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  • 1
    Digitale Medien
    Digitale Medien
    [s.l.] : Nature Publishing Group
    Nature 331 (1988), S. 607-609 
    ISSN: 1476-4687
    Quelle: Nature Archives 1869 - 2009
    Thema: Biologie , Chemie und Pharmazie , Medizin , Allgemeine Naturwissenschaft , Physik
    Notizen: [Auszug] Lake chemistry data were taken from the recent National Lake Survey (NLS)3'4, conducted by the US Environmental Protection Agency (EPA). Details on statistical design, sampling, analytical methodologies, and quality assurance protocols were provided by Linthurst et a/.3 and Landers et al4. ...
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    ISSN: 1432-1009
    Schlagwort(e): KEY WORDS: Ecoregions; Spatial analysis; Corn Belt; Iowa; GIS; Regionalization
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Energietechnik
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    Springer
    Hydrobiologia 199 (1990), S. 1-6 
    ISSN: 1573-5117
    Schlagwort(e): base cations ; conductivity ; dilute lakes ; hydrology ; Oregon Cascades
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Lake Notasha, near the crest of the Oregon Cascade mountain range, is the most dilute lake known. The measured conductivity during two visits was 1.3 and 1.6 µS cm−1 with a sum of base cations of 9 and 18 µeq L−1; bicarbonate was the dominant anion. Most of the cations in the lake can be accounted for by evapoconcentration of precipitation, although input of weathering products cannot be excluded as a source. The topographic watershed has a mixed coniferous forest, but the physical setting of the lake apparently minimizes hydrologic and ionic contributions from the watershed. This feature makes lakes such as Notasha appropriate receptors for monitoring atmospheric contaminants.
    Materialart: Digitale Medien
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  • 4
    Digitale Medien
    Digitale Medien
    Springer
    Water, air & soil pollution 95 (1997), S. 313-336 
    ISSN: 1573-2932
    Schlagwort(e): nitrogen ; acidification ; Adirondack Mountains ; atmospheric deposition
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Energietechnik
    Notizen: Abstract Assessments of the aquatic effects of acidic deposition have focused on sulfur, as have recent efforts to control the emissions of acidifying compounds. Nitrogen dynamics were excluded from most acidic deposition modeling studies because it was believed that terrestrial ecosystems strongly retain N and because modeling N is a more formidable task than modeling S due to the influence of complex biological processes on N cycling. Re-examination of available data for the Adirondack Mountains of New York suggests that N deposition may be contributing to both chronic and episodic acidification of freshwaters to a greater extent than is generally believed. Previous research concluded that N has played a limited role in acidification processes in these lakes, based on regional averages of chronic chemistry. However, it is now known that historic acidification responses have been spatially variable within the Adirondack Mountains and that the declines in lakewater pH have been less than previously believed. Lakewater NO3 − concentrations are commonly in the range of 5 to 25 μeq L−1 on a chronic basis in portions of the Adirondack region that have experienced significant chronic acidification. These NO3 − concentrations correspond in magnitude to inferred historical acidification. Furthermore, the relative importance of NO3 − as an agent of acidification increases dramatically during snowmelt when conditions are most toxic to fish. The consequence of not addressing N in formulating acidification recovery strategies for the Adirondacks includes the likelihood that we will overestimate the response of surface water to the mandated sulfur emissions reductions.
    Materialart: Digitale Medien
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  • 5
    Digitale Medien
    Digitale Medien
    Springer
    Water, air & soil pollution 95 (1997), S. 313-336 
    ISSN: 1573-2932
    Schlagwort(e): nitrogen ; acidification ; Adirondack Mountains ; atmospheric deposition
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Energietechnik
    Notizen: Abstract Assessments of the aquatic effects of acidic deposition have focused on sulfur, as have recent efforts to control the emissions of acidifying compounds. Nitrogen dynamics were excluded from most acidic deposition modeling studies because it was believed that terrestrial ecosystems strongly retain N and because modeling N is a more formidable task than modeling S due to the influence of complex biological processes on N cycling. Re-examination of available data for the Adirondack Mountains of New York suggests that N deposition may be contributing to both chronic and episodic acidification of freshwaters to a greater extent than is generally believed. Previous research concluded that N has played a limited role in acidification processes in these lakes, based on regional averages of chronic chemistry. However, it is now known that historic acidification responses have been spatially variable within the Adirondack Mountains and that the declines in lakewater pH have been less than previously believed. Lakewater NO3 - concentrations are commonly in the range of 5 to 25 μeq L-1 on a chronic basis in portions of the Adirondack region that have experienced significant chronic acidification. These NO3 - concentrations correspond in magnitude to inferred historical acidification. Furthermore, the relative importance of NO3 - as an agent of acidification increases dramatically during snowmelt when conditions are most toxic to fish. The consequence of not addressing N in formulating acidification recovery strategies for the Adirondacks includes the likelihood that we will overestimate the response of surface water to the mandated sulfur emissions reductions.
    Materialart: Digitale Medien
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  • 6
    Digitale Medien
    Digitale Medien
    Springer
    Environmental monitoring and assessment 28 (1993), S. 277-294 
    ISSN: 1573-2959
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Energietechnik
    Notizen: Abstract A probability-based sample of 48 of the 152 lakes in the Sawtooth Wilderness, Idaho was conducted in summer 1988. Results from this sample were compared to the Environmental Protection Agency's 1985 probability survey of lakes throughout the western United States, which included 17 lakes in the Sawtooth Wilderness. Although methods differed in several respects, including year, season, sampling location within the lakes, holding times, and sample size, general characterization of lake chemistry for the population of lakes in the wilderness based on the two surveys was very similar. The results indicate that general lake characterization in difficult-to-access wilderness areas of the West can be achieved with a modest investment in resources with the use of volunteers. However, accurate measurement of some non-conservative and low-level analytes such as NO 3 − ,NH 4 + , total P, and aluminiun in the lakes probably requires more rigorous attention to sampling protocols and holding times. A two-stage sampling strategy employing extensive use of conductivity on a large number of lakes and intensive detailed chemical characterization on a smaller number of lakes offers an alternative design for describing large populations of wilderness lakes. The relatively high concentrations of fluoride and sulfate in many of the study lakes reflect the weathering of minerals not usually identified on geologic maps. These natural sources of acid anions violate the assumptions in commonly employed empirical models of acidification.
    Materialart: Digitale Medien
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  • 7
    ISSN: 1573-2932
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Energietechnik
    Notizen: Abstract A survey of 1592 lakes ( 〉4 ha and ≤ 2,000 ha) was conducted in Fall, 1984. The study area was three regions of the eastern United States (Northeast, Upper Midwest, and Southeast) expected to contain the most lakes with acid neutralizing capacity (ANC) ≤400 μeq/L. The design of the survey provides statistically reliable estimates of the number, location and chemical characteristics of lakes in the study area. Frequency distribution statistics are presented for pH, ANC, sulfate and organic anion. The highest percentages and numbers of acidic lakes occurred in Florida, the Adirondaks, and the Upper Peninsula of Michigan. The highest percentages and numbers of lakes with high sulfate concentrations occurred in the Poconos/Catskills, Southern New England and Florida. The highest percentages and numbers of lakes with high organic anion concentrations occurred in Northeastern Minnesota, the Upper Great Lakes Area and Florida. The percentage of acidic lakes by sulfate concentration class revealed no discernable pattern across subregions. In contrast, the acidic lakes occur with the highest frequency in the lowest organic anion concentration class. The complex distribution of low ANC lakes cannot be explained simply by sulfate concentrations or organic acids.
    Materialart: Digitale Medien
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  • 8
    Digitale Medien
    Digitale Medien
    Springer
    Environmental monitoring and assessment 12 (1989), S. 3-21 
    ISSN: 1573-2959
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Energietechnik
    Notizen: Abstract A synoptic survey of 719 lakes representing an estimated 10,393 lakes in mountainous areas of the western United States was conducted in autumn 1985. Nearly two-thirds of the study lakes were located in wilderness areas or national parks and were sampled by ground access. The results of a comparability study of 45 wilderness lakes accessed by helicopter and ground crews indicated that the data were generally indistinguishable, making it possible to use data from lakes sampled by ground crews without modification. Wilderness lakes had lower acid neutralizing capacity (ANC), base cations, sulfate, and dissolved organic carbon than nonwilderness lakes throughout the West. The highest estimated number (849) and percentage (42.1) of low ANC (≤50 μeq L-1) wilderness lakes were located in California; the lowest number (66) was located in the Southern Rockies. The Sierra Nevada contained an estimated 808 low ANC lakes, representing the largest subpopulation of low ANC lakes associated with an individual mountain range in the West. Wilderness lakes in selected geographic areas of the Rocky Mountains generally contained higher concentrations of major ions than lakes in the far West and the concentrations generally increased from the Northern to the Southern Rockies. Comparison of wilderness lakes in the West with lakes in the Adirondack Park, New York, and the Boundary Waters Canoe Area/Voyagers National Park in Northeastern Minnesota showed that western lakes are highly sensitive resources that currently exhibit little evidence of anthropogenic acidification. Although wilderness lakes do not exhibit symptoms of chronic acidification, short-term depression of pH and ANC from snowmelt and thunderstorms occur and episodic acidification influenced by anthropogenic sources cannot be discounted on the basis of this survey.
    Materialart: Digitale Medien
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