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K. Campbell

Publications and source records attributed to K. Campbell.

34 records · Page 2Linked to original sources
USGS2003

Atmospheric deposition maps for the Rocky Mountains

Variability in atmospheric deposition across the Rocky Mountains is influenced by elevation, slope, aspect, and precipitation amount and by regional and local sources of air pollution. To improve estimates of deposition in mountainous regions, maps of average annual atmospheric deposition loadings of nitrate, sulfate, and acidity were developed for the Rocky Mountains by using spatial statistics. A parameter-elevation regressions on independent slopes model (PRISM) was incorporated to account for variations in precipitation amount over mountainous regions. Chemical data were obtained from the National Atmospheric Deposition Program/National Trends Network and from annual snowpack surveys conducted by the US Geological Survey and National Park Service, in cooperation with other Federal, State and local agencies. Surface concentration maps were created by ordinary kriging in a geographic information system, using a local trend and mathematical model to estimate the spatial variance. Atmospheric-deposition maps were constructed at 1-km resolution by multiplying surface concentrations from the kriged grid and estimates of precipitation amount from the PRISM model. Maps indicate an increasing spatial trend in concentration and deposition of the modeled constituents, particularly nitrate and sulfate, from north to south throughout the Rocky Mountains and identify hot-spots of atmospheric deposition that result from combined local and regional sources of air pollution. Highest nitrate (2.5-3.0kg/ha N) and sulfate (10.0-12.0kg/ha SO4) deposition is found in northern Colorado.

Atmospheric Environment↗
USGS2003

Chlorine-36 data at Yucca Mountain: Statistical tests of conceptual models for unsaturated-zone flow

An extensive set of chlorine-36 (36Cl) data has been collected in the Exploratory Studies Facility (ESF), an 8-km-long tunnel at Yucca Mountain, Nevada, for the purpose of developing and testing conceptual models of flow and transport in the unsaturated zone (UZ) at this site. At several locations, the measured values of 36Cl/Cl ratios for salts leached from rock samples are high enough to provide strong evidence that at least a small component of bomb-pulse 36Cl, fallout from atmospheric testing of nuclear devices in the 1950s and 1960s, was measured, implying that some fraction of the water traveled from the ground surface through 200-300 m of unsaturated rock to the level of the ESF during the last 50 years. These data are analyzed here using a formal statistical approach based on log-linear models to evaluate alternative conceptual models for the distribution of such fast flow paths. The most significant determinant of the presence of bomb-pulse 36Cl in a sample from the welded Topopah Spring unit (TSw) is the structural setting from which the sample was collected. Our analysis generally supports the conceptual model that a fault that cuts through the nonwelded Paintbrush tuff unit (PTn) that overlies the TSw is required in order for bomb-pulse 36Cl to be transmitted to the sample depth in less than 50 years. Away from PTn-cutting faults, the ages of water samples at the ESF appear to be a strong function of the thickness of the nonwelded tuff between the ground surface and the ESF, due to slow matrix flow in that unit. ?? 2002 Elsevier Science B.V. All rights reserved.

Journal of Contaminant Hydrology↗
USGS2003

Hatching success in salamanders and chorus frogs at two sites in Colorado, USA: Effects of acidic deposition and climate

The snowpack in the vicinity of the Mount Zirkel Wilderness Area is among the most acidic in the western United States. We analyzed water chemistry and examined hatching success in tiger salamanders and chorus frogs at ponds there and at nearby Rabbit Ears Pass (Dumont) to determine whether acid deposition affects amphibians or their breeding habitats at these potentially sensitive locations. We found a wide range of acid neutralizing capacity among ponds within sites; the minimum pH recorded during the experiment was 5.4 at one of 12 ponds with all others at pH ??? 5.7. At Dumont, hatching success for chorus frogs was greater in ponds with low acid neutralizing capacity; however, lowest pHs were >5.8. At current levels of acid deposition, weather and pond characteristics are likely more important than acidity in influencing hatching success in amphibian larvae at these sites.

Colorado↗
USGS2002

Nitrate stable isotopes: Tools for determining nitrate sources among different land uses in the Mississippi River Basin

A study was conducted to determine whether NO 3 – stable isotopes (δ 15 N and δ 18 O), at natural abundance levels, could discriminate among NO 3 – sources from sites with different land uses at the basin scale. Water samples were collected from 24 sites in the Mississippi River Basin from five land-use categories: (1) large river basins (>34 590 km 2 ) draining multiple land uses and smaller basins in which the predominant land use was (2) urban, (3) undeveloped, (4) crops, or (5) crops and livestock. Our data suggest that riverine nitrates from different land uses have overlapping but moderately distinct isotopic signatures. δ 18 O data were critical in showing abrupt changes in NO 3 – source with discharge. The isotopic values of large rivers resembled crop sites, sites with livestock tended to have δ 15 N values characteristic of manure, and urban sites tended to have high δ 18 O values characteristic of atmospheric nitrate.

Canadian Journal of Fisheries and Aquatic Sciences↗
USGS2001

Chemical and isotopic evidence of nitrogen transformation in the Mississippi River, 1997-98

Nitrate (NO 3 ) and other nutrients discharged by the Mississippi River are suspected of causing a zone of depleted dissolved oxygen (hypoxic zone) in the Gulf of Mexico each summer. The hypoxic zone may have an adverse affect on aquatic life and commercial fisheries. The amount of NO 3 delivered by the Mississippi River to the Gulf of Mexico is well documented, but the relative contributions of different sources of NO 3 , and the magnitude of subsequent in-stream transformations of NO 3 , are not well understood. Forty-two water samples collected in 1997 and 1998 at eight stations located either on the Mississippi River or its major tributaries were analysed for NO 3 , total nitrogen (N), atrazine, chloride concentrations and NO 3 stable isotopes (δ 15 N and δ 18 O). These data are used to assess the magnitude and nature of in-stream N transformation and to determine if the δ 15 N and δ 18 O of NO 3 provide information about NO 3 sources and transformation processes in a large river system (drainage area 2 900 000 km 2 ) that would otherwise be unavailable using concentration and discharge data alone. Results from 42 samples indicate that the δ 15 N and δ 18 O ratios between sites on the Mississippi River and its tributaries are somewhat distinctive, and vary with season and discharge rate. Of particular interest are two nearly Lagrangian sample sets, in which samples from the Mississippi River at St Francisville, LA, are compared with samples collected from the Ohio River at Grand Chain, II, and the Mississippi River at Thebes, IL. In both Lagrangian sets, mass-balance calculations indicate only a small amount of in-stream N loss. The stable isotope data from the samples suggest that in-stream N assimilation and not denitrification accounts for most of the N loss in the lower Mississippi River during the spring and early summer months.

Illinois, Iowa, Kentucky, Louisiana, Mississippi, ↗
USGS2001

Major-ion chemistry of the Rocky Mountain snowpack, USA

During 1993-97, samples of the full depth of the Rocky Mountain snowpack were collected at 52 sites from northern New Mexico to Montana and analyzed for major-ion concentrations. Concentrations of acidity, sulfate, nitrate, and calcium increased from north to south along the mountain range. In the northern part of the study area, acidity was most correlated (negatively) with calcium. Acidity was strongly correlated (positively) with nitrate and sulfate in the southern part and for the entire network. Acidity in the south exceeded the maximum acidity measured in snowpack of the Sierra Nevada and Cascade Mountains. Principal component analysis indicates three solute associations we characterize as: (1) acid (acidity, sulfate, and nitrate), (2) soil (calcium, magnesium, and potassium), and (3) salt (sodium, chloride, and ammonium). Concentrations of acid solutes in the snowpack are similar to concentrations in nearby wetfall collectors, whereas, concentrations of soil solutes are much higher in the snowpack than in wetfall. Thus, dryfall of acid solutes during the snow season is negligible, as is gypsum from soils. Snowpack sampling offers a cost-effective complement to sampling of wetfall in areas where wetfall is difficult to sample and where the snowpack accumulates throughout the winter. Copyright ?? 2001 .

Atmospheric Environment↗
USGS2001

Effect of storm trajectories on snowfall chemistry in Rocky Mountain National Park, Colorado

Snowfall samples from snowstorms lasting 1 to 4 days were collected near the Bear Lake snow telemetry (SnoTel) site in Rocky Mountain National Park, Colorado (ROMO), during the 1998-99 snowfall season to determine if storms moving in from different directions affect the chemistry of precipitation in the park. Storm pathways to Bear Lake during snowfall events were estimated using the HYSPLIT4 backward-trajectory model developed by the National Oceanic and Atmospheric Administration. Deposition of acidic ions of nitrate and sulfate in snowfall during the study varied substantially (two- to threefold) depending on storm trajectory because air masses traversing the park originated from different surrounding areas, including some having large sources of emissions of nitrate and sulfate. Concentrations of nitrate and sulfate in samples were lowest when storms reached ROMO from north and east of the park and were elevated when air masses traveled from the west where a number of power plants are located. Concentrations were highest in storms reaching ROMO from the south, a region with urban areas including Metropolitan Denver.

Conference Paper↗
USGS1999

A method for nitrate collection for δ 15 N and δ 18 O analysis from waters with low nitrate concentrations

Recently, methods have been developed to analyze NO3- for δ15N and δ18O, improving our ability to identify NO3- sources and transformations. However, none of the existing methods are suited for waters with low NO3- concentrations (0.7-10 µM). We describe an improved method for collecting and recovering NO3- on exchange columns. To overcome the lengthy collection loading times imposed by the large sample volumes (7-70 L), the sample was prefiltered (0.45 µm) with a large surface area filter. Switching to AG2X anion resin and using a coarser mesh size (100-200) than previous methods also enhanced sample flow. Placement of a cation column in front of the anion column minimized clogging of the anion column by dissolved organic carbon (DOC) accumulation. This also served to minimize transfer of unwanted oxygen atoms from DOC to the 18O portion of the NO3- sample, thereby contaminating the sample and shifting δ18O. The cat-AG2X method is suited for on-site sample collection, making it possible to collect and recover NO3- from low ionic strength waters with modest DOC concentrations (80-800 µM), relieves the investigator of transporting large volumes of water back to the laboratory, and offers a means of sampling rain, snow, snowmelt, and stream samples from access-limited sites.

Canadian Journal of Fisheries and Aquatic Sciences↗
USGS1997

Nitrogen fluxes in a high elevation Colorado Rocky Mountain basin

Measured, calculated and simulated values were combined to develop an annual nitrogen budget for Loch Vale Watershed (LVWS) in the Colorado Front Range. Nine-year average wet nitrogen deposition values were 1·6 ( s =0·36) kg NO 3 -N ha −1 , and 1·0 ( s =0·3) kg NH 4 -N ha −1 . Assuming dry nitrogen deposition to be half that of measured wet deposition, this high elevation watershed receives 3·9 kg N ha −1 . Although deposition values fluctuated with precipitation, measured stream nitrogen outputs were less variable. Of the total N input to the watershed (3·9 kg N ha −1 wet plus dry deposition), 49% of the total N input was immobilized. Stream losses were 2·0 kg N ha −1 (1125 kg measured dissolved inorganic N in 1992, 1–2 kg calculated dissolved organic N, plus an average of 203 kg algal N from the entire 660 ha watershed). Tundra and aquatic algae were the largest reservoirs for incoming N, at approximately 18% and 15% of the total 2574 kg N deposition, respectively. Rocky areas and forest stored the remaining 11% and 5%, respectively. Fully 80% of N losses from the watershed came from the 68% of LVWS that is alpine. © 1997 John Wiley & Sons, Ltd.

Hydrological Processes↗
USGS1997

Assessment of climate change and freshwater ecosystems of the Rocky Mountains, USA and Canada

The Rocky Mountains in the USA and Canada encompass the interior cordillera of western North America, from the southern Yukon to northern New Mexico. Annual weather patterns are cold in winter and mild in summer. Precipitation has high seasonal and interannual variation and may differ by an order of magnitude between geographically close locales, depending on slope, aspect and local climatic and orographic conditions. The region's hydrology is characterized by the accumulation of winter snow, spring snowmelt and autumnal baseflows. During the 2–3-month ‘spring runoff’ period, rivers frequently discharge > 70% of their annual water budget and have instantaneous discharges 10–100 times mean low flow.

Hydrological Processes↗
USGS1997

The use of bulk collectors in monitoring wet deposition at high-altitude sites in winter

Concentrations of dissolved ions from samples collected by wet/dry collectors were compared to those collected by bulk collectors at Halfmoon Creek and Ned Wilson Lake in western Colorado to determine if bulk collectors can be used to monitor wet deposition chemistry in remote, high-altitude regions in winter. Hydrogen-ion concentration was significantly lower (p < 0.05) in the bulk collectors. All other ion concentrations were significantly higher (p < 0.05) in the bulk collectors except for ammonium (p > 0.05) at Halfmoon Creek. Wet deposition concentrations were predicated from bulk deposition concentrations through linear regression analysis. Results indicate that anions (chloride, nitrate and sulfate) can be predicted with a high degree of confidence. Lack of significant differences between seasonal (winter and summer) ratios of bulk to wet deposition concentrations indicates that at sites where operation of a wet/dry collector during the winter is not practical, wet deposition concentrations can be predicted from bulk collector samples through regression analysis of wet and bulk deposition data collected during the summer.

Water, Air, & Soil Pollution↗
USGS1996

Controls on surface water chemistry in the upper Merced River basin, Yosemite National Park, California

Surface water draining granitic bedrock in Yosemite National Park exhibits considerable variability in chemical composition, despite the relative homogeneity of bedrock chemistry. Other geological factors, including the jointing and distribution of glacial till, appear to exert strong controls on water composition. Chemical data from three surface water surveys in the upper Merced River basin conducted in August 1981, June 1988 and August 1991 were analysed and compared with mapped geological, hydrological and topographic features to identify the solute sources and processes that control water chemistry within the basin during baseflow. Water at most of the sampling sites was dilute, with alkalinities ranging from 26 to 77 μequiv. l −1 . Alkalinity was much higher in two subcatchments, however, ranging from 51 to 302 μequiv. l −1 . Base cations and silica were also significantly higher in these two catchments than in the rest of the watershed. Concentrations of weathering products in surface water were correlated to the fraction of each subcatchment underlain by surficial material, which is mostly glacial till. Silicate mineral weathering is the dominant control on concentrations of alkalinity, silica and base cations, and ratios of these constituents in surface water reflect the composition of local bedrock. Chloride concentrations in surface water samples varied widely, ranging from <1 to 96 μequiv. l −1 . The annual volume-weighted mean chloride concentration in the Merced River at the Happy Isles gauge from 1968 to 1990 was 26 μequiv. l −1 , which was five times higher than in atmospheric deposition (4–5 μequiv. l −1 ), suggesting that a source of chloride exists within the watershed. Saline groundwater springs, whose locations are probably controlled by vertical jointing in the bedrock, are the most likely source of the chloride. Sulphate concentrations varied much less than most other solutes, ranging from 3 to 14 μequiv. l −1 . Concentrations of sulphate in quarterly samples collected at the watershed outlet also showed relatively little variation, suggesting that sulphate may be regulated to some extent by a within-watershed process, such as sulphate adsorption.

Hydrological Processes↗
USGS1993

Use of chemistry and stable sulfur isotopes to determine sources of trends in sulfate of Colorado lakes

The chemistry of lakes in the Mt. Zukel Wilderness Area (MZWA) and the Weminuche Wilderness Area (WWA) of Colorado has been monitored since 1985. The initial results indicate that changes have occurred in the chemistry of some lakes in both areas. Increased concentration of sulfate in lakes may be related to increased atmospheric deposition of sulfate or to changes of sulfate released by weathering and to changing dilution of sulfate by snowmelt. Stable S isotopes seem to be capable of separating the fraction of change in sulfate that is related to atmospheric and watershed sources. Because of the short period of record, it is not possible to determine whether the changes are part of a long-term trend or are merely natural fluctuations about some baseline.The chemistry of lakes in th Mt. Zirkel Wilderness Area (MZWA) and Weminche Wilderness Area (WWA) of Colorado has been monitored since 1985. The initial results indicate that changes have occurred in the chemistry of some lakes in both areas. Increased concentration of sulfate in lakes may be related to increased atmospheric deposition of sulfateor to changes of sulfate released by weathering and to changing dilution of sulfate by snowmelt. Stable S isotopes seem to be capable of separating the fraction of change in sulfate that is related to atmospheric and watershed sources. Because of the short period of record, it is not possible to determine whether the changes are part of long-term or are merely natural fluctuations about some baseline.

Water, Air, & Soil Pollution↗