Modeling of net uptake of polycyclic aromatic hydrocarbons by terrestrial plant biomonitors from atmosphere

The interaction between vegetation cover and airborne polycyclic aromatic hydrocarbons (PAHs) determines employment of plants as biomonitoring tool for ecological restoration. In this study, the mechanisms of PAHs uptake by a biomonitor plant (M. paniculata) were studied based on a material balance model. The estimated plant-air (K_PA) and particle-gas (K_P) partition coefficients justified the dynamics of PAHs partitioning into both plant and particle phases. Direct gaseous exchange (∼66% of total) between leaf and air, manifesting high air-leaf mass transfer coefficient (k_AL) of 85 cm h^-1 (average) and foliage fugacity capacity of 0.045-1.27 × 10⁴ mol m^-3Pa^-1, played a key role in accumulation of PAHs. PAHs adsorption on foliar particulate matter (PM) with subsequent movement into leaf cuticle and inner mesophyll tissue appeared to be another differential uptake pathway (contributing ∼30% of total). Despite efficient root accumulation (with high root concentration factor (RCF): 0.72-1.12), poor acropetal translocation modulated by root lipids resulted in lower distribution (∼4%) of PAHs in foliar tissues. Thus, validation of the material balance model inferred inner leaf tissue absorption and adsorption on foliar PM followed by translocation to leaf tissues are the responsible routes of PAHs uptake by a plant biomonitor.