Automobile exhaust particles retention capacity assessment of two common garden plants in different seasons in the Yangtze River Delta using open-top chambers

Abstract

Particulate matter (PM) pollution is a serious environmental problem in most of the cities in the Yangtze River Delta region. Plants can effectively filter ambient air by adsorbing PM. However, only a few studies have paid attention to the dynamic changes and seasonal differences in particle retention capacities of plants under long-term pollution. In this study, we investigated the dynamic changes in particle retention capabilities of the evergreen, broad-leaved, greening plants-Euonymus japonicus var. aurea-marginatus and Pittosporum tobira-in spring and summer. We employed an open-top chamber to simulate the severity of the tail gas pollution. The results showed that, both the plants reached a saturated state in 18-21 days, under continuous exposure to pollution (daily concentration of PM_2.5: 214.64 ± 321.33 μg·cm^-3). This was 6-8 days longer than that in the field experiments. In spring, the maximum retention of total particulate matter per unit leaf area of E. japonicus var. aurea-marginatus and P. tobira was 188.47 ± 3.72 μg cm^-2 (18 days) and 67.63 ± 2.86 μg cm^-2 (21 days), respectively. In summer, E. japonicus var. aurea-marginatus and P. tobira reached the maximum retention of the particle on the 21st day, with a net increase of 94.10 ± 3.77 μg cm^-2 and 27.81 ± 3.57 μg cm^-2, respectively. Irrespective of season, the particle retention capacity of E. japonicus var. aurea-marginatus was higher than that of P. tobira, and it showed a better effect on reducing the concentration of fine particles in the atmosphere. The particle retention of the two plants was higher in spring than that in summer. E. japonicus var. aurea-marginatus displayed a significant difference in particle retention between the seasons, while P. tobira did not show much difference. These results will provide a foundation for future studies on the dynamic changes and mechanism of particle retention in plants and management practices by employing plants for particle retention in severely polluted areas.

Keywords: Dynamic change in particle retention; Evergreen broad-leaved greening plants; Seasonal differences; The saturation time of particle retention; Yangtze river delta.