Questa baseline and pre-mining ground-water quality investigation. 25. Summary of results and baseline and pre-mining ground-water geochemistry, Red River Valley, Taos County, New Mexico, 2001-2005

Nordstrom, D. Kirk

doi:10.3133/pp1728

Cited by 27 publications

(21 citation statements)

References 26 publications

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“…Near the end of the test, silica, Mg, and SO 4 concentrations rose, and the pH remained buffered very consistently at approximately 4, most likely by an aluminosilicate mineral such as kaolinite or another clay, as suggested in the Questa, New Mexico, study (Nordstrom, 2008). Results for weeks 228 to the end of the test (week 332) showed increasing and equimolar concentrations of Mg and silica (see Figure 8) and slightly increasing concentrations of Ni, Al, and K. The increasing Mg and silica concentrations could result from dissolution of a Mg-rich olivine (forsterite).…”

Section: Polymet Projectmentioning

confidence: 68%

A geochemical examination of humidity cell tests

Maest¹,

Nordstrom

2017

Applied Geochemistry

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Humidity cell tests (HCTs) are long-term (20 to >300 weeks) leach tests that are considered by some to be the among the most reliable geochemical characterization methods for estimating the leachate quality of mined materials. A number of modifications have been added to the original HCT method, but the interpretation of test results varies widely. We suggest that the HCTs represent an underutilized source of geochemical data, with a year-long test generating approximately 2,500 individual chemical data points. The HCT concentration peaks and valleys can be thought of as a "chromatogram" of reactions that may occur in the field, whereby peaks in concentrations are associated with different geochemical processes, including sulfate salt dissolution, sulfide oxidation, and dissolution of rock-forming minerals, some of which can neutralize acid. Some of these reactions occur simultaneously, some do not, and geochemical modeling can be used to help distinguish the dominant processes. Our detailed examination, including speciation and inverse modeling, of HCTs from three projects with different geology and mineralization shows that rapid sulfide oxidation dominates over a limited period of time that starts between 40 and 200 weeks of testing. The applicability of laboratory tests results to predicting field leachate concentrations, loads, or rates of reaction has not been adequately demonstrated, although early flush releases and rapid sulfide oxidation rates in HCTs should have some relevance to field conditions. Knowledge of possible maximum solute

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Section: Polymet Projectmentioning

confidence: 68%

A geochemical examination of humidity cell tests

Maest¹,

Nordstrom

2017

Applied Geochemistry

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“…Many of these constituents are 2-20 times the ground-water quality standards. Details of these results can be found in Nordstrom (2008). Current groundwater chemistry at the mine site ranges substantially from background concentrations up to 1-2 orders of magnitude greater than estimated pre-mining concentrations.…”

Section: Discussionmentioning

confidence: 87%

What was the groundwater quality before mining in a mineralized region? Lessons from the Questa project

Nordstrom

2008

Geosci J

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The U.S. Geological Survey, in cooperation with the New Mexico Environment Department and supported by Molycorp, Inc (currently Chevron Minerals), has completed a 5-year investigation (2001)(2002)(2003)(2004)(2005)(2006) to determine the pre-mining groundwater quality at Molycorp's Questa molybdenum mine in northern New Mexico. Current mine-site ground waters are often contaminated with mine-waste leachates and no data exists on premining ground-water quality so that pre-mining conditions must be inferred. Ground-water quality undisturbed by mining is often worse than New Mexico standards and data are needed to help establish closure requirements. The key to determining pre-mining conditions was to study the hydrogeochemistry of a proximal natural analog site, the Straight Creek catchment. Main rock types exposed to weathering include a Tertiary andesite and the Tertiary Amalia tuff (rhyolitic composition), both hydrothermally altered to various degrees. Two types of ground water are common in mineralized areas, acidic ground waters in alluvial debris fans with pH 3-4 and bedrock ground waters with pH 6-8. Siderite, ferrihydrite, rhodochrosite, amorphous to microcrystalline Al(OH)3, calcite, gypsum, barite, and amorphous silica mineral solubilities control concentrations of Fe(II), Fe(III), Mn(II), Al, Ca, Ba, and SiO2, depending on pH and solution composition. Concentrations at low pH are governed by element abundance and mineral weathering rates. Concentrations of Zn and Cd range from detection up to about 10 and 0.05 mg/L, respectively, and are derived primarily from sphalerite dissolution. Concentrations of Ni and Co range from detection up to 1 and 0.4 mg/L, respectively, and are derived primarily from pyrite dissolution. Concentrations of Ca and SO4 are derived from secondary gypsum dissolution and weathering of calcite and pyrite. Metal:sulfate concentration ratios are relatively constant for acidic waters, suggesting consistent weathering rates, independent of catchment. These trends, combined with lithology, mineralogy, and mineral solubility controls, provide useful constraints on pre-mining ground-water quality for the mine site where the lithology is known.

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“…Silica concentrations of the mine discharge, in contrast to other bedrock-derived constituents, are typically similar in concentration to Fourmile Creek, with the maximum concentration (25 mg/L) only about double upstream concentrations. In rivers with circumneutral pH (such as Fourmile Creek), dissolved SiO 2 concentrations are often below 30 mg/L because quartz and aluminosilicate minerals are resistant to weathering processes and the upper limit of dissolved silica concentration is controlled by precipitation of amorphous or microcrystalline silica and clay minerals (e.g., kaolinite and halloysite; Hem, 1985;Nordstrom, 2008). Thus, input of mine water does not alter SiO 2 concentrations of Fourmile Creek, in contrast to other bedrock-derived constituents.…”

Section: Role Of Previous Disturbancesmentioning

confidence: 99%

Fire, Flood, and Drought: Extreme Climate Events Alter Flow Paths and Stream Chemistry

et al. 2018

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Extreme climate events—such as hurricanes, droughts, extreme precipitation, and wildfires—have the potential to alter watershed processes and stream response. Yet due to the destructive and hazardous nature and unpredictability of such events, capturing their hydrochemical signal is challenging. A 5‐year postwildfire study of stream chemistry in the Fourmile Creek watershed, Colorado Front Range, USA, focused on high‐frequency storm sampling. During the study, the watershed was impacted by three additional extreme climate events—drought and two periods of extreme rainfall totals. These events altered concentration‐discharge relationships in ways that elucidate how hydrologic flow paths and source material availability affect stream water chemistry. Reduced infiltration after wildfire led to overland flow during thunderstorms, which conveyed ash and soil into streams. This resulted in elevated stream concentrations of constituents elevated in ash—Ca, K, Mg, alkalinity, and dissolved organic carbon—along with sediment and nitrate. Subsurface flow paths were bypassed, leading to low concentrations of Na and SiO2, which are bedrock derived and not elevated in ash. During drought conditions, when stream discharge was <20% of average, concentrations of sediment, dissolved organic carbon, and Ca fell below average concentrations, but SiO2 did not. Extreme rainfall totals saturated the subsurface and led to prolonged elevated stream discharge. Concentration‐discharge relationships for bedrock‐derived constituents, such as Ca and SiO2, were altered in that time period, while those for dissolved organic carbon were not. Previous disturbances, including historical mining, also affect stream chemistry, and water‐quality impairment can be exacerbated by extreme climate events.

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Questa baseline and pre-mining ground-water quality investigation. 25. Summary of results and baseline and pre-mining ground-water geochemistry, Red River Valley, Taos County, New Mexico, 2001-2005

Cited by 27 publications

References 26 publications

A geochemical examination of humidity cell tests

A geochemical examination of humidity cell tests

What was the groundwater quality before mining in a mineralized region? Lessons from the Questa project

Fire, Flood, and Drought: Extreme Climate Events Alter Flow Paths and Stream Chemistry

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