Uptake pathway and accumulation of polycyclic aromatic hydrocarbons in spinach affected by warming in enclosed soil/water-air-plant microcosms

The partition of polycyclic aromatic hydrocarbons (PAHs) among water-soil-air is temperature-dependent. Thus, we hypothesized that climate warming will affect the accumulation and uptake pathway of PAHs in plants. To test this hypothesis, enclosed soil/water-air-plant microcosm experiments were conducted to investigate the impact of warming on the uptake and accumulation of four PAHs in spinach (Spinacia oleracea L.). The results showed that root uptake was the predominant pathway and its contribution increased with temperature due to the promoted acropetal translocation. Owing to the increase in freely dissolved concentrations of PAHs in soil pore water, the four PAH concentrations in roots increased by 60.8-111.5% when temperature elevated from 15/10 to 21/16 degrees C. A model was established to describe the relationship between bioconcentration factor of PAHs in root and temperature. Compared with 15/10 degrees C, the PAH concentrations in leaves at both 18/13 and 21/16 degrees C elevated due to the increase in PAH concentrations in air, while slightly decreased when temperature elevated from 18/13 to 21/16 degrees C because the PAH concentrations in air decreased, resulting from accelerated biodegradation of PAHs in topsoil. This study suggests that warming will generally enhance the PAH accumulation in plant, but the effect will differ among different plant tissues.