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At least 1,045 records · Page 58Linked to original sources
USGS1987

Measuring and computing natural ground-water recharge at sites in south-central Kansas

To measure the natural groundwater recharge process, two sites in south-central Kansas were instrumented with sensors and data microloggers. The atmospheric-boundary layer and the unsaturated and saturated soil zones were monitored as a single regime. Direct observations also were used to evaluate the measurements. Atmospheric sensors included an anemometer, a tipping-bucket rain gage, an air-temperature thermistor, a relative-humidity probe, a net radiometer, and a barometric-pressure transducer. Sensors in the unsaturated zone consisted of soil-temperature thermocouples, tensiometers coupled with pressure transducers and dial gages, gypsum blocks, and a neutron-moisture probe. The saturated-zone sensors consisted of a water-level pressure transducer, a conventional float gage connected to a variable potentiometer, soil thermocouples, and a number of multiple-depth piezometers. Evaluation of the operation of these sensors and recorders indicates that certain types of equipment, such as pressure transducers, are very sensitive to environmental conditions. A number of suggestions aimed at improving instrumentation of recharge investigations are outlined. Precipitation and evapotranspiration data, taken together with soil moisture profiles and storage changes, water fluxes in the unsaturated zone and hydraulic gradients in the saturated zone at various depths, soil temperature, water table hydrographs, and water level changes in nearby wells, describe the recharge process. Although the two instrumented sites are located in sand-dune environments in area characterized by a shallow water table and a sub-humid continental climate, a significant difference was observed in the estimated total recharge. The estimates ranged from less than 2.5 mm at the Zenith site to approximately 154 mm at the Burrton site from February to June 1983. The principal reasons that the Burrton site had more recharge than the Zenith site were more precipitation, less evapotranspiration, and a shallower depth to the water table. Effective recharge took place only during late winter and spring. No summer or fall recharge was observed at either site during the observation period of this study. (Author 's abstract)

Water-Resources Investigations Report↗
USGS1995

Simulated response of the High Plains aquifer to ground-water withdrawals in the Upper Republican Natural Resources District, Nebraska

The U.S. Geological Survey, in cooperation with the National Soil Tilth Laboratory of the U.S. Department of Agriculture, Agricultural Research Service, conducted a study as part of the multi- scale, interagency Management Systems Evaluation Area (MSEA) program to evaluate the effects of agricultural management (farming) systems on water quality. Data on surface flow, tileflow, and streamflow in the Walnut Creek watershed just south of Ames, Iowa, were collected during April 1991-September 1993 at five sites with drainage areas ranging from 366 to 5,130 hectares. Precipitation, flow discharge, and concentration, loads, and yields of nitrate as nitrogen, atrazine, and metolachlor were analyzed to relate the transport of agricultural chemicals to major water-flow processes and to examine and transport differences among three subwatersheds. Antecedent conditions and basin-characteristic differences had significant effects on the flow response from the subwatersheds. Monthly streamflow-to- precipitation ratios were greater than 1.0, as a result of snowmelt, and negative when streamflow was lost to the ground-water system in the downstream subwatershed. Dry antecedent conditions resulted in ratios less than 0.3 (July 1992), whereas wet antecedent conditions resulted in ratios from 0.7 to almost 1.0 (July 1993) during months with similar large rainfall amounts. Most of the streamflow from the upland subwatersheds came from tileflow. Surface flow (surface runoff, interflow, and return flow0 was highly variable and intermittent, usually lasting for only a few days after a storm, although it could be the dominant source of flow when stormflow was large. Tileflow was less variable and much more persistent, ceasing only after prolonged dry periods. Large quantities of nitrate as nitrogen were transported in Walnut Creek, with concen- trations often greater than the Maximum Contaminant Level of 10 milligrams per liter established by the U.S. Environmental Protection Agency for finished drinking water. In the upland subwatersheds, ground-water flow from the tiles appears to have been the primary means of transport to the streams. Concentrations in tileflow and streamflow generally were 4 to 16 milligrams per liter, with the lower concen- trations often the result of dilution by surface runoff. Loss ratios, chemical yields expressed as a percentage of average application rates of nitrate as nitrogen for October 1992-September 1993, were about 10 percent for surface flow and more than 100 percent for tileflow from the 366-hectare basin and were more than 200 percent for streamflow from the downstream subwatershed. Concentrations of atrazine and metolachlor in streamflow, typically, were less than the Maximum Contaminant Level of 3.0 micrograms per liter, but were as high as 59 and 80 micrograms per liter, respectively, during stormflow. Concentrations as high as 170 micrograms per liter occurred in tileflow, but these were related to surface flow through surface inlets. The transport of herbicides was extremely variable, with most of the loads occurring during stormflow. Atrazine appeared more susceptable to transport losses to streamflow than did metolachlor. Loss ratios for streamflow from the subwatersheds for April- September periods were 0.3 to 20 percent for atrazine and 0.1 to 2.9 percent for metolachlor. Chemical loss ratios indicated differences in the transport characteristics of the three subwatersheds. The downstream subwatershed, which has steeper terrain, a more-developed natural drainage system, and fewer tiles than the two upland subwatersheds, had the largest loss rates for all three chemicals--206 percent for nitrate as nitrogen (October 1992-September 1993) and 20 percent for atrazine and 2.9 percent for metolachlor (April-September 1993). For May-July 1993, when most of the herbicides were transported, the downstream subwatershed also had the largest cumulative unit discharge and the largest streamflow-to-precipitation ra

Water-Resources Investigations Report↗
USGS1995

Estimated natural ground-water recharge, discharge, and budget for the Dixie Valley area, west-central Nevada

The Dixie Valley area includes seven valleys in west-central Nevada (Dixie, Fairview, Stingaree, Cowkick, Eastgate, Pleasant, and Jersey Valleys; total, 2,380 square miles). Dixie Valley receives surface-water and ground-water flow from Stingaree, Cowkick, Eastgate, Pleasant, and Jersey Valleys and subsurface flow from Fairview Valley, which is a topographically closed basin. The relation between precipitation and altitude was re-evaluated for the Dixie Valley area using new data, and empirical estimates of recharge were revised accordingly. The revised estimate of total recharge is 23,000 acre-feet per Re-evaluation of ground-water discharge focused on Dixie Valley as the largest basin in the study area. Phreatophytic vegetation was mapped and partitioned into nine zones on the basis of species composition and foliage density. For woody phreatophytes, annual evapotranspiration rates of 0.7 cubic feet of water per cubic foot of foliage for greasewood and 1.1 cubic feet of water per cubic foot of foliage for rabbitbrush were adapted from lysimeter studies near Winnemucca, Nevada. These rates were multiplied by the foliage density of the respective phreatophytes in each zone to estimate a specific rate for that zone. Rates for salt-grass (0.5 to 0.8 foot per year) and the playa surface (0.1 to 0.3 foot per year) were based on a range of rates. used in other recent studies in western and central Nevada. These rates were multiplied by the areas of the zones to produce estimates of the annual volume of ground water discharged. The discharge estimated for Dixie Valley is between 17,000 and 28,000 acre-feet per year. The revised discharge estimate for the entire Dixie Valley area is between 20,000 and 31,000 acre-feet per year. The revised ground-water budget for the entire Dixie Valley study area has a total recharge of about 23,000 acre-feet per year. This is within the range of estimates of natural discharge--from 20,000 to 31,000 acre-feet per year. For Dixie Valley alone, the total recharge of about 8,900 acre-feet per year and the estimated subsurface inflow from tributary areas of about 11,000 acre-feet per year produce an estimated total inflow of about 20,000 acre-feet per year. This compares with the discharge estimate of 17,000 to 28,000 acre-feet per year.

Water-Resources Investigations Report↗
USGS1995

Geochemical processes and the effects of natural organic solutes on the solubility of selenium in coal-mine backfill samples from the Powder River basin, Wyoming

Geochemical processes and the effects of natural organic solutes on the solubility of selenium in coal-mine backfill aquifers were investigated. Backfill and ground-water samples were collected at coal mines in the Powder River Basin, Wyoming. Backfill was generally dominated by aluminum (14,400 to 49,000 mg/kg (milligrams per kilogram)), iron (3,330 to 23,200 mg/kg), and potassium (7,950 to 18,000 mg/kg). Backfill saturated-paste selenium concentrations ranged from 1 to 156 mg/kg (microsiemens per kilogram). Ground-water total selenium concentrations ranged from 3 to 125 mg/L. Dissolved organic carbon in all ground-water samples was dominated by hydrophobic and hydrophilic acids (38 to 84 percent). Selenite sorption/desorption experiments were conducted using background solutions of distilled-deionized water, 0.1 molar calcium chloride, and isolated hydrophobic and hydrophilic acids. Selenite sorption was larger when 0.1 molar calcium chloride was used. The addition of hydrophilic acid decreased selenite sorption more than the addition of hydrophobic acids. Geochemical modelling was used to predict the solid phases controlling dissolved selenium concentrations and to evaluate the effects of dissolved organic carbon on selenium solubility. Results suggested that 55 to 90 percent of selenium in backfill precipitation/dissolution extracts was dominated by magnesium selenate ion pairs. Dissolved organic carbon had little effect on selenium speciation. A redox chamber was constructed to control Eh and pH in water and backfill-core sample suspensions. The response of selenite and selenate in water samples to redox conditions did not follow thermodynamic predictions. Reduction of selenate in water samples did not occur at any of the redox levels tested.

Water-Resources Investigations Report↗
USGS1997

Reconnaissance of surface-water quality in the North Platte Natural Resources District, western Nebraska, 1993

In 1993, the U.S. Geological Survey and the North Platte Natural Resources District began a 3-year study to determine the geohydrology and water quality of the North Platte River alluvial aquifer near Oshkosh, Garden County, Nebraska. The objectives of the study were to determine the geohydrologic properties of the North Platte River alluvial aquifer, to establish a well network for long- term monitoring of concentrations of agricultural chemicals including nitrate and herbicides, and to establish baseline concentrations of major ions in the ground water. To meet these objectives, monitor wells were installed at 11 sites near Oshkosh. The geohydrologic properties of the aquifer were estimated from water-level measurements at selected irrigation wells located in the study area and short- term constant-discharge aquifer tests at two monitor wells. Water samples were collected bimonthly and analyzed for specific conductance, pH, water temperature, dissolved oxygen, and nutrients including dissolved nitrate. Samples were collected semiannually for analysis of major ions, and annually for triazine and acetamide herbicides. Evaluation of the aquifer-test data indicates the hydraulic conductivities of the North Platte River alluvial aquifer range between 169 and 184 feet per day and transmissivities ranged from 12,700 to 26,700 feet-squared per day. The average specific yield for the alluvial aquifer, based on the two aquifer tests, was 0.2. Additional hydrologic data for the alluvial aquifer include a horizontal gradient of about 0.002 foot per foot and estimated ground- water flow velocities of about 0.1 to 1.8 feet per day. Evaluation of the water-quality data indicates that nitrate concentrations exceed the U.S. Environmental Protection Agency's (USEPA) Maximum Contamination Level of 10 milligrams per liter for drinking water in areas to the east and west of Oshkosh. In these areas, nitrate concentrations generally are continuing to rise. West of Oshkosh the highest concentrations are now exceeding 50 milligrams per liter. With the exception of one sample, nitrate concentrations exceeding the Maximum Contamination Level were not detected in three wells used to monitor the ground water flowing into and out of the study area, nor in a monitor well located near a municipal well. Results of the study also indicate that an influx of water from Lost Creek Valley, north of the study area, may be mixing with ground water near Oshkosh and diluting concentrations of nitrate.

Water-Resources Investigations Report↗
USGS1998

Surface-water quality at fixed sites in the Western Lake Michigan Drainages, Wisconsin and Michigan, and the effects of natural and human factors, 1993-95

Streamwater samples were collected from April 1993 through July 1995 at 11 fixed sites in the Western Lake Michigan Drainages Study Unit of the U.S. Geological Survey's National Water-Quality Assessment Program. Water samples were collected monthly at all Fixed Sites, and an additional two to four samples were collected each year during periods of high flow. Streamflow was monitored continuously at the Fixed Sites for the duration of the study period. This report describes field techniques used to collect the water samples, and the analytical methods used for laboratory analyses, statistical analyses of the data, and an attempt to determine the effect of natural and anthropogenic factors on concentrations of nutrients and selected major ions and suspended solids. Locations of eight of the Fixed Sites were selected to represent areas with unique combinations of land use/land cover, surficial deposits, and bedrock geology and are referred to as 'indicator sites.' The remaining three sites were located near the mouths of major rivers and are referred to as 'integrator sites.' The integrator sites represent a large part of the total flow from the Study Unit to Green Bay and western Lake Michigan, and drain various combinations of land use, bedrock, and surficial deposits. These data indicate that land use and surficial deposits may be the primary factors affecting nitrate and total phosphorus concentrations in this Study Unit. Median concentrations of nitrate at the forested sites were less than the National Median Concentration (NMC), and those at urban fixed sites were similar to the NMC. Median nitrate concentrations at the Tomorrow River, North Branch Milwaukee River, and Duck Creek agricultural indicator sites were twice the NMC, but median concentrations at the remaining agricultural indicator sites were similar to the NMC. Nitrate concentrations at one agricultural indicator site exceeded the U. S. Environmental Protection Agency (USEPA) maximum contaminant level in three run-off samples in the growing seasons of 1994 and 1995. Median concentrations of total phosphorus at the forested indicator sites were below the NMC. Tomorrow River was the only agricultural indicator site where the median total-phosphorus concentration was less than the NMC; median concentrations at the remaining agricultural Fixed Sites were similar to the NMC and exceeded 0.1 mg/L, the USEPA suggested total-phosphorus concentration in flowing water. The USEPA recommends that total-phosphorus concentration not exceed this limit to discourage excessive aquatic plant growth in flowing waters. Median total-phosphorus concentration at the urban indicator site was less than the urban NMC. Median concentrations for both nitrate and total phosphorus at the mouth of the Fox River and the Milwaukee River integrator sites were similar to the NMC for the dominant land use, agriculture, within their basins, and were lower than that at the Menominee River integrator site with a dominant forest land use. During this study, potassium concentrations were generally highest in areas of clay-dominated surficial deposits, silica was generally highest in areas of sandy surficial deposits, iron generally highest in areas of igneous/metamorphic bedrock, and calcium generally highest in areas of carbonate bedrock. The highest median fluoride concentration occurred at an urban site that receives treated water.

Michigan, Wisconsin↗
USGS1998

Peak-discharge frequency and potential extreme peak discharge for natural streams in the Brazos River basin, Texas

The 2-, 5-, 10-, 25-, 50-, and 100-year peak discharges were estimated for 186 streamflow-gaging stations with at least 8 years of data for natural streams in and near the Brazos River Basin, Texas. Multiple regression equations were developed to estimate peak-discharge frequency for the 2-, 5-, 10-, 25-, 50-, and 100-year recurrence intervals for each of three hydrologic regions that compose the Brazos River Basin. The equations for each region are a function of significant basin characteristics (explanatory variables). The significant explanatory variables among six that were tested are the contributing drainage area and stream slope for regions 1 and 2 and the contributing drainage area for region 3. For the three sets of equations, the coefficient of determination ranges from 0.59 to 0.93, and the standard error ranges from 0.184 to 0.391 log units. A larger coefficient of determination and a lower standard error generally are associated with the equations for hydrologic regions 2 and 3. Statistics from the regression analysis allow computation of the prediction interval associated with a given significance level for a peak-discharge frequency estimate. The regression equations can be used to estimate peak discharges for sites at, near, or away from sites with streamflow-gaging stations. The potential extreme peak-discharge curves as related to contributing drainage area were estimated for each of the three hydrologic regions from measured extreme peaks of record at 186 sites with streamflow-gaging stations and from measured extreme peaks at 37 sites without streamflow-gaging stations in and near the Brazos River Basin. The potential extreme peak-discharge curves generally are similar for hydrologic regions 1 and 2, and the curve for region 3 consistently is below the curves for regions 1 and 2, which indicates smaller peak discharges.

Texas↗
USGS1999

Site-specific estimation of peak-streamflow frequency using generalized least-squares regression for natural basins in Texas

The U.S. Geological Survey, in cooperation with the Texas Department of Transportation, has developed a computer program to estimate peak-streamflow frequency for ungaged sites in natural basins in Texas. Peak-streamflow frequency refers to the peak streamflows for recurrence intervals of 2, 5, 10, 25, 50, and 100 years. Peak-streamflow frequency estimates are needed by planners, managers, and design engineers for flood-plain management; for objective assessment of flood risk; for cost-effective design of roads and bridges; and also for the desin of culverts, dams, levees, and other flood-control structures. The program estimates peak-streamflow frequency using a site-specific approach and a multivariate generalized least-squares linear regression. A site-specific approach differs from a traditional regional regression approach by developing unique equations to estimate peak-streamflow frequency specifically for the ungaged site. The stations included in the regression are selected using an informal cluster analysis that compares the basin characteristics of the ungaged site to the basin characteristics of all the stations in the data base. The program provides several choices for selecting the stations. Selecting the stations using cluster analysis ensures that the stations included in the regression will have the most pertinent information about flooding characteristics of the ungaged site and therefore provide the basis for potentially improved peak-streamflow frequency estimation. An evaluation of the site-specific approach in estimating peak-streamflow frequency for gaged sites indicates that the site-specific approach is at least as accurate as a traditional regional regression approach.

Texas↗
USGS1967

Definition of stage-discharge relation in natural channels by step-backwater analysis

The step-backwater method was investigated as a technique for defining the upper part of stage-discharge relation in a natural channel. State-discharge relations at 28 sites were computed by using this technique and compared with corresponding stage-discharge relations defined by current-meter measurements. In general, the agreement is remarkably good, and the step-backwater method should prove useful at many sites where current-meter measurements are not obtained.

Water Supply Paper↗
USGS1979

Magnitudes, nature, and effects of point and nonpoint discharges in the Chattahoochee River Basin, Atlanta to West Point Dam, Georgia

During the period April 1975 to June 1978, the U.S. Geological Survey conducted a river-quality assessment of the Upper Chattahoochee River basin in Georgia. One objective of the study was to assess the magnitudes, nature, and effects of point and non-point discharges in the Chattahoochee River basin from Atlanta to the West Point Dam. On an average annual basis and during the storm period of March 1215, 1976, non-point-source loads for most constituents analyzed were larger than point-source loads at the Whitesburg station, located on the Chattahoochee River about 40 river miles downstream of Atlanta. Most of the non-point-source constituent loads in the Atlanta-to-Whitesburg reach were from urban areas. Average annual point-source discharges accounted for about 50 percent of the dissolved nitrogen, total nitrogen, and total phosphorus loads, and about 70 percent of the dissolved phosphorus loads at Whitesburg. During weekends, power generation at the upstream Buford Dam hydroelectric facility is minimal. Streamflow at the Atlanta station during dry-weather weekends is estimated to be about 1,200 ft3/s (cubic feet per second). Average daily dissolved-oxygen concentrations of less than 5.0 mg/L (milligrams per liter) occurred often in the river, about 20 river miles downstream from Atlanta during these periods from May to November. During a low-flow period, June 1-2, 1977, five municipal point sources contributed 63 percent of the ultimate biochemical oxygen demand, 97 percent of the ammonium nitrogen, 78 percent of the total nitrogen, and 90 percent of the total phosphorus loads at the Franklin station, at the upstream end of West Point Lake. Average daily concentrations of 13 mg/L of ultimate biochemical oxygen demand and 1.8 mg/L of ammonium nitrogen were observed about 2 river miles downstream from two of the municipal point sources. Carbonaceous and nitrogenous oxygen demands caused dissolved-oxygen concentrations between 4.1 and 5.0 mg/L to occur in a 22-mile reach of the river downstream from Atlanta. Nitrogenous oxygen demands were greater than carbonaceous oxygen demands in the reach from river mile 303 to 271, and carbonaceous demands were greater from river mile 271 to 235. The heat load from the Atkinson-McDonough thermoelectric power-plants caused a decrease in the dissolved-oxygen concentrations of about 0.2 mg/L. During a critical low-flow period, a streamflow at Atlanta of about 1,800 ft3/s, with present (1977) point-source flows of 185 ft3/s containing concentrations of 45 mg/L of ultimate biochemical oxygen demand and 15 mg/L of ammonium nitrogen, results in a computed minimum dissolved-oxygen concentration of 4.7 mg/L in the river downstream from Atlanta. In the year 2000, a streamflow at Atlanta of about 1,800 ft3/s with point-source flows of 373 ft3/s containing concentrations of 45 mg/L of ultimate biochemical oxygen demand and 5.0 mg/L of ammonium nitrogen, will result in a computed minimum dissolved-oxygen concentration of 5.0 mg/L. A streamflow of about 1,050 ft3/s at Atlanta in the year 2000 will result in a dissolved-oxygen concentration of 5.0 mg/L if point-source flows contain concentrations of 15 mg/L of ultimate biochemical oxygen demand and 5.0 mg/L of ammonium nitrogen. Phytoplankton concentrations in West Point Lake, about 70 river miles downstream from Atlanta, could exceed 3 million cells per milliliter during extended low-flow periods in the summer with present point- and non-point-source nitrogen and phosphorus loads. In the year 2000, phytoplankton concentrations in West Point Lake are not likely to exceed 700,000 cells per milliliter during extended low-flow periods in the summer, if phosphorus concentrations do not exceed 1.0 mg/L in point-source discharges.

Georgia↗
USGS2011

Status and Natural History of Emballonura Semicaudata Rotensis on Aguiguan, Mariana Islands

Pacific sheath-tailed bats ( Emballonura semicaudata rotensis ) in the Mariana Islands declined greatly in abundance and distribution during the 20th century. The small island of Aguiguan now supports the only persisting population. We studied abundance and natural history of this population from 1995–2008. There was a likely population increase during the study, with 359–466 (minimum and maximum) bats counted at caves in 2008. Bats roosted only in caves, primarily those of relatively larger size. Bats were detected in only seven of 95 caves; three caves were always occupied when surveyed. One cave consistently had the largest colony ( ± SD = 333 ± 33.6 in 2008). Others held 1–64 bats. Cave environments showed no complexities in temperature or humidity. Preliminary observations indicate a litter size of one and the possibility of birthing timed to coincide with the transitional period leading into the rainy season (June–July). We review potential threats to E. s. rotensis on Aguiguan and make suggestions for conservation.

Acta Chiropterologica↗
USGS2022

Natural and anthropogenic factors influencing nesting ecology of the American crocodile in Florida, United States

Nesting ecology of American crocodiles ( Crocodylus acutus ) in Florida has been both positively and negatively influenced by anthropogenic and natural factors since the species was placed on the federally endangered species list in 1975. This includes a shift in nesting sites and an expansion of nesting to anthropogenic habitat. Using a 50-year record of monitoring data (1970-2020), we assessed factors influencing nesting ecology (number of nests, nest morphology, success rate, and habitat use) from a total of 3,013 nests recorded across South Florida. We detected a change in nesting success rate, increasing from 61% in the 1970’s to near 90% since 2010. Our hot spot analysis illustrates that nesting sites in northeastern Florida Bay and Flamingo/Cape Sable (Everglades National Park) were important for American crocodiles. Anthropogenic habitats, such as canals provided vital habitat nesting in areas such as Flamingo/Cape Sable (Everglades National Park), Turkey Point Power Plant, and Crocodile Lake National Wildlife Refuge for the current Florida population. Environmental parameters suspected to affect nesting success have shown an increasing trend over the past 50 years and minimum temperature and rainfall, during the summer season, are correlated with increased nesting success and temporal variation across South Florida. The adaptive capacity that American crocodiles exhibited in Florida gave the species advantages to face changes in climate and landscape over the last 50 years, however, it does not imply that the adaptive capacity of the species to face these changes (evolutionary potential) cannot reach a limit if changes continue. Here, we document C. acutus nesting ecology population responses to ecosystem restoration efforts in Florida; and further demonstrate the value of protecting and restoring habitat to support recovery of listed species.

Florida↗
USGS2015

The effect of natural organic matter on mercury methylation by Desulfobulbus propionicus 1pr3

Methylation of tracer and ambient mercury ( 200 Hg and 202 Hg, respectively) equilibrated with four different natural organic matter (NOM) isolates was investigated in vivo using the Hg-methylating sulfate-reducing bacterium Desulfobulbus propionicus 1pr3. Desulfobulbus cultures grown fermentatively with environmentally representative concentrations of dissolved NOM isolates, Hg[II], and HS − were assayed for absolute methylmercury (MeHg) concentration and conversion of Hg(II) to MeHg relative to total unfiltered Hg(II). Results showed the 200 Hg tracer was methylated more efficiently in the presence of hydrophobic NOM isolates than in the presence of transphilic NOM, or in the absence of NOM. Different NOM isolates were associated with variable methylation efficiencies for either the 202 Hg tracer or ambient 200 Hg. One hydrophobic NOM, F1 HpoA derived from dissolved organic matter from the Florida Everglades, was equilibrated for different times with Hg tracer, which resulted in different methylation rates. A 5 day equilibration with F1 HpoA resulted in more MeHg production than either the 4 h or 30 day equilibration periods, suggesting a time dependence for NOM-enhanced Hg bioavailability for methylation.

Frontiers in Microbiology↗
USGS2014

Use of natural and applied tracers to guide targeted remediation efforts in an acid mine drainage system, Colorado Rockies, USA

Stream water quality in areas of the western United States continues to be degraded by acid mine drainage (AMD), a legacy of hard-rock mining. The Rico-Argentine Mine in southwestern Colorado consists of complex multiple-level mine workings connected to a drainage tunnel discharging AMD to passive treatment ponds that discharge to the Dolores River. The mine workings are excavated into the hillslope on either side of a tributary stream with workings passing directly under the stream channel. There is a need to define hydrologic connections between surface water, groundwater, and mine workings to understand the source of both water and contaminants in the drainage tunnel discharge. Source identification will allow targeted remediation strategies to be developed. To identify hydrologic connections we employed a combination of natural and applied tracers including isotopes, ionic tracers, and fluorescent dyes. Stable water isotopes (δ 18 O/δD) show a well-mixed hydrological system, while tritium levels in mine waters indicate a fast flow-through system with mean residence times of years not decades or longer. Addition of multiple independent tracers indicated that water is traveling through mine workings with minimal obstructions. The results from a simultaneous salt and dye tracer application demonstrated that both tracer types can be successfully used in acidic mine water conditions.

Water↗
USGS2021

Non-native Pond Sliders cause long-term decline of native Sonora Mud Turtles: A 33-year before-after study in an undisturbed natural environment

Using a before-after study design in a stable, largely undisturbed pond habitat and a dataset spanning 33 years, we document and describe the decline of native Sonora mud turtles (Kinosternon sonoriense) after the introduction of non-native pond sliders (Trachemys scripta). The Sonora mud turtle population in Montezuma Well in central Arizona, USA, declined to less than 25% of previous numbers, from 372 ± 64 in 1983 to 80 ± 21 in 2011. We trapped and removed the non-native turtles between 2007 and 2012 and after removal of the non-natives, the Sonora mud turtle population increased to 139 ± 34 in 2015. The native turtles also significantly increased basking activity after removal of the non-natives, paralleling results of small-scale mesocosm studies showing that pond sliders negatively affect basking rates of native turtle species. Reproductive rates of female Sonora mud turtles (numbers of females with eggs) were lower during the period of peak non-native turtle abundance, and increased after removal of the non-native turtles. We hypothesize that the reduction in effective reproductive rate links interference competition (reflected in reduced basking rates) to the long-term decline of the native mud turtles. Results from the undisturbed natural system of Montezuma Well provide new insights on the overall occurrence, magnitude, and mechanisms of negative effects of introduced pond sliders on native turtle species. Sonora mud turtles are very different in their morphology, behavior, and ecology from pond sliders and from native turtles in other studies, suggesting that impacts of non-native pond sliders are more pervasive than previously thought.

Aquatic Invasions↗
USGS2020

Tests in a semi-natural environment suggest that bait and switch strategy could be used to control invasive Common Carp

Common Carp ( Cyprinus carpio Linnaeus, 1758), is a highly invasive species that has had profound effects on biodiversity and ecosystem services. Many Carp management methods have been applied including physical removal, pesticide treatments of whole lakes, and water drawdowns. Herein, we tested key elements of a potential “bait and switch” approach in which corn could be used to induce feeding aggregations of Carp and then switched for corn pellets with a pesticide Antimycin-A (ANT-A) to selectively target the Carp. First, laboratory experiments were used to determine if addition of lethal concentrations of ANT-A to corn pellets deterred Carp from eating corn-based food pellets. Second, a pond experiment tested if a corn-based bait containing ANT-A functioned as a species-specific Carp management tool in a semi-natural environment with three common native fishes: White Sucker ( Catostomus commersonii Lacepède, 1803), Yellow Perch ( Perca flavescens Mitchill, 1814), and Bluegill ( Lepomis macrochirus Rafinesque, 1819). The use of baited sites by Carp and native species was monitored using passive integrated transponder (PIT) tags. Mortality of each species and presence of corn in their digestive tracts was also monitored. Our laboratory experiment showed that presence of ANT-A did not deter Carp from consuming the pellets. The pond experiment showed that only Carp perished in significant numbers once toxic bait was applied. Further, only Carp increased their use of baited sites once baiting began, and only Carp had corn in their digestive tracts. Overall, our results indicate that corn might function as a species-specific Carp attractant in systems of North American Midwest and that corn-based bait can be used to effectively conceal a lethal dose of ANT-A. Further research is necessary to refine this potential management tool, specifically investigating the behavioral and social dynamics of Carp aggregating at sites baited with corn to enhance the temporal and spatial specificity of pesticide application.z

Management of Biological Invasions↗
USGS2024

Resource stewardship objectives and actions for climate change-sensitive cultural and natural resources in Wrangell-St. Elias National Park and Preserve: Outputs from January–February 2022 climate change adaptation strategy development

This report presents climate change-informed resource stewardship strategies for diverse Wrangell-St. Elias National Park and Preserve natural and cultural resources. The strategies were developed in early 2022 by park staff and other subject-matter experts in a scenario-based climate change adaptation planning process. Strategy development was facilitated by National Park Service (NPS) climate change adaptation specialists. Strategies address critical climate change implications for park resources identified in an immediately preceding (fall-2021) climate-resource scenario development process. The overall, nearly-year-long scenario- and strategy-development process was entirely virtual due

Report↗
USGS1999

Properties of samples containing natural gas hydrate from the JAPEX/JNOC/GSC Mallik 2L-38 gas hydrate research well, determined using Gas Hydrate And Sediment Test Laboratory Instrument (GHASTLI)

As part of an ongoing laboratory study, preliminary acoustic, strength, and hydraulic conductivity results are presented from a suite of tests conducted on four natural-gas-hydrate-containing samples from the Mackenzie Delta JAPEX/JNOC/GSC Mallik 2L-38 gas hydrate research well. The gas hydrate samples were preserved in pressure vessels during transport from the Northwest Territories to Woods Hole, Massachusetts, where multistep tests were performed using GHASTLI (Gas Hydrate And Sediment Test Laboratory Instrument), which recreates pressure and temperature conditions that are stable for gas hydrate. Properties and changes in sediment behaviour were measured before, during, and after controlled gas hydrate dissociation. Significant amounts of gas hydrate occupied the sample pores and substantially increased acoustic velocity and shear strength.

Bulletin of the Geological Survey of Canada↗