Effect of total dissolved gas supersaturation on the passage behavior of silver carp (Hypophthalmichthys molitrix) and ya-fish (Schizothorax prenanti) through an experimental vertical slot fishway.

Total dissolved gas (TDG) supersaturation caused by flood discharge water poses a threat to vital activities such as migration, foraging, and evasion in fish species upstream of the Yangtze River, which may impair the ability of fish to pass through fishways during the migration period, causing poor utilization of fishways. Previous studies have shown that TDG supersaturation reduces the critical and burst swimming abilities of fish, suggesting potential adverse effects on swimming performance. However, studies focusing on the impact of TDG on fish swimming behavior in experimental vertical-slot fishways remain scarce. Therefore, in this study, silver carp (Hypophthalmichthys molitrix) and ya-fish (Schizothorax prenanti) were used as the study species, and comparative passage experiments were carried out in an experimental vertical slot fishway to systematically analyze the effects of TDG supersaturation on their passage behavior. The passage success of the silver carp was 57%, 39%, 26%, and 27% at TDG levels of 100%, 110%, 120%, and 130%, respectively. Passage success of ya-fish was 73%, 37%, 31%, and 35% at TDG concentrations of 100%, 110%, 120%, and 130%, respectively. The passage time for both species increased significantly with increasing TDG levels. Furthermore, the passage routes of silver carp changed significantly compared to the control group, whereas the passage routes of ya-fish changed insignificantly. High levels of TDG supersaturation (≥120%) also contributed to a higher mortality rate of ya-fish passing through the vertical slot fishway. The research results provide valuable data on the influence of TDG supersaturation on fish movement behavior responses in experimental vertical slot fishways, offering a reference for the design of fishways and the formulation of reservoir operation schemes.

Measuring ecosystem services supply and demand in rural areas: cases from China's key counties to receive assistance in pursuing rural revitalization.

There is a considerable challenge to meeting the Sustainable Development Goals (SDGs) of ending poverty and maintaining ecosystems' function in rural areas, largely due to that the rural people's livelihood relied heavily on fragile ecosystems. China is ambitious to solve this issue by enacting economic stimulus policies such as ecological protection compensation and payment for ecosystem services (ESs). However, these interventions are generally based on stockholders' willingness and lack of scientific basis. Here, we firstly combined InVEST model and social-economic data to evaluate the ecosystem services supply and demand (ESSD), by taking 25 key counties to receive assistance in pursuing rural revitalization in Sichuan province as the study cases. The coupling coordination degree model was then employed to measure the coordination relationship of ESSD. Finally, the driving factors were analyzed based on correlation analysis and stepwise regression method. The results showed that all ESs, except carbon sequestration, were oversupplied with significant spatial heterogeneity. From 2000 to 2020, the supply of all ESs increased, in which the food production had the most notable increase ratio amounting to 48.20%, while the demand of water retention and air purification decreased substantially. Due to the inconsistency between cultivated land area and population changes, significant spatial heterogeneity existed in the coordination relationship of food production. The counties with the highest and the lowest annual average coordination index were Yanyuan (0.9950) and Rangtang (0.1208), respectively. The rural employees and the agricultural gross output value were the key positive factors influencing the quantity and coordination of ESSD, while ecological compensation and financial expenditure had no significant impact, further indicating that these policies were not linked to the performance of ecosystems' function. Finally, policy implications were raised. This study provides a scientific framework for enacting the interventions towards ecological sustainability and poverty ending from ESSD perspective.

Photosensitized Anti-Markovnikov Hydroesterification of Unactivated Alkenes.

Hydrofunctionalization of alkenes represents a fundamental strategy in synthetic organic chemistry. Herein, we describe a visible-light-promoted approach for the anti-Markovnikov hydrooxygenation of unactivated alkenes. Our protocol features the utilization of a cost-effective, bench-stable, and easy-to-handle oxime ester as the reagent, enabled by energy-transfer catalysis. This methodology exhibits excellent functional group tolerance and mild reaction conditions, rendering it suitable for the hydroesterification of pharmaceutically relevant molecule-derived alkenes.

Co-benefits assessment of integrated livestock and cropland system based on emergy, carbon footprint and economic return.

The rapid specialization of livestock production contributes to spatially decoupled crop and livestock production. Relinking croplands and livestock to promote wastes and by-products exchange has been suggested to provide opportunities for sustainable intensification of agriculture systems. However, the environmental and economic performances of such crop-livestock systems remain highly context specific and unclear. This study proposed an emergy-LCA-based framework to study the GHG mitigation and ecological and economic benefits of the integrated crop planting and livestock feeding systems, by taking wheat maize rotation-swine systems (WMRS), tea-swine systems (TS) and citrus alfalfa intercropping-swine systems (CAIS) as the empirical cases. The results showed the three case modes can generally promote GHG mitigation and ecological and economic benefits. CAIS had the lowest carbon footprint per kcal product (0.12 g CO2-eq kcal-1), followed by TS (0.61 g CO2-eq kcal-1) and MWRS (0.66 g CO2-eq kcal-1). The significant difference in this indicator can be attributed to their different upstream input and manure management. Due to the lower dependence on purchased resources, CAIS also had the best performance on emergy-based sustainability and economic benefits. Based on our results, the policy implications, including promoting wastes and by-products exchange, choosing reasonable manure treatment mode and conducting systematic planning have been suggested to provide opportunities for GHG mitigation and sustainable intensification of agro-systems.

Techno-ecological synergies of hydropower plants: Insights from GHG mitigation.

Hydropower is a source of climate-friendly energy; however, its ecological impacts have been criticized. Few studies have considered the greenhouse gas (GHG) emissions resulting from ecosystem restoration. This study proposes a techno-ecological synergy framework based on life cycle assessment (LCA) to evaluate 34 hydropower plants (HPs) in the upper reaches of the Yangtze River from GHG supply and demand side perspectives. Our results show that the demand unit carbon footprint of the 34 HPs ranged from 5.43 to 49.36 g CO2-eq/kWh, while the imputed GHG emissions from ecosystem restoration occupied 1.22 % to 30.35 %. The unit carbon footprint of large HPs were larger than those of small HPs, and both were positively correlated with the installed capacity of the HPs. All the HPs were unsustainable at the local scale and relied on regional ecosystem supplies. The Sobol' sensitivity analysis and Monte Carlo simulations demonstrated the reliability of our results. Finally, our results were used to consider the related policy implications.

Removal of phosphate from aqueous solution by chitosan coated and lanthanum loaded biochar derived from urban dewatered sewage sludge: adsorption mechanism and application to lab-scale columns.

A lanthanum modified sludge biochar chitosan (La-SBC-CS) microsphere was successfully synthesized by dropping sludge biochar (BC) and chitosan into a lanthanum chloride solution. Batch adsorption experiments were conducted to investigate the adsorption kinetics and isotherm. Application of continuous phosphate removal was achieved via lab-scale column reactors. The phosphate adsorption equilibrium data of the La-SBC-CS fitted well with the Freundlich isotherm, with a maximum adsorption amount of 81.54 mg p/g at 25 °C. Characterization of the adsorbent using scanning electron microscopy analysis (SEM), X-ray energy spectrum analysis (EDS), X-ray diffraction analysis (XRD) and Fourier infrared analysis (FTIR) techniques suggested that the possible adsorption mechanisms were electrostatic interaction, ligand exchange and complexation. The La-SBC-CS kept 76.37% phosphate removal efficiency after eight recycles. The results of continuous column reactor experiment demonstrated that the breakthrough time increased with an increase in adsorbent filling height, while it decreased with an increase in initial phosphate concentration or flow velocity. The Yoon model was applied to the continuous experimental data to predict breakthrough curves and determined the characteristic adsorption parameters for process design. This study indicated the potential for the practical application of La-SBC-CS in phosphate removal from wastewater.

Effect of temperature and duration of pyrolysis on spent tea leaves biochar: physiochemical properties and Cd(II) adsorption capacity.

We analyzed the effects of pyrolysis temperature and duration on the physiochemical properties and Cd(II) adsorption capacity of spent tea leaves (STL) biochar. The STL biochar was produced by pyrolysis at 300, 400, 500 and 600 °C for 1 and 2 h. The pyrolysis temperature was positively correlated to the ash content, pH, electrical conductivity, specific surface area (SBET), pore volume (PV) and C content, and negatively with the total yield, O, H and N content, and the O/C and H/C atomic ratios. Furthermore, the surface porosity of STL biochar increased, the density of oxygen-containing functional groups decreased, and the formation of aromatic structures was enhanced at higher pyrolysis temperatures. The adsorption of Cd(II) onto STL biochar fitted with the pseudo-second-order kinetics and Langmuir isotherms model. The STL biochar produced at 600 °C for 2 h showed the maximum Cd(II) adsorption capacity of 97.415 mg/g. In addition, Cd(II) adsorption was mainly physical and occurred in monolayers. Thus, STL biochar is a suitable low-cost adsorbent for wastewater treatment.

Performance and microbial community of the CANON process in a sequencing batch membrane bioreactor with elevated COD/N ratios.

In this study, the effects of elevated chemical oxygen demand/nitrogen (COD/N) ratios on nitrogen removal, production and composition of the extracellular polymer substances (EPS) and microbial community of a completely autotrophic nitrogen removal via nitrite (CANON) process were studied in a sequencing batch membrane bioreactor (SBMBR). The whole experiment was divided into two stages: the CANON stage (without organic matter in influent) and the simultaneous partial nitrification, anaerobic ammonia oxidation and denitrification (SNAD) stage (with organic matter in influent). When the inflow ammonia nitrogen was 420 mg/L and the COD/N ratio was no higher than 0.8, the addition of COD was helpful to the CANON process; the total nitrogen removal efficiency (TNE) was improved from approximately 65% to more than 75%, and the nitrogen removal rate (NRR) was improved from approximately 0.255 kgN/(m3·d) to approximately 0.278 kgN/(m3•d), while the TNE decreased to 60%, and the NRR decreased to 0.236 kgN/(m3•d) when the COD/N ratio was elevated to 1.0. For the EPS, the amounts of soluble EPS (SEPS) and loosely bound EPS (LB-EPS) were both higher in the CANON stage than in the SNAD stage, while the amount of tightly bound EPS (TB-EPS) in the SNAD stage was significantly higher due to the proliferation of heterotrophic bacteria. The metagenome sequencing technique was used to analyse the microbial community in the SBMBR. The results showed that the addition of COD altered the structure of the bacterial community in the SBMBR. The amounts of Candidatus 'Anammoxoglobus' of anaerobic ammonia oxidation bacteria (AAOB) and Nitrosomonas of ammonia oxidizing bacteria (AOB) both decreased significantly, and Nitrospira of nitrite oxidizing bacteria (NOB) was always in the reactor, although the amount changed slightly. A proliferation of denitrifiers related to the genera of Thauera, Dokdonella and Azospira was found in the SBMBR.