BIOAVAILABILITY OF ORGANIC CONTAMINANTS DURING TRANSPORT: IMPACT OF INITIAL SOIL ENVIRONMENT CONDITIONS | ||||
| Journal of Soil Sciences and Agricultural Engineering | ||||
| Article 1, Volume 29, Issue 4, April 2004, Page 2137-2155 PDF (981.65 K) | ||||
| Document Type: Original Article | ||||
| DOI: 10.21608/jssae.2004.241899 | ||||
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| Author | ||||
| H. M. Gaber | ||||
| Soli and Water Sciences Department, Alexandria University, Alexandria 21545, Egypt | ||||
| Abstract | ||||
| Bioavallabilily of organic contaminants may be ,0nfO\.Jnded by several processes operating simultaneously in soil subsurtace. Model preoirtions 01 tare aod transport o( organic contaminants in soils and groundwaler are sensitive to assumptions conceminq rates of microbial degradation. In the current study, the herbicide 2,4-0 was chosen as a model compound, since i1 is an aromatic chlorinated molecule, whIch Is strvctu~lIy similar 10 numerous other compoundS of co/rent interest The objective was to illustrale the impact of the inltlat soil environment conditions on 2,4·0 bklavailabHity under batch and column transport conditions. These condiUons tociude: moisture content, initial concentratlon, stlrroo reactor versus stationary batch, biOmass, a&fObk versus anaerobic conoiuons. and pore water veiocuv (I.e., residence time), Modeling 2,4-0 degradatlon with first-order kinetics yieided poor predictions 01 de1)l1!datJon behavior and half, life In SOIl. Accounting for bloavailabifity through the use 01 lha modified first-order and 1091slic models presented more accurate predicUons of both the rate and e)((enl of 2,4·0 degradation. In the transport erwirorvnent, It Is no! dear whether microbial biomass concentration responslble tot 2.4-0 degradallon rernaln constant under the tasted range 01 pore water velocities, Apparent ~radaUon rate consiants rnav decrease with increasing pore water velocity due to d€0e8sas in residence time per unit length (thoughl of as IOC<J/ opportunity lime). In summary, the effects 01 residence time on contamlnanr bloavailability may be confounded by several processes operating simultane<lusfy. These findings emphasize the difficulty irI accurately predicting the degradation and transport of organic contamtnants In SO~5 across a range o( flow conditions using independenUy determined rate parameters. | ||||
| Keywords | ||||
| Biodegradation; residence time; rate-limlted; 2; 4·0; kinetics | ||||
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