Contribution of Atmospheric Fallout to the Soil–Root–Leaf Transfer of PAHs in Higher Plants

Wet deposition of atmospheric polycyclic aromatic hydrocarbons (PAHs) is considered an important source of these potentially toxic compounds in soils. In addition to affecting soil quality, they might be taken up by higher plants, potentially causing phytotoxicity or being accumulated in various organs. Plants are exposed to atmospheric PAHs via the aerial parts and via the soil-root system. The primary aim of this study was to present an experimental setup which can be properly used to quantify PAH accumulation investigating both potential pathways. Rocket (Eruca sativa Mill.) was selected as the model species. The test was conducted following the No. 227 OECD Vegetative Vigor Test. Plants were sprayed with the extract of particles generated during the operation of a diesel-powered vehicle simulating the air–aerial parts–root pathway, while the same extract was used to treat the soil simulating the soil–root–aerial parts pathway. In the soil–root–stem–leaf pathway, the total PAH concentration was 108 μg/kg in the soil, 143 μg/kg in the roots, 92.3 μg/kg in the stems, and 62.5 μg/kg in the leaves. Results showed that higher molecular weight PAHs were mostly accumulated in the roots, but their transfer to above-ground parts cannot be excluded. This study supports the importance of wet deposition in transferring atmospheric PAHs to soils.