Biodegradation of PAHs in soil: Influence of chemical structure, concentration and multiple amendment.

The influence of PAH chemical structure and concentration, added in either single (75 or 300 mg kg(-1)) or multiple (2 × 75, 2 × 150 or 4 × 75 mg kg(-1)) applications as single- or multiple-contaminant systems, on the development of PAH biodegradation in a pristine soil was investigated. Development in microbial catabolic ability was assessed at 0, 28, 56 and 84 d by monitoring (14)C-naphthalene, (14)C-phenanthrene and (14)C-pyrene mineralisation over 14 d in respirometric assays. The presence of other contaminants influenced the ability of the indigenous microflora to mineralise structurally different contaminants over time. (14)C-Naphthalene mineralisation was inhibited by the presence of other contaminants; whereas the presence of naphthalene significantly enhanced rates of mineralisation in multiple-contaminant systems containing (14)C-phenanthrene and (14)C-pyrene. Generally, increasing the number of contaminant applications has implications for catabolic activity of soil microbes. It is suggested the toxic nature of PAHs retarded mineralisation at increased contaminant concentrations.