Detection and identification of substituted phenols as intermediates of concurrent bacterial degradation of the phenoxy herbicides MCPP and 2,4-D

The concurrent bacterial degradation of 2-(2-methyl-4-chlorophenoxy)propionic acid and 2,4-dichlorophenoxyacetic acid was studied using a stirred tank reactor and a bacterial culture which had been originally derived by enrichment with MCPP. High pressure liquid chromatographic methodology was used to measure both herbicides and it also resolved the corresponding phenols as intermediates, i.e., 2-methyl-4-chlorophenol and 2,4-dichlorophenol. Gas chromatography-mass spectrometry was used to verify the intermediates. UV scans of spent cultures showed that the wave-length of maximum absorption shifted from 282 nm to 280 nm toward the end of incubation, but the characteristic peaks of maximum absorption of these compounds could not be used resolved because of the overlap.     

Long-term changes of bacterial abundance,hydrocarbon concentration and toxicity during a biostimulation treatment of oil-amended organic and mineral sub-Antarctic soils

A field study was initiated in December 2000 in two selected sub-Antarctic soils (Kerguelen Archipelago) with the objective of determining the long-term effects of a fertilizer addition on the degradation rate and the toxicity of oil residues under severe sub-Antarctic conditions. Two soils were selected. The first site was an organic soil supporting an abundant vegetal cover while the second one was a mineral soil, free from vegetation. Both soils were located in the vicinity of the permanent station of Port-aux-Français (69°42′E?49°19′S). Two series of five experimental plots (0.75 × 0.7 5 m) were settled firmly into each of the studied soils. Each plot received 500 ml of diesel fuel or Arabian light crude oil and some of them were treated with a bioremediation agent: the slow release fertilizer Inipol EAP-22^® (Elf Atochem). All plots were sampled on a regular basis over a 4-year period. The microbial response was improved by bioremediation treatments but fertilizer addition had a greater impact on the mineral soil when compared to the organic one. The rate of degradation was significantly improved by bioremediation treatments. However, even after 4 years, the toxicity of oiled soils as determined by Microtox solid phase tests showed a persistent response in spite of an apparent significant degradation of alkanes and aromatics. Despite the very small amount of contaminant used in this experiment, 4 years of bioremediation was not sufficient to obtain a complete return to pristine conditions