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Soil contamination with heavy metal(loid)s may influence microbial activities in the soil, and consequently jeopardize soil health. Microbial responses to soil contamination play an important role in ecological risk assessment. This study investigated the effect of heavy metal(loid)s contamination on microbial community structure and abundance in the surrounding soil of an abandoned antimony (Sb) smelter in Qinglong county, Guizhou province, Southwest China. A total of 46 soil samples were collected from ten sampling sites (labelled as A–I, and CK) across the study area at depths of 0–2, 2–10, 10–20, 20–30, 30–40, and 40–50 cm. The soil samples were analyzed for total and bioavailable heavy metal(loid) concentrations, bacterial, fungal, and archaeal community structures, diversities, and functions, together with soil basic physicochemical properties. Much greater ecological risk of Sb and arsenic (As) was present in the surface soil (0–2 cm) compared to that in the subsoils. The activities of dominant microorganisms tended to be associated with soil pH and heavy metal(loid)s (i.e., Sb, As, lead (Pb), cadmium (Cd), and chromium (Cr)). Bacteria associated with IMCC26256, Rhizobiales, Burkholderiales, and Gaiellales, and archaea associated with Methanocellales were estimated to be tolerant to high concentrations of Sb and As in the soil. In addition, the magnitude of soil microbial responses to Sb and As contamination was in the order of archaea > bacteria > fungi. In contrast to the negligible response of fungi and negative response of bacteria to Sb and As contamination, there was a strongly positive correlation between archaeal activity and total Sb and As concentrations in the soil. Our findings provide a theoretical basis for the remediation of Sb smelter-affected soil.

Research on greenhouse gas (GHG; CO2, CH4, N2O) emissions from hydropower reservoirs has attracted widespread attention due to the potential effect on global climate change. However, few attempts have been made to conduct the research progress in this field from a global perspective. In this study, knowledge mapping research was conducted by applying scientometric analysis to explore research hotspots, frontiers and emerging trends of this field from 1993 to 2021, and five research priorities were recommended for the further study. The results showed that the research on GHG emissions from hydropower reservoirs was interdisciplinary, and there was an exponential increase in yearly publication outputs. Additionally, China, Brazil, Canada, America, and France were the leading contributors with high publication outputs, and the Chinese Academy of Science was the most productive and influential institution. Furthermore, the research hotspots in the field mainly focused on CO2, CH4, and N2O emissions and their spatiotemporal characteristics due to great contributions to greenhouse effect and heterogeneities of the GHG emissions from hydropower reservoirs. Research frontiers mainly concentrated on the Three Gorges Reservoir, bubble-mediated gas exchange, GHG emissions across different interfaces and gas transfer velocity. Meanwhile, the first three research frontiers were regarded as emerging trends in recent years. Although great progress has been made in the field, there were still some research challenges. Future research priorities were recommended to strengthen: 1) Application of remote sensing in the research on GHG emissions from hydropower reservoirs, 2) improvement of life cycle assessment research, 3) standardization research on the measurement methods, 4) anthropogenic impacts on carbon dynamics, and 5) international cooperation and database construction. Finally, several mitigation measures were suggested to provide useful insights into the management and control of GHG emissions. In contrast to previous reviews, this paper provides an insight for the visual study of the research on GHG emissions from hydropower reservoirs, helping researchers understand the current research status and future perspectives from a global perspective.

With the conspicuous contradiction between water use inside and outside rivers, ecological reservoir operation has become a feasible approach to coordinate the relationship between socio-economic water use and ecological water use in rivers. However, ecological water demand in rivers remains difficult to be satisfied in areas facing serious water shortages, resulting in an imbalance between ecological and socio-economic water use. To satisfy the instream ecological water demands in water shortage areas, efforts were made on seeking an optimal reservoir operation scheme to balance the water supply for ecology and socio-economy. This study applied the index of guarantee rate of ecological water (GREW) to ecological river management, improved the previous reservoir operation rules, and constructed an optimization model of ecological reservoir operation rules based on dual-control management indexes. The Dagu River in Qingdao City, China, was selected as a study area to apply this model. The results showed that both the recommended scheme and the scheme without considering ecology could meet the socio-economic water demands, but the satisfaction degree of ecological water demand of the recommended scheme was significantly higher than that of the scheme without considering ecology. The scheme without considering ecology cannot ensure the ecological water demand in the Dagu River, especially for the non-flood season. Comparisons between the recommended scheme and the operation results without considering ecology demonstrated that the optimization model of ecological reservoir operation rules could effectively balance the ecological and socio-economic water use. In conclusion, the optimization model of reservoir operation rules with GREW can solve the problem of competitive water use inside and outside rivers, providing an important scientific basis for water resources management.