Bioavailability of hydrocarbons during microbial remediation of a sandy soil |
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Authors: | C Löser H Seidel P Hoffmann A Zehnsdorf |
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Institution: | UFZ Umweltforschungszentrum Leipzig-Halle GmbH, Sektion Sanierungsforschung, Leipzig, Germany. |
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Abstract: | The microbial degradation of hydrocarbons was studied in an artificially contaminated sandy soil, using a pilot-scale percolator
system. After a short lag period, an intensive degradation occurred, which diminished in time and completely stopped in the
end, despite large residual contaminations (residues of 56% diesel fuel, 20% n-hexadecane and 3.5% phenanthrene at the initial loadings of each 3000 mg/kg). The remaining pollutant content was influenced
by the kind of hydrocarbon but was nearly independent of its initial loading. According to a model-aided analysis of the carbon
dioxide production during remediation, the observed stagnation of degradation was caused by a limited bioavailability of the
pollutants. The degradation in the soil-free aqueous phase was more extensive than in the soil, which suggests that the limited
bioavailability in the soil can be attributed mainly to matrix-dependent rather than substrate-dependent influences. Generally,
fine particles and organic matter are mainly responsible for the adsorption of pollutants to the soil matrix. Our sandy soil
also bound hydrocarbons adsorptively although it contained neither silty material nor significant amounts of organic matter.
As shown by Brunauer Emmett Teller (BET) analysis, the soil particles were covered by micropores, which enlarged the soil
surface by a factor of 120 in comparison with the macroscopic surface area. The microporosity is the reason for the hydrocarbons
being more strongly adsorbed to the sandy soil than expected.
Received: 13 July 1998 / Received revision: 22 September 1998 / Accepted: 26 September 1998 |
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