Identifying and protecting key carbon sink areas is critical for maintaining regional ecological security and promoting the healthy development of ecosystems. This study investigated the spatial matching relationship between the supply and demand of carbon sequestration service (CSS), visualized the direction and scale of CSS flows, and combined the XGBoost-SHAP model with Bayesian networks to identify driving factors. Results indicated that the Shanxi section in Yellow River Basin (SYRB) generally displayed a carbon surplus, with the supply-demand ratio of CSS forming a spatial pattern of "low in urban areas and high in mountainous regions." High-elevation areas such as the Lvliang Mountains, Taiyue Mountains, and Zhongtiao Mountains supplied CSS to deficit regions including Taiyuan City, Linfen City, and Yuncheng City through diverse flow paths. The ellipticity and azimuth angle of the standard deviation ellipse showed minimal change, indicating a stable spatial distribution of carbon surplus and deficit (CSD). Elevation and mean annual precipitation exerted positively effect on CSD, while GDP and population had significant negative impacts. From 2000 to 2020, the first-priority areas expanded from 7.82 & times; 103 km2 to 13.98 & times; 103 km2 (a 78.7% increase), while the second-priority areas shrank from 34.89 & times; 103 km2 to 18.00 & times; 103 km2 (a 48.4% decrease). This study enriches the theoretical research on basin-scale ecosystem services and contributes to the ecological restoration of the Yellow River Basin and the achievement of carbon neutrality goals.

The shells of testate amoebae are decay-resistant and well preserved in lake sediments, making them excellent biological indicators of climate change. In this study, the identification method for testate amoebae was initially optimized based on the collection of surface sediments from Dali Lake, and statistical analyses were conducted to investigate the community distribution characteristics and key environmental factors driving the testate amoeba species composition. According to the results, the testate amoeba species diversity in the surface sediments of Dali Lake was relatively low. A total of eight species belonging to five genera were identified, and the dominant species were Arcella discoides (35.64% of the total abundance), Phryganella acropodia (24.75%), and Arcella gibbosa (11.39%). All the identified testate amoeba taxa are common in global freshwater sediments, and no new species was discovered in this study. The testate amoeba community composition exhibited strong correlations with the total organic carbon, total nitrogen, dissolved inorganic phosphorus, and total phosphorus and weak correlations with the electrical conductivity and Chlorophyll-a.

Shanxi section of the Yellow River Basin is the key region for ecological conservation and high-quality development in the Yellow River Basin, where the spatiotemporal variation in gross primary productivity directly affects regional carbon sequestration capacity and ecological security. Based on MODIS data of gross primary productivity from 2000 to 2024, we combined the XGBoost-SHAP model with the GeoDetector method to examine the spatiotemporal variations of gross primary productivity in the Shanxi section of the Yellow River Basin and to quantify the contribution of multiple driving factors to gross primary productivity and their spatial interaction effects. The results showed that gross primary productivity in the Shanxi section of the Yellow River Basin exhibited a fluctuating upward trend from 2000 to 2024, with an average annual growth rate of 13.21 g C·m-2·a-1 and an annual mean value of 665.35 g C·m-2·a-1. Spatially, gross primary productivity displayed a "low-high-low-high" pattern from northwest to southeast. Gross primary productivity showed an extremely significant increasing trend in 96.1% of the study area. The XGBoost-SHAP analysis indicated that tree cover was consistently the dominant factor influencing gross primary productivity changes across all selected study years. Precipitation and temperature, as key regulatory factors, exhibited significant stage-specific differences in their effects on gross primary productivity. The GeoDetector results showed that the interaction between tree cover and precipitation had the strongest explanatory power for the spatial differentiation of gross primary productivity. Residual analysis indicated that the contribution rates of natural factors and human activities to gross primary productivity changes were 62.6% and 35.9%, respectively. Under the combined effects of those two factors, gross primary productivity increased in approximately 98.9% of the study area during the study period.

The effectiveness of rural domestic sewage treatment significantly impacts the living environment and quality of life of residents. A rural domestic sewage treatment facility in Yuncheng City, Shanxi Province, China, was utilized to investigate the operational effect and CO2 flux of a sewage treatment process. This process involved anaerobic pretreatment, followed by the application of two sets of constructed wetlands (CWs) for advanced treatment. One group of CWs incorporated local folk-story elements, and the landscape of 'Carps Leaping over the Dragon Gate' was created through plants collocation (CW1). The other group adopted a regular row design (CW2). The results indicated that the removal rates for chemical oxygen demand (COD) (72.41-92.91%), ammoniacal nitrogen (NH4+-N) (94.80-99.33%), and total phosphorus (TP) (27.56-67.62%) in CW1 were comparable to those in CW2. However, the removal rate of total nitrogen (TN) (51.64-85.59%) was higher than that in CW2. Meanwhile, the substrate CO2 flux in CW1 (145.68-1637.11 mg/m2/h) was slightly higher than that in CW2 (131.22-1597.22 mg/m2/h). The decline in the daily average temperature, which caused reduced microbial activity and plant wilting, was the primary factor contributing to the changes in the pollutant removal rate and CO2 flux. Pennisetum giganteum z. x. lin and Arundo donax L. var. versicolor Stokes grew in clusters, and the root biomass was large, enabling them to secrete more organic compounds to enhance the activity of rhizosphere microorganisms. Variations in plant species led to different rates of root carbon fixation, which, in turn, affected the CO2 emissions from the CW substrate layer. Actinobacteriota, Proteobacteria, Chloroflexi, Acidobacteriota, and Bacteroidota were the dominant phyla and could utilize the nutrients and oxygen transported by plant roots to enhance nitrification and denitrification processes. This study provides a reference for the promotion of domestic sewage treatment in rural areas of China.

Clarifying the spatial distribution and evolutionary characteristics of ecosystem services (ESs) across multiple scales is crucial for maintaining ecological stability and sustainability. This study assessed the spatiotemporal changes of ESs in the Shanxi section of the Yellow River Basin (SYRB) from 2005 to 2020 using the InVEST model. We analyzed the multi-ecosystem service landscape index and their driving factors, explored the trade-offs and synergy at the county and 1-km scale, and formulated differentiated ecological management strategies based on local ecological characteristics. The findings demonstrated that (1) land use change was the dominant driver influencing ESs (2) carbon storage (CS) and habitat quality (HQ) showed a stronger synergistic relationship at both the county and 1-km scales; and (3) ecosystem service bundles were divided into four types: CS–HQ synergistic bundle, low synergistic bundle, key synergistic bundle, and integrated ecological bundle at the 1-km scale, while CS–HQ synergistic bundle, key synergistic bundle, water purification–water yield–soil conservation synergistic bundle, and integrated ecological bundle revealed at the county scale. From 2005 to 2020, an increasing number of regions transitioned from single ES to synergistic ESs. This study reveals the spatial mechanisms of trade-offs and synergies among ESs in SYRB, and constructs an effective partitioning scheme and targeted ecological management strategy for SYRB, which are of great significance for regional ecological conservation and sustainable development.

Shanxi Province acts as a critical ecological barrier in the Yellow River Basin (YRB) and is an important area for ecological protection and high-quality development. With the data of land use, elevation, and gross domestic product (GDP) of the Shanxi section of the Yellow River Basin (SYRB) in 2000, 2010, and 2020, we employed the InVEST, Fragstats, and multi-scale geographically weighted regression (MGWR) models to investigate the distribution characteristics of habitat quality and its influencing factors within the SYRB. The results showed that cultivated land, forest, and grassland were the predominant land use types, followed by construction land and water area, while unused land accounted for small proportion. Between 2000 and 2020, the area of cultivated land in the SYRB had decreased and that of construction land had continuously increased. Habitat quality in the SYRB exhibited a declining trend, with a significant increase in the area of low-quality habitat, while change in high-qua-lity habitat area was not pronounced. Spatially, the habitat quality exhibited a pattern with higher values in the southeast and northwest, and lower values in the central and southwestern regions. The GDP and the rate of land urbanization negatively impacted habitat quality, exhibiting significant negative influences on the Zhongtiao Mountains in the south, the Taiyue Mountains in the east, and the Lyuliang Mountains in the west. Conversely, the aggregation index positively influenced habitat quality, with the range gradually expanding from the central area to the periphery and diminishing over time. The contagion index primarily exhibited negative impact on area with low habitat quality. The patch richness index mainly demonstrated a negative influence on area with high habitat quality. The Shannon evenness index predominantly affected habitat quality negatively in area with high vegetation coverage. Our results indicated the complex interaction between ecosystems and human activities. This study would provide a theoretical basis for the formulation of effective ecological protection policies and the sustainable development of ecosystems.

This study aimed to decipher the influence of red mud on the mechanical properties, pore structure, and microstructure of basic magnesium sulfate cements (BMSCs). The results showed that BMSC prepared with an appropriate addition of red mud exhibited improved mechanical properties and yielded the highest compressive strength of 94.54 MPa after curing for 28 days. Adding red mud reduced the total porosity and optimized the pore structure of BMSC. The microstructure and hydration products of the specimens were examined using X-ray diffraction, scanning electron microscopy, and energy-dispersive spectroscopy. The results illustrate that the addition of 50% red mud did not affect the amount of the main strength phase 5-1-7 produced in BMSC. It could also reduce the residual amount of MgO and the generation of Mg(OH)2. The red mud and the M-S-H gel generated by the reaction between active SiO2 and α-MgO in the red mud together filled the pore structure of BMSC, making its microstructure denser and higher-strength. This study aims to improve the comprehensive use of red mud, and the results show that red mud can improve the mechanical properties of BMSCs, protecting the environment and simultaneously reducing BMSC production costs to create good economic benefits.

Red mud (RM) and spent oyster mushroom substrate (SOMS), by-products of industrial and agricultural production, can be recycled for polluted freshwater purification, bringing about a win-win situation. In this study, unacidified RM and RM acidified with oxalic acid (O-RM) and hydrochloric acid (H-RM), respectively, were mixed with SOMS to produce a porous ceramsite as a potential constructed wetlands (CWs) substrate. The results showed that the O-RM, H-RM, and RM ceramsites displayed fine compressive strengths of 7.75 ± 1.14, 8.40 ± 1.30, and 8.84 ± 0.69 MPa after calcining at 950 °C for 30 min, respectively. The phosphorus adsorption capacities of H-RM, O-RM, and RM ceramsite at a solid-liquid ratio of 25 g/L were 1.18 mg/g, 0.88 mg/g, and 1.06 mg/g, respectively. Toxicity release experiments showed that the ceramsites did not cause secondary environmental pollution, except for arsenic (ranging from 0.210 to 0.238 mg/L). The H-RM ceramsite was tested in a tidal flow-vertical flow CW (TF-VFCW) with Iris pseudacorus L. and Canna indica L plants. In the TF-VFCW, the average chemical oxygen demand (COD), ammonia nitrogen (NH4+-N), total nitrogen (TN), and total phosphorus (TP) removal rates were 81.01, 90.25, 66.90, and 77.32 %, respectively. Plant growth had less impact on COD and NH4-N removal but had greater limited TN and TP removal. Scanning electron microscopy, Fourier-transform infrared spectroscopy, and X-ray diffraction analysis confirmed that acid pretreatment and the incorporation of SOMS significantly increased the surface and interior porous structures of the ceramsite and enhanced phosphate adsorption by the polyhydroxyl aluminum-iron complex ions. Bacteroides and Campylobacter used the energy produced during polyhydroxyalkanoic acid (PHA) catabolism to absorb phosphorus. Therefore, the synergistic effect of the substrate, plants, and microorganisms achieved the removal of phosphorus from CWs and offered effective and environmentally friendly recycling of RM and SOMS.

Shanxi Province holds an important strategic position in the overall ecological pattern of the Yellow River Basin.To investigate the changes of the ecological environment in the Shanxi section of the Yellow River Basin from 2000 to 2020,we selected MODIS remote sensing image data to determine the remote sensing ecological index(RSEI)based on the principal component analysis of greenness,humidity,dryness,and heat.Then,we analyzed the spatial and temporal variations of ecological quality in this region to explore the influencing factors.We further used the CA-Markov model to simulate and predict the ecological environment under different development scenarios in the Shanxi section of the Yellow River Basin in 2030.The results showed that RSEI had good applicability in the Shanxi section of the Yellow River Basin which could be used to monitor and evaluate the spatiotemporal variations in its ecological environment.From 2000 to 2020,the Shanxi section of the Yellow River Basin was dominated by low quality habitat areas,in which the ecological environment quality continued to improve from 2000 to 2010 and decreased from 2010 to 2020.The high quality habitat areas mainly located on the mountainous areas with superior natural conditions and rich biodiversity,while the low ecological quality areas were mainly in the Taiyuan Basin and the northern part of the study area,where the mining industry developed well.Climate factors were negatively corre-lated with ecological environment quality in the northern and central parts of the study area,and positively correla-ted with that in the mountainous area.Under all three development scenarios,the area of cultivated land,forest,water and construction land increased in 2030 compared to that in 2020.Compared to the natural development sce-nario and the cultivated land protection scenario,the ecological constraint scenario with RSEI as the limiting factor had the highest area of new forest and the lowest expansion rate of cultivated land and construction land.The results would provide a reference for land space planning and ecological environment protection in the Shanxi section of the Yellow River Basin.

Chlorination has been demonstrated to be an effective method for the prevention and reduction in emitter biological blockage in drip irrigation systems. The injected chlorine dose is generally determined by chlorine concentration at the terminal of the laterals which may lead to a high concentration of residual chlorine at the front of the system and bring detrimental impact to the soil environment and growth of crops, especially in large irrigation units with long laterals. A two-season experiment was undertaken to determine the effects of chlorine disinfection and lateral length on soil NO3-N, enzyme activities, and maize yield under wastewater drip irrigation. The experiments were constructed with lateral lengths ranging from 20 to 80 m and injection chlorine concentrations at the end of laterals ranging from 2 to 6 mg L−1. Lateral length had a major impact on enzyme activities in the partial growth stage, although the effects of lateral length and chlorine concentration on soil nitrogen content and maize yield were negligible. Enzyme activity and soil nitrogen concentration decreased throughout the lateral length as a result of chlorination. A higher detrimental impact on soil characteristics and maize yield is probably going to result from a high concentration of chlorine and a long lateral length mode. The maize yield peaked at L80 with a concentration of 2 mg L−1 chlorine, while it peaked at L40 with 6 mg L−1 chlorine concentration. A chlorination scheme with long lateral length and low chlorine concentration is recommended in consideration of maize yield and minimizing potential negative effects on the soil environment.

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Syringa oblata (So) and its variety S. oblata var. alba (Soa) are famous flowering shrubs with high ornamental value due to their beautiful inflorescence. The flower colors of So (purple) and Soa (white) differ significantly. In this study, pigment contents were detected and flavonoid and anthocyanin metabolites were determined by UPLC-ESI-MS/MS methods. Combined with transcriptome analysis, the key genes related to anthocyanin accumulation were obtained to explore the reasons for the difference in flower colors. The results showed that the total anthocyanin content was obviously higher in So than in Soa. The differential metabolites annotated in anthocyanin biosynthesis were significantly up-regulated, and conversely, the differential metabolites in biosynthesis of secondary metabolites and flavone and flavonol biosynthesis were down-regulated in So compared by Soa, with similar results revealed by the analysis of the top 20 fold change metabolites. It is explained that the anthocyanins and chlorophylls were the key pigment for the difference in flower color between So and Soa. Furthermore, the quantitative analysis of anthocyanins showed that delphinidin-3-O-rutino- O-rutino- side and cyanidin-3-O-rutinoside O-rutinoside were the major anthocyanins in So, and their contents were significantly higher than other anthocyanins. However, the levels of major anthocyanins in Soa were very low, resulting in its white flower. In addition, high levels of kaempferol-3-O-rutinoside, O-rutinoside, rutin, quercetin-3-O-glucoside O-glucoside and naringenin were detected in flowers. These metabolites could play the roles of co-pigments in So and major pigments in Soa, respectively. Cyanidin-3-O-rutinoside O-rutinoside were markedly elevated from initial flower bud (IFB) to flower bud (FB), which contributed to the anthocyanin accumulation and the flower color change in So, while the reduction of chlorophyll content was the main reason for the change in flower color from green to white in Soa. The integrated analysis showed that the genes ( F3GT, FLS and F3H) ) might play the key roles in flower color formation. The study revealed the reason for the flower color variation between So and Soa and the flower color change during the development. It will provide the metabolites fundamental for research on flower color breeding in Syringa. .

Evaluating the quality and establishing an ecological network are beneficial for maintaining ecosystem health and stability and optimizing the national ecological spatial pattern. This study used morphological spatial pattern analysis (MSPA) and the remote sensing ecological index (RSEI) to identify ecological sources (ESs) in the Shanxi section of the Yellow River Basin (SYRB). Comprehensive resistance surface is constructed and corrected based on the index weight. The ecological corridor was identified by the Linkage Mapper tool, and the ecological node and barrier points were determined on the basis of the minimum cost path theory to establish the ecological security pattern (ESP) of the SYRB. 108 ESs were identified, with a total area of 34,157.42 km2. The unevenness spatial distribution of ESs was obvious with concentrated areas of higher elevations and ecological environmental quality. We identified 243 ecological corridors (ECs), totaling 3,259.44 km. The main land use types in the ECs are cultivated land, forest, and grassland. Low-resistance corridors were mainly distributed in the central pearl-shaped basin, connecting the two major source distribution areas to the east and west. The high-resistance corridors were mainly in the southern part of the study area which had highly fragmented ESs at the periphery. We identified 41 ecological pinch points, mainly in the Mianshan Mountain, which plays a key role in energy exchange between ESs. The 26 ecological barrier points, which overlapped with the ECs, obstructed landscape connectivity. A comprehensive “two zones, one belt, and three corridors” ESP was established, providing solid theoretical support and practical guidance for the future sustainable development and enhanced ecological design of the SYRB.

Scientific assessment of the development status and factors influencing the urban ecological resilience of the Yellow River Basin (YRB) is highly significant for promoting its development. This study constructed an evaluation index system for urban ecological resilience considering the four dimensions of pressure, state, response, and innovation. The spatiotemporal ecological resilience of the urban agglomeration (UA) in the Shanxi section of the YRB from 2012 to 2021 was studied using kernel density estimation, Dagum Gini coefficient, and standard deviation ellipse, and the influencing factors of urban ecological resilience were analyzed using a geographic detector. This research revealed that (1) the ecological resilience of cities in the Shanxi section of the YRB experienced a fluctuation process of rise—fall—rise. The urban ecological resilience generally reflected a gradient decreasing spatial pattern of Central Shanxi UA > South Shanxi UA > North Shanxi UA, and gradually changed from the dual core of “Taiyuan—Jincheng City” to the single core of Taiyuan City. (2) The migration trajectory of urban ecological resilience center of gravity fluctuated in the direction of “northwest-southeast,” and moved 12.63 km to the southeast overall. (3) The water supply per ten thousand Yuan GDP, occupied area of construction land per ten thousand Yuan GDP, green coverage rate in built-up areas, ratio of research and experimental development funds (R&D) to GDP, proportion of science and technology expenditure in local fiscal expenditure, and patent licensing quantity index have a high influence on urban ecological toughness at all stages. This influence was further strengthened by the interaction between factors. This study provides an important scientific basis for shaping high-quality development advantages in the YRB and creating a resilient and livable environment.

Identifying and evaluating the ecological security pattern (ESP) of region can provide a solid foundation for optimizing regional ecosystem elements and improving regional ecological security. The PLUS model, InVEST model, and circuit theory were used to analyze the ecosystem services and ESP of the Shanxi section of the Yellow River Basin (SYRB) between 2005 and 2035. The findings revealed that 1) The total area of land use shift across categories between 2005 and 2020 was 6,080.99 km2, or 5.22% of the SYRB’s total area. Under the natural development scenario, the total land transfer area from 2020 to 2035 was predicted to be 4,605.10 km2. Among these, the tendency for construction and forest land was expanding, while the tendency for cultivated land, grassland, water area, and unused land was shrinking; 2) From 2005 to 2035, the SYRB’s water yield and soil conservation all decreased, while the habitat quality and carbon storage showed a declining tendency; 3) The ecological source increased from 35,767.00 km2 in 2005 to 39,931.00 km2 in 2035; the total length of the ecological corridors expanded from 2,792.24 km to 3,553.18 km between 2005 and 2035; the ecological pinch points increased from 27 in 2005 to 40 in 2035; the ecological barrier points increased from 21 in 2005 to 28 in 2035, which show that the ESP remained unstable; 4) According to the ecosystem service characteristics of the SYRB in 2020, an ESP of “one axis, two zones, four corridors, and multiple points” was constructed. This study could provide useful guidance for improving the spatial pattern of land use and maintaining ecosystem services.

Investigating the evolution of land use and its impact on carbon storage is of significant importance for mitigating regional climate change and promoting green low-carbon development. Ningwu County is located in the source region of the Fenhe and Sanggan River, and its ecological status significantly influences the carbon storage (CS) of the watershed ecosystem. In this study, the PLUS-InVEST model was employed to analyze the land use evolution from 1990 to 2020 in Ningwu County, Shanxi Province, as well as their impacts on CS. Additionally, the study simulated and predicted land use changes in Ningwu County by 2040 under four scenarios: natural development (NDS), ecological protection (EPS), cultivated land protection (CLPS), and urban development (UDS), while estimating the corresponding changes in ecosystem CS. Furthermore, the study utilized optimal parameters-based geographical detector to explore the mechanisms underlying the spatial differentiation of CS. The results indicated that the areas of forest land and construction land in the study area consistently increased from 1990 to 2020, whereas the area of cultivated land continuously declined, with grassland, water bodies, and unused land exhibiting a fluctuating increasing trend. The spatial distribution of CS was highest in the northwest, second highest in the southeast, and lowest in the middle region. Over these 3 decades, CS had shown a continuous increase. It is projected that by 2040, the areas of forest and grassland will experience the most significant increase under the EPS; cultivated land only increase under the CLPS; while construction land display the greatest increase under the UDS. Compared to 2020, these four scenarios for 2040 indicate an increase in regional CS, with the EPS showing the largest increment. The primary factors influencing the spatial differentiation of CS in Ningwu County are human activities, followed by topography and climate change; the interactions among these factors exhibit a reinforcing relationship, with the interaction between the distance from construction land and slope having the most substantial impact on the spatial differentiation of CS.

Phosphorus (P) is a key nutrient for crop growth and yield. The use of drip irrigation systems to apply phosphate fertilizer may enhance the migration distance and improve usage rates. However, emitter clogging poses a substantial challenge to phosphorus drip irrigation systems. In this study, we evaluated the influences of the phosphorus fertilizer type on soil-available phosphorus (P), plant growth, yield, and drip emitter clogging. Experiments were conducted in both seasons using different phosphorus fertilizers, including urea phosphate (UP, F1), monoammonium phosphate (MAP, F2), and a combination of urea phosphate and monoammonium phosphate (UP + MAP, F3). A treatment without phosphate fertigation (F0) was used as the control. Applying phosphorus fertilizers enhanced soil-available P content, increased plant height, and improved the leaf area index (LAI) to a larger extent than those without P fertilizer. This promoted photosynthesis and increased the dry matter mass, plant P and N uptake, and aboveground plant biomass. The maximum yield of 14,764.2 and 14,778.2 kg ha−1 was obtained under urea phosphate (F1) and monoammonium phosphate (F2) in 2022 and 2023 seasons, respectively. Phosphorus fertilization changes the composition and diversity of bacterial and fungal communities in the emitter biofilm. Urea phosphate and monoammonium phosphate increased the abundance of Proteobacteria and decreased the abundance of Acidobacteriota. Acidobacteriota was strongly positively correlated with extracellular protein, whereas Proteobacteria was negatively correlated with extracellular polysaccharides, extracellular protein, and extracellular polymer. The content of extracellular polymer and solid particles decreased by 30.1%–42.0% and 39.8%–79.7%, respectively, inducing a higher relative emitter discharge for the treatment with phosphorus fertilizers. Acidic phosphorus fertilizers, such as urea phosphate and monoammonium phosphate, can maintain the high performance of drip irrigation and produce high crop yield.

Carbon burial patterns in lakes and their dynamic changes significantly impact terrestrial carbon sink fluxes and global carbon budgets. In this study, multi-indicator analysis of sediment core samples (P1, P2, and P3) from Pipahai Lake was conducted. Integrating the chronological sequences of 210Pb and 137Cs, we identified the historical changes and spatial characteristics of total organic carbon (TOC) and inorganic carbon (TIC) burial in Pipahai Lake since 1884. The results show that the TOC content was higher than that of the TIC. They exhibited an increasing trend with decreasing depth. Linear regression results indicated that the variation of TOC is less directly affected by precipitation (R = 0.39) and temperature (R = 0.58), while temperature may have a greater impact on TOC. From 1884 to 1995, nutrients were not the primary factor influencing changes in TOC. The synchronous variation in TIC and TOC contents reflects a higher contribution of external inputs to carbon burial in the Pipahai Lake basin. After 1996, nutrients may have begun to affect variations in TOC. The TOC primarily originates from distal aeolian transport or autochthonous sources, though human activity has played a role in its evolution. The TIC content is controlled by the TOC content and autochthonous sources. This study will contribute to the understanding of the carbon cycling dynamics and their influencing mechanisms in a high-altitude lake ecosystem.

A synthetic flocculant of aluminum (Al) and iron (Fe) extracted from red mud (RM) has been widely used in sewage treatment, while the remaining RM residue has been ignored. This study aimed to synthesize polymeric aluminum ferric sulfate (PAFS) flocculant from RM by acid leaching and then use the acidified RM residue to produce an acid RM-based ceramsite (ARMC) by mixing bentonite, hydroxypropyl methylcellulose, and starch. Our results showed that sintering, reaction temperature, H2SO4 concentration, reaction time, and liquid-to-solid ratio had an obvious effect on the leaching of Al and Fe in RM, which was a necessary prerequisite for the efficient PAFS flocculants. At a PAFS dosage of 60 mg/L, turbidity and phosphate removal rates were 95.21 ± 0.64% and 89.17 ± 0.52%, respectively. When the pH value was 8.0, the turbidity and phosphate removal efficiency were 99.22 ± 0.66% and 95.98 ± 1.63%, respectively. Considering the adsorption capacity and mechanical properties, the best conditions for ARMC production included using 60% ARM and ceramsite calcination at 600 °C, with the BET surface area 56.16 m2/g and a pore volume of 0.167 cm3/g. Thermogravimetric analysis indicated that 400 °C was a reasonable preheating temperature to enhance the ARMC mechanical strength, as this temperature allows the removal of surface-adsorbed and constituent water. Under a scanning electron microscope, the ARMC appeared rough before adsorption, while relatively uniform pores occupied it after adsorption. Our conclusion will help to improve the zero-waste strategy of RM and speed up the industrial production of RM in flocculants as well as utilizing ARMC as a new type of adsorbent for phosphorus adsorption in sewage treatment.

Taiyuan City in the eastern Loess Plateau has experienced severe ecological problems caused by urban expansion. For cities undergoing rapid urbanization, building an ecological security pattern (ESP) is an effective means to improve urban resilience. Here, geographic information systems (GIS) were used to analyze, manipulate, and visualize urban ecological multi-source information and remote sensing (RS) for the history of land use/land-cover (LULC) changes and the structure of the urban ecological system. Four important ecosystem service functions were estimated: soil conservation, habitat quality, water yield, and carbon storage. The minimum cumulative resistance (MCR) model was combined with the circuit theory method to determine the ecological corridors, pinch points, and barrier points. Our results showed that: (1) from 1980 to 2020, Taiyuan’s built-up area showed increased construction land and enhanced landscape fragmentation. The decline in cultivated land was mainly attributed to construction land. During the period from 2000 to 2010, a greater amount of land was changed in Taiyuan than in other periods; (2) The ecosystem service evaluation based on the LULC in 2020 revealed that the central urban area was lower than the other areas; (3) 38 ecological source sites were identified, accounting for 16% of the total study area. An area of 106 km2 was allocated to construct 79 ecological corridors. We identified 31 ecological pinch points and 6 ecological barrier points; (4) an ESP optimization governance model of “two rings, four zones, and nine corridors” was proposed. Our study provides theoretical guidance for sustainable development and ecological design in Taiyuan City and other regions.