Microbial and geochemical controls on waste rock weathering and drainage quality

Blackmore, Sharon; Vriens, Bas; Sorensen, Melanie; Power, Ian M.; Smith, Leslie; Hallam, Steven J.; Mayer, K. Ulrich; Beckie, Roger

doi:10.1016/j.scitotenv.2018.05.374

Cited by 40 publications

(30 citation statements)

References 51 publications

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“…In a minority of field barrels bearing intrusive PAG waste rock with NPR < 1 (3 out of 49 barrels), drainage pH values reached pH < 3 after 5–10 years (Figure 2). The observed release of elevated sulfate and metals such as Fe, Cu, or Zn (concentrations >100 mg/L; Figure S2) from PAG compared to NAG waste rock (concentrations <1 mg/L) aligns with previous research at Antamina 2,52,54,55 and the general notion that weathering of predominantly high-sulfide, low-carbonate waste rock can generate acidic drainage conditions that mobilizes sulfate and metals at high levels. 1,5…”

Section: Resultssupporting

confidence: 87%

“…Unfortunately, useful As/S or Sb/S ratios in the individual field barrel drainage chemistries to substantiate the dissolution of the aforementioned pure As– and Sb–sulfides are obscured by the presence of a myriad of sulfidic minerals and the precipitation of secondary sulfates, mainly gypsum. 2,52…”

Section: Resultsmentioning

confidence: 99%

“…Details of these analytical methods have been described previously. 2,51,52 Detection limits for solid-phase elemental content measurements were typically <2 mg/kg; for bulk mineralogy analyses, <0.1 wt %. A summary of the geochemical characteristics of the initial, unweathered waste rock is given in Figure 1b; detailed waste-rock properties are given in Table S1 (bulk elemental content), Table S2 (bulk mineralogy), and Figure S1 (particle size distributions).…”

Section: Methodsmentioning

confidence: 99%

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Mobilization of Metal(oid) Oxyanions through Circumneutral Mine Waste-Rock Drainage

et al. 2019

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Most studies on the weathering of mine waste rock focus on the generation of acidic drainage with high metal concentrations, whereas metal(loid) release under neutral-rock drainage (NRD) conditions has received limited attention. Here, we present geochemical and mineralogical data from a long-term (>10 years) kinetic testing program with 50 waste-rock field barrels at the polymetallic Antamina mine in Peru. The weathering of most rock lithologies in the field experiments generated circumneutral to alkaline drainage (6 < pH < 9) but with concentrations of the oxyanion-forming metal(loid)s As, Mo, Se, and Sb in the mg/L range. The mobilization of As and Sb was particularly efficient from intrusive, marble and hornfels rocks that contained labile As- and Sb-sulfides, irrespective of bulk elemental content or waste-rock reactivity. High-alkalinity drainage from these materials sustained neutral-pH conditions that are unfavorable to oxyanion adsorption onto Fe-(oxyhydr)oxides and, therefore, enhanced As and Sb leaching. The release of Mo and Se from sulfidic skarn and intrusive waste rock was more proportional to elemental content but equally enhanced by pH-inhibited adsorption and negligible secondary mineral precipitation under NRD conditions. Our results demonstrate that oxyanion concentrations of environmental concern may be conveyed by neutral- to alkaline-pH waste-rock drainage and should be a focus of mine wastewater monitoring programs.

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Section: Resultssupporting

confidence: 87%

Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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Mobilization of Metal(oid) Oxyanions through Circumneutral Mine Waste-Rock Drainage

et al. 2019

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“…Although particle‐size distributions and porosities of the borehole waste rock were not determined, a comparison of the measured average moisture content with the average porosity of bulk Antamina waste rock obtained from previous studies (Vriens et al, 2019; Blackmore et al, 2014) shows that the average pore‐water saturation in the boreholes was 0.77 (Table 1). The lack of response to seasonal recharge (i.e., reflecting pore‐water infiltration) may be explained by the physical heterogeneity of the waste rock (i.e., variable particle‐size distributions due to end‐dumping sorting effects and traffic surface compaction) and by the overlapping of annual infiltration fronts (estimated flow velocities of ∼11 m yr −1 indicate that precipitation requires >10 yr to penetrate the current height of the continuously expanding waste‐rock pile; Vriens et al, 2019; Blackmore et al, 2018).…”

Section: Resultsmentioning

confidence: 99%

Localized Sulfide Oxidation Limited by Oxygen Supply in a Full‐Scale Waste‐Rock Pile

Vriens

Arnault

Laurenzi

et al. 2018

Vadose Zone Journal

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Open-pit mines produce large amounts of waste rock that is placed on-site, often in tall, mixed-composition piles. These waste-rock piles pose environmental risks because their weathering (i.e., sulfide oxidation) may generate acidic and metalladen drainage. However, the reaction and transport limitations controlling sulfide oxidation remain poorly described at field scales. Here, we present comprehensive multiyear data from two instrumented boreholes in an operational waste-rock pile at the Antamina mine in Peru. Localized but significant (?20 m) sections of reactive waste rock with up to 20% (w/w) sulfide existed at depths of up to 100 m in the pile, and their oxidation with rates of up to 1 × 10 −7 kg S m −3 s −1 completely consumed pore-gas O 2 and generated temperatures >40°C. Using mass-transport calculations, we show that advective rather than diffusive O 2 ingress controlled the sulfide oxidation rates in reactive regions of the waste-rock pile. Sulfide weathering rates in the less reactive zones of the pile were not limited by O 2 ingress, independent of the gas transport mechanism, with the exception of fine-grained waste rock at or near complete water saturation. Our results demonstrate the pronounced effects of physical and mineralogical heterogeneity on O 2 supply to waste-rock piles and controls of gas transport on waste-rock weathering rates.Abbreviations: AP, acid production potential; bgs, below ground surface; NP, neutralization potential.Waste rock is typically the largest waste fraction produced by open-pit mines, with millions of tonnes produced around the world annually (Lottermoser, 2010). Waste rock is often stored on-site in mixed-composition, heterogeneous piles or "dumps" that can be hundreds of meters high. The weathering of these exposed waste-rock piles bears significant environmental risks because the oxidation of reactive sulfide minerals, if present, can produce acidic drainage with high metal concentrations (Amos et al., 2015;Dold, 2017) The rate of waste-rock weathering, and thus ultimately the drainage quality from waste-rock piles, is determined by a number of intricately coupled processes, including chemical-reaction kinetics (Singer and Stumm, 1970;Strömberg and Banwart, 1994), biological catalysis (Johnson and Hallberg, 2003;Blackmore et al., 2018), gas transport (Ritchie, 2003), and hydrological flow (Amos et al., 2015;Nordstrom et al., 2015).During waste-rock weathering, the oxidation of sulfidic gangue minerals consumes O 2 and H 2 O and releases acidity and heat, whereas the acid-buffering dissolution of carbonate minerals (when present) releases CO 2 . It has been previously observed that sulfide oxidation in waste-rock piles can lead to locally elevated temperatures >60°C (Lefebvre et al., 2001b), virtually complete O 2 depletion (Dold, 2017;Parbhakar-Fox and Lottermoser, 2015), and, in carbonate-rich waste-rock piles, to CO 2 levels >2% (v/v) (Lorca et al., 2016). Fast reaction kinetics and relatively slow mass-and heat-transport mechanisms in unsaturated waste-rock ...

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“…Some studies have proposed that "pyrite disease" may indeed have a bacterial component. Bacterial attack (e.g., Acidithiobacillus ferrooxidans, A. thiooxidans) on pyrite is widely studied for environmental reasons, as a significant contributor to AMD and metals release (Nordstrom et al, 2015;Blackmore et al, 2018). Bioleaching of metal sulfides has become an important process in mining (Vera et al, 2013).…”

Section: Introductionmentioning

confidence: 99%

A review of “pyrite disease” for paleontologists, with potential focused interventions

Tacker¹

2020

Palaeontol Electron

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A literature review of the chemical reactions involved in pyrite oxidation/hydration ("pyrite disease") in geological or fossil collections gives direction to a suite of focused interventions. Reactions on the pyrite surface lie at the heart of the chemical process, accompanied by the movement of electrons on and through the pyrite semiconductor. Control of these electrons ultimately may be futile, but examination of the reactions at the atomic level leads to new possibilities for treatment, and identifies why some treatments are ineffective. This review also identifies gaps in our understanding of the oxidation and hydration reactions. Fossil biomaterials-bone or shell-often contain or are partially replaced by pyrite. Acidity produced by pyrite decay destroys these materials. Older treatments focus on acid neutralization, and humidity control as solutions for megascopic problems. Focused interventions target specific steps in the chemical reactions at the atomic scale. Interventions are informed by identification of all the minerals participating in the process, and accurate characterization of the bone, pyrite and sedimentary matrix. Bone minerals and pyrite are structurally and chemically heterogeneous, so each intervention requires bench testing, complimented by analytical measurements. Chemically passivating the unreacted pyrite surface shows the greatest promise. Anticipation of a new specimen's susceptibility to decay is key. Decay may be accelerated using techniques of humidity buffering with saturated salt solutions. Conductivity of pyrite (which varies over four orders of magnitude) may be measured. A database of pyrite conductivity is highly desirable.

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Microbial and geochemical controls on waste rock weathering and drainage quality

Cited by 40 publications

References 51 publications

Mobilization of Metal(oid) Oxyanions through Circumneutral Mine Waste-Rock Drainage

Mobilization of Metal(oid) Oxyanions through Circumneutral Mine Waste-Rock Drainage

Localized Sulfide Oxidation Limited by Oxygen Supply in a Full‐Scale Waste‐Rock Pile

A review of “pyrite disease” for paleontologists, with potential focused interventions

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