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Dennis A. Wentz

Publications and source records attributed to Dennis A. Wentz.

17 recordsLinked to original sources
USGS2014

Mercury in the nation's streams - Levels, trends, and implications

Mercury is a potent neurotoxin that accumulates in fish to levels of concern for human health and the health of fish-eating wildlife. Mercury contamination of fish is the primary reason for issuing fish consumption advisories, which exist in every State in the Nation. Much of the mercury originates from combustion of coal and can travel long distances in the atmosphere before being deposited. This can result in mercury-contaminated fish in areas with no obvious source of mercury pollution. Three key factors determine the level of mercury contamination in fish - the amount of inorganic mercury available to an ecosystem, the conversion of inorganic mercury to methylmercury, and the bioaccumulation of methylmercury through the food web. Inorganic mercury originates from both natural sources (such as volcanoes, geologic deposits of mercury, geothermal springs, and volatilization from the ocean) and anthropogenic sources (such as coal combustion, mining, and use of mercury in products and industrial processes). Humans have doubled the amount of inorganic mercury in the global atmosphere since pre-industrial times, with substantially greater increases occurring at locations closer to major urban areas. In aquatic ecosystems, some inorganic mercury is converted to methylmercury, the form that ultimately accumulates in fish. The rate of mercury methylation, thus the amount of methylmercury produced, varies greatly in time and space, and depends on numerous environmental factors, including temperature and the amounts of oxygen, organic matter, and sulfate that are present. Methylmercury enters aquatic food webs when it is taken up from water by algae and other microorganisms. Methylmercury concentrations increase with successively higher trophic levels in the food web—a process known as bioaccumulation. In general, fish at the top of the food web consume other fish and tend to accumulate the highest methylmercury concentrations. This report summarizes selected stream studies conducted by the U.S. Geological Survey (USGS) since the late 1990s, while also drawing on scientific literature and datasets from other sources. Previous national mercury assessments by other agencies have focused largely on lakes. Although numerous studies of mercury in streams have been conducted at local and regional scales, recent USGS studies provide the most comprehensive, multimedia assessment of streams across the United States, and yield insights about the importance of watershed characteristics relative to mercury inputs. Information from other environments (lakes, wetlands, soil, atmosphere, glacial ice) also is summarized to help understand how mercury varies in space and time.

Circular↗
USGS2013

Mercury and methylmercury dynamics in the hyporheic zone of an Oregon stream

The role of the hyporheic zone in mercury (Hg) cycling has received limited attention despite the biogeochemically active nature of this zone and, thus, its potential to influence Hg behavior in streams. An assessment of Hg geochemistry in the hyporheic zone of a coarse-grained island in the Coast Fork Willamette River in Oregon, USA, illustrates the spatially dynamic nature of this region of the stream channel for Hg mobilization and attenuation. Hyporheic flow through the island was evident from the water-table geometry and supported by hyporheic-zone chemistry distinct from that of the bounding groundwater system. Redox-indicator species changed abruptly along a transect through the hyporheic zone, indicating a biogeochemically reactive stream/hyporheic-zone continuum. Dissolved organic carbon (DOC), total Hg, and methylmercury (MeHg) concentrations increased in the upgradient portion of the hyporheic zone and decreased in the downgradient region. Total Hg (collected in 2002 and 2003) and MeHg (collected in 2003) were correlated with DOC in hyporheic-zone samples: r 2 =0.63 (total Hg-DOC, 2002), 0.73 (total Hg-DOC, 2003), and 0.94 (MeHg-DOC, 2003). Weaker Hg/DOC association in late summer 2002 than in early summer 2003 may reflect seasonal differences in DOC reactivity. Observed correlations between DOC and both total Hg and MeHg reflect the importance of DOC for Hg mobilization, transport, and fate in this hyporheic zone. Correlations with DOC provide a framework for conceptualizing and quantifying Hg and MeHg dynamics in this region of the stream channel, and provide a refined conceptual model of the role hyporheic zones may play in aquatic ecosystems.

Water, Air, & Soil Pollution↗
USGS2010

Long-term hydrologic and biogeochemical responses of a soft water seepage lake in north central Wisconsin

Hydrologic and chemical budgets were determined for the period October 1980 through September 1988 for Vandercook Lake, a 43-ha soft water seepage lake located in predominantly sandy outwash in northern Wisconsin. The 1951–1980 mean annual precipitation for the lake, based on nearby National Weather Service (NWS) stations, was 825 mm; volume-weighted p H of bulk atmospheric deposition during the 8-year study averaged 4.7. From October 1980 through September 1983, annual precipitation was 108% of the 30-year NWS average, annual recharge was 144% of the 8-year study period average, and annual groundwater inflow to the lake ranged from 5 to 9% of the total inflow. From October 1986 through September 1988, annual precipitation was 90% of the NWS average, annual recharge was 30% of the study period average, and the lake received no groundwater inflow. During the study, the lake changed from a system whose buffering mechanism was significantly influenced by mineral weathering in inflowing groundwater to one dominated by in-lake sulfate reduction. The functional differences exhibited by this lake during the 8 years of study demonstrate the tenuousness with which conclusions based on shorter-term studies of similar systems must be considered.

Wisconsin↗
USGS2009

Data on mercury in water, bed sediment, and fish from streams across the United States, 1998-2005

The U.S. Geological Survey (USGS) National Water-Quality Assessment (NAWQA) and Toxic Substances Hydrology Programs conducted the National Mercury Pilot Study in 1998 to examine relations of mercury (Hg) in water, bed sediment and fish in streams across the United States, including Alaska and Hawaii. Water and bed-sediment samples were analyzed for total Hg (THg), methylmercury (MeHg), and other constituents; fish were analyzed for THg. Similar sampling was conducted at additional streams across the country in 2002 and 2004-05. This report summarizes sample collection and processing protocols, analytical methods, environmental data, and quality-assurance data for stream water, bed sediment, and fish for these national studies. To extend the geographic coverage of the data, this report also includes four regional USGS Hg studies conducted during 1998-2001 and 2004. The environmental data for these national and regional Hg studies are provided in an electronic format.

Data Series↗
USGS2009

Mercury in fish, bed sediment, and water from streams across the United States, 1998-2005

Mercury (Hg) was examined in top-predator fish, bed sediment, and water from streams that spanned regional and national gradients of Hg source strength and other factors thought to influence methylmercury (MeHg) bioaccumulation. Sampled settings include stream basins that were agricultural, urbanized, undeveloped (forested, grassland, shrubland, and wetland land cover), and mined (for gold and Hg). Each site was sampled one time during seasonal low flow. Predator fish were targeted for collection, and composited samples of fish (primarily skin-off fillets) were analyzed for total Hg (THg), as most of the Hg found in fish tissue (95-99 percent) is MeHg. Samples of bed sediment and stream water were analyzed for THg, MeHg, and characteristics thought to affect Hg methylation, such as loss-on-ignition (LOI, a measure of organic matter content) and acid-volatile sulfide in bed sediment, and pH, dissolved organic carbon (DOC), and dissolved sulfate in water. Fish-Hg concentrations at 27 percent of sampled sites exceeded the U.S. Environmental Protection Agency human-health criterion of 0.3 micrograms per gram wet weight. Exceedances were geographically widespread, although the study design targeted specific sites and fish species and sizes, so results do not represent a true nationwide percentage of exceedances. The highest THg concentrations in fish were from blackwater coastal-plain streams draining forests or wetlands in the eastern and southeastern United States, as well as from streams draining gold- or Hg-mined basins in the western United States (1.80 and 1.95 micrograms THg per gram wet weight, respectively). For unmined basins, length-normalized Hg concentrations in largemouth bass were significantly higher in fish from predominantly undeveloped or mixed-land-use basins compared to urban basins. Hg concentrations in largemouth bass from unmined basins were correlated positively with basin percentages of evergreen forest and also woody wetland, especially with increasing proximity of these two land-cover types to the sampling site; this underscores the greater likelihood for Hg bioaccumulation to occur in these types of settings. Increasing concentrations of MeHg in unfiltered stream water, and of bed-sediment MeHg normalized by LOI, and decreasing pH and dissolved sulfate were also important in explaining increasing Hg concentrations in largemouth bass. MeHg concentrations in bed sediment correlated positively with THg, LOI, and acid-volatile sulfide. Concentrations of MeHg in water correlated positively with DOC, ultraviolet absorbance, and THg in water, the percentage of MeHg in bed sediment, and the percentage of wetland in the basin.

Scientific Investigations Report↗
USGS2008

Total Mercury, Methylmercury, and Ancillary Water-Quality and Streamflow Data for Selected Streams in Oregon, Wisconsin, and Florida, 2002-06

Field and analytical methods, mercury and ancillary water-quality data, and associated quality-control data are reported for eight streams in Oregon, Wisconsin, and Florida from 2002 to 2006. The streams were sampled as part of a U.S. Geological Survey National Water-Quality Assessment Program study of mercury cycling, transport, and bioaccumulation in urban and nonurban stream ecosystems that receive mercury predominantly by way of atmospheric deposition.

Data Series↗
USGS2008

Total Mercury, Methylmercury, and Carbon and Nitrogen Stable Isotope Data for Biota from Selected Streams in Oregon, Wisconsin, and Florida, 2002-04

The U.S. Geological Survey National Water-Quality Assessment Program conducted a multidisciplinary study to investigate the bioaccumulation of mercury from 2002 to 2004. Study areas were located in Oregon, Wisconsin, and Florida. Each study area included one urban site, and one or two nonurban sites that had the following attributes: high-percent wetland or low-percent wetland. Periphyton, macroinvertebrates, and forage fish were collected twice per year (during 2003 and 2004) to capture seasonality. Top predators, specifically largemouth bass (Micropterus salmoides), brown trout (Salmo trutta), and cutthroat trout (Oncorhynchus clarkii), were collected once per year (Oregon, Wisconsin, and Florida in 2003; Florida only in 2004). All biota were identified to the lowest possible taxonomic category and were analyzed for mercury and stable carbon and nitrogen isotopes. Periphyton and invertebrates were analyzed for total mercury and methylmercury; fish were analyzed for total mercury only. This report presents (1) methodology and data on mercury, methylmercury, stable isotopes, and (2) other ecologically relevant measurements in biological tissues of periphyton, invertebrates, forage fish, and predator fish.

Data Series↗
USGS2008

Procedures for Collecting and Processing Aquatic Invertebrates and Fish for Analysis of Mercury as Part of the National Water-Quality Assessment Program

Mercury studies conducted as part of the U.S. Geological Survey's National Water-Quality Assessment (NAWQA) Program have included nationwide reconnaissance samplings of hundreds of stream sites, as well as detailed, process-oriented research at selected sites. These reconnaissance and detailed studies are intended to provide a better understanding of methylmercury bioaccumulation in stream ecosystems over a range of environmental settings. This publication describes trace-element-clean techniques used for collection and processing of aquatic invertebrates and fish to be analyzed for total mercury, methylmercury, and stable isotopes as part of NAWQA studies.

Open-File Report↗
USGS1999

Environmental setting of the Willamette basin, Oregon

The Willamette Basin, Oregon, is one of more than 50 large river basins and aquifer systems (referred to as study units) across the United States where the status and trends of water quality and the factors controlling water quality are being studied by the National Water-Quality Assessment Program of the U.S. Geological Survey. The 12,000-square-mile Willamette Basin Study Unit consists of the Willamette and Sandy River Basins, which are tributary to the Columbia River. The Willamette River is the 13th largest in the conterminous United States in terms of discharge and is the largest of all major United States rivers in terms of discharge per square mile of drainage area. The environmental setting of a study unit includes all natural and human related, land based factors that have the potential to influence the physical, chemical, and/or biological quality of its surface and ground water resources. For the Willamette Basin, these include primarily ecoregions, hydrogeology, climate, hydrology, land use/land cover, and crop types.

Water-Resources Investigations Report↗
USGS1998

Water quality in the Willamette Basin, Oregon, 1991-95

This report is intended to summarize major findings that emerged between 1991 and 1995 from the water-quality assessment of the Willamette Basin Study Unit and to relate these findings to water-quality issues of regional and national concern. The information is primarily intended for those who are involved in water-resource management. Yet, the information contained here may also interest those who simply wish to know more about the quality of water in the rivers and aquifers in the area where they live.

Oregon↗
USGS1989

Interrelationships among hydrologic-budget components of a northern Wisconsin seepage lake and implications for acid-deposition modeling

Components of the hydrologic budget for a northern Wisconsin seepage lake were analyzed by applying correlation and regression techniques to monthly data. Analyses for the 1981–83 water years revealed a statistically significant, direct relationship between storage change and precipitation-evaporation balance. Ground-water outflow was negatively correlated with ground-water inflow, and this relationship was influenced by similar relationships for both hydraulic gradients and cross-sectional areas in outflow versus inflow regions of the lake. Neither ground-water outflow nor inflow was significantly related to precipitation, evaporation, storage change, or lake stage; this may reflect a lag in response time of the ground-water system compared to the lake. The results (1) emphasize the complexity of factors that influence ground-water interactions with seepage lakes and (2) suggest the importance of completing detailed hydrologic studies of these systems before mechanistic models, such as those developed to predict effects of acid deposition, are applied.

Wisconsin↗
USGS1982

Effects of a floodwater-retarding structure on the hydrology and ecology of Trout Creek in southwestern Wisconsin

The primary effects of a floodwater-retarding structure (FRS) on the streamflow of Trout Creek, Wisconsin, are attenuation of flood peaks and extension of the time base of flood hydrographs. Reduction of flood peaks ranged from 58 to 91 percent during the study period from 1975 to 1979. There is an inverse relation between sediment concentration and outflow from the FRS during floods. As water went into storage in the flood pool in March 1976, the daily-mean total-sediment concentration in the FRS outflow dropped from 562 to 147 milligrams per liter. Sediment concentration subsequently increased to 809 milligrams per liter as the discharge from the FRS dropped; concentrations remained more than 400 milligrams per liter for several weeks thereafter. Most sediment stored in the flood pool during flood flows is released from the reservoir during subsequent reduced discharge. Sediment trapping efficiency of the FRS was about 7 percent for the 4-year period of the study. The bankfull capacity of the channel was reduced from 154 cubic feet per second upstream from the flood pool of the FRS to 65 cubic feet per second just downstream from the FRS. This latter discharge corresponds closely to the normal FRS outflow of 58 to 71 cubic feet per second during floods. Mean bankfull depth downstream from the FRS has adjusted to a value 45 percent less than upstream from the structure due to sedimentation of materials transported from the FRS during reduced flows. The hydraulic geometry and relationships between channel geometry and drainage area indicate little effect of the FRS near the mouth of Trout Creek, 2.4 miles downstream from the FRS. The arthropod fauna of Trout Creek is large and diverse. No effects of the FRS on these fauna were observed from April 1975 to October 1979. From fall 1975 to winter 1978, the most important factor contributing to increased brown trout egg survival and fry emergence in Trout Creek during a single reproductive season is higher water temperatures in the upper reaches of the stream. The FRS was not found to have any significant effect on trout reproduction during that period. From 1960 to 1979, winter floods seem to have had the greatest adverse effect on the survival of brown trout eggs and sac fry. Although construction of the FRS has eliminated some spawning gravels in the flood pool owing to sedimentation, the wild trout have adapted by using spawning grounds above the flood pool more extensively and intensively. The FRS has not blocked the upstream migration of spawning trout, but it has eliminated similar migrations of fish that compete with and prey on the trout. Controlled streamflows downstream from the FRS have had a stabilizing influence on the limited trout reproduction in this region.

Wisconsin↗
USGS1980

Water-quality characteristics of selected lakes and reservoirs in Colorado

During the summers and autumns of 1973, 1974, and 1975, water-quality data were collected and compiled for 56 lakes and reservoirs in Colorado. The lakes and reservoirs sampled range from large reservoirs in the eastern part of the State to smaller natural lakes in the higher western parts of the Colorado Plateaus. The smallest body of water sampled was Anderson Reservoir No. 1 with a surface area of 47 acres in Mesa County, and the largest was Najajo Reservoir with a surface area of 15,600 acres in Archuleta County. The report includes physical, chemical, and biological water-quality data collected as a part of each lake or reservoir reconnaissance. Also included are data on drainage area, water-surface altitude, surface area,depth, storage capacity, and principal uses, obtained from various governmental agencies or the owner or regulating agency of each lake or reservoir. A subjective evaluation of the trophic (enrichment) state is presented based on nutrient and phytoplankton concentrations and the dissolved-oxygen distribution. In addition, a numerical trophic-state index, based on Secchi-disk transparency (a measure of light penetration) is reported, to show trophic comparisons between lakes and reservoirs. (USGS)

Open-File Report↗
USGS1974

Effects of metal-mine drainage on water quality in selected areas of Colorado, 1972-73

Colorado is a child of mining. In the past, towns such as Cripple Creek, Leadville, Creede, and many others were the lifeblood of the economy. While metal mining is still economically important to Colorado, another legacy of this past activity is attracting increasing attention—the detrimental effects of drainage from abandoned and active mines and tailings piles (waste rock piles) on streams. Concern with metal-mine drainage is due to the acid resulting from oxidation of pyritic material. The acid itself can be harmful to aquatic organisms, and can make the water unusable for various recreational and industrial needs. Just as importantly, however, the acid dissolves metals from ores and tailings piles and releases them into the streams. Many of the metals are toxic to aquatic organisms, humans, and livestock; and, like excess acidity, the metals can make streams unusable for some types of recreation and industry. In July 1971, a study of the effects of both metal- and coal-mine drainage on surface-water quality in Colorado was undertaken by the U.S. Geological Survey in cooperation with the Colorado Water Pollution Control Commission. Based on the reconnaissance phase of this project (Wentz, 1974), 17 areas judged to be adversely affected by metal-mine drainage were chosen for further study. One additional area was included because it is the only place found in Colorado that potentially could be affected by coal-mine drainage. The present report summarizes the intensive study of these areas; it is the second product of the mine-drainage study. The first report was published as Colorado Water Resources Circular 21.

Colorado↗
USGS1974

Effect of mine drainage on the quality of streams in Colorado, 1971-72

In July 1971, a study of the effects of mine drainage on Colorado's streams was begun in cooperation with the Colorado Water Pollution Control Commission. The objectives of this study were to determine the extent and magnitude of the problem as a whole, and to gain a greater understanding of the processes and their potential ramifications by detailed definition of problems in specific areas. In order to accomplish these objectives, a three-pronged approach was devised to include: (1) a reconnaissance of the entire State to locate problem areas, (2) the detailed study of selected problem areas on a short-term basis, and (3) the monitoring of selected problem areas on a long-term basis. This report summarizes the results of the reconnaissance phase. It describes some basic physical, chemical, and biological water-quality characteristics of the streams, discusses observed effects of mine drainage on the surface-water environment, delineates problem areas, and provides a list of streams where intensive study and subsequent monitoring might provide further insight into the various problems encountered.

Colorado↗