Impacts of simulated atmospheric cadmium deposition on the physiological response and cadmium accumulation of Sedum plumbizincicola.

Atmospheric cadmium (Cd) deposition contributes to the accumulation of Cd in the soil-plant system. Sedum plumbizincicola is a Cd and Zn hyperaccumulator commonly used for the phytoremediation of Cd-contaminated soil. However, studies on the effects of atmospheric Cd deposition on the accumulation of Cd and physiological response in S. plumbizincicola are still limited. A Cd solution spraying pot experiment was conducted with S. plumbizincicola at three atmospheric Cd deposition concentrations (4, 8, and 12 mg/L). Each Cd concentration levels was divided into two groups, non-mulching (foliar-root uptake) and mulching (foliar uptake). The soil type used in the experiment was reddish clayey soil collected from a farmland. The results showed that compared with the non-mulching control, the fresh weight of S. plumbizincicola in non-mulching with high atmospheric Cd deposition (12 mg/L) increased by 11.35%. Compared with those in the control group, the malondialdehyde (MDA) content in the non-mulching and mulching S. plumbizincicola groups increased by 0.88-11.06 nmol/L and 0.96-1.32 nmol/L, respectively. Compared with those in the non-Cd-treated control group, the shoot Cd content in the mulching group significantly increased by 11.09-180.51 mg/kg. Under high Cd depositions, the Cd in S. plumbizincicola mainly originated from the air and was stored in the shoots (39.7-158.5%). These findings highlight that the physiological response and Cd accumulation of S. plumbizincicola were mainly affected by high Cd deposition and suggest that atmospheric Cd could directly be absorbed by S. plumbizincicola. The effect of atmospheric deposition on S. plumbizincicola cannot be ignored.

[Strengthening the effect of Bacillus megaterium on remediation of Cd-contaminated farmland soil by Sedum plumbizincicola]. / 巨大芽孢杆菌对伴矿景天修复镉污染农田土壤的强化作用.

Sedum plumbizincicola is a Cd and Zn hyperaccumulator, widely used for the phytoremediation of Cd-contaminated soil. Bacillus megaterium, a phosphate-solubilizing bacteria, can promote plant growth and improve the bioavailability of heavy metals in soil, and thus has a strengthening effect on the remediation of heavy metal-contaminated soil. Here, a pot experiment was carried out with S. plumbizincicola as a hyperaccumulator to investigate the effects of different inoculation amounts (10-60 mL) of B. megaterium on the phytoremediation efficiency of Cd-contaminated farmland soils. The results showed that inoculation of B. megaterium increased soil available Cd content by 15.0%-45.0% compared with the CK. Biomass of shoots and roots of S. plumbizincicola increased by 8.7%-66.7% and 13.6%-81.8%, respectively. Shoot Cd concentration was significantly increased by the application of B. megaterium by 29.2%-60.4%. Under the conditions of S. plumbizincicola inoculated with B. megaterium, Cd removal rate of soil reached 26.7%-42.9%. In conclusion, application of B. megaterium in phytoremediation significantly enhanced the Cd removal efficiency and increased plant biomass, which promoted Cd remediation efficiency.