Toxic effects of cadmium deposition on pakchoi (Brassica rapa var. chinensis (L.) Kitamura) seedlings exposed to simulated atmospheric fine particulate matter

This study investigated the toxic effects of different concentrations and gradients of cadmium (Cd) (0, 150, 300, and 500 μg/m³) in fine particulate matter following deposition on pakchoi (Brassica rapa var. chinensis (L.) Kitamura). After treatment, the growth status, relative chlorophyll content (SPAD), antioxidant enzyme activity, malondialdehyde (MDA) content, and heavy metal enrichment in pakchoi seedlings were measured. Results showed that mild, heavy, and severe concentrations of Cd deposition in atmospheric fine particulate matter initially promoted stem, root, and leaf length, and fresh weight of pakchoi on day 7. On day 19, compared with the control, the severe pollution conditions significantly reduced stem and leaf length, root length, and fresh weight of pakchoi by 8.05%, 13.82%, and 9.80%, respectively. During the whole experimental period, severe pollution significantly reduced the SPAD of pakchoi. On day 19, compared with the control, the SPAD of pakchoi under severe pollution conditions decreased significantly by 17.54%. Mild, heavy, and severe concentrations of Cd in fine particulate matter significantly increased MDA content and peroxidase (POD) activity. Furthermore, Cd accumulation in the aboveground parts of pakchoi increased with the increase in Cd concentration, and Cd accumulation was the highest under severe pollution conditions. These results indicated that Cd deposition in fine particulate matter significantly affects growth, SPAD, antioxidant enzymes, and Cd accumulation in pakchoi.