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At least 217 records · Page 12Linked to original sources
USGS2017

Geophysics- and geochemistry-based assessment of the geochemical characteristics and groundwater-flow system of the U.S. part of the Mesilla Basin/Conejos-Médanos aquifer system in Doña Ana County, New Mexico, and El Paso County, Texas, 2010–12

One of the largest rechargeable groundwater systems by total available volume in the Rio Grande/Río Bravo Basin (hereinafter referred to as the “Rio Grande”) region of the United States and Mexico, the Mesilla Basin/Conejos-Médanos aquifer system, supplies water for irrigation as well as for cities of El Paso, Texas; Las Cruces, New Mexico; and Ciudad Juárez, Chihuahua, Mexico. The U.S. Geological Survey in cooperation with the Bureau of Reclamation assessed the groundwater resources in the Mesilla Basin and surrounding areas in Doña Ana County, N. Mex., and El Paso County, Tex., by using a combination of geophysical and geochemical methods. The study area consists of approximately 1,400 square miles in Doña Ana County, N. Mex., and 100 square miles in El Paso County, Tex. The Mesilla Basin composes most of the study area and can be divided into three parts: the Mesilla Valley, the West Mesa, and the East Bench. The Mesilla Valley is the part of the Mesilla Basin that was incised by the Rio Grande between Selden Canyon to the north and by a narrow valley (about 4 miles wide) to the southeast near El Paso, Tex., named the Paso del Norte, which is sometimes referred to in the literature as the “El Paso Narrows.” Previously published geophysical data for the study area were compiled and these data were augmented by collecting additional geophysical and geochemical data. Geophysical resistivity measurements from previously published helicopter frequency domain electromagnetic data, previously published direct-current resistivity soundings, and newly collected (2012) time-domain electromagnetic soundings were used in the study to detect spatial changes in the electrical properties of the subsurface, which reflect changes that occur within the hydrogeology. The geochemistry of the groundwater system was evaluated by analyzing groundwater samples collected in November 2010 for physicochemical properties, major ions, trace elements, nutrients, pesticides (reported but not used in the assessment), and environmental tracers. The data obtained from these samples (with the exception of the pesticide data) were used to gain insights into processes controlling the groundwater movement through the groundwater system in the study area. Results from the geophysical and geochemical assessments facilitated the interpretation of the geochemical characteristics of the groundwater sources and geochemical groups within the groundwater system. The groundwater-flow system in the study area consists primarily of the Mesilla Basin aquifer system, which can be divided into four hydrogeologic units by using an informal classification scheme based on basin-fill stratigraphy and sedimentology with an emphasis on aquifer characteristics. The four hydrogeologic units are (1) the Rio Grande alluvium, which is the shallow aquifer of the Mesilla Basin within the confines of the Mesilla Valley, and the three hydrogeologic units that compose the Santa Fe Group: (2) the lower part of the Santa Fe Group, which is the least productive zone, (3) the middle part of the Santa Fe Group, which is the primary water-bearing hydrogeologic unit in the basin and is generally saturated, and (4) the upper part of the Santa Fe Group, which is the most productive water-bearing unit within the Santa Fe Group but is only partially saturated in the north and largely unsaturated in the south and western parts of the Mesilla Basin. The helicopter frequency domain electromagnetic survey results indicated that approximately half of the resistivity values were less than 10 ohm-meters at depths of 50 and 100 feet with a transition where the resistivity values changed from relatively high values (greater than 20 ohm-meters) to relatively low resistivity values (less than 10 ohm-meters) near Vado, New Mexico. Slightly more than 25 percent of the gridded resistivity values from the three-dimensional grid of the combined inverse modeling results of the direct-current resistivity and time-domain electromagnetic soundings were equal to or less than 10 ohm-meters with large regions of low resistivity becoming apparent in the southernmost part of the study area near the Paso Del Norte where these low resistivity features are spatially the widest at or below the top of the bedrock. These low resistivity values might represent clayey deposits, sediments composed largely of sand and gravel saturated with saline water, or both. Historical dissolved-solids-concentration data within the surface geophysical subset area of the study area were compiled and compared to the inverse modeling results of the combined direct-current resistivity and time-domain soundings; this comparison was done to strengthen the interpretation made from the combined inverse modeling results that the low resistivity features were representative of sand and gravel deposits saturated with saline water and not clayey deposits. Water-level altitudes within the Rio Grande alluvium generally decreased from north to south, with a west to east decrease in water-level altitudes near Las Cruces, New Mexico, as a result of groundwater pumping. Groundwater flow within the Santa Fe Group is more complex than the groundwater flow within the Rio Grande alluvium because of the larger lateral and vertical extent of the Santa Fe Group compared to the Rio Grande alluvium. Groundwater from the Organ Mountains flows directly south towards the Paso del Norte. Groundwater from the Robledo Mountains, the Rough and Ready Hills, and the Sleeping Lady Hills generally flows to the southeast. Groundwater flowing near the north end of the midbasin uplift generally continues east towards the Rio Grande and then flows south on the east side of the midbasin uplift. Groundwater flowing near the west side of the midbasin uplift generally continues south parallel to the faults that make up the midbasin uplift and then flows east towards the Paso del Norte when it reaches the south end of the midbasin uplift. Groundwater from the Aden Hills and the East and West Potrillo Mountains flows to the south end of the midbasin uplift and then continues east towards the Paso del Norte. Throughout most of the Mesilla Valley, the vertical hydraulic gradient was downward because the water-level altitude in the Rio Grande alluvium was higher than it was in the Santa Fe Group, but in some areas (typically in the middle and southern parts of the Mesilla Valley), the vertical hydraulic gradient was substantially reduced or even reversed to an upward hydraulic gradient. The geochemistry data indicate that there was a complex system of multiple geochemical endmembers and mixing between these endmembers with recharge to the Rio Grande alluvium and Santa Fe Group composed mostly of seepage from the Rio Grande, inflows from deeper or neighboring water systems, and mountain-front recharge. Five distinct geochemical groups were identified in the Mesilla Basin study area: (1) ancestral Rio Grande (pre-Pleistocene) geochemical group, (2) modern Rio Grande (Pleistocene to present) geochemical group, (3) mountain-front geochemical group, (4) deep groundwater upwelling geochemical group, and (5) unknown freshwater geochemical group. The ancestral Rio Grande groundwater was water that recharged into the system as seepage losses from the ancestral Rio Grande; this groundwater generally flows from north to south-southeast towards the Paso del Norte. Groundwater on the west side of the midbasin uplift generally flows south until it reaches the southern part of the study area; from the southern part of the study area, the groundwater flows east towards the Paso del Norte. Groundwater on the east side of the midbasin uplift flows south-southeast towards the Paso del Norte where it mixes with groundwater from the modern Rio Grande, uplifted areas in the west, and the deep saline source. The water type of the modern Rio Grande geochemical group ranged from calcium-sulfate water type in the northern part of the study area to sodium-chloride-sulfate water type in the southern part of the study area; from north to south there was a substantial increase in specific conductance, strontium-87/strontium-86 ratio, potassium, and the trace metals of iron and lithium, changing the water chemistry such that it became similar to the water chemistry of the deep groundwater upwelling geochemical group. From age-dating results, water in the modern Rio Grande geochemical group was recharged to the Rio Grande alluvium within the past 10 years. The mountain-front geochemical group was generally old water (apparent age was greater than 10,000 carbon-14 years before present) that was somewhat mineralized and has relatively high concentrations of fluoride and silica, which might indicate longer exposure to volcanic and siliciclastic rocks or aluminosilicate minerals. There were five different locations of recharge determined from the groundwater geochemistry within the mountain-front geochemical group, all having a slightly different geochemical signature: (1) the Rough and Ready Hills, Robledo Mountains, and the Sleeping Lady Hills, (2) the Doña Ana Mountains, (3) the Aden Hills and West Potrillo Mountains, (4) the East Potrillo Mountains, and (5) the Sierra Juárez in Mexico. The groundwater from the Rough and Ready Hills, Robledo Mountains, the Sleeping Lady Hills, and the Doña Ana Mountains generally flows toward the Rio Grande and eventually mixes together and with the modern Rio Grande groundwater. The groundwater originating from the Aden Hills and East and West Potrillo Mountains generally flows east to southeast at a slow rate and eventually mixes and continues east, where it mixes with groundwater from the ancestral Rio Grande geochemical group and with the groundwater from the Sierra Juárez. The groundwater from the Sierra Juárez flows north and then east towards the Paso del Norte where it mixes with groundwater from the uplifted areas in the west, ancestral and modern Rio Grande groundwater, and the upwelling groundwater from a deep saline source. The deep groundwater upwelling geochemical group had the highest concentrations of bicarbonate, potassium, silica, aluminum, iron, and lithium within the study area, indicating that it had been in contact with carbonate and siliciclastic rocks for a much longer period of time and at higher temperatures compared to the other geochemical groups, and was most likely ancient marine groundwater originating from the Paleozoic and Cretaceous carbonate rocks which was upwelling into the Mesilla Basin aquifer system in the southeastern part of the study area through the extensive fault systems. Direct-current resistivity and time-domain electromagnetic soundings support the interpretation of ancient marine groundwater upwelling into the Mesilla Basin aquifer system, as do the analytical results from wells, and the helicopter frequency domain electromagnetic data collected along the Rio Grande. The hydrogen-2/hydrogen-1 ratio and oxygen-18/oxygen-16 ratio isotopic results for samples in the unknown freshwater geochemical group did not plot on the Rio Grande evaporation line, indicating this group did not have a Rio Grande signature (that is, there was no isotopic evidence of a component of Rio Grande water) and it also had the lowest mineralized content of any geochemical group in the study area.

New Mexico, Texas↗
USGS1987

The chemistry and mineralogy of haloed burrows in pelagic sediment at DOMES Site A: The equatorial North Pacific

The chemical and mineralogical composition of burrowed sediment, recovered in 66 box cores at latitude 9°25′N and longitude 151°15′W in the equatorial Pacific, demonstrates the important role of infauna in determining the geochemistry of pelagic sediment. Haloed burrows, approximately 3 cm across, were present in many of the cores. Within early Tertiary sediment that was covered by less than 5 cm of surface Quaternary sediment in several cores, the burrows in cross-section consist of three units: (1) a dark yellowish-brown central zone of Quaternary sediment surrounded, by (2) a pale yellowish-orange zone (the halo) of Tertiary sediment, which is surrounded by (3) a metal-oxide precipitate; the enclosing Tertiary sediment is dusky brown. Several elements — Mn, Ni, Cu, Co, Zn, Sb and Ce — have been leached from the light-colored halo, whereas Cr, Cs, Hf, Rb, Sc, Ta, Th, U, the rare earth elements exclusive of Ce, and the major oxides have not been leached. The metal-oxide zone, 1–5 mm thick, contains as much as 16% MnO 2 , as the mineral todorokite. The composition of the todorokite, exclusive of the admixed Tertiary sediment, resembles the composition of the metal deficit of the halo and also the composition of surface ferromanganese nodules that have been interpreted as having a predominantly diagenetic origin. Thus bioturbation contributes not only to the redistribution of metals within pelagic sediment, but also to the accretion of ferromanganese nodules on the sea floor.

Marine Geology↗
USGS2011

Gas hydrate saturation from acoustic impedance and resistivity logs in the Shenhu area, south China Sea

During the China’s first gas hydrate drilling expedition -1 (GMGS-1), gas hydrate was discovered in layers ranging from 10 to 25 m above the base of gas hydrate stability zone in the Shenhu area, South China Sea. Water chemistry, electrical resistivity logs, and acoustic impedance were used to estimate gas hydrate saturations. Gas hydrate saturations estimated from the chloride concentrations range from 0 to 43% of the pore space. The higher gas hydrate saturations were present in the depth from 152 to 177 m at site SH7 and from 190 to 225 m at site SH2, respectively. Gas hydrate saturations estimated from the resistivity using Archie equation have similar trends to those from chloride concentrations. To examine the variability of gas hydrate saturations away from the wells, acoustic impedances calculated from the 3 D seismic data using constrained sparse inversion method were used. Well logs acquired at site SH7 were incorporated into the inversion by establishing a relation between the water-filled porosity, calculated using gas hydrate saturations estimated from the resistivity logs, and the acoustic impedance, calculated from density and velocity logs. Gas hydrate saturations estimated from acoustic impedance of seismic data are ∼10–23% of the pore space and are comparable to those estimated from the well logs. The uncertainties in estimated gas hydrate saturations from seismic acoustic impedances were mainly from uncertainties associated with inverted acoustic impedance, the empirical relation between the water-filled porosities and acoustic impedances, and assumed background resistivity.

Marine and Petroleum Geology↗
USGS2020

Acidification in the U.S. Southeast: Causes, potential consequences and the role of the Southeast Ocean and Coastal Acidification Network

Coastal acidification in southeastern U.S. estuaries and coastal waters is influenced by biological activity, run-off from the land, and increasing carbon dioxide in the atmosphere. Acidification can negatively impact coastal resources such as shellfish, finfish, and coral reefs, and the communities that rely on them. Organismal responses for species located in the U.S. Southeast document large negative impacts of acidification, especially in larval stages. For example, the toxicity of pesticides increases under acidified conditions and the combination of acidification and low oxygen has profoundly negative influences on genes regulating oxygen consumption. In corals, the rate of calcification decreases with acidification and processes such as wound recovery, reproduction, and recruitment are negatively impacted. Minimizing the changes in global ocean chemistry will ultimately depend on the reduction of carbon dioxide emissions, but adaptation to these changes and mitigation of the local stressors that exacerbate global acidification can be addressed locally. The evolution of our knowledge of acidification, from basic understanding of the problem to the emergence of applied research and monitoring, has been facilitated by the development of regional Coastal Acidification Networks (CANs) across the United States. This synthesis is a product of the Southeast Coastal and Ocean Acidification Network (SOCAN). SOCAN was established to better understand acidification in the coastal waters of the U.S. Southeast and to foster communication among scientists, resource managers, businesses, and governments in the region. Here we review acidification issues in the U.S. Southeast, including the regional mechanisms of acidification and their potential impacts on biological resources and coastal communities. We recommend research and monitoring priorities and discuss the role SOCAN has in advancing acidification research and mitigation of and adaptation to these changes.

Florida, Georgia, North Carolina, South Carolina↗
USGS2016

Mercury correlations among blood, muscle, and hair of northern elephant seals during the breeding and molting fasts

Mercury (Hg) biomonitoring and toxicological risk assessments for marine mammals commonly sample different tissues, making comparisons to toxicity benchmarks and among species and regions difficult. Few studies have examined how life history events, such as fasting, influence the relationship between total Hg (THg) concentrations in different tissues. We evaluated the relationships between THg concentrations in blood, muscle, and hair of female and male northern elephant seals ( Mirounga angustirostris ) at the start and end of the breeding and molting fasts. The relationships between tissues varied among tissue pairs and differed by sampling period and sex. Blood and muscle were generally related at all time periods; however, hair, an inert tissue, did not strongly represent the metabolically active tissues (blood and muscle) at all times of year. The strongest relationships between THg concentrations in hair and those in blood or muscle were observed during periods of active hair growth (end of the molting period) or during time periods when internal body conditions were similar to those when the hair was grown (end of the breeding fast). Our results indicate that THg concentrations in blood or muscle can be translated to the other tissue type using the equations we developed, but that THg concentrations in hair were generally a poor index of internal THg concentrations except during the end of fasting periods.

California↗
USGS2009

The stable carbon isotope biogeochemistry of acetate and other dissolved carbon species in deep subseafloor sediments at the northern Cascadia Margin

Ocean drilling has revealed the existence of vast microbial populations in the deep subseafloor, but to date little is known about their metabolic activities. To better understand the biogeochemical processes in the deep biosphere, we investigate the stable carbon isotope chemistry of acetate and other carbon-bearing metabolites in sediment pore-waters. Acetate is a key metabolite in the cycling of carbon in anoxic sediments. Its stable carbon isotopic composition provides information on the metabolic processes dominating acetate turnover in situ. This study reports our findings for a methane-rich site at the northern Cascadia Margin (NE Pacific) where Expedition 311 of the Integrated Ocean Drilling Program (IODP) sampled the upper 190 m of sediment. At Site U1329, δ 13 C values of acetate span a wide range from −46.0‰ to −11.0‰ vs. VPDB and change systematically with sediment depth. In contrast, δ 13 C values of both the bulk dissolved organic carbon (DOC) (−21.6 ± 1.3‰ vs. VPDB) and the low-molecular-weight compound lactate (−20.9 ± 1.8‰ vs. VPDB) show little variability. These species are interpreted to represent the carbon isotopic composition of fermentation products. Relative to DOC, acetate is up to 23.1‰ depleted and up to 9.1‰ enriched in 13 C. Broadly, 13 C-depletions of acetate relative to DOC indicate flux of carbon from acetogenesis into the acetate pool while 13 C-enrichments of pore-water acetate relative to DOC suggest consumption of acetate by acetoclastic methanogenesis. Isotopic relationships between acetate and lactate or DOC provide new information on the carbon flow and the presence and activity of specific functional microbial communities in distinct biogeochemical horizons of the sediment. In particular, they suggest that acetogenic CO 2 -reduction can coexist with methanogenic CO 2 -reduction, a notion contrary to the hypothesis that hydrogen levels are controlled by the thermodynamically most favorable electron-accepting process. Further, the isotopic relationship suggests a relative increase in acetate flow to acetoclastic methanogenesis with depth although its contribution to total methanogenesis is probably small. Our study demonstrates how the stable carbon isotope biogeochemistry of acetate can be used to identify pathways of microbial carbon turnover in subsurface environments. Our observations also raise new questions regarding the factors controlling acetate turnover in marine sediments.

Geochimica et Cosmochimica Acta↗
USGS2014

Inorganic elements in green sea turtles ( Chelonia mydas ): relationships among external and internal tissues

Inorganic elements from anthropogenic sources have entered marine environments worldwide and are detectable in marine organisms, including sea turtles. Threatened and endangered classifications of sea turtles have heretofore made assessments of contaminant concentrations difficult because of regulatory restrictions on obtaining samples using nonlethal techniques. In the present study, claw and skin biopsy samples were examined as potential indicators of internal tissue burdens in green sea turtles (Chelonia mydas). Significant relationships were observed between claw and liver, and claw and muscle concentrations of mercury, nickel, arsenic, and selenium (p < 0.05). Similarly, significant relationships were observed between skin biopsy concentrations and those in liver, kidney, and muscle tissues for mercury, arsenic, selenium, and vanadium (p < 0.05). Concentrations of arsenic, barium, chromium, nickel, strontium, vanadium, and zinc in claws and skin biopsies were substantially elevated when compared with all other tissues, indicating that these highly keratinized tissues may represent sequestration or excretion pathways. Correlations between standard carapace length and cobalt, lead, and manganese concentrations were observed (p < 0.05), indicating that tissue concentrations of these elements may be related to age and size. Results suggest that claws may indeed be useful indicators of mercury and nickel concentrations in liver and muscle tissues, whereas skin biopsy inorganic element concentrations may be better suited as indicators of mercury, selenium, and vanadium concentrations in liver, kidney, and muscle tissues of green sea turtles.

Environmental Toxicology and Chemistry↗
USGS2019

India National Gas Hydrate Program Expedition-02: Operational and technical summary

The India National Gas Hydrate Program is being steered by the government of India's Ministry of Petroleum and Natural Gas (MoPNG) with participation of Directorate General of Hydrocarbons (DGH), Oil and Natural Gas Corporation Limited (ONGC), and the National Oil Companies and Research Institutes of India. The India National Gas Hydrate Program Expedition 01 (NGHP-01) established the presence of gas hydrate in the Krishna Godavari (KG) and Mahanadi Basins and in the offshore area of the Andaman Sea Basin. However, the gas hydrates discovered during NGHP-01 were mainly distributed as fracture-filling material in fine-grained clay-rich sediments. The India National Gas Hydrate Program Expedition 02 (NGHP-02) was carried out with an objective to discover gas hydrate in sand-rich sediment along the eastern offshore margin of India. ONGC planned and executed NGHP-02 on the behalf of the MoPNG. NGHP-02 started on March 3, 2015 and was completed on July 28, 2015 (total 147 days) using the Japanese scientific Drilling Vessel Chikyu (D/V Chikyu). During NGHP-02, 42 holes at 25 sites were drilled, cored, and/or surveyed with downhole logging tools. These sites were located in four areas along the eastern margin of India and formally named Area A (Mahanadi Basin, three sites), Area B (northern part of the KG-Basin, twelve sites), Area C (central part of the KG-Basin, six sites), and Area E (southern part to the KG-Basin, four sites). All 25 sites established during NGHP-02 were first drilled and logged with logging-while-drilling (LWD) tools and an additional 17 holes were then drilled and/or cored with conventional coring tools (HPCS/ESCS) or pressure coring tools (PCTB). Wireline logging was conducted in 10 holes and formation tests using a dual packer Modular Formation Dynamics Tester (MDT) tool were carried out in two holes. The onboard science team used the laboratory facilities on the D/V Chikyu to examine and analyse the physical properties, geochemistry, and sedimentology of all the cores collected during the expedition. Core samples were also analysed in additional post-expedition shore-based studies conducted in numerous domestic and international gas hydrate research laboratories. The NGHP-02 sediment cores were archived at the National Gas Hydrate Core Repository in Mumbai (India), which is associated with the ONGC Gas Hydrate Research and Technology Centre (GHRTC). The necessary data for characterizing the occurrence of gas hydrate, such as interstitial water chlorinities, core-derived gas chemistry, physical and sedimentological properties, thermal images of the recovered cores, pressure core and downhole measured logging data (LWD and/or conventional wireline log data), were obtained from most of the drill sites established during NGHP-02. Almost all the drill sites yielded evidence for the occurrence of gas hydrate; however, the inferred in situ concentration of gas hydrate varied substantially from site to site. For the most part, the interpretation of downhole logging data, core thermal images, interstitial water analyses, and pressure core images from the sites established during NGHP-02 indicate that the occurrence of concentrated gas hydrate is mostly associated with coarser grained (sand-rich) sediments. This paper presents the operational and technical summary of NGHP-02. NGHP-02 started on March 3, 2015 and was completed on July 28, 2015 (total 147 days) using the Japanese scientific Drilling Vessel Chikyu (D/V Chikyu). During NGHP-02, 42 holes at 25 sites were drilled, cored, and/or surveyed with downhole logging tools. These sites were located in four areas along the eastern margin of India and formally named Area A (Mahanadi Basin, three sites), Area B (northern part of the KG-Basin, twelve sites), Area C (central part of the KG-Basin, six sites), and Area E (southern part to the KG-Basin, four sites). All 25 sites established during NGHP-02 were first drilled and logged with logging-while-drilling (LWD) to

Journal of Marine and Petroleum Geology↗
USGS2004

Population ecology and shell chemistry of a phytal ostracode species (Loxoconcha matagordensis) in the Chesapeake Bay watershed

Population ecology and shell chemistry were studied in the phytal ostracode Loxoconcha matagordensis (Swain 1955) collected from Zostera marina seagrass beds in the Chesapeake Bay to provide seasonal constraints on shell secretion time for paleothermometry. Population density and age structure were defined by two main breeding cycles that occurred between 01 to 15 June and 02 to 16 August 2001. The time interval between breeding cycles was ???2 months and total juvenile standing crop increased almost three-fold between the first and second breeding cycles. Dark brown over-wintered adults comprised the majority of the population between March and April 2001, while newly secreted translucent adults were predominant between June and September. Seasonal shell Mg/Ca and Sr/Ca ratios were positively correlated with water temperature at both sites, with the strongest correlations occurring between June and September from newly secreted shells at Dameron Marsh. Old, dark brown shells contained 10% to 23% and 1% to 6% less Mg/Ca and Sr/Ca, respectively, than new shells. Because a fossil assemblage of L. matagordensis will contain ???30% old shells (dark-brown), these results suggest that fossil Mg/Ca ratios yield an integrated late spring to summer temperature signal. Shell Mg/Ca and Sr/Ca ratios of specimens of L. matagordensis collected from living Zostera were positively correlated, suggesting that temperature may influence both elemental ratios. Mg/Ca and Sr/Ca ratios of fossil shells of the related species Loxoconcha sp. A obtained from four sediment cores were also studied and exhibited a weaker correlation between the two elemental ratios. ?? 2004 Elsevier B.V. All rights reserved.

Marine Micropaleontology↗
USGS1994

Relation among cytochrome P450, AH-active PCB congeners and dioxin equivalents in pipping black-crowned night-heron embryos

Pipping black-crowned night-heron (Nycticorax nycticorax) embryos were collected from a relatively uncontaminated site (next to Chincoteague National Wildlife Refuge, VA) and three polluted sites (Cat Island, Green Bay, Lake Michigan, WI; Bair Island, San Francisco Bay, CA; West Marin Island, San Francisco Bay, CA). Hepatic cytochrome P-450-associated monooxygenases and cytochrome P-450 proteins, induced up to 85-fold relative to the reference site, were associated with concentrations of total polychlorinated biphenyls (PCBs) and 11 PCB congeners that are presumed to express toxicity through the arylhydrocarbon (Ah) receptor. Multiple regression revealed that up to 86% of the variation of cytochrome P450 measurements was accounted for by variation in the concentration of these PCB congeners. Toxic equivalents (TEQs) of sample extracts, predicted mathematically (summed product of PCB congener concentrations and toxic equivalency factors), and dioxin equivalents (TCDD-EQs), derived by bioassay (ethoxyresorufin-O-dealkylase activity of treated H4IIE rat hepatoma cells), were greatest in Cat Island samples. Cytochrome P450-associated monooxygenases and cytochrome P450 proteins were related to TEQs and TCDD-EQs; adjusted r-2 often exceeded 0.5 for the relation among mathematically predicted TEQs and cytochrome P450 measurements. These data extend previous observations in heron embryos of an association between P450 and total PCB burdens to include Ah-active PCB congeners, and presumably other compounds, which interact similarly with the Ah receptor. Benzyloxyresorufin O-dealkylase, ethoxyresorufin O-dealkylase, and cytochrome P450 1A appear to be the most reliable measures of exposure to Ah-active PCB congeners in black-crowned night-heron embryos. These findings provide further evidence that cytochrome P450-associated parameters have considerable value as a biomarker for assessing environmental contamination of wetlands.

Environmental Toxicology and Chemistry↗
USGS2022

Elevated mercury concentrations and isotope signatures (N, C, Hg) in yellowfin tuna (Thunnus albacares) from the Galápagos Marine Reserve and waters off Ecuador

We examined how dietary factors recorded by C and N influence Hg uptake in 347 individuals of yellowfin tuna ( Thunnus albacares ), an important subsistence resource from the Galápagos Marine Reserve (GMR) and the Ecuadorian mainland coast (EMC) in 2015-2016. We found no differences in total Hg (THg) measured in red muscle between the two regions and no seasonal differences, likely due to the age of the fish and slow elimination rates of Hg. Our THg concentrations are comparable to other studies in the Pacific (0.06–2.88 mg/kg wet weight), but a subset of individuals exhibited the highest mercury concentrations yet reported in yellowfin tuna. Mercury isotope values differed between Δ199Hg and δ202Hg in both regions (Δ199Hg = 2.86±0.04‰ vs. Δ199Hg = 2.33 ± 0.07‰), likely related to shifting food webs and differing photochemical processing of Hg prior to entry into the food web. There were significantly lower values of both δ15N and δ13C in tuna from GMR (δ15N: 8.5–14.2‰, δ13C: -18.5–-16.1‰) compared to those from the EMC (δ15N: 8.3–14.4‰, δ13C: -19.4–-11.9‰), of which δ13C values suggest spatially-constrained movements of tunas. Results from the pooled analysis, without considering region, indicated that variations in δ13C and δ15N values tracked changes of Hg stable isotopes. Our data indicate that the individual tuna from this study were resident fish of each region and heavily influenced by upwellings related to the Eastern Pacific Oxygen Minimum Zone and the Humboldt Current System. C, N, and Hg isotopes reflect foraging behavior mainly on epipelagic prey in shallow waters and that food web shifts drive Hg variations between these populations of tuna.

Galápagos Marine Reserve, Pacific Ocean↗
USGS2000

Formation of ferromanganese crusts on northwest intertropical Pacific seamounts: Electron photomicrography and microprobe chemistry

Seven ferromanganese crusts from the northwest intertropical Pacific seamounts were analyzed for photomicroscopic growth structures, microprobe chemistry, and ages based on Co-chronometer growth rate. The crusts on the Marshall Islands seamounts are thick and ale divided into phosphatized lower older and nonphosphatized upper younger growth generations: the older crust consists of compact laminations and columns impregnated with carbonate fluoapatite (CFA), whereas the younger crust is characterized by porous botryoids and columns of ??-MnO2 and Fe oxyhydroxide. The crusts on the Federated States of Micronesia (FSM) and Palau Islands seamounts are thin and are often incorporated with inorganic opal-A in the uppermost part, comprising the younger generation. Some crusts show scours and fractures. Although the growth of crusts has been often interrupted by mass failure of slope sediments, the crusts on the Marshall Islands seamounts are estimated to have grown at rate of about 3 mm/Ma since the middle Eocene and to have been phosphatized in the late Oligocene during the host seamounts were located beneath the equatorial zone of high productivity. Prolonged infiltration of the oxygen minimum zone (OMZ) water into shallower water older crusts redistributed crust composition by precipitating CFA, enriching subsequent amounts of Mn and Ni, and removing some Co. The younger crust has formed at slower rate (about 2 mm/Ma) under the stronger influence of bottom-water circulation in the north of the equatorial zone, concentrating abundant Co. In the uppermost part of some crusts, siliceous skeletons transform with burial to inorganic opal-A and Si-rich Fe oxyhydroxide, suggesting that biosilica diagenesis can enhance crust growth. (C) 2000 Elsevier Science B.V.

Marine Geology↗
USGS1993

Biomonitoring environmental contamination with pipping black-crowned night heron embryos: Induction of cytochrome P450

Cytochrome P450-associated monooxygenase activities and cytochrome P450 proteins were measured in pipping black-crowned night heron ( Nycticorax nycticorax ) embryos collected from a reference site (next to the Chincoteague National Wildlife Refuge, VA) and three polluted sites (Cat Island, Green Bay, Lake Michigan, WI; Bair Island, San Francisco Bay, CA; West Marin Island, San Francisco Bay, CA). In a laboratory study, artificially incubated night heron embryos from the reference site were treated with 3-methylcholanthrene (200 μg administered into the air cell 2 d before pipping) or phenobarbital (2 mg daily for 2 d before pipping). Compared to controls (untreated + vehicle-treated embryos), 3-methylcholanthrene induced a greater than fivefold increase in activities of several monooxygenases (arylhydrocarbon hydroxylase, AHH; benzyloxyresorufin- O -dealkylase, BROD; ethoxyresorufin- O -dealkylase, EROD; pentoxyresorufin- O -dealkylase, PROD) and a greater than 100-fold increase in the concentration of immunodetected cytochrome P450 1A (CYP1A). Phenobarbital treatment resulted in only a slight increase in BROD activity but induced proteins recognized by antibodies to cytochrome P450 2B (CYP2B) by 2,000-fold. In a field study, activities of AHH, BROD, EROD, and ethoxycoumarin- O -dealkylase (ECOD) were up to 85-fold higher in pipping black-crowned night herons collected from Cat Island compared to other sites. Hepatic CYP1A and CYP2B cross-reactive proteins were detected in significantly more individuals from Cat Island than from the reference site. Greatest burdens of total PCBs and p,p ′-DDE were detected in embryos from Cat Island. Cytochrome P450-associated monooxygenase activities and cytochrome P450 proteins (AHH, BROD, EROD, ECOD, CYP1A, CYP2B) were significantly associated with total PCB burdens ( r = 0.50-0.72). These data indicate that cytochrome P450 may be a useful biomarker of exposure to some PCB mixtures in black-crowned night heron embryos.

Environmental Toxicology and Chemistry↗
USGS2022

Interlaboratory comparison of three sediment bioaccumulation tests

Standard bioaccumulation tests are commonly conducted using Macoma nasuta (clam), and Alitta virens (polychaete) for marine tests, and Lumbriculus variegatus (an oligochaete) for freshwater tests. Because the interlaboratory variability associated with these tests is unknown, four experienced laboratories conducted standard 28-day bioaccumulation tests with the above species using sediments contaminated with polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs). Chemical analysis of tissue samples was performed by a single laboratory. The intralaboratory variance among replicates was relatively low for PCB tissue concentrations, with coefficients of variation (CVs) ranging from 9% to 28% for all laboratories and species, with the exception of one laboratory reporting higher variability for L . variegatus (CV = 51%). Intralaboratory variance for PCB tissue concentrations was higher than interlaboratory variance for A. virens and L . variegatus , and the magnitude of difference (MOD) for laboratory means ranged from 1.4 to 2.0 across species. Intralaboratory variability was also low for lipid content, and lipid normalization of PCB and PAH body residues generally had little impact on variability. In addition to variability across bioassay laboratories, analytical variability was evaluated by different laboratories measuring the concentration of PCBs and total lipids in a subsample of tissue homogenate of sediment-exposed test organisms. Variability associated with tissue analysis was higher than bioassay laboratory variability only in tests with L . variegatus . Statistical differences between samples may be observed due to the low intralaboratory variability; however, the biological significance of these differences may be limited because the MOD is low. Considering the MOD when comparing bioaccumulation across treatments accounts for uncertainty related to inherent variability of the test in the interpretation of statistically significant results.

Massachusetts↗
USGS2007

Water-Quality Characteristics of Cottonwood Creek, Taggart Creek, Lake Creek, and Granite Creek, Grand Teton National Park, Wyoming, 2006

To address water-resource management objectives of the National Park Service in Grand Teton National Park, the U.S. Geological Survey in cooperation with the National Park Service has conducted water-quality sampling on streams in the Snake River headwaters area. A synoptic study of streams in the western part of the headwaters area was conducted during 2006. Sampling sites were located on Cottonwood Creek, Taggart Creek, Lake Creek, and Granite Creek. Sampling events in June, July, August, and October were selected to characterize different hydrologic conditions and different recreational-use periods. Stream samples were collected and analyzed for field measurements, major-ion chemistry, nutrients, selected trace elements, pesticides, and suspended sediment. Water types of Cottonwood Creek, Taggart Creek, Lake Creek, and Granite Creek were calcium bicarbonate. Dissolved-solids concentrations were dilute in Cottonwood Creek and Taggart Creek, which drain Precambrian-era rocks and materials derived from these rocks. Dissolved-solids concentrations ranged from 11 to 31 milligrams per liter for samples collected from Cottonwood Creek and Taggart Creek. Dissolved-solids concentrations ranged from 55 to 130 milligrams per liter for samples collected from Lake Creek and Granite Creek, which drain Precambrian-era rocks and Paleozoic-era rocks and materials derived from these rocks. Nutrient concentrations generally were small in samples collected from Cottonwood Creek, Taggart Creek, Lake Creek, and Granite Creek. Dissolved-nitrate concentrations were the largest in Taggart Creek. The Taggart Creek drainage basin has the largest percentage of barren land cover of the basins, and subsurface waters of talus slopes may contribute to dissolved-nitrate concentrations in Taggart Creek. Pesticide concentrations, trace-element concentrations, and suspended-sediment concentrations generally were less than laboratory reporting levels or were small for all samples. Water-quality characteristics of streams in the western part of the Snake River headwaters area were compared to water-quality characteristics of streams sampled in 2002 in the eastern part of the headwaters area. The median dissolved-solids concentration (55 milligrams per liter) for samples collected from western streams was smaller than the median dissolved-solids concentration (125 milligrams per liter) for samples collected from eastern streams. The small dissolved-solids concentrations in the western streams are a result of the large areas underlain by resistant Precambrian-era rocks that compose the Teton Range compared to the more erodable Mesozoic-era sedimentary rocks that compose the mountains in the eastern part of the headwaters area. The Teton Range also receives higher annual precipitation than the mountains in the east. The median total-nitrogen concentration (0.17 milligram per liter) in samples collected from streams in the western part of the Snake River headwaters area was larger than the median concentration (0.10 milligram per liter) for samples collected from streams in the eastern part of the headwaters area, in part because of larger dissolved-nitrate concentrations in samples from the western streams compared to the eastern streams. In contrast, total-phosphorus concentrations generally were larger for samples collected from eastern streams. Large total-phosphorus concentrations in the eastern streams were associated with large suspended-sediment concentrations. The source of the phosphorus and sediment probably is Mesozoic-era sedimentary rocks of marine origin that underlie parts of the eastern drainage basins.

Scientific Investigations Report↗
USGS2018

Magmatic origin for sediment-hosted Au deposits, Guizhou Province, China: In situ chemistry and sulfur isotope composition of pyrites, Shuiyindong and Jinfeng deposits

The southwest Guizhou Province, China, contains numerous sediment-hosted Au deposits with Au reserves greater than 700 tonnes. To date, the source of ore fluids that formed the Guizhou sediment-hosted Au deposits is controversial, hampering the formulation of genetic models. In this study, we selected the Shuiyindong and Jinfeng Au deposits, the largest strata-bound and fault-controlled deposits in Guizhou, respectively, for detailed research on pyrite chemistry and S isotope composition using laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) and laser ablation-multicollector-inductively coupled plasma-mass spectrometry (LA-MC-ICP-MS), respectively. Petrography and pyrite chemistry studies distinguished five generations of pyrite. Among these, pre-ore pyrite 2 and ore pyrite are the most abundant types in the deposits. Pre-ore pyrite 2 is anhedral to euhedral and with ~2,639 ppm As and wider ranges of Cu, Sb, and Pb (<~22–4,837 ppm, <~6 to 532 ppm, and <~4 to 1,344 ppm, respectively). Gold in pre-ore pyrite 2 is below the detection limit of LA-ICP-MS (~2 ppm). Pre-ore pyrite 2 is interpreted to have a sedimentary (syngenetic or diagenetic) origin. Ore pyrite commonly rims the four identified pre-ore pyrites or occurs as individual, anhedral to euhedral crystals. Ore pyrite is enriched in Au (~641 ppm), As (~9,147 ppm), Cu (~1,043 ppm), Sb (~188 ppm), Hg (~43 ppm), and Tl (~22 ppm) in both deposits. Ore pyrite formed mainly by sulfidation of Fe in Fe-bearing host rocks, mainly Fe dolomite, and As, Cu, Sb, Hg, and Tl, also in ore fluids, were incorporated into ore pyrite. In situ δ 34 S isotope ratios for pre-ore pyrite 2 and ore pyrite were measured by LA-MC-ICP-MS. Pre-ore pyrite 2 from Shuiyindong and Jinfeng deposits resulted in δ 34 S values ranging from −0.8 to +3.4‰ and from 5.1 to 10.5‰, respectively. Analyses of ore pyrite from the Shuiyindong have δ 34 S values that vary from −3.3 to +2.5‰, with a median of 0.7‰; analyses of ore pyrite from the Jinfeng range from 8.9 to 11.2‰, with a median at 10.3‰. Available bulk and in situ δ 34 S data in the literature for pre-ore pyrites 1 and 2 and ore-related sulfide minerals including ore pyrite, arsenopyrite, and late ore-stage stibnite, realgar, orpiment, and cinnabar from several Guizhou sediment-hosted Au deposits were compiled for comparison. Pre-ore-stage pyrites from Guizhou sediment-hosted Au deposits have a broad range of δ 34 S values, from −33.8 to + 17.9‰ (including in situ and available bulk δ 34 S data). Ore-related sulfide minerals in all Guizhou sediment-hosted Au deposits, except Jinfeng, have very similar δ 34 S values, and most data plot between ~−5 and +5‰. In the Jinfeng deposit, the ore-related sulfide minerals exhibit δ 34 S values ranging from 1.9 to 18.1‰, with most data plotting between 6 and 12‰. The broad range of S isotope compositions for the sedimentary pyrites (pre-ore pyrites 1 and 2) indicate that S in these pre-ore pyrites was most likely generated by bacterial reduction from marine sulfate. The narrow range of δ 34 S values (~−5–+5‰) for ore-related sulfide minerals in all Guizhou sediment-hosted Au deposits, excepting the Jinfeng deposit, suggests that the deposits may have formed in response to a single widespread metallogenic event. As the S isotope fractionation between hydrothermal fluids and sulfide minerals in a sulfide-dominated system is small (<2‰) at ~250°C, the initial ore fluids that formed the Guizhou sediment-hosted Au deposits would have had δ 34 S values similar to the ore-related sulfide minerals, between ~−5 and +5‰. At Jinfeng, initial ore fluids may have mixed with local fluids with heavier δ 34 S, possibly basin brine ( δ 34 S basin brine >18‰), resulting in elevated δ 34 S values of ore-related sulfide minerals and especially late ore-stage sulfide minerals. Although few igneous rocks are exposed in the mining area around these deposits, there is evidence of magmatic activity ~20 km away. Furthermore, gravity and magnetic geophysical investigations indicate the presence of a pluton ~5 km below the surface of the Shuiyindong district. Based on in situ S isotope results and recent data indicating proximal intrusions, we interpret a deep magmatic S source for the ore fluids that formed the Guizhou sediment-hosted Au deposits. However, as the age for Au mineralization of Guizhou sediment-hosted Au deposits is still debated, the mineralization-magma connection remains hypothetical. Identifying an ore fluid source and time frame for Guizhou Au mineralization continues to be a critically important research goal for this district.

Yunnan-Guizhou-Guangxi region↗
USGS2000

A ground electromagnetic survey used to map sulfides and acid sulfate ground waters at the abandoned Cabin Branch Mine, Prince William Forest Park, northern Virginia gold-pyrite belt

INTRODUCTION AND BACKGROUND: Prince William Forest Park is situated at the northeastern end of the Virginia Gold-Pyrite belt northwest of the town of Dumfries, VA. The U. S. Marine Corps Reservation at Quantico borders the park on the west and south, and occupies part of the same watershed. Two abandoned mines are found within the park: the Cabin Branch pyrite mine, a historic source of acid mine drainage, and the Greenwood gold mine, a source of mercury contamination. Both are within the watershed of Quantico Creek (Fig.1). The Cabin Branch mine (also known as the Dumfries mine) lies about 2.4 km northwest of the town of Dumfries. It exploited a 300 meter-long, lens-shaped body of massive sulfide ore hosted by metamorphosed volcanic rocks; during its history over 200,000 tons of ore were extracted and processed locally. The site became part of the National Capitol Region of the National Park Service in 1940 and is currently managed by the National Park Service. In 1995 the National Park Service, in cooperation with the Virginia Department of Mines, Minerals, and Energy reclaimed the Cabin Branch site. The Virginia Gold-Pyrite belt, also known as the central Virginia volcanic-plutonic belt, is host to numerous abandoned metal mines (Pavlides and others, 1982), including the Cabin Branch deposit. The belt itself extends from its northern terminus near Cabin Branch, about 50 km south of Washington, D.C., approximately 175 km to the southwest into central Virginia. It is underlain by metamorphosed volcanic and clastic (non-carbonate) sedimentary rocks, originally deposited approximately 460 million years ago during the Ordovician Period (Horton and others, 1998). Three kinds of deposits are found in the belt: volcanic-associated massive sulfide deposits, low-sulfide quartz-gold vein deposits, and gold placer deposits. The massive sulfide deposits such as Cabin Branch were historically mined for their sulfur, copper, zinc, and lead contents, but also yielded byproduct gold and silver. The environmental impact of massive sulfide deposits can be substantial. These deposits are characterized by high concentrations of heavy-metal sulfide minerals, hosted by silicate rocks. Thus, weathering of these deposits and their mine wastes has the potential to generate heavy-metal laden sulfuric acid that can have negative impacts on aquatic ecosystems. In addition, lead associated with solid mine wastes has the potential for human health impacts through ingestion. The heavy metals that are encountered in these deposits and are most likely to cause environmental impacts include copper, zinc, lead, cadmium, and arsenic. In addition, the weathering of pyrite releases large amounts of iron, and the acid generated attacks the country rocks and causes the release of large amounts of aluminum, which also can severely impact aquatic ecosystems. A reclamation attempt was made at the site in 1995, including construction of storm-water diversion trenches around the abandoned mine area, grading tailings away from the stream bank, addition of pulverized limestone and topsoil, and revegetation. The post-reclamation chemistry of shallow groundwaters (<3 meters deep) shows a neutral pH on the southwestern bank of the stream but pH of 4.1 to 4.5 on the northeastern bank. The dominant ions are Fe2+ and SO42- (Seal, Haffner, Meier, and Pollio, 1999) A ground electromagnetic survey was conducted over the site in 1999 as part of a wider study ( Seal, Haffner, and Meier, 1998a,b, 1999). It was hoped that a 3-D map of the soil conductivity derived from the survey could provide insight into the distribution of the mobilized sulfides present under the ground.

Virginia↗
USGS2003

Geohydrologic Framework of Recharge and Seawater Intrusion in the Pajaro Valley, Santa Cruz and Monterey Counties, California

Pajaro Valley is a coastal watershed of 160 square miles located along Monterey Bay north of Elkhorn Slough and south of the city of Santa Cruz. The valley has been predominantly developed for agriculture since the late 1800s. In 1984 the Pajaro Valley Water Management Agency (PVWMA) was formed and was delegated with the responsibility of the management of the water resources within the Pajaro Valley by the State of California. About 84 percent of the water is used for agriculture and 16 percent is used for industrial and municipal water supply; almost all of the demand is supplied by ground water. Ground-water pumpage varies with seasonal and climatic periods. The alluvial aquifers are composed of Quaternary- and Tertiary-aged sediments that are layered marine and terrestrial coarse-grained deposits separated by extensive fine-grained deposits that potentially restrict vertical movement of ground water and seawater intrusion in the coastal subareas. The coarse-grained deposits, which persist over large areas, control pumpage and related seawater intrusion. The Aromas Sand crops out throughout the north and central parts of the PVWMA area and offshore on the continental shelf and in Monterey submarine canyon. Because many of the wells in the coastal and inland subregions are screened at depths of 200 to 400 feet below land surface, a direct avenue is provided for seawater intrusion through the coarse-grained deposits of the shallower alluvium and Aromas Sand. Geophysical logs from monitoring wells indicate discrete zones of saline water that are related to pumpage and seawater intrusion in the aquifers of the shallower alluvium and upper Aromas Sand in the upper-aquifer system and to deeper saline waters in the lower Aromas Sand within the lower-aquifer system. The precipitation data indicate that there were at least nine dry and nine wet periods that range from 2 to 19 years during the period of record, 1880?1997. The ground-water pumpage, runoff, streamflow and related water quality of streamflow also vary with seasonal and climatic periods. Recharge occurs from deep percolation of precipitation and from infiltration of streamflow. Streamflow originates from local runoff and from outside the valley as inflow from the Pajaro River. Although partly regulated, streamflow in the Pajaro River at Chittenden is less than 200 cubic feet per second 88 percent of the time and is less than 12 cubic feet per second 50 percent of the time. Streamflow water-quality data suggest that there may be several sources of poor-quality water that contribute to elevated chloride, sulfate, and nitrate concentrations in streamflow. The poor water quality occurring during lower streamflows indicates that low flows may be an additional source of salinity for ground-water recharge as streamflow infiltration along the Pajaro River. The geochemical data from this study indicate that the two main sources of recharge are deep percolation of local runoff and streamflow infiltration of Pajaro River water. The geophysical and geochemical data suggest that only the shallow alluvial aquifer and parts of the upper Aromas Sand that constitute the upper-aquifer system are being replenished by recent recharge in the coastal areas of Pajaro Valley and represent the renewable ground-water resources. These data also suggest that there is very little vertical flow through the layered aquifer systems in the coastal regions. The confining aquitards are laterally extensive but may be missing in places owing to fluvial erosion or offsetting by fault movement. Geochemical and geophysical data indicate that the ground water from some parts of the upper and lower Aromas Sand in the coastal regions was recharged thousands of years ago and may, in part, represent nonrenewable ground-water resources. The analysis of major-ion chemistry, in combination with isotope and trace-element/chloride ratios, indicates that the coastal ground-water and surface-water samples

Water-Resources Investigations Report↗