Atmospheric deposition and vegetable uptake of polycyclic aromatic hydrocarbons (PAHs) based on experimental and computational simulations

Abstract

Experimental and computational simulations are conducted to assess the atmospheric gaseous deposition of polycyclic aromatic hydrocarbons (PAHs) and their uptake by four leafy vegetables (spinach, Chinese cabbage, Shanghai green cabbage, and romaine) during their growth in a greenhouse located in Shanghai. Sixteen individual PAHs on the US EPA priority list were measured in the aerials and roots of vegetables, air (both gas- and particle-phase), settled dust, and soil samples. Results showed that 2–3 ring PAHs were similarly dominant in the vegetable leaves, roots and airborne gas phase. However, 4–6 ring PAHs were dominant in the soils, dust, and airborne particle phase. Results also showed that the PAH concentrations in the vegetables were highest during the middle of the growth period. Both phenanthrene and anthracene in the vegetables had a significant positive correlation with chlorophyll-a and chlorophyll-b, indicating that the growth process influenced PAH concentrations in the vegetables. Furthermore, increasing dust-fall doses promoted PAH accumulation in Shanghai green cabbage and romaine, but inhibited PAH uptake in spinach and Chinese cabbage. Analyses using multivariate regressions and physical models found that gas-phase PAH absorption and soil absorption contributed to 90.6% and 9.4% of total PAH vegetable uptake, respectively. Although PAHs in the air were the dominant contributor to the total uptake, 13.2% of gas-phase PAHs resulted from soil volatilization. Atmospheric dust fall contributed to PAH uptake indirectly by increasing soil PAH concentrations. In addition, PAH uptake by vegetables via the air-shoot pathway displayed higher toxicity than the other pathways. This study provides a quantitative assessment of the pathways through which atmospheric PAHs lead to PAH contamination in a sample of commonly eaten leafy vegetables.