This page highlights selected articles from a limited group of peer-reviewed journals that may have relevance to those involved in the management of environmental risks from mining operations. The focus is on articles which provide insight into the processes that result in environmental contamination, and innovations that may allow us to mitigate the environmental resultant impacts.
APPLIED GEOCHEMISTRY (ISSN 0883-2927), Elsevier, Amsterdam
For abstracts go to http://www.elsevier.com/locate/apgeochem or http://www.sciencedirect.com
Cornelis, G., C. A. Johnson, T.V. Gerven and C. Vandecasteele (2008). "Leaching mechanisms of oxyanionic metalloid and metal species in alkaline solid waste: A review." Appl. Geochem. 25(5): 955-976.
The preferential mobility of certain elements (eg., Mo, Se, As, Cr, Sb and V) under alkaline condition is anomalous relative to the conventional, but flawed, wisdom that everything is more mobile under acidic conditions. Comelis et al. (2008) provide a detailed review of the available thermodynamic data, field and laboratory observations, and likely controlling mechanisms for these elements. Sorption and solution formation is a more likely solubility control than is precipitation of pure phases.
Sasaki, K., D. W. Blowes, C.J. Ptacek and W.D. Gould (2008). "Immobilization of Se(VI) in mine drainage by permeable reactive barriers: column performance." Appl. Geochem. 23 (5): 10.
Selenium is a particularly problematic contaminant when it occurs in ores, waste rock , effluents and runoff because of its toxicity, low regulatory limits and difficult treatment. Traditional water treatment technologies tends to be inadequate because of Se(VI) forms the oxyanion SeO42- and behaves much like SO42-. Sasaki et al. (2008) present encouraging evidence that zero-valent iron (ZVI) in combination with organic matter can act as an effective permeable engineered barrier for Se removal. Influent concentrations of 40 mg/L were reduced to less than 25 µg/L.
Bettiol, C., L. Stievano, M. Bertelle, F. Delfino and E. Argese (2008). "Evaluation of microwave-assisted extraction procedures for the determiation of metal content and potential bioavailability in sediments." Appl. Geochem. 23(5): 1140-1151.
Bettiol et al (2008) contribute to the literature related to a rational assessment of solids relative to their environmental risks for release of metals. Although such methods as Toxicity Characteristics Leaching Procedure (TCLP) and Meteoric Water Mobility Procedures (MWMP) have their place as reference points, they do little to address release mechanisms and actual environmental risk.
Martín, F., I. García, M. Díez, M. Sierra, M. Simon and C. Dorronsoro (2008). “Soil alteration by continued oxidation of pyrite tails.” Appl. Geochem. 23 (5): 1152-1165.
Massive sulfide flotation tails pose special environmental problems due to extremely high iron sulfide contents and typically high reaction rates. Martín et al. (2009) document the reactivity of 80-90 % pyrite tails freshly deposited on soils and subjected to repeated wetting, drying and cracking. Soils under a 4.5 cm deposit were acidified and otherwise mineralogically altered to a depth of 7 cm in three years. This provides anecdotal information on the potential rates of oxidation of surficial layers of subaerially deposited highly reactive tails.
Butler, B.A., J.F. Ranville, and P.E. Ross (2008). “Direct versus indirect determination of suspended sediment-associated metals in a mining-influenced watershed.” Appl. Geochem. 23 (5): 1218-1231.
The distinction between total, “suspended” and “dissolved” metal concentration is always operationally (experimentally)-defined but can be critical for comparison to compliance criteria (which are often poorly defined or even undefined). Butler et al. (2008) demonstrate that the traditionally method of determining “suspended” metal concentration by difference (i.e., total less dissolved) yields results comparable to results derived from direct analysis of suspended matter.
Fernández-Caliani, J.C., C. Barba-Brioso, R. Pérez-López. “Long-term interaction of wollastonite with acid mine water and effects on arsenic and metal removal.” Appl. Geochem. 23 (5):1288-1298.
Wollastonite (CaSiO3) is a potential constituent of skarns associated with contact metamorphic aureoles adjacent to mineralized intrusions. As such, it may be a component of waste rock. Fernández-Caliani et al. (2008) considered the potential for wollastonite to neutralize acid rock drainage (ARD) given the high equilibrium pH of clean water in contact with the mineral (10.4) due to simple dissolution. However, their investigation found that contact with ARD (as opposed to clean water) resulted in complex incongruent reactions with precipitation of gypsum, amorphous Si, Fe-Al oxyhydroxides and/or oxy-hydroxysulfates and acidic pHs. The iron solids are apparently a source of buffering maintaining a pH between 3 and 5 depending on the composition of the ARD and the amount of wollastonite reacted. Metal attenuation was determined to be due to sorption onto Fe-bearing phases but was limited due to H+ competition.
Malmström, M. E., Berglund, S., and Jarsjö, J., 2008. Combined effects of spatially variable flow and mineralogy on the attenuation of acid mine drainage in groundwater. Appl. Geochemistry 23 1419-1436.
Malmström et al. considers groundwater transport of zinc-contaminated ARD from a tailings storage facility. The extreme physical and chemical complexities of such systems are acknowledged, along with high demand for field characterization and the computational requirements of deterministic modeling approaches. To avoid some of the resulting difficulties and to improve predictions, the authors employ the LaSAR-PHREEQC approach. Individual “stream tubes”, each with different travel times, are modeled as comparatively simple flow paths resulting in an array of potential outcomes. The relative frequencies of streamtubes with different travel times in the studied transport domain are then obtained from a separate analysis of flow and advective transport.
Moldovan, B. J., Hendry, M. J., and Harrington, G. A., 2008. The arsenic source term for an in-pit uranium mine tailings facility and its long-term impact on the regional groundwater. Appl. Geochemistry 23, 1437-1450.
Moldovan et al. modeled pore water chemistry and movement in an in-pit tailings disposal facility using 3-D multi-component transport modeling. Characterization was conducted via sonic coring from a barge, and pore waters and solids were analyzed. Laboratory diffusion cells provided quantification of porosity, diffusion coefficients and sorption coefficients (KD). Sorption onto ferrihydrite was concluded to be the primary attenuation mechanism for arsenic. Using a range of loading capacities for As, concentrations in surrounding groundwater could be shown to be protective of the environment. Precipitation as Ca-As solids is also considered.
Frau, F., Biddau, R., and Fanfani, L., 2008. Effect of major anions on arsenate desorption from ferrihydrite-bearing natural samples. Appl. Geochemistry 23, 1451-1466.
Frau et al. investigated the influence of carbonate, sulfate, phosphate, nitrate and chloride on As desorption and found marked increases in desorption in the presence of phosphate and carbonate. pH effects were found to be less important than calcium. Modeling revealed inadequacies in the sulfate adsorption constants leading to strong overestimation of As release at pH 4 and overestimation at pH 7.5. Constants are provided for all anions tested.
Haffert, L. and Craw, D., 2008. Mineralogical controls on environmental mobility of arsenic from historic mine processing residues, New Zealand. Appl. Geochemistry 23, 1467-1483.
Haffert and Craw investigated high soil As concentrations surrounding a roaster at the abandoned Blackwater gold mine where arsenopyrite was the primary As-bearing mineral. Arsenolite (AsIII2O3) from roasting, soluble under oxidizing conditions, resulted in high AsV concentrations capable of precipitating and maintaining scorodite (two to five orders of magnitude less soluble than arsenolite), which formed a hard soil pan containing 30% As and encapsulating arsenolite. Complete dissolution of arsenolite results in scorodite instability in the soil environment. In downstream bog environments, arsenolite once more becomes the solubility control allowing high dissolved concentrations of As.
Rötting, T. S., Caraballo, M. A., Serrano, J. A., Ayora, C., and Carrera, J., 2008. Field application of the calcite Dispersed Alkaline Substrate (calcite-DAS) for passive treatment of acid mine drainage with high Al and metal concentrations. Appl. Geochem. 23, 1660-1674.
The authors report on the results of a pilot-scale semi-passive, down-flow tank, AMD-treatment system based on limestone sand suspended in a wood-chip matrix, completely submerged in the flow stream. Inflow was described as pH 3.3, 1400 – 1650 mg/L as CaCO3 net acidity, 317 mg/L Fe, 311 mg/L Zn and 74 mg/L Al. The system removed 56%, 25%, 5% and 93% of the acidity, Fe, Zn and Al, respectively. Experimental flows were 0.5 m3/m2/day. Although the limestone grain size prevented armoring, the operation of the tank was limited by formation of an Al-rich hardpan. Overall performance was described as “more efficient” but “less passive” than anoxic limestone drains or vertical flow wetlands.
