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USGS2020

Detrital record of the late Oligocene – Early Miocene mafic volcanic arc in the southern Patagonian Andes (~51 °S) from single-clast geochronology and trace element geochemistry

Retroarc foreland basins are important archives of continental arc magmatism and upper plate deformational processes that control the evolution of continental lithosphere. However, resolving source areas in foreland basin infill dominated from mixed mafic and recycled sediment using conventional methods such as detrital zircon geochronology poses a challenge to thorough analysis due to lower zircon fertility and the higher susceptibility to weathering of mafic lithologies. Here, we integrate whole rock 40 Ar/ 39 Ar geochronology and major and trace element geochemistry data from volcanic clasts from the lower Miocene infill of the Magallanes-Austral Basin and local Sierra Baguales intrusive rocks to understand the distribution of mafic sources and Neogene changes in arc magmatism in between multiple ridge subduction events in the southern Patagonian Andes. Potential source areas for the coarse-grained mafic detritus include the Eocene plateau lavas, the Late Jurassic-Miocene Southern Patagonian batholith, and the Late Jurassic Sarmiento Ophiolitic Complex. Published detrital zircon U-Pb age spectra suggest that all three sources are viable contributors to the basin, though the paucity of Jurassic and Eocene zircons preclude these as major sources. Here, new 40 Ar/ 39 Ar dating of the volcanic clasts from the early Miocene Río Guillermo Formation reveals latest Oligocene to early Miocene eruptive ages (∼25-22 Ma), indicating syndepositional eruption with the ancestral Río Guillermo fluvial sedimentation. A single dated clast yields a Late Cretaceous age (∼102 Ma). The clasts are dominantly basaltic andesite with Ba/Ta ∼500-1000, La/Ta >20, and Ba/La >15, indicating an arc-derived melt source. We propose that the clasts record a Miocene mafic continental arc source area in the Patagonian Andes, which has since been removed by erosion and is thus sparsely represented in the batholith. Furthermore, we suggest that this early Miocene phase of arc volcanism, which postdates Eocene and Oligocene backarc magmatism and pre-dates middle Miocene to recent Chile Ridge backarc magmatism, reflects a return to normal arc volcanism along the Patagonian margin following a cessation due to ridge subduction and subsequent slab window migration. New geochemistry and 40 Ar/ 39 Ar data from a basaltic dike in the Sierra Baguales, which crosscuts the Cenozoic stratigraphic section, records plateau magmatism ∼16 Ma associated with incipient Chile Ridge slab window volcanism.

Patagonian Andes↗

USGS2018

Insights into the emplacement of upper-crustal plutons and their relationship to large silicic calderas, from field relationships, geochronology, and zircon trace element geochemistry in the Stillwater – Clan Alpine caldera complex, western Nevada, USA

Geologic mapping, new U-Pb zircon ages, and new and published 40 Ar/ 39 Ar sanidine ages document the timing and extent of Oligocene magmatism in the southern Stillwater Range and Clan Alpine Mountains of western Nevada, where Miocene extension has exposed at least six nested silicic calderas and underlying granitic plutons to crustal depths locally ≥ 9 km. Both caldera-forming rhyolitic tuffs and underlying plutons were emplaced in two episodes, one from about 30.4–28.2 Ma that included the Deep Canyon, Job Canyon, and Campbell Creek calderas and underlying plutons, and one from about 25.3–24.8 Ma that included the Louderback Mountains, Poco Canyon, and Elevenmile Canyon calderas and underlying plutons. In these two 1–2 m.y. periods, almost the entire Mesozoic upper crust was replaced by Oligocene intrusive and extrusive rocks to depths ≥ 9 km over an estimated total area of ~ 1500 km 2 (pre-extension). Zircon trace element geochemistry indicates that some plutonic rock can be solidified residual magma from the tuff eruptions. Most plutons are not solidified residual magma, although they directly underlie calderas and were emplaced along the same structures shortly after to as much as one million years after caldera formation. Magma chambers and plutons grew by floor subsidence accommodated by downward transfer of country rocks. If other Great Basin calderas are similar, the dense concentration of shallowly exposed calderas in central Nevada is underlain by a complexly zoned mid-Cenozoic batholith assembled in discrete pulses that coincided with formation of large silicic calderas up to 2500–5000 km 3 .

Nevada↗

USGS2011

Interannual variation of rare earth element abundances in corals from northern coast of the South China Sea and its relation with sea-level change and human activities

Here we present interannual rare earth element (REE) records spanning the last two decades of the 20th century in two living Porites corals, collected from Longwan Bay, close to the estuarine zones off Wanquan River of Hainan Island and Hong Kong off the Pearl River Delta of Guangdong Province in the northern South China Sea. The results show that both coral REE contents (0.5–40 ng g −1 in Longwan Bay and 2–250 ng g −1 in Hong Kong for La–Lu) are characterized with a declining trend, which are significantly negative correlated with regional sea-level rise (9.4 mm a −1 from 1981 to 1996 in Longwan Bay, 13.7 mm a −1 from 1991 to 2001 in Hong Kong). The REE features are proposed to be resulted from seawater intrusion into the estuaries in response to contemporary sea-level rise. However, the tendency for the coral Er/Nd time series at Hong Kong site is absent and there is no significant relation between Er/Nd and total REEs as found for the coral at Longwan Bay site. The observations are likely attributed to changes of the water discharge and sediment load of Pearl River, which have been significantly affected by intense human activities, such as the construction of dams/reservoirs and riverbed sediment mining, in past decades. The riverine sediment load/discharge ratio of the Pearl River decreased sharply with a rate of 0.02 kg m −3 a −1 , which could make significant contribution to the declining trend of coral REE. We propose that coastal corals in Longwan Bay and similar unexplored sites with little influences of river discharge and anthropogenic disruption are ideal candidates to investigate the influence of sea-level change on seawater/coral REE.

South China Sea↗

USGS2017

Element migration of pyrites during ductile deformation of the Yuleken porphyry Cu deposit (NW-China)

The strongly deformed Yuleken porphyry Cu deposit (YPCD) occurs in the Kalaxiangar porphyry Cu belt (KPCB), which occupies the central area of the Central Asian Orogenic Belt (CAOB) between the Sawu’er island arc and the Altay Terrane in northern Xinjiang. The YPCD is one of several typical subduction-related deposits in the KPCB, which has undergone syn-collisional and post-collisional metallogenic overprinting. The YPCD is characterized by three pyrite-forming stages, namely a hydrothermal stage A (Py I), a syn-ductile deformation stage B (Py II) characterized by Cu-Au enrichment, and a fracture-filling stage C (Py III). In this study, we conducted systematic petrographic and geochemical studies of pyrites and coexist biotite, which formed during different stages, in order to constrain the physicochemical conditions of the ore formation. Euhedral, fragmented Py I has low Pb and high Te and Se concentration and Ni contents are low with Co/Ni ratios mostly between 1 and 10 (average 9.00). Py I is further characterized by enrichments of Bi, As, Ni, Cu, Te and Se in the core relative to the rim domains. Anhedral round Py II has moderate Co and Ni contents with high Co/Ni ratios >10 (average 95.2), and average contents of 46.5 ppm Pb and 5.80 ppm Te. Py II is further characterized by decreasing Bi, Cu, Pb, Zn, Ag, Te, Mo, Sb and Au contents from the rim to the core domains. Annealed Py III has the lowest Co content of all pyrite types with Co/Ni ratios mostly <0.1 (average 1.33). Furthermore, Py III has average contents of 3.31 ppm Pb, 1.33 ppm Te and 94.6 ppm Se. In addition, Fe does not correlate with Cu and S in the Py I and Py III, while Py II displays a negative correlation between Fe and Cu as well as a positive correlation between Fe and S. Therefore, pyrites which formed during different tectonic regimes also have different chemical compositions. Biotite geothermometer and oxygen fugacity estimates display increasing temperatures and oxygen fugacities from stage A to stage B, while temperature and oxygen fugacities decrease from stage B to stage C. The Co/Ni ratio of pyrite depends discriminates between the different mineralizing stages in the Yuleken porphyry copper deposit: Py II, associated with the deformation stage B and Cu-enrichment, shows higher Co/Ni ratios and enrichments of Pb, Zn, Mo, Te and Sb than the pyrites formed during the other two stages. The Co/Ni ratio of pyrite can not only apply to discriminate the submarine exhalative, magmatic or sedimentary origins for ore deposits but also can distinguish different ore-forming stages in a single porphyry Cu deposit. Thus, Co/Ni ratio of pyrites may act as an important exploration tool to distinguish pyrites from Cu-rich versus barren area. Furthermore, the distribution of Cu, Mo, Pb, Au, Bi, Sb and Zn in the variably deformed pyrite is proportional to the extent of deformation of the pyrites, indicating in accordance with variable physicochemical conditions different element migration behavior during the different stages of deformation and, thus, mineralisation.

Ore Geology Reviews↗

USGS2025

Alteration mapping in granitic gneiss using handheld geophysical and geochemical instruments: Implications for iron oxide-apatite and rare earth elements exploration

The Adirondack Mountains of New York, U.S.A. contain iron oxide-apatite (IOA) mineral deposits with variable concentrations of rare earth elements (REE). The IOA mineral deposits are typically hosted in the Lyon Mountain Granite Gneiss and are spatially correlated with extensive Na metasomatism (albitization) of the surrounding country rocks, although some mineral deposits also occur in metagabbro, paragneiss, and anorthosite hosts. The location of albitization zones is key to finding new IOA mineral deposits and better understanding the mineralization processes associated with their genesis. However, the Na alteration zones are generally not visibly identifiable in outcrop or hand specimens because the color and textural changes are subtle and are thus difficult to map. Here, we discuss the results from testing two spectroscopic techniques (handheld, field gamma-ray spectroscopy, and portable X-ray fluorescence (pXRF)) to characterize albitization zones surrounding IOA mineral deposits. The gamma-ray and pXRF spectrometers successfully distinguished the relative intensity of alteration in the Lyon Mountain Granite Gneiss based on the K abundance. The measured K content decreases towards the IOA mineral deposits, and the magnitude and width of the gradient are similar along the strike of each mineral deposit. Elevated Th and U values are present in host rocks adjacent to REE-bearing IOA mineral deposits. The pXRF and gamma-ray spectrometer K values are remarkably consistent with laboratory-based, whole-rock XRF compositional data and, therefore, useful for semi-quantitative analysis. Notably, albitization aureoles are consistent around REE-rich and REE-poor mineral deposits, suggesting that saline fluids are essential for the petrogenesis of IOA mineral deposits but may not be critical to REE mineralization. Ultimately, this study demonstrates the utility of handheld gamma-ray and pXRF spectrometry for identifying otherwise cryptic albitization gradients associated with IOA mineral deposits in granitic gneiss.

New York↗

USGS2008

Trace-element budgets in the Ohio/Sunbury shales of Kentucky: Constraints on ocean circulation and primary productivity in the Devonian-Mississippian Appalachian Basin

The hydrography of the Appalachian Basin in late Devonian-early Mississippian time is modeled based on the geochemistry of black shales and constrained by others' paleogeographic reconstructions. The model supports a robust exchange of basin bottom water with the open ocean, with residence times of less than forty years during deposition of the Cleveland Shale Member of the Ohio Shale. This is counter to previous interpretations of these carbon-rich units having accumulated under a stratified and stagnant water column, i.e., with a strongly restricted bottom bottom-water circulation. A robust circulation of bottom waters is further consistent with the palaeoclimatology, whereby eastern trade-winds drove upwelling and arid conditions limited terrestrial inputs of siliciclastic sediment, fresh waters, and riverine nutrients. The model suggests that primary productivity was high (~ 2??g C m- 2 d- 1), although no higher than in select locations in the ocean today. The flux of organic carbon settling through the water column and its deposition on the sea floor was similar to fluxes found in modern marine environments. Calculations based on the average accumulation rate of the marine fraction of Ni suggest the flux of organic carbon settling out of the water column was approximately 9% of primary productivity, versus an accumulation rate (burial) of organic carbon of 0.5% of primary productivity. Trace-element ratios of V:Mo and Cr:Mo in the marine sediment fraction indicate that bottom waters shifted from predominantly anoxic (sulfate reducing) during deposition of the Huron Shale Member of the Ohio Shale to predominantly suboxic (nitrate reducing) during deposition of the Cleveland Shale Member and the Sunbury Shale, but with anoxic conditions occurring intermittently throughout this period. ?? 2008 Elsevier B.V.

Palaeogeography, Palaeoclimatology, Palaeoecology↗

USGS2020

Mapping the 3-D extent of the Stillwater Complex, Montana—Implications for potential platinum group element exploration and development

Geophysical models characterize the exposed and interpreted buried extent of the Stillwater Complex, critical for understanding the origin of the layered mafic intrusion and its associated high-grade platinum group element resources. The 3D models, constrained by gravity, magnetic, xenolith, seismic, borehole, and rock property data indicate that the likely maximum extent of the Stillwater Complex beneath Phanerozoic cover is ~10 times greater than its outcrop, ~2240 km 2 . The thickness values are poorly constrained but vary from ~7000 to 12,000 m, depending on crustal and mantle density variations and depths to the top of the lower crust and mantle. This thickness may include dense metasedimentary units of the basin into which the Stillwater Complex intruded. Using the modeled thickness results in a volume estimate of ~24,700 km 3 , albeit poorly constrained. New analyses of xenoliths from the Cretaceous Sliderock and Suzie Peak intrusions produce ages of 2706–2716 Ma, corresponding to the age of the Stillwater Complex, and 2813 Ma, corresponding to the age of Archean gneissic basement. Seismic reflectors in inferred Archean crystalline basement, possibly including the Stillwater Complex, dip ~25–30° north, with segments dipping as much as 70° north. Layered reflectors beneath the Phanerozoic sedimentary section and above the inferred Archean crystalline basement may represent metasedimentary units, perhaps a southern extension of the Mesoproterozoic Belt Basin. The potential field models and the seismic reflection data suggest that the Stillwater Complex was dipping northward prior to deposition of Cambrian strata, perhaps uplifted in the late Archean or Proterozoic as previously proposed, and that during Laramide times, faulting and intrusions highly disrupted the complex. Temperature measurements from boreholes help constrain the depths of feasible mining of the complex.

Montana↗

USGS2006

Mobilization of lead and other trace elements following shock chlorination of wells

Many owners of domestic wells shock chlorinate their wells to treat for bacterial contamination or control bad odors from sulfides. Analysis of well water with four wells from Fallon, Nevada, showed that following recommended procedures for shock chlorinating wells can cause large, short-lasting increases in trace-element concentrations in ground water, particularly for Cu, Fe, Pb, and Zn. Lead concentrations increased up to 745 fold between samples collected just before the well was shock chlorinated and the first sample collected 22-24??h later; Zn concentrations increased up to 252 fold, Fe concentrations increased up to 114 fold, and Cu concentrations increased up to 29 fold. Lead concentrations returned to near background levels following pumping of about one casing volume, however, in one well an estimated 120??mg of excess Pb were pumped before concentrations returned to prechlorination levels. Total Pb concentrations were much greater than filtered (0.45????m) concentrations, indicating the excess Pb is principally particulate. Recommended procedures for purging treated wells following shock chlorination may be ineffective because a strong NaOCl solution can remain in the casing above the pump even following extended pumping. Only small changes in gross alpha and beta radioactivity occurred following shock chlorination. USEPA has not promulgated drinking-water standards for 210Pb, however, measured 210Pb activities in the study area typically were less than the Canadian Maximum Acceptable Concentration of 100??mBq/L. By consuming well water shortly after shock chlorination the public may inadvertently be exposed to levels of Pb, and possibly 210Pb, that exceed drinking-water standards.

Science of the Total Environment↗

USGS2000

The role of "blebbing" in overcoming the hydrophobic barrier during biooxidation of elemental sulfur by Thiobacillus thiooxidans

Brimstone Basin, in southeastern Yellowstone National Park, Wyoming is an ancient hydrothermal area containing solfataric alteration. Drainage waters flowing from Brimstone Basin had pH values as low as 1.23 and contained up to 1.7×10 6 MPN/ml acidophilic sulfur-oxidizing bacteria. Thiobacillus thiooxidans was the dominant sulfur-oxidizing bacterium recovered from an enrichment culture and was used in a structural examination of bacterial sulfur oxidation. Growth in these sulfur cultures occurred in two phases with cells in association with the macroscopic sulfur grains and in suspension above these grains. Colonization of sulfur grains by individual cells and microcolonies was facilitated by organic material that appeared to be responsible for bacterial adhesion. Transmission electron microscopy of negatively stained (2% [wt./vol.] uranyl acetate), sulfur-grown T. thiooxidans revealed extensive membrane blebbing (sloughing of outer membrane vesicles) and the presence of approximately 100 nm sized sulfur particles adsorbed to membrane material surrounding individual bacteria. Sulfite-grown bacteria did not possess membrane blebs. The amphipathic nature of these outer membrane vesicles appear to be responsible for overcoming the hydrophobic barrier necessary for the growth of T. thiooxidans on elemental sulfur.

Book↗

USGS2003

Evaluation of the 34S/32S ratio of Soufre de Lacq elemental sulfur isotopic reference material by continuous flow isotope-ratio mass spectrometry

Soufre de Lacq elemental sulfur reference material (IAEA-S-4) isotopically is homogeneous in amounts as small as 41 ??g as determined by continuous flow isotope-ratio mass spectrometry. The ??34S value for this reference material is +16.90 ?? 0.12??? (1??) on a scale (Vienna Can??on Diablo troilite, VCDT) where IAEA-S-1 Ag2S is -0.3??? and IAEA-S-2 Ag2S is +22.67???. Published by Elsevier Science B.V.

Chemical Geology↗

USGS2002

Rare earth element variations resulting from inversion of pigeonite and subsolidus reequilibration in lunar ferroan anorthosites

We present results of a secondary ion mass spectrometry study of the rare earth elements (REEs) in the minerals of two samples of lunar ferroan anorthosite, and the results are applicable to studies of REEs in all igneous rocks, no matter what their planet of origin. Our pyroxene analyses are used to determine solid-solid REE distribution coefficients (D = C REE in low-Ca pyroxene/C REE in augite) in orthopyroxene-augite pairs derived by inversion of pigeonite. Our data and predictions from crystal-chemical considerations indicate that as primary pigeonite inverts to orthopyroxene plus augite and subsolidus reequilibration proceeds, the solid-solid Ds for orthopyroxene-augite pairs progressively decrease for all REEs; the decrease is greatest for the LREEs. The REE pattern of solid-solid Ds for inversion-derived pyroxene pairs is close to a straight line for Sm-Lu and turns upward for REEs lighter than Sm; the shape of this pattern is predicted by the shapes of the REE patterns for the individual minerals. Equilibrium liquids calculated for one sample from the compositions of primary phases, using measured or experimentally determined solid-liquid Ds, have chondrite-normalized REE patterns that are very slightly enriched in LREEs. The plagioclase equilibrium liquid is overall less rich in REEs than pyroxene equilibrium liquids, and the discrepancy probably arises because the calculated plagioclase equilibrium liquid represents a liquid earlier in the fractionationsequence than the pyroxene equilibrium liquids. “Equilibrium” liquids calculated from the compositions of inversion-derived pyroxenes or orthopyroxene derived by reaction of olivine are LREE depleted (in some cases substantially) in comparison with equilibrium liquids calculated from the compositions of primary phases. These discrepancies arise because the inversion-derived and reaction-derived pyroxenes did not crystallize directly from liquid, and the use of solid-liquid Ds is inappropriate. The LREE depletion of the calculated liquids is a relic of formation of these phases from primary LREE-depleted minerals. Thus, if one attempts to calculate the compositions of equilibrium liquids from pyroxene compositions, it is important to establish that the pyroxenes are primary. In addition, our data suggest that experimental studies have underestimated solid-liquid Ds for REEs in pigeonite and that REE contents of liquids calculated using these Ds are overestimates. Our results have implications for Sm-Nd age studies. Our work shows that if pigeonite inversion and/or subsolidus reequilibration between augite and orthopyroxene occurred significantly after crystallization, and if pyroxene separates isolated for Sm-Nd studies do not have the bulk composition of the primary pyroxenes, then the Sm-Nd isochron age and ε Nd will be in error.

Geochimica et Cosmochimica Acta↗

USGS1998

Rare earth element metasomatism in hydrothermal systems: The Willsboro-Lewis wollastonite ores, New York, USA

Wollastonite ores and garnet-pyroxene skarns in the Willsboro-Lewis district, New York, USA were formed in a complex hydrothermal system associated with the emplacement of a large anorthosite pluton. Contact-metamorphic marbles were replaced by wollastonite, garnet, and clinopyroxene during infiltration metasomatism involving large volumes of water of chiefly meteoric origin. Rare earth elements (REE) in these rocks show large departures from the protolith REE distribution, indicative of substantial REE mobility. Three types of chondrite-normalized REE distribution patterns are present. The most common, found in ores and skarns containing andradite-rich garnet, is convex-up in the light REE (LREE) with a maximum at Pr and a positive Eu anomaly. Europium anomalies and Pr/Yb ratios are correlated with X(Ad) in garnet. This pattern (type C) results from uptake of REE from hydrothermal fluids by growing crystals of calcsilicate minerals, principally andradite, with amounts of LREE controlled by the difference in ionic radius between Ca++ and REE3+ in garnet X sites. The Eu anomaly results either from prior interaction of the fluids with plagioclase-rich, Eu-positive anorthositic rocks in and near the ore zone, or by enrichment of divalent Eu on growth surfaces of garnet followed by entrapment, or both. Relative enrichment in heavy REE (type H) occurs in ores and skarn where calcsilicates, including grossularitic garnet, in contact-metamorphic marble have been concentrated by dissolution of calcite. In most cases a negative Eu anomaly is inherited from the marble protolith. Skarns containing titanite and apatite exhibit high total REE, relative light REE enrichment, and negative Eu anomalies (type L). These appear to be intrusive igneous rocks (ferrodiorites or anorthositic gabbros) that have been converted to skarn by Ca metasomatism. REE, sequestered in titanite, apatite, and garnet, preserve the approximate REE distribution pattern of the igneous protolith. Post-ore granulite facies metamorphism homogenized zoned mineral grains without causing complete intergranular reequilibration and does not appear to have significantly affected the whole-rock REE distributions. These results demonstrate that extensive REE metasomatism can occur in hydrothermal systems at shallow to intermediate depths and that REE geochemistry may be useful in discerning the origin of skarns and skarn-related ore deposits.

Geochimica et Cosmochimica Acta↗

USGS2011

Copper localization, elemental content, and thallus colour in the copper hyperaccumulator lichen Lecanora sierrae from California

An unusual dark blue-green lichen, Lecanora sierrae , was discovered over 30 years ago by Czehura near copper mines in the Lights Creek District, Plumas County, Northern California. Using atomic absorption spectroscopy, Czehura found that dark green lichen samples from Warren Canyon contained 4% Cu in ash and suggested that its colour was due to copper accumulation in the cortex. The present study addressed the hypothesis that the green colour in similar material we sampled from Warren Canyon in 2008, is caused by copper localization in the thallus. Optical microscopy and electron microprobe analysis of specimens of L. sierrae confirmed that copper localization took place in the cortex. Elemental analyses of L. sierrae and three other species from the same localities showed high enrichments of copper and selenium, suggesting that copper selenates or selenites might occur in these lichens and be responsible for the unusual colour.

Lichenologist↗

USGS2002

Concentration method for the spectrochemical determination of seventeen minor elements in natural water

A method for the quantitative spectrochemical determination of microgram amounts of 17 minor elements in water is given. The chelating reagents 8-quinolinol, tannic acid, and thionalide are utilized to concentrate traces (1 to 500 μ g.) of aluminum, cobalt, chromium, copper, iron, gallium, germanium, manganese, nickel, titanium, vanadium, bismuth, lead, molybdenum, cadmium, zinc, and beryllium. Indium is added as a buffer, and palladium is used as an internal standard. The ashed oxides of these 17 metals are subsequently subjected to direct current arcing conditions during spectrum analysis. The method can be used to analyze waters with dissolved solids ranging from less than 100 to more than 100,000 p.p.m. There is no limiting concentration range for the determination of the heavy metals since any volume of sample can be used that will contain a heavy metal concentration within the analytical range of the method. Both the chemical and spectrographic procedures are described, and precision and accuracy data are given.

Analytical Chemistry↗

USGS2017

Effects of an extreme flood on trace elements in river water—From urban stream to major river basin

Major floods adversely affect water quality through surface runoff, groundwater discharge, and damage to municipal water infrastructure. Despite their importance, it can be difficult to assess the effects of floods on streamwater chemistry because of challenges collecting samples and the absence of baseline data. This study documents water quality during the September 2013 extreme flood in the South Platte River, Colorado, USA. Weekly time-series water samples were collected from 3 urban source waters (municipal tap water, streamwater, and wastewater treatment facility effluent) under normal-flow and flood conditions. In addition, water samples were collected during the flood at 5 locations along the South Platte River and from 7 tributaries along the Colorado Front Range. Samples were analyzed for 54 major and trace elements. Specific chemical tracers, representing different natural and anthropogenic sources and geochemical behaviors, were used to compare streamwater composition before and during the flood. The results differentiate hydrological processes that affected water quality: (1) in the upper watershed, runoff diluted most dissolved constituents, (2) in the urban corridor and lower watershed, runoff mobilized soluble constituents accumulated on the landscape and contributed to stream loading, and (3) flood-induced groundwater discharge mobilized soluble constituents stored in the vadose zone.

Colorado↗

USGS2002

Determination of selected elements in whole coal and in coal ash from the eight argonne premium coal samples by atomic absorption spectrometry, atomic emission spectrometry, and ion-selective electrode

Methods for the determination of 24 elements in whole coal and coal ash by inductively coupled argon plasma-atomic emission spectrometry, flame, graphite furnace, and cold vapor atomic absorption spectrometry, and by ion-selective electrode are described. Coal ashes were analyzed in triplicate to determine the precision of the methods. Results of the analyses of NBS Standard Reference Materials 1633, 1633a, 1632a, and 1635 are reported. Accuracy of the methods is determined by comparison of the analysis of standard reference materials to their certified values as well as other values in the literature.

Energy & Fuels↗

USGS2010

New technique for quantification of elemental hg in mine wastes and its implications for mercury evasion into the atmosphere

Mercury in the environment is of prime concern to both ecosystem and human health. Determination of the molecular-level speciation of Hg in soils and mine wastes is important for understanding its sequestration, mobility, and availability for methylation. Extended X-ray absorption fine structure (EXAFS) spectroscopy carried out under ambient P-T conditions has been used in a number of past studies to determine Hg speciation in complex mine wastes and associated soils. However, this approach cannot detect elemental (liquid) mercury in Hg-polluted soils and sediments due to the significant structural disorder of liquid Hg at ambient-temperature. A new sample preparation protocol involving slow cooling through the crystallization temperature of Hg(0) (234 K) results in its transformation to crystalline α-Hg(0). The presence and proportion of Hg(0), relative to other crystalline Hg-bearing phases, in samples prepared in this way can be quantified by low-temperature (77 K) EXAFS spectroscopy. Using this approach, we have determined the relative concentrations of liquid Hg(0) in Hg mine wastes from several sites in the California Coast Range and have found that they correlate well with measured fluxes of gaseous Hg released during light and dark exposure of the same samples, with higher evasion ratios from samples containing higher concentrations of liquid Hg(0). Two different linear relationships are observed in plots of the ratio of Hg emission under light and dark conditions vs % Hg(0), corresponding to silica−carbonate- and hot springs-type Hg deposits, with the hot springs-type samples exhibiting higher evasion fluxes than silica−carbonate type samples at similar Hg(0) concentrations. Our findings help explain significant differences in Hg evasion data for different mine sites in the California Coast Range.

Environmental Science & Technology↗

USGS2010

Evaluating the behavior of gadolinium and other rare earth elements through large metropolitan sewage treatment plants

A primary pathway for emerging contaminants (pharmaceuticals, personal care products, steroids, and hormones) to enter aquatic ecosystems is effluent from sewage treatment plants (STP), and identifying technologies to minimize the amount of these contaminants released is important. Quantifying the flux of these contaminants through STPs is difficult. This study evaluates the behavior of gadolinium, a rare earth element (REE) utilized as a contrasting agent in magnetic resonance imaging (MRI), through four full-scale metropolitan STPs that utilize several biosolids thickening, conditioning, stabilization, and dewatering processing technologies. The organically complexed Gd from MRIs has been shown to be stable in aquatic systems and has the potential to be utilized as a conservative tracer in STP operations to compare to an emerging contaminant of interest. Influent and effluent waters display large enrichments in Gd compared to other REEs. In contrast, most sludge samples from the STPs do not display Gd enrichments, including primary sludges and end-product sludges. The excess Gd appears to remain in the liquid phase throughout the STP operations, but detailed quantification of the input Gd load and residence times of various STP operations is needed to utilize Gd as a conservative tracer.

Environmental Science & Technology↗