Search Results (55)

The Eastern Huang–Huai region of China is a representative mining area with a high groundwater level. High-intensity underground mining activities have not only induced land cover and land use changes (LUCC) but also significantly changed the watershed hydrological behavior. This study integrated the land use prediction model PLUS and the hydrological simulation model MIKE 21. Taking the Bahe River Watershed in Huaibei City, China, as an example, it simulated the hydrological response trends of the watershed in 2037 under different land use scenarios. The results demonstrate the following: (1) The land use predictions for each scenario exhibit significant variation. In the maximum subsidence scenario, the expansion of water areas is most pronounced. In the planning scenario, the increase in construction land is notable. Across all scenarios, the area of cultivated land decreases. (2) In the maximum subsidence scenario, the area of high-intensity waterlogging is the greatest, accounting for 31.35% of the total area of the watershed; in the planning scenario, the proportion of high-intensity waterlogged is the least, at 19.10%. (3) In the maximum subsidence scenario, owing to the water storage effect of the subsidence depression, the flood peak is conspicuously delayed and attains the maximum value of 192.3 m³/s. In the planning scenario, the land reclamation rate and ecological restoration rate of subsidence area are the highest, while the regional water storage capacity is the lowest. As a result, the total cumulative runoff is the greatest, and the peak flood value is reduced. The influence of different degrees of subsidence on the watershed hydrological behavior varies, and the coal mining subsidence area has the potential to regulate and store runoff and perform hydrological regulation. The results reveal the mechanism through which different land use scenarios influence hydrological processes, which provides a scientific basis for the territorial space planning and sustainable development of coal mining subsidence areas. Full article

In water-scarce regions such as Jordan, accurate tracking of water flows is critical for informed water management. This study applied the Water Accounting Plus (WA+) framework using open-source remote sensing data from the FAO WaPOR portal to develop agricultural water accounting (AWA) for the Amman–Zarqa Basin (AZB) during 2014–2022. Inflows, outflows, and water consumption were quantified using WaPOR and other open datasets. The results showed a strong correlation between WaPOR precipitation (P) and rainfall station data, while comparisons with other remote sensing sources were weaker. WaPOR evapotranspiration (ET) values were generally lower than those from alternative datasets. To improve classification accuracy, a correction of the WaPOR-derived land cover map was performed. The revised map achieved a producer’s accuracy of 15.9% and a user’s accuracy of 86.6% for irrigated areas. Additionally, ET values over irrigated zones were adjusted, resulting in a fivefold improvement in estimates. These corrections significantly enhanced the reliability of key AWA indicators such as basin closure, ET fraction, and managed fraction. The findings demonstrate that the accuracy of P and ET data strongly affects AWA outputs, particularly the estimation of percolation and beneficial water use. Therefore, calibrating remote sensing data is essential to ensure reliable water accounting, especially in agricultural settings where data uncertainty can lead to misleading conclusions. This study recommends the use of open-source datasets such as WaPOR—combined with field validation and calibration—to improve agricultural water resource assessments and support decision making at basin and national levels. Full article

Land use and landscape changes undermine the balance between humans and the environment, threatening sustainable regional development, yet their driving mechanisms and future trends remain insufficiently understood, particularly in arid areas. This study establishes a long-term analytical framework for the temporal evolution and driving mechanisms of land use and landscape patterns in arid areas, based on Landsat remote sensing imagery and socio-economic data. We investigate spatiotemporal evolution trends, driving mechanisms, and spatial non-stationarity of regional landscapes, and apply the Patch-generating Land Use Simulation (PLUS) model to predict future landscape changes under business-as-usual (BAU), economic development (ED), and ecological protection (EP) scenarios. The results show that: (1) Grassland and unused land together account for over 80% of the total area. From 1990 to 2020, built-up land expanded by 1471.58 km², an increase of 190.09%. The comprehensive land use dynamic degree in the Urumqi–Changji–Shihezi (UCS) region was 0.22%, with the highest value observed between 2000 and 2010. (2) At the class level, spatial heterogeneity and fragmentation of different landscape types increased, enhancing regional landscape diversity. (3) Spatiotemporal changes in land use and landscape patterns were driven by the combined effects of natural factors, socio-economic conditions, and policy influences. (4) By 2030, under all three scenarios, unused land is expected to decrease, with the most significant reduction under the EP scenario. Grassland will increase most notably under the EP scenario, built-up land will expand, especially under the ED scenario, and cropland will also grow, mainly under the EP scenario. Forest and water areas will show slight decreases with minimal fluctuations. Overall, the proposed framework effectively captures the spatiotemporal dynamics and driving forces of land use and landscape changes, providing support for the formulation of long-term sustainable development policies. Full article

The accelerating process of global urbanization has substantially reshaped land use patterns, exerting profound influences on the dynamics of ecosystem service provision. Effective and adaptive ecosystem management necessitates the quantitative identification and analysis of spatiotemporal variations in ecosystem services and their underlying driving mechanisms. Using the Beijing–Tianjin–Hebei urban agglomeration as a case study, this research examines land use dynamics from 2000 to 2020 and projects land use patterns for 2030 under alternative development scenarios. Building upon this foundation, the study quantifies the spatiotemporal evolution of four key ecosystem services—Carbon Storage (CS), Water Yield (WY), Habitat Quality (HQ), and Soil Retention (SDR)—from 2000 to 2030, while elucidating the differential impacts and underlying mechanisms of the driving factors on these services. The findings indicate that: (1) Between 2000 and 2020, cultivated land remained the dominant land use type (47.71%), followed by forestland (21.44%) and grassland (16.23%), whereas built-up land expanded significantly from 8.12% to 12.74%; (2) the proportion of medium-to-high CS areas reached 47.65%, high-value WY areas increased by 4.9%, low-value HQ areas expanded by 4.28%, and low-value SDR areas accounted for 84.44%; (3) the PLUS model validation yielded a Kappa coefficient of 86.1%, indicating high simulation accuracy. Scenario-based predictions suggest that under an ecological protection scenario, the proportion of medium-to-high CS areas would increase by 0.59%, whereas under an economic development scenario, these areas would decline by 2.57%, with low-value HQ areas expanding by 2.04%; (4) slope (X₂) was identified as the dominant factor influencing CS (q = 0.22), HQ (q = 0.36–0.42), and SDR (q = 0.42), while mean annual precipitation (X₄) played a crucial role in determining WY. Furthermore, socioeconomic activities, particularly increasing population density, exhibited a growing negative impact on HQ and CS, highlighting the intensifying role of anthropogenic interventions in shaping ecosystem service patterns. This study unveils the spatial heterogeneity of ecosystem services and their driving mechanisms in the context of urbanization, offering valuable insights to inform regional ecological conservation and sustainable development policies. Full article

Research on the characteristics of land use change in urban agglomerations and its influences on ecosystem service value has important theoretical significance and practical value for supporting spatial development and guaranteeing ecological security. Located in the upper reaches of China’s Yellow River, the Lanzhou–Xining urban agglomeration is situated in the mosaic of the transition from the Qinghai–Tibet Plateau to the Loess Plateau. It is a substantial industrial base and economic region of western China. It is also the essence of a relatively concentrated population and dense cities. It is not only a key development area but also an essential ecological barrier in western China, shouldering the important responsibility of ensuring a win-win situation for both economic and social development and ecological and environmental protection. This research takes the Lanzhou–Xining urban agglomeration as a case region, investigates the characteristics of changes in land use and ecosystem service value from 2000 to 2020, and applies the PLUS model to emulate land use changes and ecosystem service value in 2030 in three scenarios: the natural development scenario, cultivated land protection scenario, and ecological conservation scenario. The results indicate that: (1) The land use type of the Lanzhou–Xining urban agglomeration from 2000 to 2020 was dominated by grassland, accounting for 60.32~61.25% of the gross area. The reciprocal transfer between cultivated land and grassland was the most significant, and the expansion of construction land mainly took over cultivated land and grassland, accounting for 58.23% and 34.84%. (2) As a result of ecological rehabilitation projects and the continuous increase of water areas, the ecosystem service value of Lanzhou–Xining urban agglomeration continued to increase between 2000 and 2020, with a cumulative total of 56.84 × 10⁸ yuan and a growth rate of 2.67%. Grassland donated the most to the ecosystem service value, constituting 52.56~53.44%. Among the individual ecosystem service values, hydrological regulation and climate regulation contributed the most, and together accounted for 50.86~51.69% of the ecosystem service value. (3) Under the natural development scenario, unrestricted urban sprawl has taken possession of cultivated land and grassland. Under the cultivated land protection scenario, cultivated land has maintained a relatively stable level while construction has been subject to certain constraints. Under the ecological conservation scenario, ecological land has been largely protected and the encroachment of construction onto ecological land has been curbed. (4) Of the three scenarios, only the ecological conservation scenario saw an increase in the ecosystem service values compared to 2020. The reduction in grassland and water area was the main cause for the decrease of the ecosystem service values in the natural development scenario and cultivated land protection scenario. The results can supply a solid foundation for decision-making for future development of the Lanzhou–Xining urban agglomeration and the rational use of land, as well as offer references for the ecological conservation and high-quality development of urban agglomerations in the upper reaches of the Yellow River. Full article

Tailings generated by mining account for the largest world-wide waste from industrial activities. As an element, copper is relatively uncommon, with low concentrations in sediments and waters, yet is very elevated around mining operations. On the Keweenaw Peninsula of Michigan, USA, jutting out into Lake Superior, 140 mines extracted native copper from the Portage Lake Volcanic Series, part of an intercontinental rift system. Between 1901 and 1932, two mills at Gay (Mohawk, Wolverine) sluiced 22.7 million metric tonnes (MMT) of copper-rich tailings (stamp sands) into Grand (Big) Traverse Bay. About 10 MMT formed a beach that has migrated 7 km from the original Gay pile to the Traverse River Seawall. Another 11 MMT are moving underwater along the coastal shelf, threatening Buffalo Reef, an important lake trout and whitefish breeding ground. Here we use remote sensing techniques to document geospatial environmental impacts and initial phases of remediation. Aerial photos, multiple ALS (crewed aeroplane) LiDAR/MSS surveys, and recent UAS (uncrewed aircraft system) overflights aid comprehensive mapping efforts. Because natural beach quartz and basalt stamp sands are silicates of similar size and density, percentage stamp sand determinations utilise microscopic procedures. Studies show that stamp sand beaches contrast greatly with natural sand beaches in physical, chemical, and biological characteristics. Dispersed stamp sand particles retain copper, and release toxic levels of dissolved concentrations. Moreover, copper leaching is elevated by exposure to high DOC and low pH waters, characteristic of riparian environments. Lab and field toxicity experiments, plus benthic sampling, all confirm serious impacts of tailings on aquatic organisms, supporting stamp sand removal. Not only should mining companies end coastal discharges, we advocate that they should adopt the UNEP “Global Tailings Management Standard for the Mining Industry”. Full article

The estimation of water requirements constitutes a critical prerequisite for delineating water scarcity hotspots and mitigating intersectoral competition, particularly in endorheic basins in arid or semi-arid regions where hydrological closure exacerbates resource allocation conflicts. Under conditions of water scarcity, water supplied locally by precipitation and shallow groundwater bodies should be taken into account to estimate the net water requirements to be met with water conveyed from off-site sources. This concept is embodied in the distinction of blue ET (BET) and green ET (GET). In this study, the Budyko hypothesis (BH) method was optimized to partition the total ET into GET and BET during 2001–2018 in the Heihe River Basin. In this region, a better knowledge of net water requirements is even more important due to water allocation policies which reduced water supply to irrigated lands in the last 15 years. This study proposes a modified BH method based on a new vegetation-specific parameter (${\omega }_v$) which was optimized for different vegetation types using precipitation and actual ET data obtained from remote sensing observations. The results show that the BH method partitioned GET and BET reasonably well, with a percent bias of 23.8% and 37.4% and a root mean square error of 84.8 mm/a and 113.6 mm/a, respectively, when compared with reported data, which are superior to that of the precipitation deficit and soil water balance methods. A sensitivity experiment showed that the BH method exhibits a low sensitivity to uncertainties of input data. The results documented differences in the contribution of GET and BET to total ET across different land cover types in the Heihe River Basin. As expected, rainfed forest and grassland ecosystems are predominantly governed by GET, with 81.3% and 87.2% of total ET, respectively. In contrast, croplands and shrublands are primarily regulated by BET, with contributions of 61.5% and 84.3% to total ET. The improved BH method developed in this study paves the way for further analyses of the net water requirements in arid and semi-arid regions. Full article

Fly ash is commonly used as a partial replacement for cement. Although extensive research has been conducted on mixed design schemes for fly ash concrete, these studies commonly overlook carbonation durability, which may lead to an insufficient service life. This study investigates the strength development and optimal low-carbon design of composite concrete that incorporates fly ash. Initially, a regression analysis was performed to assess the compressive strength of concrete with various fly ash (FA) to FA plus cement (C) mass ratios (FA/(C + FA)), ranging from 0% to 55%, and water-to-binder mass ratios (W/(C + FA)), between 0.30 and 0.50 in the following different stages: early-term (3 and 7 days), mid-term (28 and 56 days), and long-term (90 and 180 days). The correlation coefficient between the predicted and actual strength values was 0.98208. The parameter analysis indicates that, for a given FA/(C + FA) ratio or curing duration, the relative strength of the concrete increases more rapidly with a lower W/(C + FA) ratio. Following this, with the water content held constant at 170 kg/m³, the CO₂ emissions of the cementitious materials in the concrete and the CO₂ emissions per unit of concrete strength were calculated. As the FA/(C + FA) ratio increased from 0% to 55%, the CO₂ emissions per unit of strength decreased. Similarly, reducing the W/(C + FA) ratio from 0.50 to 0.30 also lowers the CO₂ emissions per unit of strength. Finally, a genetic algorithm was employed for the optimization of the low-carbon design. As the water content decreases and the concentration of CO₂ increases, the critical design strength of the concrete must also increase to meet the requirements for carbonation durability. The fly ash replacement rate in each optimized mix design reached the maximum allowable replacement rate. Compared with considering only the carbon emissions of materials, the optimal mix ratios for each case remain unchanged when accounting for transportation and production processes; only the corresponding carbon emissions differ. Full article

The expansion of urban areas and unsustainable land use associated with human activities have brought about a decline in habitat quality (HQ), especially in arid regions with fragile ecosystems. A precise prediction of land use and habitat quality changes across different scenarios is crucial for the sustainable maintenance of ecological diversity. In this article, the InVEST model was employed to assess both the quality and degradation levels of habitats in the Turpan–Hami Basin (THB) spanning 1990~2020. Additionally, the InVEST-PLUS coupling model was employed to forecast habitat conditions under three different scenarios in 2050. Specifically, it involved the comparison of land use changes and spatial distribution of HQ across natural development (ND) scenarios, town development (UD) scenarios, and ecological protection (EP) scenarios, along with the analysis of hot spots of HQ spanning 1990~2050. The outcomes revealed the following: (1) The primary land use in the THB was categorized as unused land, alongside notable expansions in cultivated land, grassland, and built-up land. Conversely, there was a considerable decline observed in forests, water bodies, and unused land spanning 1990~2020. (2) The HQ within the THB exhibited evident spatial clustering characteristics. Between 1990 and 2020, areas with low HQ accounted for over 85%, areas with unchanged HQ constituted 88.19%, areas experiencing deteriorated HQ comprised approximately 5.02%, and areas displaying improved HQ encompassed around 6.79%. (3) Through the comparison of HQ for the ND, UD, and EP scenarios in 2050, it was observed that the average HQ under the EP scenario ranked highest, exhibiting the lowest degree of degradation on average. This indicates that the EP scenario is most advantageous for preserving HQ. Conclusively, this research provides valuable viewpoints for making decisions aimed at enhancing HQ in ecologically fragile arid regions. Full article

Due to their immense economic and recreational value, the monitoring of Great Lakes water quality is of utmost importance to the region. Historically, this has taken place through a combination of ship-based sampling, buoy measurements, and physical models. However, these approaches have spatial and temporal deficiencies which can be improved upon through satellite remote sensing. This study details a new approach for using long time series of satellite remote sensing data to identify historical and near real-time anomalies across a range of data products. Anomalies are traditionally detected as deviations from historical climatologies, typically assuming that there are no long-term trends in the historical data. However, if present, such trends could result in misclassifying ordinary events as anomalous or missing actual anomalies. The new anomaly detection method explicitly accounts for long-term trends and seasonal variability by first decomposing a 10-plus year data record of satellite remote sensing-derived Great Lakes water quality parameters into seasonal, trend, and remainder components. Anomalies were identified as differences between the observed water quality parameter from the model-derived expected value. Normalizing the anomalies to the mean and standard deviation of the full model remainders, the relative anomaly product can be used to compare deviations across parameters and regions. This approach can also be used to forecast the model into the future, allowing for the identification of anomalies in near real time. Multiple case studies are detailed, including examples of a harmful algal bloom in Lake Erie, a sediment plume in Saginaw Bay (Lake Huron), and a phytoplankton bloom in Lake Superior. This new approach would be best suited for use in a water quality dashboard, allowing users (e.g., water quality managers, the research community, and the public) to observe historical and near real-time anomalies. Full article

Electronic waste stream grows day by day; printed circuit boards are a kind of solid waste that accounts for 6% of electronic waste. When these are discarded, they can cause soil, water, and air contamination; however, if recycled, these can be considered as a secondary source of metals. Physical comminution of printed circuit boards generates particles with sizes smaller than 250 µm, which are typically not included in the recycling process because they are considered as dust and unvaluable; nevertheless, precious and base metals can be found in these particles. The concentration of metals like silver, among others, from these particles can be achieved by reverse froth flotation in a flotation column followed by magnetic separation of the tails products. A mass balance of the flotation column feed, concentrate, and tails indicates that using a pulp modified with 5 ppm methyl isobutyl carbinol plus 5 g/ton oleic acid (both biodegradable reagents), the concentration of the products improved, resulting in recoveries of 86.13 and 13.87% in the concentrate and tails zones, respectively, with a grade of 74.4% in the tails flow. Magnetic separation of the tails product increases slightly the concentration of silver, reaching a silver grade of 74.5%, a recovery amount similar to those obtained employing complex and environmentally unfriendly processes. Full article

Enhancing carbon storage in terrestrial ecosystems has become a key strategy for mitigating climate change. The Tibetan Plateau holds a pivotal position in achieving carbon neutrality, with the structural pattern of its land use types directly impacting the region’s ecosystem carbon storage capacity. However, there is still a lack of understanding of the spatial distribution of carbon storage in their ecosystems. This study targeted the Tibetan Plateau, utilizing land use data from 2000 to 2020, and employed the Patch-generating Land Use Simulation (PLUS) model to project land use patterns for 2030. By integrating future climate change projections, this study forecasted land use under SSP1-2.6, SSP2-4.5, and SSP5-8.5 scenarios. The Integrated Valuation of Ecosystem Services and Tradeoffs (InVEST) model was employed to quantify carbon storage from 2000 to 2030, while the GeoDetector model was used to explore the driving influences of factors such as the Normalized Difference Vegetation Index (NDVI), Normalized Difference Water Index (NDWI), Leaf Area Index (LAI), Net Primary Productivity (NPP), population density, and road network density on carbon storage. The results revealed that: (1) Grassland predominated the land use types on the Tibetan Plateau, with most types having a stability of over 70%, whereas significant changes were observed in the western Tibet Autonomous Region and southern Xinjiang Uygur Autonomous Region. (2) Carbon storage on the Tibetan Plateau generally followed a tendency towards an initial decrease followed by an increase, with an average annual reduction of 50,107,371.79 Mg. The SSP1-2.6 scenario demonstrated the most substantial increase in carbon storage, being 18 times the natural trend, while the SSP5-8.5 scenario indicated the largest decrease. (3) Over the two decades, NDVI emerged as the most influential driver of carbon storage on the Tibetan Plateau, which was maintained at around 0.4, with the interaction between NDVI and NDWI exerting the strongest driving force, which was maintained at around 0.45. The conversion to forestland and grassland was the primary factor accounting for the change in carbon storage. Based on these results, despite the absence of empirical carbon density data, the SSP1-2.6 scenario could be regarded as a reference pathway for carbon storage changes on the Tibetan Plateau. Solely focusing on enhancing carbon storage by converting low-carbon land uses to high-carbon land uses is misguided; sustainable development represents the optimal approach for augmenting carbon storage on the Tibetan Plateau. Full article

Intensive economic and human activities present challenges to the carbon storage capacity of terrestrial ecosystems, particularly in arid regions that are sensitive to climate change and ecologically fragile. Therefore, accurately estimating and simulating future changes in carbon stocks on the northern slope economic belt of Tianshan Mountains (NSEBTM) holds great significance for maintaining ecosystem stability, achieving high-quality development of the economic belt, and realizing the goal of “carbon neutrality” by 2050. This study examines the spatiotemporal evolution characteristics of the NSEBTM carbon stocks in arid regions from 1990 to 2050, utilizing a combination of multi-source data and integrating the Patch-generating Land use Simulation (PLUS) and Integrated Valuation of Ecosystem Services and Trade-offs (InVEST) models. Additionally, an attribution analysis of carbon stock changes is conducted by leveraging land use data. The findings demonstrate that (1) the NSEBTM predominantly consists of underutilized land, accounting for more than 60% of the total land area in the NSEBTM. Unused land, grassland, and water bodies exhibit a declining trend over time, while other forms of land use demonstrate an increasing trend. (2) Grassland serves as the primary reservoir for carbon storage in the NSEBTM, with grassland degradation being the leading cause of carbon loss amounting to 102.35 t over the past three decades. (3) Under the ecological conservation scenario for 2050 compared to the natural development scenario, there was a net increase in carbon storage by 12.34 t; however, under the economic development scenario compared to the natural development scenario, there was a decrease in carbon storage by 25.88 t. By quantitatively evaluating the land use change in the NSEBTM and its impact on carbon storage in the past and projected for the next 30 years, this paper provides scientific references and precise data support for the territorial and spatial decision making of the NSEBTM, thereby facilitating the achievement of “carbon neutrality” goals. Full article

In order to study the underground coal-gasification process, Aspen Plus software was used to simulate the lignite underground gasification process, and a variety of unit operation modules were selected and combined with the kinetic equations of coal underground gasification. The model can reflect the complete gasification process of the coal underground gasifier well, and the simulation results are more in line with the experimental results of the lignite underground gasification model test. The changes in the temperature and pressure of oxygen, gasification water, spray water, and syngas in pipelines were studied, and the effects of pipe diameters on pipeline conveying performance were investigated as well. The effects of the oxygen/water ratio, processing capacity, and spray-water volume on the components of syngas and components in different reaction zones were studied. In addition, the change tendency of gasification products under different conditions was researched. The results indicate that: (1) The depth of injection and the formation pressure at that depth need to be taken into account to determine a reasonable injection pressure. (2) The liquid-water injection process should select a lower injection pressure. (3) Increasing the oxygen/water ratio favors H₂ production and decreasing the oxygen/water ratio favors CH₄ production. (4) The content of CO₂ is the highest in the oxidation zone, the lowest in the reduction zone, and then increases a little in the methanation reaction zone for the transform reaction. The content of CO is the lowest in the oxidation zone and the highest in the reduction zone. In the methanation reaction zone, CO partially converts into H₂ and CO₂, and the content of CO is reduced. (5) The injection of spray water does not affect the components of the gas but will increase the water vapor content in the gas; thus, this changes the molar fraction of the wet gas. Full article

Background: This study explores how different post-processing methods affect the mechanical properties and degree of conversion of 3d-printed polyurethane aligners made from Tera Harz TC-85 resin. Methods: Using Fourier-transform infrared (FTIR) spectroscopy, the degree of conversion of liquid resin and post-processed materials was analyzed. This investigation focused on the effects of various post-curing environments (nitrogen vs. air) and rinsing protocols (centrifuge, ethanol, isopropanol, and isopropanol + water). The assessed mechanical properties were flexural modulus and hardness. Results: The degree of conversion showed no significant variance across different groups, though the polymerization environment influenced the results, accounting for 24.0% of the variance. The flexural modulus varied considerably, depending on both the rinsing protocol and the polymerization environment. The standard protocol (centrifugation followed by nitrogen polymerization) exhibited the highest flexural modulus of 1881.22 MPa. Hardness testing revealed significant differences, with isopropanol treatments showing increased resistance to wear in comparison to the centrifuge and ethanol rinse treatments. Conclusions: This study conclusively demonstrates the adverse effects of oxygen on the polymerization process, underscoring the critical need for an oxygen-free environment to optimize material properties. Notably, the ethanol rinse followed by nitrogen polymerization protocol emerged as a viable alternative to the conventional centrifuge plus nitrogen method. Full article