Impact of single and binary mixtures of phenanthrene and N-PAHs on microbial utilization of 14C-glucose in soil

Microbes are susceptible to contaminant effects, and high concentration of chemicals in soil can impact on microbial growth, density, viability and development. The impact of single and binary mixtures of phenanthrene and its nitrogen-containing polycyclic aromatic hydrocarbon analogues (N-PAHs) on microbial metabolism of 14C-glucose in soil was measured over a 90 d soil-contact time. Impacts were assessed by measuring the rates and mean overall extents of mineralisation (%), as well as the incorporation of 14C-glucose into the microbial biomass. The result revealed that the extents of 14C-glucose mineralisation were consistently greater in N-PAH amended soils than the control and phenanthrene soils with increased incubations. This indicates a trend of increasing diversion of C from biosynthesis to maintenance requirement by soil microorganisms. Furthermore, biomass uptake in the amended soils showed reduced substrate utilization (fixed-kEC), suggesting that N-PAHs decreased the amount of substrate-C that was incorporated into the microbial biomass. This however, signifies that N-PAHs imposes oxidative stress on soil microbial community.