Mass Transfer Limitation of Biotransformation: Quantifying Bioavailabiity

• Published in: Environmental science & technology Vol. 31; no. 1; p. 248
• Main Authors: Bosma, Tom NP, Middeldorp, Peter JM, Schraa, Gosse, Zehnder, Alexander JB
• Format: Journal Article
• Language: English
• Published: 01.01.1997
• ISSN: 0013-936X

The reduced bioavailability of pollutants in soil is caused by the slow mass transfer to the degrading microorganisms, with pollutants becoming unavailable when the rate of mass transfer is zero. A unifying concept to understand and quantify the limitation of biodegradation by mass transfer kinetics is presented on the basis of the microscopic distribution of bacteria and contaminants in natural porous media, and a simple quantitative expression for the threshold concentration resulting from the microbial maintenance requirements is derived. All underlying numerical expressions are presented and discussed. The approach is illustrated by application to published data on alpha -hexachlorocyclohexane biotransformation in soil slurries and to 3-chlorodibenzofuran biotransformation in percolation columns. It is shown that a reduced bioavailability causes bacteria to live a famine existence at polluted sites, even at high pollutant concentrations.