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M. Alisa Mast

Publications and source records attributed to M. Alisa Mast.

79 records · Page 5Linked to original sources
USGS1999

Environmental characteristics and water quality of hydrologic benchmark network stations in the Midwestern United States, 1963-95

This report describes the environmental characteristics and water quality at 14 benchmark basins in the Midwestern United States. The information in this report was compiled to aid in the application and interpretation of historical water-quality data collected by the U.S. Geological Survey Hydrologic Benchmark Network program. The streams discussed in this report drain either forested areas or grasslands with a variety of land-use activities that range from recreational use, timber harvesting, and military training on publicly owned land to agriculture and residential development on privately owned land.

Circular↗
USGS1999

Trends in precipitation and stream-water chemistry in the northeastern United States, water years 1984-96

Trends in precipitation and stream-water chemistry during water years 1984-96 were examined at eight precipitation monitoring sites and five nearby streams operated by the U.S. Geological Survey in the northeastern United States. The statistical analyses indicate the following: 1)Stream-water sulfate (SO4) concentrations decreased at seven of eight precipitation monitoring sites and in each of five streams. 2)Calcium plus magnesium (Ca + Mg) concentrations decreased at seven of eight precipitation monitoring sites and in three of five streams. 3)Precipitation acidity decreased at five of eight precipitation monitoring sites, but alkalinity increased in only one stream. These results indicate that decreases in atmospheric deposition of SO4 have resulted in decreased precipitation acidity. The chemical response of stream water to changes in precipitation chemistry was complex. Decreases in stream-water SO4 concentrations generally matched decreases of precipitation SO4. In stream water, increases in alkalinity were uncommon because decreases in SO4 concentrations often were accompanied by decreases in Ca + Mg concentrations. The decreases in Ca + Mg concentrations might be related to depletion of base cations from soil caused by long-term exposure to acidic deposition. Increases in streamwater alkalinity might not occur until rates of acidic deposition are reduced to substantially less than the rate of cation resupply by weathering and atmospheric deposition. In areas where forests are aggrading, recovery of stream-water alkalinity will be delayed further because of the acidifying effect of biomass accumulation.

Fact Sheet↗
USGS1998

Winter fluxes of CO 2 and CH 4 from subalpine soils in Rocky Mountain National Park, Colorado

Fluxes of CO 2 and CH 4 through a seasonal snowpack were measured in and adjacent to a subalpine wetland in Rocky Mountain National Park, Colorado. Gas diffusion through the snow was controlled by gas production or consumption in the soil and by physical snowpack properties. The snowpack insulated soils from cold midwinter air temperatures allowing microbial activity to continue through the winter. All soil types studied were net sources of CO 2 to the atmosphere through the winter, whereas saturated soils in the wetland center were net emitters of CH 4 and soils adjacent to the wetland were net CH 4 consumers. Most sites showed similar temporal patterns in winter gas fluxes; the lowest fluxes occurred in early winter, and maximum fluxes occurred at the onset of snowmelt. Temporal changes in fluxes probably were related to changes in soil-moisture conditions and hydrology because soil temperatures were relatively constant under the snowpack. Average winter CO 2 fluxes were 42.3, 31.2, and 14.6 mmol m −2 d −1 over dry, moist, and saturated soils, respectively, which accounted for 8 to 23% of the gross annual CO 2 emissions from these soils. Average winter CH 4 fluxes were −0.016, 0.274, and 2.87 mmol m −2 d −1 over dry, moist, and saturated soils, respectively. Microbial activity under snow cover accounted for 12% of the annual CH 4 consumption in dry soils and 58 and 12% of the annual CH 4 emitted from moist and saturated soils, respectively. The observed ranges in CO 2 and CH 4 flux through snow indicated that winter fluxes are an important part of the annual carbon budget in seasonally snow-covered terrains.

Global Biogeochemical Cycles↗
USGS1997

Strontium 87/strontium 86 as a tracer of mineral weathering reactions and calcium sources in an alpine/subalpine watershed, Loch Vale, Colorado

Sr isotopic ratios of atmospheric deposition, surface and subsurface water, and geologic materials were measured in an alpine/subalpine watershed to characterize weathering reactions and identify sources of dissolved Ca in stream water. Previous studies have noted an excess of Ca in stream water above that expected from stoichiometric weathering of the dominant bedrock minerals. Mixing calculations based on 87 Sr/ 86 Sr indicate that on an annual basis, 26 ± 7% of Ca export in streams is atmospherically derived, 23 ± 1% is from weathering of plagioclase, and the remainder is from weathering of calcite present in trace amounts in the bedrock. A potential source of error when applying Sr isotopes in catchment studies is determination of the 87 Sr/ 86 Sr of Sr released by mineral weathering, which is complicated by the wide range of mineral isotopic compositions, particularly in older rocks, and the variable rates at which the minerals weather. In this study, base-flow stream chemistry was used to represent the 87 Sr/ 86 Sr of Sr derived from mineral weathering because it effectively integrates the potentially variable isotopic composition of Sr released by weathering in the alpine environment.

Colorado↗
USGS1995

Composition of precipitation, bulk deposition, and runoff at a granitic bedrock catchment in the Loch Vale watershed, Colorado, USA

The chemical composition of precipitation, bulk deposition, and runoff from a 30-m2 granitic bedrock catchment in the Loch Vale Watershed in Rocky Mountain National Park was monitored over a 6-week period in the summer of 1994 to determine the importance of dry deposition in the alpine zone. Concentrations of acid anions and base cations were 1.1 to 4 times higher in bulk deposition than in precipitation. Concentrations of the same solutes were 3 to 10 times higher in runoff from the bedrock catchment than in bulk deposition, and during individual runoff events, the concentrations of most ions were highest in the initial runoff. Evaporation from the rock surface accounted for only a 15% increase in solute concentrations indicating that most of the dissolved load in bedrock runoff is derived from the dissolution of dry deposition that accumulates on the bedrock between storm events. These results indicate that dry deposition may be an important source of solutes to this alpine ecosystem.

Biogeochemistry of seasonally snow-covered catchme↗
USGS1991

Hydrologic pathways and chemical composition of runoff during snowmelt in Loch Vale Watershed, Rocky Mountain National Park, Colorado, USA

Intensive sampling of a stream draining an alpine-subalpine basin revealed that depressions in pH and acid neutralizing capacity (ANC) of surface water at the beginning of the spring snowmelt in 1987 and 1988 were not accompanied by increases in strong acid anions, and that surface waters did not become acidic (ANC<0). Samples of meltwater collected at the base of the snowpack in 1987 were acidic and exhibited distinct ‘pulses’ of nitrate and sulfate. Solutions collected with lysimeters in forest soils adjacent to the stream revealed high levels of dissolved organic carbon (DOC) and total Al. Peaks in concentration of DOC, Al, and nutrient species in the stream samples indicate a flush of soil solution into the surface water at the beginning of the melt. Infiltration of meltwater into soils and spatial heterogeneity in the timing of melting across the basin prevented stream and lake waters from becoming acidic.

Colorado↗