Bioaccessibility of 14C-phenanthrene from root amended contaminated soil

Plants and their roots, in particular, may be important in stimulating microbial degradation of organic contaminants in soil. It is also known that bioaccessibility is important in controlling the biodegradation of organic contaminants in soil. This study aimed to assess the impact of plant roots on the biodegradation and bioaccessibility of 14C-phenanthrene in soil in the presence of plant root biomass. To do this, changes in the 14C-phenanthrene mineralisable and hydroxypropyl-β-cyclodextrin (HPCD) extractable fractions were evaluated. After 1, 25, 50 and 100 days of PAH-soil contact time, 12/14C-phenanthrene-spiked soil was amended with roots from two grasses and one legume. Mineralisation and HPCD extractability of 14C-phenanthrene were measured after 1, 21 and 42 days PAH-root-soil contact time. Findings revealed that mineralisation of 14C-phenanthrene was enhanced following the amendment with plant root biomass regardless their species or form, especially in the soils that been aged for ≥50 days soil-PAH contact time. Overall, this study showed that greater levels of phenanthrene biodegradation may be achieved by incorporating root biomass into the contaminated soil, particularly where indigenous catabolic activity has developed. The findings reported here contribute to the understanding of how plant root biomass may impact on contaminant bioaccessibility and stimulate the more effective indigenous biodegradation of hydrocarbons in soil. [Display omitted] •Plant roots can modify the bioaccessibility of phenanthrene in soil.•Time is key on the effect that roots will have on bioaccessibility of phenanthrene.•Roots can limit the bioaccessibility of phenanthrene in soil.