Effect of Environmental Factors on the Degradation of 2,6-Dichlorophenol in Soil

Chlorinated phenols (CP) are frequently found as harmful soil contaminants. Depending on the environment, CP may persist for extended periods of time. The influence of environmental factors on the degradation of 2,6-dichlorophenol (2,6-DCP) in unsaturated soil was examined using Ralstonia basilensis RK1 as inoculum for bioaugmentation. The disappearance of 2,6-DCP in soil microcosms was caused by bacterial mineralization. This was proved using U-¹⁴C-labeled 2,6-DCP. After 5 days of incubation, 61% of the initial activity was detected as ¹⁴CO₂, while only 20% of the radioactivity remained in the soil, and 2,6-DCP was not detected. The relative importance of individual factors and possible two-factor interactions was assessed using a fractional-factorial experimental design. The following individual factors were identified as important:  2,6-DCP concentration, temperature, inoculum size, and the presence of an additional substrate. The strongest factorial interaction was observed between bacterial inoculation and 2,6-DCP concentration. For practical reasons, the influence of oxygen, organic matter, and the age of the contamination were not included in the factorial design; however, these factors were analyzed separately and found to significantly affect the biodegradation of 2,6-DCP. The findings of this study are important for the design of bioremediation techniques as well as the prediction of natural attenuation.