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A comparison study of selected static leaching and acid–base accounting (ABA) methods using a mineralogically diverse set of 12 modern-style, metal mine waste samples was undertaken to understand the relative performance of the various tests. To complement this study, in-depth mineralogical studies were conducted in order to elucidate the relationships between sample mineralogy, weathering features, and leachate and ABA characteristics. In part one of the study, splits of the samples were leached using six commonly used leaching tests including paste pH, the U.S. Geological Survey (USGS) Field Leach Test (FLT) (both 5-min and 18-h agitation), the U.S. Environmental Protection Agency (USEPA) Method 1312 SPLP (both leachate pH 4.2 and leachate pH 5.0), and the USEPA Method 1311 TCLP (leachate pH 4.9). Leachate geochemical trends were compared in order to assess differences, if any, produced by the various leaching procedures. Results showed that the FLT (5-min agitation) was just as effective as the 18-h leaching tests in revealing the leachate geochemical characteristics of the samples. Leaching results also showed that the TCLP leaching test produces inconsistent results when compared to results produced from the other leaching tests. In part two of the study, the ABA was determined on splits of the samples using both well-established traditional static testing methods and a relatively quick, simplified net acid–base accounting (NABA) procedure. Results showed that the traditional methods, while time consuming, provide the most in-depth data on both the acid generating, and acid neutralizing tendencies of the samples. However, the simplified NABA method provided a relatively fast, effective estimation of the net acid–base account of the samples. Overall, this study showed that while most of the well-established methods are useful and effective, the use of a simplified leaching test and the NABA acid–base accounting method provide investigators fast, quantitative tools that can be used to provide rapid, reliable information about the leachability of metals and other constituents of concern, and the acid-generating potential of metal mining waste.

Background: In 2010, Médecins Sans Frontières discovered a lead poisoning outbreak linked to artisanal gold processing in northwestern Nigeria. The outbreak has killed approximately 400 young children and affected thousands more. Objectives: Our aim was to undertake an interdisciplinary geological- and health-science assessment to clarify lead sources and exposure pathways, identify additional toxicants of concern and populations at risk, and examine potential for similar lead poisoning globally. Methods: We applied diverse analytical methods to ore samples, soil and sweep samples from villages and family compounds, and plant foodstuff samples. Results: Natural weathering of lead-rich gold ores before mining formed abundant, highly gastric-bioaccessible lead carbonates. The same fingerprint of lead minerals found in all sample types confirms that ore processing caused extreme contamination, with up to 185,000 ppm lead in soils/sweep samples and up to 145 ppm lead in plant foodstuffs. Incidental ingestion of soils via hand-to-mouth transmission and of dusts cleared from the respiratory tract is the dominant exposure pathway. Consumption of water and foodstuffs contaminated by the processing is likely lesser, but these are still significant exposure pathways. Although young children suffered the most immediate and severe consequences, results indicate that older children, adult workers, pregnant women, and breastfed infants are also at risk for lead poisoning. Mercury, arsenic, manganese, antimony, and crystalline silica exposures pose additional health threats. Conclusions: Results inform ongoing efforts in Nigeria to assess lead contamination and poisoning, treat victims, mitigate exposures, and remediate contamination. Ore deposit geology, pre-mining weathering, and burgeoning artisanal mining may combine to cause similar lead poisoning disasters elsewhere globally.

The 7–8 August 2008 eruption of Kasatochi Island volcano blanketed the island in newly generated pyroclastic deposits and deposited ash into the ocean and onto nearby islands. Concentrations of water soluble Fe, Cu, and Zn determined from a 1:20 deionized water leachate of the ash were sufficient to provide short-term fertilization of the surface ocean. The 2008 pyroclastic deposits were thicker in concavities at bases of steeper slopes and thinner on steep slopes and ridge crests. By summer 2009, secondary erosion had exposed the pre-eruption soils along gulley walls and in gully bottoms on the southern and eastern slopes, respectively. Topographic and microtopographic position altered the depositional patterns of the pyroclastic flows and resulted in pre-eruption soils being buried by as little as 1 m of ash. The different erosion patterns gave rise to three surfaces on which future ecosystems will likely develop: largely pre-eruptive soils; fresh pyroclastic deposits influenced by shallowly bu...

Some barrier-island dunes damaged or destroyed by Hurricane Sandy's storm surges in October 2012 have been reconstructed using sediments dredged from back bays. These sand-, clay-, and iron sulfide-rich sediments were used to make berm-like cores for the reconstructed dunes, which were then covered by beach sand. In November 2013, we sampled and analyzed partially weathered materials collected from the cores of reconstructed dunes. There are generally low levels of metal toxicants in the reconstructed dune materials. However oxidation of reactive iron sulfides by percolating rainwater produces acid-sulfate pore waters, which evaporate during dry periods to produce efflorescent gypsum and sodium jarosite salts. The results suggest use of sulfidic sediments in dune reconstruction has both drawbacks (e.g., potential to generate acid runoff from dune cores following rainfall, enhanced corrosion of steel bulwarks) and possible benefits (e.g., efflorescent salts may enhance structural integrity).

Evaluation of metal leaching using a single leach test such as the Toxicity Characteristic Leaching Procedure (TCLP) is often questionable. The pH, redox potential (E(h)), particle size and contact time are critical variables in controlling metal stability, not accounted for in the TCLP. This paper compares the leaching behavior of metals in mineral processing waste via short-term extraction tests such as TCLP, Field Leach Test (FLT) used by USGS and deionized water extraction tests. Variation in the extracted amounts was attributed to the use of different particle sizes, extraction fluid and contact time. In the controlled pH experiments, maximum metal extraction was obtained at acidic pH for cationic heavy metals such as Cu, Pb and Zn, while desorption of Se from the waste resulted in high extract concentrations in the alkaline region. Precipitation of iron, caused by a pH increase, probably resulted in co-precipitation and immobilization of Cu, Pb and Zn in the alkaline pH region. A sequential extraction procedure was performed on the original waste and the solid residue from the E(h)-pH experiments to determine the chemical speciation and distribution of the heavy metals. In the as-received waste, Cu existed predominantly in water soluble or sulfidic phases, with no binding to carbonates or iron oxides. Similar characteristics were observed for Pb and Zn, while Se existed mostly associated with iron oxides or sulfides. Adsorption/co-precipitation of Cu, Se and Pb on precipitated iron hydroxides was observed in the experimental solid residues, resulting in metal immobilization above pH 7.

In a joint project, the mine waste-piles at the Rattler Mine near Idaho Springs, Colorado, were sampled and analyzed by scientists from the U.S. Geological Survey (USGS) and the Colorado School of Mines (CSM). Separate sample collection, sample leaching, and leachate analyses were performed by both groups and the results were compared. For the study, both groups used the USGS sampling procedure and the USGS Field Leach Test (FLT). The leachates generated from these tests were analyzed for a suite of elements using ICP-AES (CSM) and ICP-MS (USGS). Leachate geochemical fingerprints produced by the two groups for composites collected from the same mine waste showed good agreement. In another set of tests, CSM collected another set of Rattler mine waste composite samples using the USGS sampling procedure. This set of composite samples was leached using the Colorado Division of Minerals and Geology (CDMG) leach test, and a modified Toxicity Characteristic Leaching Procedure (TCLP) leach test. Leachate geochemical fingerprints produced using these tests showed a variation of more than a factor of two from the geochemical fingerprints produced using the USGS FLT leach test. We have concluded that the variation in the results is due to the different parameters of the leaching tests and not due to the sampling or analytical methods.

Many natural or human-caused disasters release potentially hazardous materials (HM) that may pose threats to the environment and health of exposed humans, wildlife, and livestock. This chapter summarizes the environmentally and toxicologically significant physical, mineralogical, and geochemical characteristics of materials produced by a wide variety of recent disasters, such as volcanic eruptions, hurricanes and extreme storms, spills of mining/mineral-processing wastes or coal extraction by-products, and the 2001 attacks on and collapse of the World Trade Center towers. In describing these characteristics, this chapter also illustrates the important roles that geochemists and other earth scientists can play in environmental disaster response and preparedness. In addition to characterizing in detail the physical, chemical, and microbial makeup of HM generated by the disasters, these roles also include (1) identifying and discriminating potential multiple sources of the materials; (2) monitoring, mapping, and modeling dispersal and evolution of the materials in the environment; (3) understanding how the materials are modified by environmental processes; (4) identifying key characteristics and processes that influence the materials' toxicity to exposed humans and ecosystems; (5) estimating shifts away from predisaster environmental baseline conditions; and (6) using geochemical insights learned from past disasters to help estimate, prepare for, and increase societal resilience to the environmental and related health impacts of future disasters.

An analytical method using high-performance liquid chromatography separation with inductively coupled plasma mass spectrometry (ICP-MS) detection previously developed for the determination of Cr(III) and Cr(VI) has been adapted to allow the determination of As(III), As(V), Se(IV), Se(VI), Cr(III), and Cr(VI) under the same chromatographic conditions. Using this method, all six inorganic species can be determined in less than 3 min. A dynamic reaction cell (DRC)–ICP-MS system was used to detect the species eluted from the chromatographic column in order to reduce interferences. A variety of reaction cell gases and conditions may be utilized with the DRC–ICP-MS, and final selection of conditions is determined by data quality objectives. Results indicated all starting standards, reagents, and sample vials should be thoroughly tested for contamination. Tests on species stability indicated that refrigeration at 10 °C was preferential to freezing for most species, particularly when all species were present, and that sample solutions and extracts should be analyzed as soon as possible to eliminate species instability and interconversion effects. A variety of environmental and geological samples, including waters and deionized water [leachates] and simulated biological leachates from soils and wildfire ashes have been analyzed using this method. Analytical spikes performed on each sample were used to evaluate data quality. Speciation analyses were conducted on deionized water leachates and simulated lung fluid leachates of ash and soils impacted by wildfires. These results show that, for leachates containing high levels of total Cr, the majority of the chromium was present in the hexavalent Cr(VI) form. In general, total and hexavalent chromium levels for samples taken from burned residential areas were higher than those obtained from non-residential forested areas. Arsenic, when found, was generally in the more oxidized As(V) form. Selenium (IV) and (VI) were present, but typically at low levels.

In 2007-09, California experienced several large wildfires that damaged large areas of forest and destroyed many homes and buildings. The U.S. Geological Survey collected samples from the Harris, Witch, Grass Valley, Ammo, Santiago, Canyon, Jesusita, and Station fires for testing to identify any possible characteristics of the ashes and soils from burned areas that may be of concern for their impact on water quality, human health, and endangered species. The samples were subjected to analysis for bulk chemical composition for 44 elements by inductively coupled plasma mass spectrometry (ICP-MS) after acid digestion and de-ionized water leach tests for pH, alkalinity, conductivity, and anions. Water leach tests generated solutions ranging from pH 10-12, suggesting that ashes can generate caustic alkalinity in contact with rainwater or body fluids (for example, sweat and fluids in the respiratory tract). Samples from burned residential areas in the 2007 fires had elevated levels for several metals, including: As, Pb, Sb, Cu, Zn, and Cr. In some cases, the levels found were above the U.S. Environmental Protection Agency (USEPA) preliminary remediation goals (PRG) for soils. Speciation analyses were conducted on de-ionized water and simulated lung fluid leachates for As(III), As(V), Se(IV), Se(VI), Cr(III), and Cr(VI). All species were determined in the same analytical run using an ion-pairing HPLC-ICP-MS method. For leachates containing high levels of total Cr, the majority of the chromium was present in the hexavalent, Cr(VI), form. Higher total and hexavalent chromium levels were observed for samples collected from burned residential areas. Arsenic was also generally present in the more oxidized, As(V), form. Selenium (IV) and (VI) were present, but typically at levels below 2 ppb for most samples. Stability studies of leachate solutions under different storage conditions were performed and the suitability of different sample preservation methods for speciation analysis will be discussed. Introduction This report contains slides and speaker’s notes used for an oral presentation given at the 2010 National Environmental Monitoring Conference (http://www.nemc.us/) held in Washington, D.C., in August 2010. The slides discuss the growing concern for the high number of acres burned each year in the United States by wildfires and work done by the U.S. Geological Survey in evaluating the potential effects on human and ecosystem health. The U.S. Geological Survey has collected samples of ash and burned soils from a variety of locations in southern California during the 2007 and 2009 fire seasons. Data from samples collected from the Harris, Grass Valley, Jesusita, and Station fires have been analyzed for total metal content. Selected samples with elevated levels of arsenic, selenium, and chromium were analyzed to determine the speciation or chemical form of these elements present. Several tables of results taken from Plumlee and others (2007) are presented in the slides as well as maps depicting locations of the 2007 fires in southern California. The slides also contain preliminary results for the speciation analysis of arsenic, selenium, and chromium by High Performance Liquid

Concentrations of 31 metals, metalloids, and other elements were measured in insects and insectivorous bird tissues from three drainages with different geochemistry and mining histories in Summit Co., Colorado, in 2003, 2004, and 2005. In insect samples, all 25 elements that were analyzed in all years increased in both Snake and Deer Creeks in the mining impacted areas compared to areas above and below the mining impacted areas. This distribution of elements was predicted from known or expected sediment contamination resulting from abandoned mine tailings in those drainages. Element concentrations in avian liver tissues were in concordance with levels in insects, that is with concentrations higher in mid-drainage areas where mine tailings were present compared to both upstream and downstream locations; these differences were not always statistically different, however. The lack of statistically significant differences in liver tissues, except for a few elements, was due to relatively small sample sizes and because many of these elements are essential and therefore well regulated by the bird's homeostatic processes. Most elements were at background concentrations in avian liver tissue except for Pb which was elevated at mid-drainage sites to levels where delta-aminolevulinic acid dehydratase activity was inhibited at other mining sites in Colorado. Lead exposure, however, was not at toxic levels. Fecal samples were not a good indication of what elements birds ingested and were potentially exposed to.

The highly oxidizing environment of a wildfire has the potential to convert any chromium present in the soil or in residential or industrial debris to its more toxic form, hexavalent chromium, a known carcinogen. In addition, the highly basic conditions resulting from the combustion of wood and wood products could result in the stabilization of any aqueous hexavalent chromium formed. Samples were collected from the October 2007 wildfires in Southern California and subjected to an array of test procedures to evaluate the potential effects of fire-impacted soils and ashes on human and environmental health (Plumlee and others, http://pubs.usgs.gov/of/2007/1407/). Soil and ash samples were leached using de-ionized water to simulate conditions resulting from rainfall on fireimpacted areas (Hageman and others, 2007, http://pubs.usgs.gov/tm/2007/05D03/). The resulting leachates were of high pH (10–13) and many, particularly those of ash from burned residential areas, contained elevated total chromium as much as 33 micrograms per liter. Samples were also leached using a near-neutral pH simulated lung fluid (Plumlee and others, 2006) to model potential chemical interactions of inhaled particles with fluids lining the respiratory tract. High Performance Liquid Chromatography coupled to Inductively Coupled Plasma Mass Spectrometry (Wolf and others, 2007) was used to separate and detect individual species (for example, Cr, Cr, As, As, Se, and Se). These procedures were used to determine the form of the chromium present in the de-ionized water and simulated lung fluid leachates.

Samples of dust deposited around lower Manhattan by the September 11, 2001, World Trade Center (WTC) collapse have inorganic chemical compositions that result in part from the variable chemical contributions of concrete, gypsum wallboard, glass fibers, window glass, and other materials contained in the buildings. The dust deposits were also modified chemically by variable interactions with rain water or water used in street washing and fire fighting. Chemical leach tests using deionized water as the extraction fluid show the dust samples can be quite alkaline, due primarily to reactions with calcium hydroxide in concrete particles. Calcium and sulfate are the most soluble components in the dust, but many other elements are also readily leached, including metals such as Al, Sb, Mo Cr, Cu, and Zn. Indoor dust samples produce leachates with higher pH, alkalinity, and dissolved solids than outdoor dust samples, suggesting most outdoor dust had reacted with water and atmospheric carbon dioxide prior to sample collection. Leach tests using simulated lung fluids as the extracting fluid suggest that the dust might also be quite reactive in fluids lining the respiratory tract, resulting in dissolution of some particles and possible precipitation of new phases such as phosphates, carbonates, and silicates. Results of these chemical characterization studies can be used by health scientists as they continue to track and interpret health effects resulting from the short-term exposure to the initial dust cloud and the longer-term exposure to dusts resuspended during cleanup.

Precipitation-induced runoff from historical mine-waste located adjacent to the headwaters of the Snake River, Deer Creek, Saints John Creek, Grizzly Gulch, Stevens Gulch, and Leavenworth Creek contributes to the degradation of water quality in these streams. Because historical mine-waste piles have had long-term exposure to the atmosphere, it is surmised that runoff from these piles, induced by meteorological events such as cloudbursts and snowmelt, may cause mobility of acid and metals into a watershed due to dissolution of soluble minerals. For this study, 13 mine-waste composite samples from various mine-wastes in these drainage basins were leached using both a short-term and a long-term leach test. Analytical results from this combination of leach tests are tools that allow the investigator to quantify (fingerprint) which geochemical components could be expected in runoff from these piles if they were leached by a cloudburst (5-minute leach test), as well as what the “worst-case” geochemical profile would look like if the material were subject to extended leaching and breakdown of the mine-waste material (18hour leach test). Also, this combination of leach tests allows the geoscientist the ability to see geochemical changes in the mine-waste leachate over time. That is, does the leachate become more or less acidic over time; does the specific conductance increase or decrease; and are there changes in the concentrations of major or trace elements? Further, use of a ranking scheme described herein will aid in prediction of which historical mine-waste piles have the greatest potential for impact on a watershed should runoff occur. Because of long-term weathering of these historical mine-waste piles, geochemical profiles, leachate time-trends, and relative ranking of the mine-wastes produced from analysis of the leachates are

When assessing the environmental impact from mining operations, an immediate question arises about potential impact and toxicity of mine-waste piles. This question is particularly difficult to assess for waste piles on abandoned mine lands in the western United States and coal-waste piles in the eastern United States. In many of these situations, there is no water in direct contact with the piles, except during meteorological events, yet it appears that the pile has caused significant ecological disturbance. For the past several years, scientists at the Colorado School of Mines and the U.S. Geological Survey have been studying the toxicity potential of waste-rock piles. Simple and practical methods have been developed for determining the potential of a waste- rock pile to cause significant contamination. For example, quick inexpensive field leaching tests have been developed that offer an evaluation of acid and trace-metal release from mine-waste material. Additionally, two-dimensional hydrologic and erosion models might be used to assess acid and metal sources and sinks. Such methods are presented for evaluating mine-waste piles from watershed scale, site scale, and microscopic scale, using geophysical, geochemical, and mineralogical methods. Current methods used to determine bioaccessibility and bioavailability of metals from wastes, such as extraction techniques, are described and assessed. Case studies with field and laboratory data illustrate these methods. These applications are used as the basis for a simple decision tree that has been developed to assess the potential impact of a waste-rock pile, and the scientific background that serves as the basis for decisions. Workshop Time: 8:30 am – 4:00 pm, June 1, 2003 Workshop Organizers: Dr. Thomas R. Wildeman Dr. Kathleen S. Smith Dept. of Chemistry & Geochemistry U.S. Geological Survey Colorado School of Mines M.S. 973, Denver Federal Cntr. Golden, CO 80401 Denver, CO 80225-0046 Phone: 303-273-3642 Phone: 303-236-5788 E mail: twildema@mines.edu E mail: ksmith@usgs.gov

This report details chemistry data derived from leaching of mine-waste composite samples using a modification of E.P.A. Method 1312, Synthetic Precipitation Leaching Procedure (SPLP). In 1998, members of the U.S. Geological Survey Mine Waste Characterization Project collected four mine-waste composite samples from mining districts in southwestern New Mexico (CAR and PET) and near Leadville, Colorado (TUC and MII). Resulting leachate pH values for the four composites ranged from 5.45 to 8.84 and ranked in the following order: CAR < TUC < MII < PET. Specific conductivity values ranged from 85 μS/cm to 847 μS/cm in the following order: PET < MII < CAR < TUC. Geochemical data generated from this investigation reveal that leachate from the CAR composite contains the highest concentrations of Pb, Zn, Ni, Mn, Cu, Cd, and Al Introduction Assessing acid and metal mobility from abandoned mine-waste piles is an area of concern for Federal land management agencies and others. Drainage and runoff from these piles can present water quality concerns similar to acid mine drainage. Mine-waste piles that contain metal and sulfide reservoirs can become sources of acidic drainage when exposed to surface conditions of oxygen and water. Continuing work on Abandoned Mine Lands projects has demonstrated the need for rapid, accurate characterization of these waste materials in order to aid in the screening, geochemical assessment, and prioritization of a large number of mine-waste piles for remediation. One of the methods currently used to characterize mine-waste material is E.P.A. Method 1312 Synthetic Precipitation Leaching Procedure (SPLP). Because this test has been used in many studies involving mine-waste it was the method we chose for the geochemical characterization of the samples in this study. It is important to note, that we have observed while conducting this and other studies, that some of the procedures required when using EPA Method 1312, such as particle size reduction, end-over-end rotary agitation, and extended extraction time (18 hours) probably remove most realistic approximations of simulating runoff from mine-waste. Purpose of Investigation The purpose of this investigation is two-fold: First, it provides our collaborators an assessment of EPA Method 1312 leachate chemistry data for solid mine-waste composite samples collected from four different mine-waste sites. Second, data from this investigation were used for comparative studies as part of a larger effort to develop a field leach test (Hageman and Briggs, in press) which is designed and used as a screening tool for evaluation of historic mine-waste piles.

1 U.S. Geological Survey, Box 25046, MS 973, Denver, Co. 80225-0046 ABSTRACT An important tool for use in the geochemical assessment of abandoned mine-waste piles is a leach procedure that can easily be done in the field and used for on-site screening of historic mine-waste material. We have developed a simple field leach test that is an effective indicator of waste pile geochemistry and can be used in order to establish the. relative geochemical fingerprint for a given pile. This simple procedure also provides indication of the potential chemical composition of run-off from the weathered surface of these piles. As part of developing this technique, a comparative study was carried out on eight mine-waste composite samples from different deposit types. Splits of all eight composites were leached using the field leach test procedure and a modified version of EPA Method 1312 (SPLP). We found that the field leach test consistently provides relative indication of leachate geochemical trends comparable to leachate data derived from the more regulated, time consuming, and laborious EPA Method 1312 (SPLP).

1 U.S. Geological Survey, MS. 973, Denver Federal Center, Denver, CO 80225-0046 ksmith@usgs.guv 2 EnviroStat, Inc., P.O. Box 636, Fort Collins, CO 80522 EnviroStat@compuserve.com 3 US. Geological Survey, MS. 973, Denver Federal Center, Denver, CO 80225-0046 phageman@usgs.gov ABSTRACT We developed a statistically based strategy for sampling the surficial material of mine-waste dumps for use in screening and prioritizing historic dumps on abandoned mine lands. This sampling strategy entails the collection of a representative composite sample from individual dumps and allows for regional or watershed-based assessments. One 30-increment dump-composite sample collected using this sampling strategy contains as much information, relative to average value, as 30 individual grab samples at 1/30 of the analytical cost.

A U.S. Geological Survey report is presented detailing the analytical results and sample locality map of stream-sediment and panned-concentrate samples from the Baboquivari Peak Wilderness Study Area, Pima County, Arizona.