This study collected the surface soil samples (0~10cm) from the freshwater (salinity: 0) and mesohaline (salinity:10~15) P. australis marshes in the six main estuaries in China, which are the Liao River Estuary, Yellow River Estuary, Yangtze River Estuary, Oujiang River Estuary, Minjiang River Estuary, and Pearl River Estuary. The production rates of soil CH₄ and CO₂ were measured using laboratory anaerobic slurry incubation method, and the extracellular enzyme activity and abundance of methanogen functional genes (mcrA) were also measured. Mean CH₄ production rate in the freshwater and saltwater P. australis marshes was (2.69±1.63) and (2.97±1.71) ng CH₄/(g·d), respectively. Mean CO₂ production rate was (7.64±4.94)and (10.28±6.84)µg CO₂/(g·d), respectively. CO₂ production rate in the freshwater P. australis marshes was significantly lower than that in mesohaline P. australis marshes, but no significant difference in CH₄ production rate was observed between freshwater and mesohaline marshes. Soil pH and soil organic carbon (SOC) content were identified as the main factors influencing extracellular enzyme activity and methanogen abundance. A decrease in pH led to a significant reduction in the production rates of CH₄ and CO₂. Total carbon, total nitrogen, SOC, activity of five extracellular enzymes, and abundance of mcrA were identified as the key factors influencing CH₄ and CO₂ production. Our research results suggest that across the Chinese coastal estuarine freshwater and mesohaline P. australis marshes, salinity is not a main factor controlling CH₄ production, however, the increase in salinity perhaps raise soil anaerobic mineralization rates, which indicates that sea level rise and saltwater intrusion will cause carbon emission increase from estuarine P. australis marshes.

The Net Anthropogenic Nitrogen Input (NANI) model was utilized to estimate nitrogen inputs to Quzhou for the period from 2003 to 2022, and its spatial and temporal patterns, variations in components, and determining factors were examined. The results indicated that the average NANI for Quzhou over the past two decades was 12925kg/(km²·a), with a peak of 15698kg/(km²·a)in 2011. The spatial distribution was found to demonstrate an east-high and west-low pattern, which was consistent with land-use configurations. The predominant component of NANI was nitrogen fertilizer, which contributed 27% to 41%, followed by net nitrogen input from food/feed at 22% to 42%, atmospheric nitrogen deposition at 21% to 33%, and nitrogen fixation at 7% to 11%. The variations in NANI were primarily driven by nitrogen fertilizer application between 2003 and 2008, food/feed inputs between 2009 and 2014, and atmospheric deposition in recent years. Strategies were proposed to mitigate NANI, including promoting new energy vehicles, reducing nitrogen fertilizer application to align with standards of agriculturally advanced nations, and regulating livestock and poultry farming to match local demand. It was anticipated that these measures would decrease NANI by approximately 833, 893, and 896kg/(km²·a), respectively, achieving a cumulative reduction of about 2622kg/(km²·a), positioning it among the lower levels globally.

Based on the ISfinder database and reference meta-analysis, this study conducted a systematic study of the diversity of 5812 insertion sequences (ISs) and their co-occurrence with functional genes. The study found significant differences in the distribution of different IS families among hosts, as well as in their co-occurrence with functional genes. DDE-type ISs are predominant, with the IS5 and IS3 families containing the most ISs, while the ISH6 family contains the fewest. ISs are widely found in bacteria and archaea, and several IS families show host specificity, being found only in either bacteria or archaea. The study demonstrated that IS co-occur with various functional genes, such as antibiotic resistance, heavy metal resistance, and stress resistance, indicating their significant role in environmental adaptation and the spread of antibiotic resistance genes among pathogens. Some IS exhibited co-occurrence with multiple functional genes, suggesting broader ecological adaptability, while others showed functional specificity. Future research should focus on experimentally validating the mechanisms through which IS mediate gene transfer and host adaptation, to reveal the mechanism of microbial evolution and ecological adaptation.

The spatiotemporal evolution of water quality in the Yangtze River Basin since the impoundment of the Three Gorges Reservoir is critical for formulating comprehensive basin management strategies. Using stepwise multiple linear regression analysis, key water quality indicators influencing the basin from 2003 to 2024 were identified as total phosphorus (TP), permanganate index(COD_Mn), ammonia nitrogen (NH₃-N), lead (Pb), and dissolved oxygen (DO). Evaluations via the single-factor method and the WQI_min index demonstrated that the average water quality across the entire Yangtze River Basin has reached an excellent level. However, secondary basins—including the Wu River Basin, Min-Tuo River Basin, and Taihu Lake water system—exhibited relatively severe pollution, with TP and NH₃-N being the most prominent contaminants. Significant spatial heterogeneity in water quality was observed. Linear regression and seasonal Kendall tests indicated a statistically significant upward trend in the overall water quality of the Yangtze River Basin. All secondary basins, except the Han River Basin, demonstrated significant improvements. Following the Three Gorges Reservoir impoundment, TP concentrations in the upper reaches of the Yangtze River (specifically the Jialing River Basin, Wu River Basin, and the mainstream section from Yibin to Yichang) initially increased and subsequently declined. Similarly, NH₃-N concentrations in the middle reaches (e.g., Dongting Lake and Poyang Lake water systems) and the Wu River Basin located in the upper Yangtze River exhibited comparable trends of initial rise followed by reduction. Conducting research on the spatiotemporal evolution characteristics of water quality across the entire Yangtze River Basin, incorporating secondary tributaries through multi-scale, long-term time series, and multi-indicator analyses, provides critical scientific support for precise pollution mitigation strategies in the region. Such an integrated approach enables a comprehensive understanding of water quality dynamics, identifies pollution hotspots, and informs spatially differentiated management actions, thereby enhancing the efficacy of basin-wide environmental governance.

In order to explore the effect of biodegradable polylactic acid microplastics (PLA-MPs) on nitrogen conversion in sediments, a laboratory experimental sediment system was constructed, and 0 (control), 0.05%, 0.5% and 5% (W/W) PLA-MPs were added to freshwater sediments, then the incubation experiment was performed for 45d at 25℃ and light intensity of 40µE/(m²·s). The concentration of dissolved organic carbon (DOC) decreased significantly and the concentration of dissolved organic carbon (DOC)increased significantly (P<0.05), and the formation of CO₂ and CH₄ was promoted. At the end of the experiment, the concentration of NH₄⁺-N was reduced by the addition of PLA-MPs, and the concentrations of NO₃^--N and TN in the 0.05% and 0.5% PLA-MPs treatment group were lower than those in the control group (compared with the control group, the TN concentrations of the overlying water decreased by 68.44% and 61.83%, respectively). On the contrary, the TN accumulation in the 5% PLA-MPs treatment group was recorded (the TN concentration in the overlying water was 5.71mg/L at the end of the experiment) and was significantly higher than that in the control group (P<0.05). The NO₂^--N concentration in the 0.5% and 5% PLA-MPs treatment groups decreased and the release of N₂O was reduced, while the concentration of NO₂^--N in the 0.05% and 5% PLA-MPs treatment groups was increased. The addition of PLA-MPs promoted the expression of nitrogen-fixing genes nifH and nitrification genes amoA, and the denitrification genes nirS and nosZ were enriched in the 0.05% and 0.5% PLA-MPs treatment groups. However, the abundance of denitrification gene narG was only up-regulated in the 0.5% PLA-MPs treatment group. The abundance of narG and nirS genes in the 5%PLA-MPs treatment group was down-regulated, and the expression of nosZ gene was inhibited but then promoted. The results show that PLA-MPs changes the properties of the overlying water and sediment, promotes nitrogen fixation and nitrification, and provide carbon source to enhance denitrification and denitrification under 0.05% and 0.5% PLA-MPs treatments, but the reduction of NO₃^--N and NO₂^--N is inhibited due to low pH in 5% PLA-MPs treatment, resulting in TN accumulation.

To clarify the temporal and spatial variation patterns of methane emissions from landfills and their influencing mechanisms, a case study was conducted at a municipal solid waste landfill in Qingdao. The static chamber method was used to measure the diurnal dynamics of methane emission fluxes across different seasons. The results indicate significant seasonal variations in methane emission fluxes from the landfill, with the highest emissions occurring in winter at (115.67±65.34) mmol/(m²·h) and the lowest in summer at (61.51±74.57) mmol/(m²·h). The diurnal methane emission fluxes also varied markedly between seasons, with summer fluxes exhibiting a bimodal curve and autumn and winter fluxes showing a unimodal curve. Correlation analysis revealed that methane emission fluxes were significantly related to atmospheric pressure, air temperature, relative humidity, wind speed, soil temperature, and soil relative humidity. In summer and autumn, methane emission fluxes showed a significant positive correlation with atmospheric relative humidity and a negative correlation with air temperature, whereas the opposite was true in winter.

This research addressed the issue of low-carbon development in hydropower, provided a review of the key factors influencing the carbon footprint of hydropower and the regional variations in these footprints. The findings of this research indicated an increasing global focus on research into the carbon footprint of hydropower. Case studies revealed that the primary contributors to the hydropower carbon footprint were the manufacture of construction materials and engineering activities during the construction phase, as well as energy consumption by equipment during the operation and maintenance phase. This research identified key factors affecting hydropower carbon emissions, including the type of hydropower, installed capacity, water storage volume, reservoir area, and life cycle stages. Furthermore, from a geographical perspective, it explored the regional variation in hydropower carbon emissions, highlighting the impact of differences in climate, precipitation, and ecological environment due to geographical location on the hydropower carbon footprint.

An Approximate Homogeneous Turbulence Simulation system was employed to systematically explore algal responses to the interactive effects of turbulence and salinity by integrating the regulatory roles of these interactions on photosynthesis, nutrient metabolism, extracellular polymeric substances secretion, and grazing activities. It was demonstrated that at the biomass level, the damage to algae caused by turbulence was enhanced at 1‰ salinity, with Chl-a content in the low- and high-turbulence groups being 0.37 and 1.41 times that of the still-water group, respectively. At 4‰ salinity, damage was mitigated, with Chl-a content in these groups being 0.82 and 2.29 times that of the still-water group. This phenomenon was attributed to the regulation of algal photosynthetic efficiency and nutrient utilization rate by salinity. At the community structure level, the energy metabolism was enhanced by the increased salinity, which resulted in a lower water pH, thereby providing a competitive advantage to diatoms and leading to their dominance within the phytoplankton community. However, gas exchange and the shift in zooplankton composition were intensified by the elevated turbulence, mitigating the competitive advantage of diatoms caused by increased salinity. Consequently, the proportion of cyanobacteria increases, reinstating them as the dominant phylum.

In this study, the components of dissolved organic matter (DOM) during the anaerobic-anoxic-aerobic (A²O) biological wastewater treatment process was analyzed by using fluorescence emission excitation matrix combined with parallel factor analysis(3D EEMs-PARAFAC), and the generation of nitrous oxide (N₂O) in each unit was also quantified. Additionally, machine learning model was employed to further predict the response relationship between DOM components and N₂O generation. Results showed that DOM in the influent of the wastewater treatment plants (WWTP) was primarily composed of four components, including tryptophan (C1), fulvic acid (C2), humic acid (C3), and tyrosine (C4), while C1 and C4 being the dominant components. The concentration of DOM decreased progressively throughout the treatment process, while the removal efficiency of readily biodegradable DOM (such as C1and C4) were significantly higher than that of C2 and C3. N₂O emission was the major component of direct carbon emissions and showed significant spatial heterogeneity. The N₂O emission amount of each unit ranked from high to low were observed in the following order: oxic tank, secondary sedimentation tank, anoxic tank, anaerobic tank, grille, and primary sedimentation tank. Shapley Additive exPlanation (SHAP) analysis revealed that C1 and C2 would significantly affect the N₂O generation process, while the effects of C3 and C4 were negligible. Specifically, C1would enhance N₂O generation, while C2 had an adverse effect. High-throughput sequencing results indicated that Methylotenera and Terrimonas, which could utilize readily biodegradable organic matter for denitrification, were the dominant bacterial genera in the sludge of WWTP. Overall, this study revealed disparate response between N₂O generation and different DOM components during the A²O process, which would help to improve the current carbon emission accounting method of WWTPs and provide theoretical support for optimizing their low-carbon operation processes.

This paper reviewed the occurrence characteristics and abundance of microplastics (MPs) in disinfection processes of water treatment plants both inside and outside China, and analyzed the MPs removal effectiveness of chlorine, ozone and ultraviolet disinfection, followed by an in-depth discussion of the effects of MPs presence on disinfection and its secondary pollution. The results showed significant differences in the abundance of MPs across different water treatment plants, primarily existing in the forms of fibers and fragments, predominantly composed of polyethylene terephthalate (PET), polyethylene (PE), and polypropylene (PP), with most sizes less than 1.0mm and colors mostly black, white, or transparent. The removal rate of the chlorine disinfection unit ranged from 0% to 71.38%; but part of the water treatment plants had seen a rise in MPs abundance after the ozone and ultraviolet disinfection. The removal mechanisms of MPs by disinfection processes remained required further research. Additionally, the trihalomethane formation potential (THMFP) of microplastic-derived dissolved organic matter (MP-DOM) in the chlorine disinfection process could reach as high as 453.3µg/mg, higher than the formation potential of typical aquatic natural organic matter and algae organic matter, pointing to greater health risks.