Geology topics

R. Blaine McCleskey

Publications and source records attributed to R. Blaine McCleskey.

At least 73 records · Page 4Linked to original sources

USGS2015

Cr(VI) occurrence and geochemistry in water from public-supply wells in California

Hexavalent chromium, Cr(VI), in 918 wells sampled throughout California between 2004 and 2012 by the Groundwater Ambient Monitoring and Assessment-Priority Basin Project (GAMA-PBP) ranged from less than the study reporting limit of 1 microgram per liter (μg/L) to 32 μg/L. Statewide, Cr(VI) was reported in 31 percent of wells and equaled or exceeded the recently established (2014) California Maximum Contaminant Level (MCL) for Cr(VI) of 10 μg/L in 4 percent of wells. Cr(VI) data collected for regulatory purposes overestimated Cr(VI) occurrence compared to spatially-distributed GAMA-PBP data. Ninety percent of chromium was present as Cr(VI), which was detected more frequently and at higher concentrations in alkaline (pH ≥ 8), oxic water; and more frequently in agricultural and urban land uses compared to native land uses. Chemical, isotopic (tritium and carbon-14), and noble-gas data show high Cr(VI) in water from wells in alluvial aquifers in the southern California deserts result from long groundwater-residence times and geochemical reactions such as silicate weathering that increase pH, while oxic conditions persist. High Cr(VI) in water from wells in alluvial aquifers along the west-side of the Central Valley results from high-chromium in source rock eroded to form those aquifers, and areal recharge processes (including irrigation return) that can mobilize chromium from the unsaturated zone. Cr(VI) co-occurred with oxyanions having similar chemistry, including vanadium, selenium, and uranium. Cr(VI) was positively correlated with nitrate, consistent with increased concentrations in areas of agricultural land use and mobilization of chromium from the unsaturated zone by irrigation return.

California↗

USGS2015

An environmental survey of Serpentine Hot Springs: Geology, hydrology, geochemistry, and microbiology

Serpentine Hot Springs is the most visited site in the Bering Land Bridge National Preserve. The hot springs have traditionally been used by the Native people of the Seward Peninsula for religious, medicinal and spiritual purposes and continue to be used in many of the same ways by Native people today. The hot springs are also popular with non-Native users from Nome and other communities, recreational users and pilots from out of the area, and hunters and hikers.

Alaska↗

USGS2014

Vibrational, X-ray absorption, and Mössbauer spectra of sulfate minerals from the weathered massive sulfide deposit at Iron Mountain, California

The Iron Mountain Mine Superfund site in California is a prime example of an acid mine drainage (AMD) system with well developed assemblages of sulfate minerals typical for such settings. Here we present and discuss the vibrational (infrared), X-ray absorption, and Mössbauer spectra of a number of these phases, augmented by spectra of a few synthetic sulfates related to the AMD phases. The minerals and related phases studied in this work are (in order of increasing Fe 2 O 3 /FeO): szomolnokite, rozenite, siderotil, halotrichite, römerite, voltaite, copiapite, monoclinic Fe 2 (SO 4 ) 3 , Fe 2 (SO 4 ) 3 ·5H 2 O, kornelite, coquimbite, Fe(SO 4 )(OH), jarosite and rhomboclase. Fourier transform infrared spectra in the region 750–4000 cm −1 are presented for all studied phases. Position of the FTIR bands is discussed in terms of the vibrations of sulfate ions, hydroxyl groups, and water molecules. Sulfur K-edge X-ray absorption near-edge structure (XANES) spectra were collected for selected samples. The feature of greatest interest is a series of weak pre-edge peaks whose position is determined by the number of bridging oxygen atoms between Fe 3+ octahedra and sulfate tetrahedra. Mössbauer spectra of selected samples were obtained at room temperature and 80 K for ferric minerals jarosite and rhomboclase and mixed ferric–ferrous minerals römerite, voltaite, and copiapite. Values of Fe 2+ /[Fe 2+ + Fe 3+ ] determined by Mössbauer spectroscopy agree well with those determined by wet chemical analysis. The data presented here can be used as standards in spectroscopic work where spectra of well-characterized compounds are required to identify complex mixtures of minerals and related phases.

California↗

USGS2014

Towards understanding the puzzling lack of acid geothermal springs in Tibet (China): Insight from a comparison with Yellowstone (USA) and some active volcanic hydrothermal systems

Explanations for the lack of acid geothermal springs in Tibet are inferred from a comprehensive hydrochemical comparison of Tibetan geothermal waters with those discharged from Yellowstone (USA) and two active volcanic areas, Nevado del Ruiz (Colombia) and Miravalles (Costa Rica) where acid springs are widely distributed and diversified in terms of geochemical characteristic and origin. For the hydrothermal areas investigated in this study, there appears to be a relationship between the depths of magma chambers and the occurrence of acid, chloride-rich springs formed via direct magmatic fluid absorption. Nevado del Ruiz and Miravalles with magma at or very close to the surface (less than 1–2 km) exhibit very acidic waters containing HCl and H 2 SO 4 . In contrast, the Tibetan hydrothermal systems, represented by Yangbajain, usually have fairly deep-seated magma chambers so that the released acid fluids are much more likely to be fully neutralized during transport to the surface. The absence of steam-heated acid waters in Tibet, however, may be primarily due to the lack of a confining layer (like young impermeable lavas at Yellowstone) to separate geothermal steam from underlying neutral chloride waters and the possible scenario that the deep geothermal fluids below Tibet carry less H 2 S than those below Yellowstone.

Tibet, Yellowstone National Park↗

USGS2013

New Method for Electrical Conductivity Temperature Compensation

Electrical conductivity (κ) measurements of natural waters are typically referenced to 25 °C (κ 25 ) using standard temperature compensation factors (α). For acidic waters (pH < 4), this can result in a large κ 25 error (δκ 25 ). The more the sample temperature departs from 25 °C, the larger the potential δκ 25 . For pH < 4, the hydrogen ion transport number becomes substantial and its mode of transport is different from most other ions resulting in a different α. A new method for determining α as a function of pH and temperature is presented. Samples with varying amounts of H 2 SO 4 and NaCl were used to develop the new α, which was then applied to 65 natural water samples including acid mine waters, geothermal waters, seawater, and stream waters. For each sample, the κ and pH were measured at several temperatures from 5 to 90 °C and κ 25 was calculated. The δκ 25 ranged from −11 to 9% for the new method as compared to −42 to 25% and −53 to 27% for the constant α (0.019) and ISO-7888 methods, respectively. The new method for determining α is a substantial improvement for acidic waters and performs as well as or better than the standard methods for circumneutral waters.

Environmental Science & Technology↗

USGS2013

Eruptions at Lone Star Geyser, Yellowstone National Park, USA, part 1: energetics and eruption dynamics

Geysers provide a natural laboratory to study multiphase eruptive processes. We present results from a four–day experiment at Lone Star Geyser in Yellowstone National Park, USA. We simultaneously measured water discharge, acoustic emissions, infraredintensity, and visible and infrared video to quantify the energetics and dynamics of eruptions, occurring approximately every three hours. We define four phases in the eruption cycle: 1) a 28 ± 3 minute phase with liquid and steam fountaining, with maximum jet velocities of 16–28 m s − 1 , steam mass fraction of less than &sim; 0.01. Intermittently choked flow and flow oscillations with periods increasing from 20 to 40 s are coincident with a decrease in jet velocity and an increase of steam fraction; 2) a 26 ± 8 minute post–eruption relaxation phase with no discharge from the vent, infrared (IR) and acoustic power oscillations gliding between 30 and 40 s; 3) a 59 ± 13 minute recharge period during which the geyser is quiescent and progressively refills, and 4) a 69 ± 14 minute pre–play period characterized by a series of 5–10 minute–long pulses of steam, small volumes of liquid water discharge and 50–70 s flow oscillations. The erupted waters ascend froma 160 − 170° C reservoir and the volume discharged during the entire eruptive cycle is 20.8 ± 4.1 m 3 . Assuming isentropic expansion, we calculate a heat output from the geyser of 1.4–1.5 MW, which is < 0.1% of the total heat output from Yellowstone Caldera.

Wyoming↗

USGS2012

Comparison of electrical conductivity calculation methods for natural waters

The capability of eleven methods to calculate the electrical conductivity of a wide range of natural waters from their chemical composition was investigated. A brief summary of each method is presented including equations to calculate the conductivities of individual ions, the ions incorporated, and the method's limitations. The ability of each method to reliably predict the conductivity depends on the ions included, effective accounting of ion pairing, and the accuracy of the equation used to estimate the ionic conductivities. The performances of the methods were evaluated by calculating the conductivity of 33 environmentally important electrolyte solutions, 41 U.S. Geological Survey standard reference water samples, and 1593 natural water samples. The natural waters tested include acid mine waters, geothermal waters, seawater, dilute mountain waters, and river water impacted by municipal waste water. The three most recent conductivity methods predict the conductivity of natural waters better than other methods. Two of the recent methods can be used to reliably calculate the conductivity for samples with pH values greater than about 3 and temperatures between 0 and 40°C. One method is applicable to a variety of natural water types with a range of pH from 1 to 10, temperature from 0 to 95°C, and ionic strength up to 1 m.

Limnology and Oceanography: Methods↗

USGS2012

Simultaneous oxidation of arsenic and antimony at low and circumneutral pH, with and without microbial catalysis

Arsenic and Sb are common mine-water pollutants and their toxicity and fate are strongly influenced by redox processes. In this study, simultaneous Fe(II), As(III) and Sb(III) oxidation experiments were conducted to obtain rates under laboratory conditions similar to those found in the field for mine waters of both low and circumneutral pH. Additional experiments were performed under abiotic sterile conditions to determine the biotic and abiotic contributions to the oxidation processes. The results showed that under abiotic conditions in aerated Fe(III)–H 2 SO 4 solutions, Sb(III) oxidizes slightly faster than As(III). The oxidation rates of both elements were accelerated by increasing As(III), Sb(III), Fe(III), and Cl − concentrations in the presence of light. For unfiltered circumneutral water from the Giant Mine (Yellowknife, NWT, Canada), As(III) oxidized at 15–78 μmol/L/h whereas Sb(III) oxidized at 0.03–0.05 μmol/L/h during microbial exponential growth. In contrast, As(III) and Sb(III) oxidation rates of 0.01–0.03 and 0.01–0.02 μmol/L/h, respectively, were obtained in experiments performed with acid unfiltered mine waters from the Iberian Pyritic Belt (SW Spain). These results suggest that the Fe(III) formed from microbial oxidation abiotically oxidized As(III) and Sb(III). After sterile filtration of both mine water samples, neither As(III), Sb(III), nor Fe(II) oxidation was observed. Hence, under the experimental conditions, bacteria were catalyzing As and Sb oxidation in the Giant Mine waters and Fe oxidation in the acid waters of the Iberian Pyrite Belt.

Applied Geochemistry↗

USGS2012

Solute and geothermal flux monitoring using electrical conductivity in the Madison, Firehole, and Gibbon Rivers, Yellowstone National Park

The thermal output from the Yellowstone magma chamber can be estimated from the Cl flux in the major rivers in Yellowstone National Park; and by utilizing continuous discharge and electrical conductivity measurements the Cl flux can be calculated. The relationship between electrical conductivity and concentrations of Cl and other geothermal solutes (Na, SO 4 , F, HCO 3 , SiO 2 , K, Li, B, and As) was quantified at monitoring sites along the Madison, Gibbon, and Firehole Rivers, which receive discharge from some of the largest and most active geothermal areas in Yellowstone. Except for some trace elements, most solutes behave conservatively and the ratios between geothermal solute concentrations are constant in the Madison, Gibbon, and Firehole Rivers. Hence, dissolved concentrations of Cl, Na, SO 4 , F, HCO 3 , SiO 2 , K, Li, Ca, B and As correlate well with conductivity ( R 2 > 0.9 for most solutes) and most exhibit linear trends. The 2011 flux for Cl, SO 4 , F and HCO 3 determined using automated conductivity sensors and discharge data from nearby USGS gaging stations is in good agreement with those of previous years (1983–1994 and 1997–2008) at each of the monitoring sites. Continuous conductivity monitoring provides a cost- and labor-effective alternative to existing protocols whereby flux is estimated through manual collection of numerous water samples and subsequent chemical analysis. Electrical conductivity data also yield insights into a variety of topics of research interest at Yellowstone and elsewhere: (1) Geyser eruptions are easily identified and the solute flux quantified with conductivity data. (2) Short-term heavy rain events can produce conductivity anomalies due to dissolution of efflorescent salts that are temporarily trapped in and around geyser basins during low-flow periods. During a major rain event in October 2010, 180,000 kg of additional solute was measured in the Madison River. (3) The output of thermal water from the Gibbon River appears to have increased by about 0.2%/a in recent years, while the output of thermal water for the Firehole River shows a decrease of about 10% from 1983 to 2011. Confirmation of these trends will require continuing Cl flux monitoring over the coming decades.

Wyoming↗

USGS2012

A new method of calculating electrical conductivity with applications to natural waters

A new method is presented for calculating the electrical conductivity of natural waters that is accurate over a large range of effective ionic strength (0.0004–0.7 mol kg −1 ), temperature (0–95 °C), pH (1–10), and conductivity (30–70,000 μS cm −1 ). The method incorporates a reliable set of equations to calculate the ionic molal conductivities of cations and anions (H + , Li + , Na + , K + , Cs + , NH 4 + , Mg 2+ , Ca 2+ , Sr 2+ , Ba 2+ , F − , Cl − , Br − , SO 4 2- , HCO 3 - , CO 3 2- , NO 3 - , and OH − ), environmentally important trace metals (Al 3+ , Cu 2+ , Fe 2+ , Fe 3+ , Mn 2+ , and Zn 2+ ), and ion pairs (HSO 4 - , NaSO 4 - , NaCO 3 - , and ). These equations are based on new electrical conductivity measurements for electrolytes found in a wide range of natural waters. In addition, the method is coupled to a geochemical speciation model that is used to calculate the speciated concentrations required for accurate conductivity calculations. The method was thoroughly tested by calculating the conductivities of 1593 natural water samples and the mean difference between the calculated and measured conductivities was −0.7 ± 5%. Many of the samples tested were selected to determine the limits of the method and include acid mine waters, geothermal waters, seawater, dilute mountain waters, and river water impacted by municipal waste water. Transport numbers were calculated and H + , Na + , Ca 2+ , Mg 2+ , NH 4 + , K + , Cl − , SO 4 2- , HCO 3 - , CP 3 2- , F − , Al 3+ , Fe 2+ , NO 3 - , and substantially contributed (>10%) to the conductivity of at least one of the samples. Conductivity imbalance in conjunction with charge imbalance can be used to identify whether a cation or an anion measurement is likely in error, thereby providing an additional quality assurance/quality control constraint on water analyses.

Geochimica et Cosmochimica Acta↗

USGS2012

Water chemistry and electrical conductivity database for rivers in Yellowstone National Park, Wyoming

Chloride flux has been used to estimate heat flow in volcanic environments since the method was developed in New Zealand by Ellis and Wilson (1955). The method can be applied effectively at Yellowstone, because nearly all of the water discharged from its thermal features enters one of four major rivers (the Madison, Yellowstone, Snake, and Falls Rivers) that drain the park, and thus integration of chloride fluxes from all these rivers provides a means to monitor the total heat flow from the entire Yellowstone volcanic system (Fournier and others, 1976; Fournier, 1979). Fournier (1989) summarized the results and longterm heat-flow trends from Yellowstone, and later efforts that applied the chloride inventory method to estimate heat flow were described by Ingebritsen and others (2001) and Friedman and Norton (2007). Most recently, the U.S. Geological Survey (USGS), in conjunction with the National Park Service, has provided publicly accessible reports on solute flux, based on periodic sampling at selected locations (Hurwitz and others, 2007a,b). While these studies have provided a wealth of valuable data, winter travel restrictions and the great distances between sites present significant logistical challenges and have limited collection to a maximum of 28 samples per site annually. This study aims to quantify relations between solute concentrations (especially chloride) and electrical conductivity for several rivers in Yellowstone National Park (YNP), by using automated samplers and conductivity meters. Norton and Friedman (1985) found that chloride concentrations and electrical conductivity have a good correlation in the Falls, Snake, Madison, and Yellowstone Rivers. However, their results are based on limited sampling and hydrologic conditions and their relation with other solutes was not determined. Once the correlations are established, conductivity measurements can then be used as a proxy for chloride concentrations, thereby enabling continuous heat-flow estimation on a much finer timescale and at lower cost than is currently possible with direct sampling. This publication serves as a repository for all data collected during the course of the study from May 2010 through July 2011, but it does not include correlations between solutes and conductivity or recommendations for quantification of chloride through continuous electrical conductivity measurements. This will be the object of a future document.

Wyoming↗

USGS2012

Water chemistry of surface waters affected by the Fourmile Canyon wildfire, Colorado, 2010-2011

In September 2010, the Fourmile Canyon fire burned about 23 percent of the Fourmile Creek watershed in Boulder County, Colo. Water-quality sampling of Fourmile Creek began within a month after the wildfire to assess its effects on surface-water chemistry. Water samples were collected from five sites along Fourmile Creek (above, within, and below the burned area) monthly during base flow, twice weekly during snowmelt runoff, and at higher frequencies during storm events. Stream discharge was also monitored. Water-quality samples were collected less frequently from an additional 6 sites on Fourmile Creek, from 11 tributaries or other inputs, and from 3 sites along Boulder Creek. The pH, electrical conductivity, temperature, specific ultraviolet absorbance, total suspended solids, and concentrations (dissolved and total) of major cations (calcium, magnesium, sodium, and potassium), anions (chloride, sulfate, alkalinity, fluoride, and bromide), nutrients (nitrate, ammonium, and phosphorus), trace metals (aluminum, arsenic, boron, barium, beryllium, cadmium, cobalt, chromium, copper, iron, mercury, lithium, manganese, molybdenum, nickel, lead, rubidium, antimony, selenium, strontium, vanadium, and zinc), and dissolved organic carbon are here reported for 436 samples collected during 2010 and 2011.

Colorado↗

USGS2012

Effects of wildfire on source-water quality and aquatic ecosystems, Colorado Front Range

Watershed erosion can dramatically increase after wildfire, but limited research has evaluated the corresponding influence on source-water quality. This study evaluated the effects of the Fourmile Canyon wildfire (Colorado Front Range, USA) on source-water quality and aquatic ecosystems using high- frequency sampling. Dissolved organic carbon (DOC) and nutrient loads in stream water were evaluated for a one-year period during different types of runoff events, including spring snowmelt, and both frontal and summer convective storms. DOC export from the burned watershed did not increase relative to the unburned watershed during spring snowmelt, but substantial increases in DOC export were observed during summer convective storms. Elevated nutrient export from the burned watershed was observed during spring snowmelt and summer convective storms, which increased the primary productivity of stream biofilms. Wildfire effects on source-water quality were shown to be substantial following high-intensity storms, with the potential to affect drinking-water treatment processes.

Colorado↗

USGS2012

Effects of flow regime on stream turbidity and suspended solids after wildfire, Colorado Front Range

Wildfires occur frequently in the Colorado Front Range and can alter the hydrological response of watersheds, yet little information exists on the impact of flow regime and storm events on post-wildfire water quality. The flow regime in the region is characterized by base-flow conditions during much of the year and increased runoff during spring snowmelt and summer convective storms. The impact of snowmelt and storm events on stream discharge and water quality was evaluated for about a year after a wildfire near Boulder, Colorado, USA. During spring snowmelt and low-intensity storms, differences in discharge and turbidity at sites upstream and downstream from the burned areas were minimal. However, high-intensity convective storms resulted in dramatic increases in discharge and turbidity at sites downstream from the burned area. This study highlights the importance of using high-frequency sampling to assess accurately wildfire impacts on water quality downstream.

Colorado↗

USGS2011

Electrical conductivity of electrolytes applicable to natural waters from 0 to 100 degrees C

The electrical conductivities of 34 electrolyte solutions found in natural waters ranging from (10 -4 to 1) molkg -1 in concentration and from (5 to 90) °C have been determined. High-quality electrical conductivity data for numerous electrolytes exist in the scientific literature, but the data do not span the concentration or temperature ranges of many electrolytes in natural waters. Methods for calculating the electrical conductivities of natural waters have incorporated these data from the literature, and as a result these methods cannot be used to reliably calculate the electrical conductivity over a large enough range of temperature and concentration. For the single-electrolyte solutions, empirical equations were developed that relate electrical conductivity to temperature and molality. For the 942 molar conductivity determinations for single electrolytes from this study, the mean relative difference between the calculated and measured values was 0.1 %. The calculated molar conductivity was compared to literature data, and the mean relative difference for 1978 measurements was 0.2 %. These data provide an improved basis for calculating electrical conductivity for most natural waters.

Journal of Chemical and Engineering Data↗

USGS2011

Fluoride geochemistry of thermal waters in Yellowstone National Park: I. Aqueous fluoride speciation

Thermal water samples from Yellowstone National Park (YNP) have a wide range of pH (1–10), temperature, and high concentrations of fluoride (up to 50 mg/l). High fluoride concentrations are found in waters with field pH higher than 6 (except those in Crater Hills) and temperatures higher than 50 °C based on data from more than 750 water samples covering most thermal areas in YNP from 1975 to 2008. In this study, more than 140 water samples from YNP collected in 2006–2009 were analyzed for free-fluoride activity by ion-selective electrode (ISE) method as an independent check on the reliability of fluoride speciation calculations. The free to total fluoride concentration ratio ranged from <1% at low pH values to >99% at high pH. The wide range in fluoride activity can be explained by strong complexing with H + and Al 3+ under acidic conditions and lack of complexing under basic conditions. Differences between the free-fluoride activities calculated with the WATEQ4F code and those measured by ISE were within 0.3–30% for more than 90% of samples at or above 10 −6 molar, providing corroboration for chemical speciation models for a wide range of pH and chemistry of YNP thermal waters. Calculated speciation results show that free fluoride, F − , and major complexes ( HF ( aq ) 0 "> HF(aq)0 , AlF 2+ , AlF 2 + "> AlF2+ and AlF 3 0 "> AlF30 ) account for more than 95% of total fluoride. Occasionally, some complex species like AlF 4 - "> AlF4- , FeF 2+ , FeF 2 + "> FeF2+ , MgF + and BF 2 ( OH ) 2 - "> BF2(OH)2- may comprise 1–10% when the concentrations of the appropriate components are high. According to the simulation results by PHREEQC and calculated results, the ratio of main fluoride species to total fluoride varies as a function of pH and the concentrations and ratios of F and Al.

Yellowstone National Park↗

USGS2011

Ammonium in thermal waters of Yellowstone National Park: Processes affecting speciation and isotope fractionation

Dissolved inorganic nitrogen, largely in reduced form (NH 4 (T)≈NH 4(aq) + +NH 3(aq) o ), has been documented in thermal waters throughout Yellowstone National Park, with concentrations ranging from a few micromolar along the Firehole River to millimolar concentrations at Washburn Hot Springs. Indirect evidence from rock nitrogen analyses and previous work on organic compounds associated with Washburn Hot Springs and the Mirror Plateau indicate multiple sources for thermal water NH 4 (T), including Mesozoic marine sedimentary rocks, Eocene lacustrine deposits, and glacial deposits. A positive correlation between NH 4 (T) concentration and δ 18 O of thermal water indicates that boiling is an important mechanism for increasing concentrations of NH 4 (T) and other solutes in some areas. The isotopic composition of dissolved NH 4 (T) is highly variable (δ 15 N = −6‰ to +30‰) and is positively correlated with pH values. In comparison to likely δ 15 N values of nitrogen source materials (+1‰ to +7‰), high δ 15 N values in hot springs with pH >5 are attributed to isotope fractionation associated with NH 3(aq) o loss by volatilization. NH 4 (T) in springs with low pH typically is relatively unfractionated, except for some acid springs with negative δ 15 N values that are attributed to NH 3(g) o condensation. NH 4 (T) concentration and isotopic variations were evident spatially (between springs) and temporally (in individual springs). These variations are likely to be reflected in biomass and sediments associated with the hot springs and outflows. Elevated NH 4 (T) concentrations can persist for 10s to 1000s of meters in surface waters draining hot spring areas before being completely assimilated or oxidized.

Yellowstone National Park↗

USGS2011

Spring runoff water-chemistry data from the Standard Mine and Elk Creek, Gunnison County, Colorado, 2010

Water samples were collected approximately every two weeks during the spring of 2010 from the Level 1 portal of the Standard Mine and from two locations on Elk Creek. The objective of the sampling was to: (1) better define the expected range and timing of variations in pH and metal concentrations in Level 1 discharge and Elk Creek during spring runoff; and (2) further evaluate possible mechanisms controlling water quality during spring runoff. Samples were analyzed for major ions, selected trace elements, and stable isotopes of oxygen and hydrogen (oxygen-18 and deuterium). The Level 1 portal sample and one of the Elk Creek samples (EC-CELK1) were collected from the same locations as samples taken in the spring of 2007, allowing comparison between the two different years. Available meteorological and hydrologic data suggest that 2010 was an average water year and 2007 was below average. Field pH and dissolved metal concentrations in Level 1 discharge had the following ranges: pH, 2.90 to 6.23; zinc, 11.2 to 26.5 mg/L; cadmium, 0.084 to 0.158 mg/L; manganese, 3.23 to 10.2 mg/L; lead, 0.0794 to 1.71 mg/L; and copper, 0.0674 to 1.14 mg/L. These ranges were generally similar to those observed in 2007. Metal concentrations near the mouth of Elk Creek (EC-CELK1) were substantially lower than in 2007. Possible explanations include remedial efforts at the Standard Mine site implemented after 2007 and greater dilution due to higher Elk Creek flows in 2010. Temporal patterns in pH and metal concentrations in Level 1 discharge were similar to those observed in 2007, with pH, zinc, cadmium, and manganese concentrations generally decreasing, and lead and copper generally increasing during the snowmelt runoff period. Zinc and cadmium concentrations were inversely correlated with flow and thus apparently dilution-controlled. Lead and copper concentrations were inversely correlated with pH and thus apparently pH-controlled. Zinc, cadmium, and manganese concentrations near the mouth of Elk Creek did not display the pronounced increase observed during high flow in 2007, again perhaps due to remedial activities at the mine site or greater dilution in 2010. Zinc and cadmium loads near the mouth of Elk Creek were generally greater than those at the Level 1 portal for the six sample days in 2010. Whereas metal loads in September 2007 suggested that Level 1 portal discharge was the primary source of metals to the creek, metal loads computed for this study suggest that this may not have been the case in the spring of 2010. d18O values are well correlated with flow, becoming lighter (more negative) during snowmelt in both Level 1 discharge and Elk Creek. Seasonal variations in the chemistry of Level 1 discharge, along with portal flow tracking very closely with creek flow, are consistent with geochemical and environmental tracer data from 2007 that indicate short residence times (<1 year) for groundwater discharging from the Standard Mine.

Colorado↗