Environmental fate of polycyclic aromatic hydrocarbons under different plant traits in urban soil as affected by nitrogen deposition

Nitrogen deposition and contamination with anthropogenic substances such as polycyclic aromatic hydrocarbons (PAHs) increasingly threaten ecosystems, in particular, urban systems. We planted different plant communities (Holcus lanatus, Lotus corniculatus, Picea abies, Calluna vulgaris) in N-deficient urban soil to test whether the divergent plant–soil systems differ in their ability to affect the fate of phenanthrene and pyrene in the soil, and whether the ability of the system to sequester external N would differ between the plant and soil systems. Importantly, the influence of the N input as affecting PAH dynamics under the plant communities was explored. The effects of plants on soil microbial biomass (PLFA) and microbial activity (basal respiration) were studied. Although plant type did not affect the dynamics of phenanthrene and pyrene in the soil, N addition had a positive effect on phenanthrene retention in each plant–soil treatment. The content of soil extractable phenanthrene decreased due to N addition especially in soils growing P. abies. This conifer also sequestered the added N to its shoots most efficiently suggesting restoration success of urban soils to be plant trait dependent.