Effects of Vallisneria natans on H 2 S and S 2- releases in black-odorous waterbody under additional nitrate: Comprehensive performance and microbial community structure.

Releases of hydrogen sulphide (H ₂ S) and sulphur ions (S ^2- ) through sulphate reduction in black-odorous waterbody is a great environmental health concern. Aquatic planting for blackening and odour controls has received great attention in research and practice. Nitrate concentration in black-odorous waterbody can vary significantly but little is known about the responses of aquatic plants on H ₂ S and S ^2- releases under different nitrate levels. This controlled laboratory study explored the changes of H ₂ S and S ^2- releases in simulated black-odorous waterbody planted with Vallisneria natans and artificial plants (control). V. natans growth was stimulated by additional nitrate (6.6 mg/L NO ₃ ^- -N), resulting in an increase of dissolved oxygen (DO) and pH in overlying water and an 11.0% decrease in removal efficiency of chemical oxygen demand (COD). At relatively low nitrate level (i.e., 2.0 mg/L NO ₃ ^- -N in the absence of additional nitrate), V. natans after the 48th day inhibited H ₂ S and S ^2- releases by 81.5% and 66.8%, respectively, and their inhibition efficiencies were improved to 95.7% and 98.8% by the presence of additional nitrate. Additional nitrate reduced the relative abundance of sulphate-reducing bacteria (SRB) in the sediments while increased the relative abundance of sulphur-oxidizing bacteria (SOB) and nitrate-reducing sulphur-oxidizing bacteria (NR-SOB) in the leaf biofilms of V. natans and artificial plants. Genus compositions in leaf biofilms showed host specificity. Pearson correlation analysis showed that DO, pH, and nitrate concentration had a positive correlation with the relative abundance of SOB (Aeromonas) and NR-SOB (Hydrogenophaga), while were negatively correlated with the relative abundance of SRB (MSBL7). These results indicated that V. natans under additional nitrate altered microbial community to be unfavourable for H ₂ S and S ^2- releases. This study clarified the inhibition of H ₂ S and S ^2- releases by aquatic planting under additional nitrate and provided theoretical basis for improving black-odorous waterbody restoration technology.
(Copyright © 2022 Elsevier Ltd. All rights reserved.)