Nitrogen and phosphorus concentrations in lakes are indicative indicators of water eutrophication. To explore the impact of nitrogen and phosphorus release from sediments in Hengshui Lake on the evolution of water environment quality, a hydrodynamics-water quality-sediment model of Hengshui Lake was constructed based on the EFDC model. The "source" and "sink" transformation processes of nutrients such as nitrogen and phosphorus at the sediment-water interface and the magnitude of nutrient fluxes were analyzed. Through scenario simulation analysis, the impact of internal nutrient release in Hengshui Lake on lake water quality was evaluated, and the regulatory capacity of lake sediments on water quality under the conditions of large input of external pollutants or implementation of dredging projects was discussed. The results showed that the release fluxes of ammonia nitrogen, nitrate nitrogen and phosphate in the sediments of Hengshui Lake exhibited obvious temporal and spatial variations. During water replenishment, the annual net fluxes of ammonia nitrogen, nitrate nitrogen and phosphate in the Wangkou Gate area increased by 48%, 86% and 75% respectively compared with the average values in the central part of the lake. In the plant area, the annual net deposition flux of ammonia nitrogen was 2.7 times higher than that in the non-plant area in the central part of the lake, and the annual net release flux of phosphate was 3.75 times higher. In the scenario simulation settings, the TN concentration in the water body decreased by 10%~25% when sediments were present compared with when there were no sediments, while the TP concentration increased by 4%~33%, which revealed the risk of internal TP release in Hengshui Lake. When the input of external nutrients increased sharply, a large amount of nutrients were caused to settle into the sediments at the bottom of the lake, and the nutrient content in the sediments tended to reach a new equilibrium state after about 2 years. When dredging was excessive, it took about 3 years for the lake sediments to recover to the dynamic equilibrium state of the lake.

The water environmental capacity of alpine fragile rivers, constrained by hydrological-biogeochemical coupling processes, has long lacked robust quantitative investigations. Herein, we selected specific reaches of the Taohe River as the study area, leveraging the SWAT (Soil and Water Assessment Tool) model to simulate watershed runoff dynamics, and integrating the WASP (Water Analysis Simulation Program) model for analyzing riverine water quality indicators. A coupled SWAT-WASP water quality model was thereby constructed, accompanied by the establishment of a quantitative calculation framework for water environmental capacity, to assess the spatiotemporal patterns of water environmental capacity in the alpine watershed at the northeastern margin of the Qinghai-Tibet Plateau. Model simulations exhibited strong concordance with measured data, with correlation coefficients exceeding 0.6 for water discharge and runoff depth. Under Class Ⅰ water quality standards, the annual water environmental capacities for BOD, TP, and DO were 157.6, 2.067, and 221.8 tons, respectively; in contrast, TN required relaxation to Class Ⅳ standards, yielding an annual capacity of 50.38 tons. Spatially, the water environmental capacities of BOD, TP, and DO in the upstream section accounted for 9.9%~10.3% of those in the downstream, while temporally, their capacities in January (dry season) represented 10.1%~34.2% of those in July (wet season). These findings underscore the dominant roles of hydrodynamic conditions and seasonal hydrological drivers in alpine fragile watersheds, defining the sustainable development thresholds for such systems. With TN identified as the priority control factor, a spatiotemporally coordinated allocation strategy is proposed, offering a scientific foundation for adaptive water quality management in alpine fragile water source regions.

Based on hydrodynamic, water quality, and aquatic ecology models, the ecological flow requirements needed to meet water quality standards, suppress algal blooms, and support fish spawning in the middle and lower Hanjiang River were quantified, and temporally and spatially coupled ecological flow regimes by period, type, and region were proposed. The spatiotemporal coupling indicated that ecological flows at the Huangjiagang, Xiangyang, Huangzhuang, Shayang, and Xiantao sections ranged from 330~904m³/s, 366~1135m³/s, 514~1160m³/s, 632~1236m³/s, and 486~1013m³/s, respectively. From February to April of the subsequent year, ecological flow was governed by algal bloom control requirements; from June to September, it was driven by water quality compliance; and from October to November, it was dictated by fish spawning needs. During the dry season, ecological flow in the midstream region was determined by algal bloom prevention and control, whereas in the downstream section it was determined by fish spawning requirements. During the flood season, ecological flow across the entire middle and lower Hanjiang River was governed by the attainment of water quality standards. This work provided a new perspective for the systematic study of ecological flow in rivers and offered scientific evidence and a theoretical foundation for river ecosystem improvement and related engineering applications.

To explore the status of net anthropogenic phosphorus input (NAPI) and its influencing factors in the Beijing-Tianjin-Hebei region, this study took 13 prefecture-level cities as research units, collected relevant statistical data and NAPI model parameters from 1990 to 2022, analyzed the spatiotemporal characteristics of NAPI and the variation trends of its components over the 33 years, and used redundancy analysis (RDA) to quantitatively reveal the impacts of different types of factors on NAPI and its components. The results showed that:(1) The overall NAPI in the Beijing-Tianjin-Hebei region showed a fluctuating upward trend, with a significant increase from 1990 to 2006 and a slight decrease from 2006 to 2022. The annual average value was 1906kg/(km²·a), which was 5.6times the national level. Phosphorus input from chemical fertilizers was the most important source, with an average annual contribution rate of 54.90%, followed by phosphorus input from food and feed, with an average annual contribution rate of 41.18%. Affected by terrain, the spatial distribution of NAPI showed a trend of gradually decreasing from south to north. Handan City had the highest NAPI value, accounting for 15.76% of the entire study area, while Chengde City had the lowest NAPI value, accounting for 1.52%. The average uncertainty range of NAPI from 2018 to 2022 was -14.81% to 14.56%. (2) The order of influence of different factors on NAPI and its components was: land use factors > economic factors > social factors, and the combined explanatory rate of the three types of factors was 81.77%. Among them, NAPI and its components were only negatively correlated with the proportion of forest and grassland areas, and positively correlated with other influencing factors. Among the indicators, the proportion of construction land area had the highest individual explanatory rate of 45.70%, and had the strongest positive correlation with food/feed phosphorus and non-food phosphorus, making it the most critical factor affecting NAPI and its components. The increase in the proportion of construction land area is often accompanied by intense human activities, such as the increase in food consumption and detergent use. Therefore, the positive impact of the proportion of construction land on food/feed phosphorus and non-food phosphorus leads to its highest individual explanatory rate.

This study conducted field research in the summer and autumn seasons of 2023 and 2024 at a typical drainage ditch in the Yihe Canal, Hetao Irrigation District. Water quality samples (TN, TP, EC, pH) and UAV multispectral reflectance data were collected to build an inversion model based on statistical regression (SR) and extreme gradient boosting (XGBoost), exploring the correlation between water quality parameters and spectral indices for high-precision inversion. The results indicate that the SR-XGBoost model achieved average R² values of 0.872 and 0.880 in the training and validation sets, respectively, with RRMSE values of 3.46% and 3.23%, significantly outperforming single-band and other combined models. The autumn model exhibited better fitting performance than the summer model, with an average R² increase of 11.50% and an average RRMSE reduction of 1.76%. Spatial distribution results show that pollutant concentrations are higher upstream of the drainage ditch than downstream, with higher concentrations in summer than in autumn and more significant distribution differences. This study reveals the correlation between water quality parameters and spectral indices, validates the high accuracy and stability of the SR-XGBoost model, and provides scientific evidence for applying multispectral remote sensing technology in water quality monitoring.

Based on the Biome-BGC ecological process model, the spatial and temporal dynamics of carbon and water flux, water use efficiency (WUE), and its driving factors in the past 24 years were simulated and analyzed, and the soil moisture vegetation carrying capacity of different stands was estimated. The carbon and water fluxes increased year by year, and the average annual growth rates of GPP and ET were 6.42g C/m² and 5.45kg H₂O/m², respectively. WUE decreased by 0.006g C/kg H₂O, showing a trend of carbon efficiency and water consumption imbalance. Interspecific competition significantly affected the dynamic stability of WUE. The shrub pure forest showed stronger adaptability in the carbon and water regulation relationship. The increase of CO₂ concentration was the main driving factor leading to the decrease of WUE, and had a significant indirect effect through temperature (indirect path coefficient 0.435) and NDVI (indirect path coefficient 0.808). Moderate regulation of stand structure and surface vegetation coverage can effectively improve regional WUE. The results of soil moisture vegetation carrying capacity showed that there was still room for improvement in the current planting density of arbor forest, shrub forest and shrub-shrub mixed forest, which could be increased by 15.07%, 3.78% and 16.72%, respectively. The study is helpful to clarify the water use mechanism of different vegetation types in arid and semi-arid areas, define the ecological limits of vegetation restoration projects under the constraints of water resources, and provide theoretical support and decision-making basis for regional 'planting by water' policy formulation and sustainable management of sandy ecosystem.

Trichloroethylene (TCE), a common chlorinated hydrocarbon and volatile organic compound (VOC), poses significant risks to environmental and human health. Its volatilization and diffusion in fractured porous media are complex and difficult to characterize. The volatilization behavior of TCE at the air-soil interface of complex dual media remains poorly understood experimentally. Simulation experiments of NAPL-phase TCE leakage in dual-media systems, combined with finite difference numerical technique, were used to qualitatively assess the influences of fracture and pore structure geometry on TCE volatilization and diffusion. The diffusional fluxes of TCE volatizedfrom the aqueous phase, calculated using effective diffusion coefficients (D_e) obtained from four empiricalandsemi-empirical models, werecompared. In addition, the contribution of volatilization fluxes of TCE from the non-aqueous phase liquid (NAPL)was also analyzed. We find the volatilization flux of TCE at the air-soil interface of the complex structure P5F3 constructed with permeable blocks made of 3~5mm gravel (P5) and a 3mm-aperture vertical fracture (F3) was lower than thatof structure P3F1. Comparison the TCE diffusional flux volatilized from the aqueous phase at the air-soil interface over the upstream-source, source, and downstream-source regions, thehighest vapor flux was estimated overfracture region, followed by the downstream-source region, with the upstream-source region showing the lowest flux. TCE vapor diffusional flux from aqueous phaseoverfracture region accounts for 3% and 5% of the total fluxover entire regionwhenthe ratio of fracture width to permeable block length is 1:150 and 1:50, respectively. The interface diffusional fluxbased on D_e from the Bartelt-Hunt model is the largest, while that from the Currie model is the smallest. The amount of vapor TCE volatized from Napl-phaseis significantly greater than that fromaqueous phase, the former may account for more than 78% of total gas-phase TCE, based on the discrepancy between the gas-phase TCE concentration measured under the sealed air chamber in the lab and the value estimated numerically from the aqueous phase alone.

To assess the habitat quality of wild Chinese giant salamanders (Andrias davidianus) and promote the conservation of their conservation, a survey on the community structure and driving factors of macroinvertebrates was conducted in May 2023 in the Guangdong Liannan Giant Salamander Provincial Nature Reserve. The results indicated that streams in the reserve maintained a high level of benthic macroinvertebrate biodiversity, with 180 species, belonging to six phyla, seven classes, 16orders, 71 families, and 167 genera recorded across 32 sampling sites. Among them, aquatic insects accounted for 94.6% (172species) of the total species richness. The dominant species included Cheumatopsyche sp. (12.1%), Hydropsyche sp. (11.6%), Togoperla sp. (6.7%), Baetis sp. (6.0%), and Stenopsyche sp. (5.5%), which all belong to the orders Ephemeroptera, Plecoptera, and Trichoptera (EPT). A comparison of sampling sites in three regions—Wankeng River, Sanjiachong River (upstream, located in the core area), and Paiduhou River (downstream, in the experimental area)—revealed no significant differences in benthic invertebrate species richness, density, Simpson index, Shannon index, and Pielou's evenness index. The community composition was also similar across the three regions, with EPT and Diptera (sensitive taxa) being the dominant groups. The nMDS ordination plot showed substantial overlap among the three regions. Redundancy analysis (RDA) indicated that key environmental factors influencing the benthic community included altitude, dissolved oxygen, and substrate type, while key spatial factors included 12PCNM variables representing large- (PCNM axes 1, 3, 4, 6~8), medium- (10, 12, 13, 15), and small-scale (23, 28) spatial patterns. Variation partitioning analysis (VPA) showed that environmental factors alone explained 4.7% of the community variation, spatial factors alone explained 5.0%, and their combined effect explained 8.4%, indicating that environmental and spatial factors contributed similarly to the variation in benthic communities. Overall, the stream habitats in both the core and experimental zones of the Liannan giant salamander reserve were in excellent condition, with clean water and high benthic diversity, although the habitat quality in the experimental zone was slightly inferior to that of the core zone. The high-quality stream habitats and rich benthic biodiversity provide favorable conditions for the survival and reproduction of the giant salamander. In the future, long-term monitoring and management of the stream ecosystems in the reserve should be strengthened to continuously improve the habitat quality for wild giant salamanders and provide scientific support for the stability and recovery of their populations.

A strain of polycyclic aromatic hydrocarbons (PAHs) degrading bacteria, QYQ-1, was isolated from the sediments of the Jialing River bed. Through 16S rRNA sequence alignment, calculation of average nucleotide identity, and whole-genome phylogenetic analysis, it was identified as Pseudomonas jessenii. The strain QYQ-1 exhibits a wide adaptive range for temperature (15~40℃) and pH (5~9), excellent salt tolerance (0.5%~5%), and good heavy metal resistance (Cu²⁺, Zn²⁺, Co²⁺, Mn²⁺, Cd²⁺). It has a unique advantage in withstanding low temperatures (15℃), high salinity (5%), and heavy metals. The optimal degradation conditions are at a temperature of 35℃ and a pH of 7, achieving a degradation rate of 97.7% for 100mg/L naphthalene within 48hours. Additionally, it can efficiently degrade aromatic compounds such as benzoic acid and phenol. Genomic analysis indicates that the strain QYQ-1 possesses various key genes involved in the degradation of multiple PAHs, including a complete pathway for benzoate degradation and a meta-cleavage pathway for catechol. It also contains critical genes related to PAHs degradation, such as salicylate hydroxylase, cytochrome P450, and protocatechuate 3,4-dioxygenase. Additionally, it carries a significant number of resistance genes for heavy metals such as copper, zinc, cobalt, manganese, and cadmium. Furthermore, strain QYQ-1 has a robust iron uptake system. This expands the application range of strain QYQ-1, making it suitable not only for environmental remediation of PAHs-contaminated sites but also for potential use in environments contaminated with both heavy metals and PAHs.

A heterotrophic nitrifying-aerobic denitrifying bacterium, identified as Thauera butanivorans SVT, was isolated from spice wastewater. Genomic DNA of the isolate was extracted for whole-genome sequencing to analyze and predict nitrogen metabolic pathways. The nitrogen metabolism characteristics were investigated using 100mg/L NH₄⁺-N, NO₃^--N, or NO₂^--N as sole nitrogen sources. The effects of different carbon sources (sodium acetate anhydrous, sodium citrate, sodium succinate, sucrose, and glucose), C/N ratios (1, 5, 10, 15, 30), temperatures (10℃, 20℃, 30℃, 40℃, 50℃), and pH levels (4.0, 6.5, 7.5, 8.5, 10.0) on its heterotrophic nitrification-aerobic denitrification performance were systematically investigated. Results showed total nitrogen removal rates of (86.96±1.03)%, (60.52±4.70)%, and (64.32±1.40)% within 48hours when using NH₄⁺-N, NO₃^--N, and NO₂^--N as sole nitrogen sources, respectively. Strain SVT demonstrated growth and nitrogen removal capabilities under all tested conditions, with optimal performance achieved using sodium acetate anhydrous as carbon source at 30℃, C/N=10, and pH 7.5. Genomic analysis identified six nitrogen metabolism-related functional enzyme genes (napAB, nxrAB, nirBD, nirS, norBC, and nosZ). Combined with KEGG database alignment and single nitrogen source metabolism results, the proposed nitrogen metabolic pathways include: ammonium assimilation (NH₄⁺-N→L-glutamate→L-glutamine), nitrification (NH₄⁺-N→NO₂^--N→NO₃^--N), denitrification (NO₃^--N→NO₂^--N→NO→N₂O→N₂), and DNRA pathway (NO₃^--N→NO₂^--N→NH₄⁺-N). This study demonstrates that strain SVT exhibits efficient heterotrophic nitrification-aerobic denitrification capabilities, showing promising potential for wastewater treatment applications.