods based on direct measurement of DIC and CO2 (Methods #1 and 2) were greater than the estimates the diffusive-flux model (Method #3). This comparison demonstrates the need for more direct measurements of CO2 if we are to account for carbon export from streams and mine waters

Isotopic evidence of enhanced carbonate dissolution at a coal mine drainage site in Allegheny County, Pennsylvania, USA

18 O SO4 isotopic signatures of the mine drainage and the presence of presumptive SO 4 -reducing bacteria suggest that SO 4 reduction activity also contributes C depleted in 13 C isotope to the total DIC pool. With distance downstream from the mine portal, C isotope signatures in the drainage increased , accompanied by decreased total DIC concentrations and increased pH. These data are consistent with H 2 SO 4 dissolution of carbonate rocks, enhanced by cation exchange, and C release to the atmosphere via CO 2 outgassing

Isotopic evidence of enhanced carbonate dissolution at a coal mine drainage site in Allegheny County, Pennsylvania, USA

18 O SO4 isotopic signatures of the mine drainage and the presence of presumptive SO 4 -reducing bacteria suggest that SO 4 reduction activity also contributes C depleted in 13 C isotope to the total DIC pool. With distance downstream from the mine portal, C isotope signatures in the drainage increased , accompanied by decreased total DIC concentrations and increased pH. These data are consistent with H 2 SO 4 dissolution of carbonate rocks, enhanced by cation exchange, and C release to the atmosphere via CO 2 outgassing

Determination of free CO2 in emergent groundwaters using a commercial beverage carbonation meter

Dissolved CO{sub 2} in groundwater is frequently supersaturated relative to its equilibrium with atmospheric partial pressure and will degas when it is conveyed to the surface. Estimates of dissolved CO{sub 2} concentrations can vary widely between different hydrochemical facies because they have different sources of error (e.g., rapid degassing, low alkalinity, non-carbonate alkalinity). We sampled 60 natural spring and mine waters using a beverage industry carbonation meter, which measures dissolved CO{sub 2} based on temperature and pressure changes as the sample volume is expanded. Using a modified field protocol, the meter was found to be highly accurate in the range 0.2–35 mMCO{sub 2}. The meter provided rapid, accurate and precise measurements of dissolved CO{sub 2} in natural waters for a range of hydrochemical facies. Dissolved CO{sub 2} concentrations measured in the field with the carbonation meter were similar to CO{sub 2} determined using the pH-alkalinity approach, but provided immediate results and avoided errors from alkalinity and pH determination. The portability and ease of use of the carbonation meter in the field made it well-suited to sampling in difficult terrain. The carbonation meter has proven useful in the study of aquatic systems where CO{sub 2} degassing drives geochemical changes that result in surficial mineral precipitation and deposition, such as tufa, travertine and mine drainage deposits

Determination of free CO2 in emergent groundwaters using a commercial beverage carbonation meter

Dissolved CO{sub 2} in groundwater is frequently supersaturated relative to its equilibrium with atmospheric partial pressure and will degas when it is conveyed to the surface. Estimates of dissolved CO{sub 2} concentrations can vary widely between different hydrochemical facies because they have different sources of error (e.g., rapid degassing, low alkalinity, non-carbonate alkalinity). We sampled 60 natural spring and mine waters using a beverage industry carbonation meter, which measures dissolved CO{sub 2} based on temperature and pressure changes as the sample volume is expanded. Using a modified field protocol, the meter was found to be highly accurate in the range 0.2–35 mMCO{sub 2}. The meter provided rapid, accurate and precise measurements of dissolved CO{sub 2} in natural waters for a range of hydrochemical facies. Dissolved CO{sub 2} concentrations measured in the field with the carbonation meter were similar to CO{sub 2} determined using the pH-alkalinity approach, but provided immediate results and avoided errors from alkalinity and pH determination. The portability and ease of use of the carbonation meter in the field made it well-suited to sampling in difficult terrain. The carbonation meter has proven useful in the study of aquatic systems where CO{sub 2} degassing drives geochemical changes that result in surficial mineral precipitation and deposition, such as tufa, travertine and mine drainage deposits

Geochemical Comparison of Karst and Clastic Springs in the Appalachian Valley & Ridge Province, Southeastern West Virginia and Central Pennsylvania

The Appalachian Valley and Ridge (V&R) Province extends over 11 states and is an essential water supply. The regional geology consists of more resistant clastic rocks, typically sandstones and mixed shales, which form the ridge tops and mountain flanks, and carbonate rocks that underlie the valleys. In this study, we report the geochemistry of different types of springs on and near Peter’s Mountain in Monroe County, WV. More than 250 springs have been mapped in the ~225 km2 study area on and adjacent to Peter’s Mountain. These data are compared with preliminary data collected from sandstone-sourced springs from central PA and northcentral WV. Six sandstone springs in WV and PA were sampled and monitored for comparison to the Monroe County springs. Springs were grouped by geologic and geomorphologic location: Group 1: sandstone-sourced springs in WV and PA; Group 2: springs in the Martinsburg Formation on the western flank of Peter’s Mountain; and, Group 3: springs in the carbonate valley west of Peter’s Mountain. In general, Group 1 springs are smaller and more ephemeral than the other groups; their waters have low pHs (4.1-6.0), low specific conductivities (24 to 55 μS/cm), and low concentrations of dissolved ions. Group 2 springs are also small and ephemeral but have higher pHs (6.7 -8.4) and specific conductivities (73-308 μS/cm) due to the mixture of shales and carbonates in the source formation. Temperatures in these springs range from highly consistent to highly variable. Although the Group 2 springs along Peter’s Mountain have Ca and Mg concentrations similar to the Group 3 carbonate springs, they can be distinguished by higher Ca/Mg mole ratios. In contrast, Group 3 springs have higher pHs (6.6-8.4) and higher specific conductivities (144-750 μS/cm)

Estimating Preferential Flow in Karstic Aquifers Using Statistical Mixed Models

Karst aquifers are highly productive groundwater systems often associated with conduit flow. These systems can be highly vulnerable to contamination, resulting in a high potential for contaminant exposure to humans and ecosystems. This work develops statistical models to spatially characterize flow and transport patterns in karstified limestone and determines the effect of aquifer flow rates on these patterns. A laboratory‐scale Geo‐ HydroBed model is used to simulate flow and transport processes in a karstic limestone unit. The model consists of stainless steel tanks containing a karstified limestone block collected from a karst aquifer formation in northern Puerto Rico. Experimental work involves making a series of flow and tracer injections, while monitoring hydraulic and tracer response spatially and temporally. Statistical mixed models (SMMs) are applied to hydraulic data to determine likely pathways of preferential flow in the limestone units. The models indicate a highly heterogeneous system with dominant, flow‐dependent preferential flow regions. Results indicate that regions of preferential flow tend to expand at higher groundwater flow rates, suggesting a greater volume of the system being flushed by flowing water at higher rates. Spatial and temporal distribution of tracer concentrations indicates the presence of conduit‐like and diffuse flow transport in the system, supporting the notion of both combined transport mechanisms in the limestone unit. The temporal response of tracer concentrations at different locations in the model coincide with, and confirms the preferential flow distribution generated with the SMMs used in the study.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/108043/1/gwat12084.pd

Isotopic evidence of enhanced carbonate dissolution at a coal mine drainage site in Allegheny County, Pennsylvania, USA

Stable isotopes were used to determine the sources and fate of dissolved inorganic C (DIC) in the circumneutral pH drainage from an abandoned bituminous coal mine in western Pennsylvania. The C isotope signatures of DIC (δ{sup 13}C{sub DIC}) were intermediate between local carbonate and organic C sources, but were higher than those of contemporaneous Pennsylvanian age groundwaters in the region. This suggests a significant contribution of C enriched in {sup 13}C due to enhanced carbonate dissolution associated with the release of H{sub 2}SO{sub 4} from pyrite oxidation. The Sr isotopic signature of the drainage was similar to other regional mine waters associated with the same coal seam and reflected contributions from limestone dissolution and cation exchange with clay minerals. The relatively high δ{sup 34}S{sub SO4} and δ{sup 18}O{sub SO4} isotopic signatures of the mine drainage and the presence of presumptive SO{sub 4}-reducing bacteria suggest that SO{sub 4} reduction activity also contributes C depleted in {sup 13}C isotope to the total DIC pool. With distance downstream from the mine portal, C isotope signatures in the drainage increased, accompanied by decreased total DIC concentrations and increased pH. These data are consistent with H{sub 2}SO{sub 4} dissolution of carbonate rocks, enhanced by cation exchange, and C release to the atmosphere via CO{sub 2} outgassing