Evaluation of natural and mining-related sources of metal contamination to the Red River system, northern New Mexico
Evaluation of mining-related contamination of surface water and groundwater in sulfide-mineralized areas may be complicated by contributions from natural sources of acidic, metal-laden water. Within the Red River valley, Taos County, New Mexico, acidic, metal-laden groundwater, originating from both natural and mining-related sources, discharges into the Red River. Natural sources of metal contamination originate in naturally-exposed, sulfide-rich regions while mining-related sources of metal contamination originate from waste rock dumps associated with an open-pit mine. The purpose of this investigation is to evaluate potential mining impacts to the Red River system by considering hydrogeochemical data sampled from both a naturally impacted locality and a locality potentially impacted by mining.
Groundwater, surface water, and aquifer sediment samples were collected from two primary research localities. The Hansen Creek locality, situated near the Red River along an inferred groundwater flow path below an extensive alteration scar, was selected to represent baseline hydrochemical conditions associated with natural alteration scars. The Capulin Canyon locality, positioned near the Red River along a conceptual groundwater flow path below a mining-related waste-rock dump, was selected to represent conditions associated with areas potentially impacted by mining activities. Hydrochemical data suggest that groundwater influenced by mining contains comparatively higher concentrations of dissolved species (e.g. sulfate) associated with the oxidation of sulfides and the generation of acidic waters. For example, shallow groundwater samples collected at the Capulin Canyon locality during baseflow conditions in the Red River yielded sulfate concentrations ranging from 1600-1760 mg/L; at the Hansen Creek locality sulfate concentrations ranged from 490-700 mg/L. Furthermore, analyses of surface water discharging from alteration scars and waste rock dumps support the hydrochemical differences; sulfate concentrations generated within waste rock dumps are more than 10,000 mg/L higher than sulfate concentrations in surface water collected from the Hansen alteration scar.
Partially-extracted metals from aquifer sediments also reveal a considerable
difference in metal concentrations between the two research localities.
The combined hydrogeochemical data from the Capulin and Hansen localities
suggest that past mining activities are presently impacting selected areas
of the Red River system.
New Mexico Bureau of Geology & Mineral Resources
New Mexico Institute of Mining & Technology
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Socorro, NM 87801-4796
information: (575) 835-5420
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