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  • 1
    Digitale Medien
    Digitale Medien
    Springer
    Hydrobiologia 317 (1996), S. 31-40 
    ISSN: 1573-5117
    Schlagwort(e): benthic organism ; diffusion ; mixing ; sediments ; tritium ; transport
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Increased inputs of nutrients into the waters of Lake Okeechobee has raised concern that the lake is becoming hypereutrophic. One aspect in understanding the overall cycling and dynamics of the nutrients in the system is the effect of benthic organisms on solute transport. Various diffusional models have been used to approximate the effect of benthic organisms on solute transport within sediments using diffusion coefficient values which represent the pooled contributions of molecular diffusion (D s ) and enhanced solute mixing due to macrobenthos activity (D i ). The objective of this study was to investigate the impact of benthic activity on solute transport by measuringD s (i.e., no benthic activity) and an apparent-dispersion or mixing coefficientD m (i.e., with benthic activity) for the four major sediment types of Lake Okeechobee, Florida using a reservoir technique. This method involved monitoring the depletion of a conservative tracer (tritiated water) from the overlying water (reservoir) resulting from transport into sediments using disturbed sediments repacked in cores (3.2 cm diam.) and undisturbed cores (3.2 to 12 cm diam.) obtained from the lake. Additional estimates ofD m andD s were also obtained by measuring tracer concentration profiles in the sediment cores at the end of a specified diffusion period. Molecular diffusion coefficients (D s ) measured forrepacked cores of sand, littoral, mud and peat sediments ranged from 0.90 to 1.29 cm2 d−1, and estimates ofD s were slightly higher in undisturbed cores without benthic organisms.D m values for undisturbed cores of mud, sand and littoral sediments having macrobenthic populations ranged from 2.09 to 24.78 cm2 d−1; values that were 1.6 to 15 times higher than those in sediments without benthic activity. Undisturbed cores of varying diameter from mud sediments had similar estimates ofD m for tritium; however, the undisturbed cores with larger diameters from littoral sediments yielded larger estimates ofD m , reflecting the heterogeneity of benthic population densities and activity. Therefore,D s estimates may not adequately represent transport processes for mud, sand and littoral sediments of Lake Okeechobee; hence careful consideration should be given to the role of benthic organisms in the overall transport of solutes across the sediment-water interface.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    ISSN: 1573-5036
    Schlagwort(e): cadmium bioaccumulation ; Linum usitatissimum L. ; soil type ; Triticum turgidum var. durum L.
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract Accumulation of cadmium (Cd) in crop plants is of great concern due to the potential for food chain contamination through the soil-root interface. Although Cd uptake varies considerably with plant species, the processes which determine the accumulation of Cd in plant tissues are affected by soil factors. The influence of soil type on Cd uptake by durum wheat (Triticum turgidum var. durum L.) and flax (Linum usitatissimum L.) was studied in a pot experiment under environmentally controlled growth chamber conditions. Four cultivars/lines of durum wheat (Kyle, Sceptre, DT 627, and DT 637) and three cultivars/lines of flax (Flanders, AC Emerson, and YSED 2) were grown in two Saskatchewan soils: an Orthic Gray Luvisol (low background Cd concentration; total/ABDTPA extractable Cd: 0.12/0.03 mg kg-1, respectively) and a Dark Brown Chernozem (relatively high background Cd concentration; total/ABDTPA Cd: 0.34/0.17 mg kg-1 respectively). Plant roots, stems, newly developed heads, and grain/seeds were analyzed for Cd concentration at three stages of plant growth: two and seven weeks after germination, and at plant maturity. The results showed that Cd bioaccumulation and distribution within the plants were strongly affected by both soil type and plant cultivar/line. The Cd concentration in roots leaves and stems varied at different stages of plant growth. However, all cultivars of both plant species grown in the Chernozemic soil accumulated more Cd in grain/seeds than plants grown in the Orthic Gray Luvisol soil. The different Cd accumulation pattern also corresponded to the levels of ABDTPA extractable and metal-organic complex bound soil Cd found in both soils. Large differences were found in grain Cd among the durum wheat cultivars grown in the same soil type, suggesting the importance of rhizosphere processes in Cd bioaccumulation and/or Cd transport processes within the plant. Distribution of Cd in parts of mature plants showed that durum grain contained up to 21 and 36% of the total amount of Cd taken up by the plants for the Orthic Gray Luvisol and Chernozemic soils, respectively. These results indicate the importance of studying Cd speciation, bioaccumulation and cycling in the environment for the management of agricultural soils and crops.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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