Chemical evolution and evaporation of shallow groundwaters discharging from a gold mine, southern New Zealand

Weightman, Erin; Craw, Dave; Rufaut, Cathy; Kerr, Gemma; Scott, James M.

doi:10.1016/j.apgeochem.2020.104766

Cited by 12 publications

(27 citation statements)

References 43 publications

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“…(c) Sodium and chloride concentrations in waters from two of the historic mine sites examined in this study, in relation to sea water and water in an inland evaporative salt lake ( Figure 1a) [25]. Chapman Road data [27] indicate the dominance of NaCl salts, compared to the sulphate-rich schist shallow groundwater in a that yields mainly Ca-carbonate precipitates (Figure 2c [30]). (b) Vegetation macronutrient contents of typical Otago Schist [34].…”

Section: Background Schist-dominated Substrates Water and Vegetationmentioning

confidence: 92%

“…These data have been augmented with new data that were specifically collected to quantify geological and geochemical thresholds between different geoecological zones that have been defined by the presence of distinctive vegetation species (Table 1). The background data for typical Otago Schist compositions, mineralogy, and water-rock geochemical interactions have been compiled from previous workers [22,25,30]. General methods for quantifying salinity and site-wide salinity variations at Chapman Rd and Springvale placer gold mines were outlined by previous workers at these sites [23,27].…”

Section: Methodsmentioning

confidence: 99%

“…Pyrite within the schist is readily oxidised to yield abundant dissolved sulphate in near-surface waters, but there is more than sufficient Ca-carbonate to neutralise any acid derived from this pyrite oxidation (Figure 3a). In addition, chlorite (Fe-Mg-Al silicate) also contributes to this acid neutralisation, with release of dissolved Mg (Figure 3a) [30]. Consequently, shallow groundwaters that have contact with fresh schist debris can attain high levels of dissolved constituents, as indicated by elevated electrical conductivity (EC) levels in excess of 3000 µS, especially sulphate (Figures 2d,e and 3a).…”

Section: Background Schist-dominated Substrates Water and Vegetationmentioning

confidence: 99%

“…The widespread schist-derived surficial loess is an especially effective substrate for vegetation establishment [29,31]. [30]). (b) Vegetation macronutrient contents of typical Otago Schist [34].…”

Section: Background Schist-dominated Substrates Water and Vegetationmentioning

confidence: 99%

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Geoecological Zonation of Revegetation Enhances Biodiversity at Historic Mine Sites, Southern New Zealand

Craw

Rufaut

2021

Minerals

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Rocks exposed by mining can form physically, mineralogically, and geochemically diverse surface substrates. Engineered mine rehabilitation typically involves covering these rocks with a uniform layer of soil and vegetation. An alternative approach is to encourage the establishment of plant species that are tolerant of challenging geochemical settings. The zonation of geochemical parameters can therefore lead to geoecological zonation and enhanced biodiversity. Abandoned gold mines in southern New Zealand have developed such geoecological zonations that resulted from establishment of salt-tolerant ecosystems on substrates with evaporative NaCl. A salinity threshold equivalent to substrate electrical conductivity of 1000 µS separates this ecosystem from less salt-tolerant plant ecosystems. Acid mine drainage from pyrite-bearing waste rocks at an abandoned coal mine has caused variations in surface pH between 1 and 7. The resultant substrate pH gradients have led to differential plant colonisation and the establishment of distinctive ecological zones. Substrate pH <3 remained bare ground, whereas pH 3–4 substrates host two acid-tolerant shrubs. These shrubs are joined by a tree species between pH 4 and 5. At higher pH, all local species can become established. The geoecological zonation, and the intervening geochemical thresholds, in these examples involve New Zealand native plant species. However, the principle of enhancing biodiversity by the selection or encouragement of plant species tolerant of diverse geochemical conditions on exposed mine rocks is applicable for site rehabilitation anywhere in the world.

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Section: Background Schist-dominated Substrates Water and Vegetationmentioning

confidence: 92%

Section: Methodsmentioning

confidence: 99%

Section: Background Schist-dominated Substrates Water and Vegetationmentioning

confidence: 99%

Section: Background Schist-dominated Substrates Water and Vegetationmentioning

confidence: 99%

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Geoecological Zonation of Revegetation Enhances Biodiversity at Historic Mine Sites, Southern New Zealand

Craw

Rufaut

2021

Minerals

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“…However, waters with circumneutral to mildly alkaline pH commonly contain abundant dissolved carbonate as well as sulphate, and carbonate mineral precipitation can therefore inhibit precipitation of sulphate minerals (e.g. Weightman et al, 2020). This issue can be overcome by artificially raising pH even higher, although this has significant costs and technical issues (Tolonen et al, 2015(Tolonen et al, , 2016.…”

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confidence: 99%

Potential for Pastoral Irrigation Using Sulphate-Rich Waters at Macraes Gold Mine, Southern New Zealand

Rufaut

Weightman

Craw

et al. 2022

Water Air Soil Pollut

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There is growing recognition that elevated dissolved sulphate around mines will lead to significant environmental issues within the industry that need specific management. Various sulphate attenuation engineering methods exist, and so processes that could occur within a mine site are of particular interest. In this pilot study, we investigate the possibility of using high-sulphate mine water (~ 2500 mg/L) for irrigation of farm land. This approach is made feasible from mildly alkaline (pH ~ 8), non-toxic discharge waters at a semi-arid gold mine site. Geochemical models predicted Ca-sulphate will readily precipitate from the mine water at pH 6 and potentially attenuate downstream concentrations of dissolved sulphate. We used the slightly acidic natural soil environment (pH 5–6) of the mine to test initial model predictions in the laboratory and field trials. Ca-sulphate in gypsum formed in experimental soil columns, and the pH of input water lowered by 2–3 units. In the field, only minor soil gypsum was observed, and instead Mg-sulphate and Ca-carbonate were found more readily on evaporation surfaces. Additional terrestrial effects of soil dilution, leaching, and plant uptake of sulphate are discussed. Irrigated pasture had healthy, green plants that supported a potentially dual benefit of mine water irrigation to enhancing farm productivity in the local community. Irrigation is an effective way to manage mine waters with high dissolved sulphate but requires further trials to refine methods and the feed values of pasture.

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Antimony Mobilisation and Attenuation During Ore Processing at Orogenic Gold Mines, Southern New Zealand

Weightman

Craw

Snow³

et al. 2021

Mine Water Environ

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Chemical evolution and evaporation of shallow groundwaters discharging from a gold mine, southern New Zealand

Cited by 12 publications

References 43 publications

Geoecological Zonation of Revegetation Enhances Biodiversity at Historic Mine Sites, Southern New Zealand

Geoecological Zonation of Revegetation Enhances Biodiversity at Historic Mine Sites, Southern New Zealand

Potential for Pastoral Irrigation Using Sulphate-Rich Waters at Macraes Gold Mine, Southern New Zealand

Antimony Mobilisation and Attenuation During Ore Processing at Orogenic Gold Mines, Southern New Zealand

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