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  • 1
    ISSN: 1573-0417
    Keywords: acidification ; diatoms ; sediment chemistry ; magnetic stratigraphy ; soot ; paleolimnology ; Wales
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract A variety of paleolimnological techniques, coupled with historical data on land-use and fisheries, are used to evaluate the magnitude, timing, and causes of acidification of Llyn Hir, a moorland lake in central Wales. pH reconstruction based on diatom analysis suggests a gradual decline in lakewater pH beginning ca. 1870 and intensifying in the mid-1930's, with a total decline of 1.1 pH units between 1870 and 1984. This pH decline correlates with increased sedimentary concentrations of carbonaceous particles, trace metals, and magnetic minerals, which indicate the local deposition of atmospherically transported products of fossil-fuel combustion. Pollen data and the historical record show no significant alterations in land-use or catchment vegetation, indicating that acidification of Llyn Hir is a result of the increased deposition of atmospheric pollutants, not of land-use and vegetation change.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1573-5117
    Keywords: 210Pb and 226Ra measurements ; sediments
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Lead-210 and radium-226 measurements by direct gamma assay can now provide a record of changing concentrations in lake sediments sufficiently reliable and precise to form a suitable basis for age/depth and dry-sedimentation-rate calculations. There are additional benefits in terms of non destructive sample preparation and simultaneous assay for other environmentally significant gamma-emitting radioisotopes (e.g. 137Cs and 241Am). Results from L. Fleet, S. W. Scotland illustrate the value of this approach especially in lakes with disturbed catchments where variable input of supported 210Pb has occurred.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1573-2932
    Keywords: pigments ; diatoms ; cladocera ; ostracods ; chironomids ; chrysophytes ; sediments ; Late Pleistocene ; Holocene ; crater lake ; Italy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract This paper reports the results of biological analyses (pigments, diatoms, chrysophyte cysts, cladocerans, chironomids and ostracods) of a ca. 14 m-long sediment core recovered from Lake Albano (Central Italy) in the course of the EU-funded project PALICLAS (PALaeoenvironmental analysis of Italian Crater Lake and Adriatic Sediments). A reconstruction of the environmental evolution and ecosystem response of Lake Albano during the last ca. 30 kyr was possible. Additional information on lake level oscillation is obtained from benthic and planktonic palaeocommunities. Several oscillations in the productivity and the level of the lake were detected in the oldest sediment layers (from ca. 30 kyr BP to ca. 17 kyr BP), followed by a long (ca. 5 kyr BP) period of low productivity in which cold, holomictic conditions prevailed. A period of high biological activity and, probably, meromictic conditions during the early-mid Holocene was detected. A clear impact of human activities in the catchment was found at ca. 4 kyr BP in the form of increased erosion, associated with a decline in the abundance of biological remains. Further signs of human impact on the lake ecosystem are recorded during the Roman period. Although large-scale environmental changes (e.g. regional climate changes) caused many of the observed biological changes, human activities were important during the mid-late Holocene.
    Type of Medium: Electronic Resource
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