Conference Agenda

Overview and details of the sessions of this Conference. Please select a date or location to show only sessions at that day or location. Please select a single session for a detailed view (with abstracts and downloads if available). The programme is preliminary and subject to change!

Please note that all times are shown in the time zone of the conference. The current conference time is: 31st Oct 2024, 07:46:25pm EDT

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Session Overview
Session
Mine Water Geochemistry
Time:
Friday, 26/Apr/2024:
8:30am - 9:45am

Session Chair: Charles A Cravotta III
Location: Salons A–C


1. First speaker: 8:30-8:55
2. Second speaker: 8:55-9:20
3. Third speaker: 9:20-9:45

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Presentations

The release of dissolved inorganic carbon (DIC) and CO₂ from coal mine drainages

Dorothy J Vesper1, Charles A Cravotta III2, Kyle Fredrick3, Ellen K Herman4, Lili Lei5, Jill L Riddell6, Mathew L Bell1, Lauren J Rockwell1, Camille R Schaffer7

1West Virginia University, USA; 2USGS; 3Penn West University, USA; 4Bucknell University, USA; 5Sweet Brier College, USA; 6Chatham University, USA; 7University of Pittsburgh, USA

Coal utilization contributes to the release of geologically-bound carbon directly through combustion plus indirectly by accelerated weathering of carbonate minerals. Although CO₂ from combustion is instantly added to the modern carbon cycle, sulfuric-acid driven weathering of carbonate minerals tends to release old carbon for decades. Coal mine drainage (CMD) commonly contains elevated concentrations of dissolved inorganic carbon (DIC) derived from weathering of overburden minerals, with corresponding partial pressure of CO₂ ranging from 10 to 1000 times greater than atmospheric equilibrium. Depending on the pH, the release of DIC can be in the form of CO₂, which degasses to the atmosphere, or as dissolved bicarbonate exported downstream. The sulfuric-acid driven weathering of carbonate rocks in coal may have important implications for global carbon cycles because the old carbon is released without the concomitant drawdown of atmospheric carbon as with carbonic-acid driven weathering.

Our work employs the Anton Paar Carbonation Meter to obtain accurate and precise concentrations of CO₂ and DIC in water. By obtaining data via this method, we avoid the pitfalls from determining CO₂ via back-calculation from either alkalinity or conventional DIC analysis. Furthermore, this approach allows us to determine the CO₂ concentration in low-pH waters; these are generally excluded in studies of carbon flux from terrestrial waters.

We have collected DIC and CO₂ data from CMD sites in the northern Appalachian Basin, including mines in West Virginia and from both the bituminous and anthracite regions of Pennsylvania. The DIC concentrations almost always exceed atmospheric equilibrium values. Based on published and measured data, the release of DIC from individual mine discharges exceeds estimates and reported concentrations for carbonate springs or most terrestrial surface waters. Furthermore, DIC at a given CMD source can be relatively consistent or vary significantly over various time scales. Diurnal cycles, rain events, shifts in recharge, and seasonal changes in precipitation can alter the DIC concentration and flux.

The implications of this work have yet to be fully determined although one study indicates that 140 mines in Pennsylvania have a comparable emission to a small power plant (Vesper et al. 2016, doi.org/10.1007/s12665-015-5191-z). Given that this is only a subset of the mine discharges in Pennsylvania, this emission is an underestimate of the total flux. Better regional-scale estimates will require more watershed-based spatial data and more precise discharge location information; additional sampling would help constrain possible temporal variations.



Improving Fe oxidizing/removal process by limestone addition to rice husk bed on large scale passive treatment test for AMD in Japan

Masataka Kondo, Yusei Masaki, Kana Hagihara, Koki Iguchi, Takaya Hamai, Yuki Semoto, Taro Kamiya, Masao Okumura, Naoki Sato

Japan Organization for Metals and Energy Security, Japan

In Japan, mine water drainage is treated in approximately 100 abandoned mine sites by active treatment. Since abandoned mine sites in Japan are located in mountainous area, there are few level areas available for the treatment. JOGMEC (Japan Organization for Metals and Energy Security) has been conducting research and development for compact passive treatment system to reduce the treatment cost with a short hydraulic retention time (HRT).
A large scale passive treatment test with 100 L/min flow rate has been conducted on a domestic abandoned mine site since 2020. The acid mine drainage (AMD) (pH3.6) contains 38 mg/L Fe (mainly as ferrous), 16 mg/L Zn, 4.6 mg/L Cu and 0.06 mg/L Cd. The treatment system has two steps of process with vertical downflow bioreactors; Fe oxidizing/removal process and sulfate-reducing process.
For Fe oxidation and removal, the bioreactor filled with rice husk at a 0.5 m thickness (HRT of 2 hours) for the bed of Fe oxidizing bacteria and for trapping iron precipitates (mainly as schwertmannite). The AMD is introduced into the reactor from above water surface to increase the concentration of dissolved oxygen (DO) over 5.8 mg/L at water surface from approximately 0 mg/L for oxidation of ferrous by Fe oxidizing bacteria. The pH value and soluble Fe concentrations in effluent were approximately pH 3.0 and 7 mg/L (Fe removal rates were 80%) on average from the start of the test, respectively.
To improve Fe removal rate by increasing the pH value of the effluent, the content of the reactor was changed to a mixture of rice husk and limestone (20-40cm) with a 0.5 m thickness. Weight ratios of rice husk/limestone were set 1/4 by considering balance of clogging speed and pH elevation range from the preliminary test results. As a result, the pH value and soluble iron concentrations in effluent were approximately pH 3.7 and 4 mg/L (Fe removal rates were 90%), respectively. Since the effluent pH met the range of 2-4 in which schwertmannite formed, iron precipitates were almost the same as the former condition. The test is continuously being conducted to evaluate its sustainability.



Diurnal cycles of dissolved inorganic carbon and dissolved metals at Lambert Run, Harrison County, WV

Jill L Riddell1, Dorothy J Vesper2

1Chatham University, United States of America; 2West Virginia University, United States of America

Diurnal cycling of dissolved metals has been observed in waters affected by coal mine drainage, or CMD, (Riddell, 2015; Vesper and Smilley, 2010) and metal mine drainage (Gammons et al., 2010; Nimick et al., 2005; Sullivan et al., 1998). Cycling of inorganic carbon (CO2) has been observed in karst rivers (Kurz et al., 2013) and concurrently with dissolved metals in mountain headwater streams (Poulson and Sullivan, 2010) and in a metal mine affected river (Parker et al., 2010). Fewer studies have examined the diurnal cycles of metals in CMD systems containing high CO2. The biological and geochemical effects on metal cycling in CMD during the daily solar cycle and seasonal temperature cycles have implications for water quality monitoring and evaluating the effects of CMD remediation techniques.

This study reports diurnal concentrations of dissolved metals and dissolved inorganic carbon (DIC) at two locations across three seasons (winter, spring, and summer) in a CMD passive treatment system. The first location was 50 m from the mine outflow in a channel lined with limestone riprap, and the second location was 138 m from the outflow in an altered natural wetland. DIC, dissolved oxygen (DO), pH, temperature, total Fe, and reduced Fe were measured in the field. Water samples were collected for laboratory analysis of dissolved metals and d13CDIC. Data were analyzed by fitting the measured concentrations to a cosine curve to confirm statistically significant diurnal behavior.

Parameters exhibiting diurnal behavior were pH, temperature, DO, DIC, d13CDIC, CO2, K, Al, Zn, reduced Fe, total Fe, As, Ni, Mn, and Y however this behavior was variable across seasons and sites. At the upstream location, average concentrations of Fe, Al, Y, Zn, and K increased from winter to summer while CO2 and DIC remained relatively constant. At the downstream location, concentrations of the dissolved metals remained relatively constant acrossseasons and were lower than concentrations at the upstream location.

The change in concentration magnitude of metals between the upstream and downstream locations suggests that sufficient water quality data cannot be collected at a single location or time to determine the effectiveness of CMD treatment systems. These results highlight the importance of robust spatial, seasonal, and daily monitoring of treated mine drainage systems to quantify the total metal concentrations of the discharge stream. Changing seasonal and daily temperatures as well as biological productivity drive the diel behavior of DIC and dissolved metals in these systems.



 
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