Impact of activated charcoal on the mineralisation of 14C-phenanthrene in soils

The development of phenanthrene catabolism in four soils amended with varying concentrations of activated charcoal (AC) (0%, 0.1%, 1% and 5%), a type of black carbon, was investigated. Mineralisation of 14C-phenanthrene was monitored after 1, 25, 50 and 100 d soil-PAH contact time; lag phases, rates and extents of mineralisation of the 14C-phenanthrene to 14CO2 were determined. At concentrations >0.1% AC rates and extents of mineralisation were reduced by more than 99%. This revealed that the presence of >0.1% AC in soils may substantially diminish the rate at which the catabolic activity of indigenous soil microflora develops in contaminated soil. Soil C, which had the highest organic carbon (OC) content, consistently exhibited the highest extents of degradation. It is suggested that, in accordance with other researchers, OC may have blocked available phenanthrene sorption sites. This enhanced phenanthrene availability ultimately facilitated a greater level of catabolic activity within this soil. Such results reflect the complex nature of interactions between soil, biota and contaminants and their influence on the degradation of contaminants in the environment.