Multiple applications of the U.S. EPA 1312 leach procedure to mine waste from the Animas watershed, SW Colorado

David L. Fey; Stan E. Church; Rhonda L. Driscoll; Monique G. Adams

doi:10.1144/1467-7873/09-245

Home/Archive/USGS

USGS · 70005240

Multiple applications of the U.S. EPA 1312 leach procedure to mine waste from the Animas watershed, SW Colorado

David L. Fey·Stan E. Church·Rhonda L. Driscoll·Monique G. Adams

View original source ↗Export metadata ↓

Abstract

Eleven acid-sulphate and quartz-sericite-pyrite altered mine waste samples from the Animas River watershed in SW Colorado were subjected to a series of 5 to 6 successive leaches using the US EPA 1312 leach protocol to evaluate the transport of metals and loss of acidity from mine wastes as a function of time. Multi-acid digestion ICP-AES analyses, X-ray diffraction (XRD) mineral identification, total sulphur, and net acid potential (NAP) determinations were performed on the initial starting materials. Multiple leaching steps generally showed a ‘flushing' effect, whereby elements loosely bound, presumably as water-soluble salts, were removed. Aluminum, Cd, Fe, Mg, Mn, Sr, Zn, and S showed decreasing concentration trends, whereas Cu concentrations showed initially decreasing trends, followed by increasing trends in later steps. Concentrations of Zn in the first leach step were independent of whole-sample Zn content. Lead and Ba concentrations consistently increased with each step, indicating that anglesite (PbSO 4 ) and barite (BaSO 4 ), respectively, were dissolving in successive leach steps. Comparison of Fe content with NAP resulted in a modest correlation. However, using the S analyses and XRD identification of sulphide minerals to apportion S amongst enargite, barite, anglesite/galena, and sphalerite, and assigning the remaining S to pyrite, provided a useful correlation between estimated pyrite content and NAP. Whole-sample mass loss correlated well with NAP, but individual elements' behaviors varied between positive correlation (e.g. Al, Fe, Mg), no apparent correlation (Ca, Cd, Pb, Zn), and negative correlation (Cu). Comparison of the summed titrated acidities of the leachates with the whole-sample NAP values yielded an estimate of the fraction of NAP consumed, and led to an estimate of the time it would take to consume the sample acidity by weathering. We estimate, on the basis of these experiments, the acidity in the upper 30 cm would be consumed in 200–1000 years. In addition, calculations suggest that the acidity would be depleted before the complete store of the metals Cu-Cd-Zn in these mine wastes would be released to the environment.

Explore related subjects

Geochemistry: Exploration, Environment, Analysis Article

Source-reported bounding extent: 37.78075532805877° to 37.934179150985045° latitude; -107.79956817626953° to -107.53589630126953° longitude. This indicates report coverage, not an exact sampling location. View area on OpenStreetMap.

Keep this discovery

Explore connections, maps & timelines

BibTeX RIS

David L. Fey, Stan E. Church, Rhonda L. Driscoll, Monique G. Adams. 2011-08-19. Multiple applications of the U.S. EPA 1312 leach procedure to mine waste from the Animas watershed, SW Colorado. https://doi.org/10.1144/1467-7873%2F09-245

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related USGS reports

USGS2026

Using sediment chemical fractions and multivariate statistics on water to identify sources, mobility, and bioavailability of aluminum in the Florida River near Durango, Colorado

The Florida River in southwestern Colorado, USA, flows through the Southern Ute Reservation and is a cultural and water resource to Tribal and non-Tribal communities. High concentrations of total Al, up to 16 400 µg l –1 , have been detected in the Florida River. Elevated Al concentrations in water may affect aquatic organisms’ ability to regulate ions and inhibit respiratory functions. Water chemistry collected during three sampling events in 2022 from the Florida River and two of its tributaries are used here to better understand the spatial distribution, seasonality, and sources of Al concentrations in the Florida River. Streambed sediment and rock chemistry is also used to infer geologic sources of Al in the watershed. A five-stage sequential extraction was performed on streambed sediment and rock samples to help determine Al transport processes. We assessed relations between major and trace elements in water using a principal component analysis, finding that high Al concentrations in the Florida River (>3500 µg l –1 total Al) are caused by the erosion of Al-laden sediments. We used a stepwise multiple linear regression to investigate the relationship between land use and Al concentrations. Land use did not reliably predict Al concentration, though increased streamflow connected to reservoir releases – particularly in the Salt Creek tributary – were found to contribute Al to the Florida River during the irrigation season. In this study, we demonstrate that successful metal source appropriation may be achieved through limited field sampling when performed with sufficient water chemistry analysis, sequential chemical extraction of stream sediments, and statistical and land-use analysis.

Colorado↗

USGS2025

Tracking the sources of metals to the San Juan River, Four Corners Region, USA: An introduction to the thematic issue

Surface water quantity and quality is important for arid and semi-arid regions where many people, including underserved and Indigenous communities, rely on a scarce resource for drinking water, irrigation, livestock and ceremonial uses. The southwestern United States, and specifically the Four Corners Region (Colorado, Arizona, New Mexico and Utah), is an example of this situation. Elevated concentrations of metals including aluminium, arsenic and lead were identified in previous studies and this study in the San Juan River from below the Navajo Dam, through the Navajo Nation to Mexican Hat, Utah. An interdisciplinary team applied approaches and principles of geology, geochemistry, geomorphology, hydrology and statistics to gain a better understanding of the tributaries supplying the source(s) of metals to the San Juan River. This introductory paper provides an overview of the ‘Metal geochemical fingerprinting to identify sub-watershed source contributions to surface water at a regional arid watershed scale, Four Corners Region, USA’ thematic collection . An overview of sampling sites, techniques and potential sources of metals is provided. Approaches used in this study could be applied to investigations in similar systems globally.

Four Corners region↗

USGS2025

Adaptive instrument design strategy for collecting water, sediment samples and stage data in remote, ephemeral arroyos in the arid southwestern United States

Methods for collecting water, suspended sediment samples, and streamflow from rivers and streams have been documented in the literature by various science agencies. However, some projects may require data collected in difficult conditions including remote sites, sites that have limited accessibility during storms, and streamflow that occurs rarely. For these studies, adaptive approaches to sampler instrument design can yield valuable sample and streamflow data previously unobtainable. Tracking the source(s) of metals to the San Juan River required water chemistry samples, suspended sediment samples, and streamflow data collected on 28 ephemeral arroyos and five perennial streams. These tributaries to the San Juan River presented many challenges because of their remote locations, inaccessibility during storms, and ephemeral nature. A novel design, following on previous adaptive instrument designs, was created for this specific project. The design includes readily available materials (i.e. sourced from hardware stores), low cost, and allows for ease of replacement. Three instruments were designed following these design goals: a siphon sampler (water chemistry), sediment trap (suspended sediments), and a stage sensor (water level). These instruments were mounted to a t-post array in the stream channel. This installation approach, collectively named the “sed-chem gage”, was operated at each ephemeral arroyo for two consecutive field seasons. The instrument design approach, parts list, and results of operation are presented herein. This approach will be useful to scientists, water managers, and communities who need to evaluate water flow and water and sediment chemistry in a large, remote area where traditional techniques and methods may be cost prohibitive.

Arizona, Colorado, New Mexico, Utah↗