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  • Articles  (5)
  • Chemical Engineering
  • Fisheries
  • sediments
  • 2000-2004  (5)
  • Geosciences  (5)
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  • 1
    Electronic Resource
    Electronic Resource
    The role of biogeochemical cycling for the formation and preservation of varved sediments in Soppensee (Switzerland) (2000)
    Springer
    Journal of paleolimnology 24 (2000), S. 277-291 
    Details
    ISSN: 1573-0417
    Keywords: varves ; anoxia ; sediments ; Soppensee ; carbon cycle ; oxygen cycle
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract We analyzed seasonally aggregated observations of temperature, conductivity, dissolved oxygen and dissolved inorganic carbon from Soppensee (District of Lucerne, Switzerland) for the yrs 1980 to 1993. Holomictic Soppensee is characterized by a strong summer stratification with a thin epilimnion separated from an anoxic hypolimnion by a strong pycnocline formed by thermal and chemical gradients. A vertical one-dimensional model was developed to simulate the observed seasonal cycles of carbon and oxygen. The processes of net community production, mineralization of organic matter, precipitation and dissolution of calcite, gas exchange, in- and outflow, sedimentation and vertical eddy diffusion are included. According to the model, the annual net community production is estimated to about 110 g C m-2 yr-1 and the annual net primary production to about 330 to 440 g C m-2 yr-1, which is a typical value for eutrophic lakes. A mass balance of the carbon cycle indicates that most of the inflow comes from groundwater which is super-saturated with respect to atmospheric CO2. Therefore the surface waters exhibit a large capacity for calcite precipitation. The results of the model are used to constrain the conditions that favor the formation of varved sediments in Soppensee during thousands of yrs. Model calculations show that the deep waters would still turn anoxic even if the sedimentation rate of organic matter were decreased to 25%. Several physical factors such as biogenic stabilization of the deep waters due to calcite dissolution and low input of wind energy are responsible for the long term anoxia in Soppensee.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008195604287
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  • 2
    Electronic Resource
    Electronic Resource
    Geological and Historical Investigation of the 1650 Mt. Columbo (Thera Island) Eruption and Tsunami, Aegean Sea, Greece (2000)
    Springer
    Natural hazards 21 (2000), S. 83-96 
    Details
    ISSN: 1573-0840
    Keywords: eruption ; tsunami ; sediments ; magnitude assessment ; Thera ; Greece
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract This paper reviews geological andhistorical evidence for the eruption and tsunamireported to have occurred in 1650 in the areaof Mt. Columbo, Thera Island, Greece. The tsunami isbelieved to have been generated as a consequence ofthe eruption of Mt. Columbo 6.5 km NE of Thera Island.Historical documents state that the tsunami flooded upto 2 miles inland and destroyed many engineeredstructures. We present lithostratigraphic evidencefrom one abandoned trench and two trench excavationsclose to sea level in the villages of Kamari andPerissa respectively, which lie well within thereported inundation zone of the tsunami. The resultspresented show that no marine- (tsunami) depositedsediments are preserved at these locations.Alternative hypotheses of discontinuous sedimentdeposition and over estimation of the event magnitudeare considered to explain the observations presentedhere. The data may have important implications for thedevelopment of hazard zone maps, risk assessment,vulnerability reduction and for emergency managementofficials.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008178100633
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  • 3
    Electronic Resource
    Electronic Resource
    Sedimentary Trace Elements as Proxies to Depositional Changes Induced by a Holocene Fresh-Brackish Water Transition (2000)
    Springer
    Aquatic geochemistry 6 (2000), S. 325-345 
    Details
    ISSN: 1573-1421
    Keywords: Baltic Sea ; euxinic ; Holocene ; pyrite ; trace elements ; redox conditions ; sediments
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract A halocline developed in the GotlandDeep, Baltic Sea, at c. 8.0 14C ky BP, as theresult of a transition from fresh to brackish water.The sediment-water interface changed from oxic topredominantly anoxic, depositional conditions wereperiodically euxinic and pyrite formation wasextensive. This environmental change led topyritization of the upper part of earlier depositedsediments. This study discusses how the distributionof trace elements (As, Ba, Cd, Cu, Co, Mo, Mn, Ni, Pb,U, Zn and V) were affected by the changing redoxconditions, productivity and salinity. The reducingconditions led to pyritization of Cu, Co, Ni, Cd, Mo,Mn and As. Lead and Zn concentrations are very low inpyrite, in agreement with their coordination tosulfide being tetrahedral. Certain elements areenriched in those sediments deposited under euxinicconditions. This enrichment was caused by scavengingof elements dissolved in the water column and isrestricted to elements that have a comparably longresidence time in the Baltic Sea. Molybdenum appearsto be the most unambigious proxy for euxinicconditions, whereas enrichment of U also requiresbrackish water in the productive zone. In the brackishenvironment, enrichment of Ba and V are linked to thecycling of organic carbon. Manganese and As are theonly elements that have been significantly remobiliseddue to the downward moving pyritization front.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009680714930
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  • 4
    Electronic Resource
    Electronic Resource
    Effects of the emergent macrophyte Juncus effusus L. on the chemical composition of interstitial water and bacterial productivity (2000)
    Springer
    Biogeochemistry 48 (2000), S. 307-322 
    Details
    ISSN: 1573-515X
    Keywords: aquatic plants ; dissolved organic carbon ; nutrient cycling ; phosphorus ; sediments ; wetlands
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Release of oxygen from the roots ofaquatic macrophytes into anaerobic sediments canaffect the quantity of interstitial dissolved organicmatter and nutrients that are available to bacteria. Nutrient and dissolved organic carbon (DOC)concentrations were compared between subsurface(interstitial) waters of unvegetated sediments andsediments among stands of the emergent herbaceousmacrophyte Juncus effusus L. in a lotic wetlandecosystem. Concentrations of inorganic nitrogen(NH4 +, NO3 -, and NO2 -)were greater from sediments of the unvegetatedcompared to the vegetated zone. DOC concentrations ofinterstitial waters were greater in sediments of theunvegetated zone both in the winter and springcompared to those from the vegetated zone. AlthoughDOC concentrations in hydrosoils collected from bothzones increased from winter to spring, bacterialproductivity per mg DOC in spring decreased comparedto winter. Greater initial bacterial productivityoccurred on DOM collected from the vegetated comparedto the unvegetated zone in winter samples (days 1 and4), with increased bacterial productivity on samplescollected from the unvegetated zone at the end of thestudy (day 20). Bacterial productivity wassignificantly greater on all sampling days on DOM fromvegetated samples compared to unvegetated samples. In nutrient enrichment experiments, bacterialproductivity was significantly increased (p 〈 0.05)with phosphorus but not nitrogen only amendments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006208213821
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  • 5
    Electronic Resource
    Electronic Resource
    Methane turnover in exposed sediments of an Amazon floodplain lake (2000)
    Springer
    Biogeochemistry 50 (2000), S. 195-206 
    Details
    ISSN: 1573-515X
    Keywords: methane ; Amazon ; floodplain ; sediments
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract In the Amazon floodplain large areas of unvegetatedlake sediments are exposed to air during low water. Imeasured methane fluxes from exposed sediments of anAmazonian floodplain lake and assessed the regulatingfactors. Methane emission decreased from values between 10 and 40 μmol CH4 mminus 2 hminus 1to zero when the sediments were exposed to air. Meanfluxes were about 3.7 μmol CH4mminus 2 hminus 1. Fluxes were low compared tomeasurements taken from flooded habitats makingexposed lake sediments a negligible source ofatmospheric CH4. This was mainly due to the lackof ebullition which governs methane flux in theflooded phase. Methane oxidation at the sedimentsurface consumed up to 75% of the methane enteringthe oxidised zone. Compared with CO2 emissionmethane turnover was of minor importance for thecarbon budget of the sediments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006326018597
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