The role of afforestation with diverse woody species in enhancing and restructuring the soil microenvironment in polymetallic coal gangue dumps.

To elucidate the effects of long-term (20 years) afforestation with different woody plant species on the soil microenvironment in coal gangue polymetallic contaminated areas. This study analyzed the soil physicochemical properties, soil enzyme activities, soil ionophore, bacterial community structure, soil metabolite, and their interaction relationships at different vertical depths. Urease, sucrase, and acid phosphatase activities in the shallow soil layers increased by 4.70-7.45, 3.83-7.64, and 3.27-4.85 times, respectively, after the restoration by the four arboreal plant species compared to the plant-free control soil. Additionally, it reduced the content of available elements in the soil and alleviated the toxicity stress for Cd, Ni, Co, Cr, As, Fe, Cu, U, and Pb. After the long-term restoration of arboreal plants, the richness and Shannon indices of soil bacteria significantly increased by 4.77-23.81% and 2.93-7.93%, respectively, broadening the bacterial ecological niche. The bacterial community structure shaped by different arboreal plants exhibited high similarity, but the community similarity decreased with increasing vertical depth. Soils Zn, U, Sr, S, P, Mg, K, Fe, Cu, Ca, Ba, and pH were identified as important influencing factors for the community structure of Sphingomonas, Pseudarthrobacter, Nocardioides, and Thiobacillus. The metabolites such as sucrose, raffinose, L-valine, D-fructose 2, 6-bisphosphate, and oxoglutaric acid were found to have the greatest effect on the bacterial community in the rhizosphere soils for arboreal plants. The results of the study demonstrated that long-term planting for woody plants in gangue dumps could regulate microbial abundance and symbiotic patterns through the accumulation of rhizosphere metabolites in the soil, increase soil enzyme activity, reduce heavy metal levels, and improve the soil environment in coal gangue dumps.

Effects of Setaria viridis on heavy metal enrichment tolerance and bacterial community establishment in high-sulfur coal gangue.

Plant enrichment and tolerance to heavy metals are crucial for the phytoremediation of coal gangue mountain. However, understanding of how plants mobilize and tolerate heavy metals in coal gangue is limited. This study conducted potted experiments using Setaria viridis as a pioneer remediation plant to evaluate its tolerance to coal gangue, its mobilization and enrichment of metals, and its impact on the soil environment. Results showed that the addition of 40% gangue enhanced plant metal and oxidative stress resistance, thereby promoting plant growth. However, over 80% of the gangue inhibited the chlorophyll content, photoelectron conduction rate, and biomass of S. viridis, leading to cellular peroxidative stress. An analysis of metal resistance showed that endogenous S in coal gangue promoted the accumulation of glutathione, plant metal chelators, and non-protein thiols, thereby enhancing its resistance to metal stress. Setaria viridis cultivation affected soil properties by decreasing nitrogen, phosphorus, conductivity, and urease and increasing sucrase and acid phosphatase in the rhizosphere soil. In addition, S. viridis planting increased V, Cr, Ni, As, and Zn in the exchangeable and carbonate-bound states within the gangue, effectively enriching Cd, Cr, Fe, S, U, Cu, and V. The increased mobility of Cd and Pb was correlated with a higher abundance of Proteobacteria and Acidobacteria. Heavy metals, such as As, Fe, V, Mn, Ni, and Cu, along with environmental factors, including total nitrogen, total phosphorus, urease, and acid phosphatase, were the primary regulatory factors for Sphingomonas, Gemmatimonas, and Bryobacter. In summary, S. viridis adapted to gangue stress by modulating antioxidant and elemental enrichment systems and regulating the release and uptake of heavy metals through enhanced bacterial abundance and the recruitment of gangue-tolerant bacteria. These findings highlight the potential of S. viridis for plant enrichment in coal gangue areas and will aid the restoration and remediation of these environments.

Analysis of environmental biological effects and OBT accumulation potential of microalgae in freshwater systems exposed to tritium pollution.

The ecological risk of tritiated wastewater into the environment has attracted much attention. Assessing the ecological risk of tritium-containing pollution is crucial by studying low-activity tritium exposure's environmental and biological effects on freshwater micro-environment and the enrichment potential of organically bound tritium (OBT) in microalgae and aquatic plants. The impact of tritium-contaminated wastewater on the microenvironment of freshwater systems was analyzed using microcosm experiments to simulate tritium pollution in freshwater systems. Low activity tritium pollution (105 Bq/L) induced differences in microbial abundance, with Proteobacteria, Bacteroidota, and Desulfobacterota occupying important ecological niches in the water system. Low activity tritium (105-107 Bq/L) did not affect the growth of microalgae and aquatic plants, but OBT was significantly enriched in microalgae and two aquatic plants (Pistia stratiotes, Spirodela polyrrhiza), with the enrichment coefficients of 2.08-3.39 and 1.71-2.13, respectively. At the transcriptional level, low-activity tritium (105 Bq/L) has the risk of interfering with gene expression in aquatic plants. Four dominant cyanobacterial strains (Leptolyngbya sp., Synechococcus elongatus, Nostoc sp., and Anabaena sp.) were isolated and demonstrated good environmental adaptability to tritium pollution. Environmental factors can modify the tritium accumulation potential in cyanobacteria and microalgae, theoretically enhancing food chain transfer.