Search Results (2,067)

Phosphogypsum (PG), a gypsum-rich by-product of wet-process phosphoric acid production, is increasingly considered for land application because it can supply calcium and sulfur and alleviate constraints such as sodicity, subsoil acidity, and vegetation establishment limitations. However, PG may also contain residual acidity, soluble salts, fluoride, heavy metals, and naturally occurring radionuclides, creating multiple exposure pathways. This critical review distinguishes direct PG evidence from gypsum or sulfate analogue evidence, life cycle assessment/material flow analysis evidence, and risk control studies. It evaluates PG land application according to receiving soil conditions, diagnosed constraints, exposure pathways, and environmental safety boundaries. The strongest evidence supports use in diagnosed sodic and saline–sodic soils, whereas applications in Al-toxic acid subsoils, flooded paddy systems, contaminated or degraded soils, and non-food vegetated systems require conditional assessment. PG should therefore be treated as a context-specific management option rather than an unrestricted disposal route. By linking waste valorization with soil demand, source quality, exposure control, and long-term monitoring, the proposed framework contributes to sustainability by integrating circular resource use with soil health, water protection, food/feed safety, and risk-informed governance, while helping to prevent the transfer of environmental burdens across ecosystems or generations. Full article

The service range of a district cooling system is strongly affected by the energy consumption of chilled-water distribution in the supply-side pipe network. With increasing cooling distance, pump operating energy consumption, pump-induced temperature-rise loss, and pipeline cooling loss all increase, which may weaken the supply-side distribution-energy advantage of centralized cooling. This study proposes a method for determining the maximum cooling distance of a district cooling system based on a supply-side energy-equivalent boundary. The boundary is defined as the distance at which the total supply-side energy consumption of the district cooling system equals that of the decentralized cooling system under the same load conditions. Unlike cost-based evaluation methods, the proposed criterion does not rely on economic parameters such as electricity price, material cost, construction cost, or maintenance cost, but determines the boundary based on supply-side energy consumption. A district cooling system in Guangzhou is used as the case study. Under the baseline condition, the maximum cooling distance is 1564 m. Increasing the supply–return water temperature difference from 7 °C to 12 °C increases the maximum cooling distance by 294.38%. Increasing the decentralized system main-pipe length from 250 m to 600 m increases it by approximately 175%. When the number of users increases from 8 to 12, the distance increases by 23.1%. A front-concentrated layout of high-load users increases the distance by 36.93% compared with a uniform layout. The proposed method provides an energy-based planning reference for cooling-source siting, user connection range determination, and district cooling pipe-network scheme evaluation. Full article

MP contamination in drinking water is an emerging public health concern, yet standardized analytical workflows and exposure assessments remain limited and fragmented. This study provides an exploratory assessment of MP exposure through drinking water, combining particle-resolved analysis with consumption-based estimates. Laser Direct Infrared (LDIR) spectroscopy was applied within the analytical workflow to characterize MPs across different drinking water supply types. Ten drinking-water samples (five bottled, two tap, two public dispensers, and one office dispenser) were analyzed within a 10–500 µm size window, and particle-resolved results were combined with a consumption survey to support preliminary exposure estimates. MPs in the 10–150 µm range were detected in six of ten samples, while tap waters and all blanks were particle-free, supporting analytical robustness. Bottled waters showed the highest MP abundances (6–148 particles L⁻¹) and mass concentrations (0.03–22.4 µg L⁻¹). Particle-size distributions were right-skewed and dominated by particles ≤ 30 µm. PET, PU, PA, and ABS predominated, consistent with packaging and dispensing origins. EDI estimates for bottled-water consumers ranged from 0.1008 to 0.3023 µg kg-bw⁻¹ day⁻¹ across three consumption scenarios (1–3 L day⁻¹). Despite the limited sample size, the results support LDIR for source discrimination and exposure screening, providing a basis for future research. Full article

Micro and nanoplastics (MNPs), defined as particles under 5 mm down to the submicron scale (<1 µm or 1–1000 nm), have shifted from an environmental concern into a general potential contaminant of our global food supply. As plastic production escalates, the fragmentation process disperses particles across soils, water bodies and the atmosphere, resulting in their reported detection in a variety of food products and, in some studies, in human biological matrices including the bloodstream to major organs. However, confirming their presence is not equivalent to tracing their journey. Current scientific understanding of how these contaminants migrate remains uncertain, since most studies focus on isolated sources rather than the interconnected stages of production and exposure. To address this, we propose the Farm-to-Table Microplastic Exposure Cascade (FT-MPEC), an integrated concept designed to describe the potential progressive accumulation of MNPs across the food continuum. This review synthesizes the trajectory of particles from primary production into the food chain, evaluating potential transfer pathways during post-harvest handling, industrial processing and domestic preparation. By mapping these routes, we identify critical knowledge gaps and research priorities necessary to improve future monitoring, exposure assessment and mitigation strategies for public health. Full article

Feeds rich in protein are the dominant nitrogen input in intensive aquaculture, yet only part of dietary nitrogen is retained as animal biomass; the remainder enters water and sediment through uneaten feed, feces, dissolved wastes, mucus, sloughed tissue, and branchial ammonia excretion. This review aims to integrate nutritional, physiological, microbial, and disease-related evidence into an evidence-graded framework that positions ammonia nitrogen as a reactive node linking feed, host, water, sediment, and pathogen risk. To assemble this evidence, we conducted a structured narrative search of Web of Science and PubMed for records in English or Chinese published from 2006 to July 2026, with no restriction on publication type, and classified evidence as direct, indirect, or conceptual. The strongest evidence shows that dietary protein supply, amino acid balance, digestibility, and feeding regime regulate nitrogen retention and ammonia output, while microbial ammonification, nitrification, denitrification, dissimilatory nitrate reduction to ammonium, anammox, and assimilation determine whether reactive nitrogen is regenerated, retained, or removed. Experimental studies further show that ammonia impairs oxidative balance, mucosal barriers, immunity, and disease resistance. In contrast, evidence that pathogen infection quantitatively alters nitrogen retention, ammonia excretion, organic nitrogen release, and sedimentary ammonium regeneration remains limited and largely indirect. Accordingly, ammonia nitrogen is framed as a measurable reactive node rather than a unique source or a universally validated causal loop. Practical management should combine precision nutrition with water, biofloc, sediment, and disease surveillance, while future factorial studies and isotope tracer studies should quantify the complete nitrogen budget under pathogen challenge. Full article

Accurately identifying organic-rich shale intervals remains a major challenge in lacustrine shale oil exploration, particularly in continental rift basins characterized by rapid environmental change and pronounced vertical heterogeneity. This study investigates the upper Jiufotang Formation in the Ludong Sag, Kailu Basin, NE China, using total organic carbon (TOC), vitrinite reflectance, multi-stage programmed rock pyrolysis, and major and trace element geochemistry to constrain the processes governing organic matter enrichment and hydrocarbon occurrence. The studied shales contain abundant organic matter, with TOC values ranging from 1.91% to 7.55% and averaging 4.22%. Type II₂ kerogen and vitrinite reflectance values of 0.60–0.94% indicate oil-prone organic matter at low-mature to mature stages within the oil generation window. Multi-stage pyrolysis shows that the hydrocarbon assemblage is dominated by bound oil and residual kerogen-derived fractions, whereas the low-temperature movable oil fraction is limited. TOC is more strongly associated with the high-temperature pyrolysis fractions than with the light free-oil fraction, indicating that organic matter abundance primarily controls residual hydrocarbon generation potential but does not directly determine present-day movable oil content. Multiple elemental proxies are collectively consistent with deposition in a hydrologically restricted, variably brackish–saline lacustrine system with water-mass differentiation. Redox-sensitive indicators, including V/(V + Ni) and Mo, suggest persistent weakly reducing to reducing bottom-water conditions. After correction for carbonate- and phosphate-associated Ca, CIA values fall within a narrow range of approximately 67–70, indicating moderate and relatively stable source area chemical weathering. Organic matter enrichment was governed by the coupled effects of organic matter supply, preservation under stratified oxygen-deficient waters, and sedimentary dilution. We therefore propose a two-stage process framework in which depositional productivity–preservation coupling first promoted organic matter accumulation, whereas subsequent thermal maturation, hydrocarbon expulsion, retention, and adsorption reshaped the present hydrocarbon occurrence state. The results demonstrate that high organic matter abundance and residual generation potential do not necessarily translate into high movable oil content and provide a well-scale geochemical basis for source rock evaluation and future multi-well assessment in continental rift lake systems. Full article

Population growth, increasing water demands for data centers, and the need for more sustainable water practices are prompting advancement of next-generation water resource management strategies including water reuse. In the Midwestern United States (U.S.), where non-traditional approaches to augmenting water supply, including water reuse, are relatively new, full advanced water treatment (AWT), which includes microfiltration/ultrafiltration (MF/UF) and reverse osmosis (RO), produces a concentrate stream that is expensive to address (i.e., brine disposal). Carbon-based advanced treatment (CBAT), which combines ozonation, biofiltration, and granular activated carbon, has been shown to be a viable alternative with select advantages over the traditional RO approach, including the lack of brine generation. Two novel pilots were conducted in the Midwestern U.S., one at a large (>100 MGD) and one at a small (~10 MGD) wastewater reclamation facility (WRF), to provide proof of concept that CBAT could meet distinct regional needs. While additional demonstration data are ultimately needed for future regulatory approvals, results from the pilots showed that water quality objectives were met with treated water quality of <0.5 mg/L total Kjeldal nitrogen (TKN), <2 mg/L total organic carbon (TOC), and substantial reduction in constituents of emerging concern (CECs). If nitrate removal is required to meet drinking water standards (10 mg/L), additional treatment optimization at the source WRFs would be required. Areas for further research identified by this effort include mitigating the potential for ozonation to contribute to the formation of disinfection byproducts such as bromate and N-nitrosodimethylamine (NDMA). Along with the treatment performance demonstrated at these pilots, the study provided an opportunity to engage with key stakeholders to build trust in the AWT approach, which is critically important for regulatory and public acceptance. Based on two field-scale pilot studies in the U.S. Midwest, this paper analyzes CBAT application advantages and challenges in municipal water reuse and identifies research directions for the industry. Full article

The increasing use of plastics in agriculture has enhanced crop productivity, water-use efficiency, and food supply stability. Nevertheless, the ongoing degradation of agricultural plastics and waste-derived materials has resulted in the widespread occurrence of microplastics (<5 mm) and nanoplastics (<1 μm) in agricultural soils, raising concerns about ecosystem functioning, food safety and human health. This review was conducted using literature obtained primarily from Web of Science, Scopus and PubMed. Publications published between 2019 and 2026 were primarily included. In addition, selected landmark studies published before 2019 were incorporated when they provided foundational concepts, methodological frameworks, or highly cited evidence that remains essential for understanding the sources, fate, and impacts of micro- and nanoplastics in agricultural systems. The review synthesizes recent scientific evidence regarding the sources, environmental fate, biological interactions, and food-chain transfer of micro- and nanoplastics within agricultural and food production systems, tracing their movement from farm to fork. Major contamination pathways include agricultural plastic materials, organic amendments, polymer-coated agrochemicals and atmospheric deposition. Mechanisms governing transport, aging, plant uptake and trophic transfer are also discussed. Current evidence suggests that agricultural soils are among the largest terrestrial reservoirs of micro- and nanoplastics; however, substantial uncertainties remain regarding environmental concentrations, plant uptake under field conditions, and human health risks due to methodological limitations and the lack of standardized analytical protocols. Future research should focus on standardized monitoring methods, enhanced risk assessment frameworks, the development of biodegradable alternatives, and integrated mitigation strategies to reduce plastic contamination. Full article

Climate-change-induced drought can increase domestic water shortage not only by reducing runoff but also by exposing weaknesses in local sources, reservoirs, and wide-area transfer networks. This study simulates domestic water shortage in the Seomjin River water system, South Korea, using the Korea-Water Evaluation and Planning system (K-WEAP), and proposes an integrated eXtreme Gradient Boosting (XGBoost)–Shapley Additive exPlanations (SHAP) framework to diagnose the explanatory factors of the simulated shortage. Representative drought scenarios were selected from an ensemble of climate projections using a dryness score based on precipitation-related extreme climate indices. K-WEAP was used to simulate shortage for eleven administrative districts, and XGBoost (version 3.2.0) models were trained for districts with sufficient shortage samples. SHAP analysis and shortage-event clustering were then applied to identify dominant explanatory factors and recurrent shortage patterns. The XGBoost models reproduced the simulated shortage rates well, with test R² values exceeding 0.91. Wide-area water supply was the dominant explanatory factor in three inland districts, whereas reservoir supply was more influential in the southern coastal district. The dependence analysis revealed threshold-type responses, in which shortage risk increased sharply once key supply variables fell below district-specific critical ranges. The results indicate that domestic water shortage is governed by district-specific supply pathways and threshold-type system responses rather than by uniform basin-wide drought effects. Full article

Very small islands face freshwater scarcity due to limited catchment areas, rainfall variability, and saline intrusion. In Indonesia, rainwater harvesting (RWH) can reduce household water stress, but its reliability as an independent source remains uncertain. This study used field surveys and a daily water-balance model to assess household RWH systems on the Belakang Padang and Mecan Islands. Representative wet (2023) and dry (2019) years were selected from a 30-year rainfall record to evaluate storage performance, rainwater supply reliability, and water saving efficiency (WSE). Simulations considered 200, 500, and 1000 L tanks under household-demand scenarios of 60–300 L/day. During the wet year, rainfall frequently refilled storage tanks and improved water availability, although overflow occurred when harvested water exceeded storage capacity. Larger tanks reduced overflow losses and extended water availability after rainfall events. In contrast, dry-year storage performance declined because rainfall was limited and concentrated within a short period. Even 1000 L tanks could not maintain sufficient storage under high demand during prolonged rainless periods. Rainwater supply reliability and water saving efficiency were higher during the wet year, ranging from 31 to 99.2% and 0.231 to 1.029 on Belakang Padang and 25.2 to 98.6% and 0.211 to 1.024 on Mecan, while dry-year reliability declined markedly as demand increased. Belakang Padang showed higher reliability than Mecan because its larger roof catchment area harvested more rainwater from the same rainfall event. Overall, household RWH is unlikely to provide a dependable independent domestic water supply on very small islands but can serve as an important supplementary source during disruptions to centralized systems. Reintroducing and maintaining household RWH, together with improvements in tank capacity, effective roof catchment area, and conveyance systems, could strengthen household water security on the Belakang Padang and Mecan Islands. Full article

Accurately depicting the spatiotemporal evolution patterns and driving mechanisms of soil drought is of great significance for regional agricultural drought warning and adaptive management of water resources. There are still shortcomings in the existing research in terms of indicator applicability, mutation detection and trend persistence collaborative diagnosis, as well as the quantification of multi-scale meteorological driving factors. In response to the above issues, this study constructs the Standardized Soil Moisture Index (SSMI) based on the principle of soil moisture supply and demand balance, and comprehensively uses BFAST structure mutation detection, autocorrelation correction Mann–Kendall (MMK) trend test, Hurst persistence analysis, and cross-wavelet transform methods to systematically analyze soil drought in the Haihe River Basin (HRB) from 2000 to 2022. Using the FLDAS reanalysis dataset and multi-source meteorological observation data, this study revealed the stage changes, seasonal evolution characteristics, and dominant meteorological driving factors of soil drought in the watershed. Key findings include: (1) the most significant structural breakpoint occurred in May 2005 (confidence interval: March–November 2005); (2) spring exhibited the strongest drying trend (mean Z_s = −0.51), while autumn showed the strongest anti-persistence (mean Hurst = 0.41), making it the most vulnerable season for future soil moisture state shifts; (3) evapotranspiration was the dominant meteorological driver, with the highest significant coherence area percentage (SCAP), followed by air humidity, soil moisture, soil temperature, air temperature, and precipitation in descending order of influence. Full article

Microbially induced calcium carbonate precipitation (MICP) is a promising biotechnology for environmental remediation; however, the high cost of conventional chemical-grade calcium sources limits its large-scale scalability. This study evaluated the feasibility of utilizing an aqueous extract of natural attapulgite clay as a sustainable, low-cost calcium source for MICP-mediated arsenic (As) immobilization in both aqueous and soil systems. Among the tested minerals, Baiyin attapulgite (group B) exhibited the highest calcium content (62,808.94 mg kg⁻¹) and minimal toxic metal impurities, providing a favorable chemical matrix for biomineralization. At an optimal solid-to-liquid ratio of 1:10, Lysinibacillus fusiformis LF and Enterococcus LZU-1 successfully induced calcite precipitation driven by the attapulgite extract. In batch aqueous remediation experiments (20 days), the attapulgite extract significantly enhanced As removal efficiency compared to the controls; As removal rates peaked at 66.4% for strain LZU-1 (with LZ1 extract) and 65.8% for strain LF (with group B extract), drastically outperforming the standard CaCl₂ groups (31.2–37.3%) and blank controls (21.8–24.5%). Concurrently, soil incubation experiments (30 days) demonstrated that the combined application of attapulgite and MICP bacteria reduced the highly bioavailable exchangeable As fraction from 0.115 to approximately 0.03 mg kg⁻¹, while effectively driving its transformation into more stable carbonate-bound and organic-bound fractions without causing secondary soil salinization. Morphological and mechanistic analyses revealed that, compared to the well-defined euhedral crystals in the CaCl₂ control, the precipitates mediated by the clay extract exhibited distinctly irregular, defect-rich rhombohedral structures. This structural disruption was governed by the natural matrix effect of attapulgite, which simultaneously supplied dissolved Ca²⁺ and provided an abundance of fine clay fragments, calcite micro-grains, and associated amorphous Fe/Al/Mn-bearing phases. These constituents acted as physical scaffolding and heterogeneous nucleation sites that became embedded in the growing CaCO₃ lattice, driving the formation of highly reactive, defect-rich clay-calcite-arsenic composite precipitates that efficiently encapsulated arsenate. Mantel analysis further revealed that the remediation efficiency was significantly correlated with key environmental variables including Ni, V, Ca. These findings highlight the dual-system potential of natural attapulgite as an inexpensive, eco-friendly calcium alternative for sustainable MICP-based remediation of As-contaminated water and agricultural soils. Full article

The Huaibei region is a critical grain and energy–chemical base in northern China, characterized by substantial water demand for industrial and agricultural production. Karst groundwater systems constitute the primary water supply source in this area. Under the superimposed impacts of intensive exploitation, climate change, and anthropogenic activities, karst aquifers have encountered a series of geo-environmental problems, including groundwater level decline and expansion of cones of depression. Most previous studies have predominantly focused on water quality assessment and groundwater resource quantification, yet systematic investigations into the multi-scale characteristics and driving mechanisms of karst groundwater level dynamics remain insufficient. In this study, based on long-term groundwater level and rainfall monitoring data (2014–2024) from three monitoring wells representing different types of karst aquifers, continuous wavelet transform (CWT) and wavelet coherence (WTC) approaches are introduced to identify the periodic patterns of karst groundwater levels and reveal the dominant controlling factors of groundwater level dynamics. The results demonstrate that groundwater levels in all types of karst aquifers exhibit distinct multi-scale periodic variations. The groundwater levels of HB01 and HB02 share dominant oscillation periods of 18~19 months and 9 months with regional rainfall, while the groundwater level at HB03 displays a more complex, multi-scale, periodic combination of 41 months, 18~19 months, and 9 months. Periodic variations in regional rainfall serve as the dominant controlling factor for the intra-annual and inter-annual periodic fluctuations of karst water levels, with a prominent resonance relationship identified between the two variables at dominant periodic scales. Distinct heterogeneity is observed in the response magnitude and lag time of different karst aquifer types to rainfall; specifically, the lag time of water level response to rainfall on the annual periodic scale ranges from 2.7 to 2.9 months. The correlation between annual average water level and pumping discharge is moderate for boreholes HB01 and HB03, whereas a strong correlation is detected for borehole HB02, implying that its water level regime is likely subjected to pronounced pumping disturbance. The degree of karst development, aquifer burial depth, and overlying stratum architecture are the key geological factors accounting for such heterogeneous response patterns. For the first time, this study utilizes long-term water level time series data from the karst water exploitation zone of the Huaibei Plain, complemented by synchronous precipitation and pumping records. Integrated with regional hydrogeological settings, wavelet analysis is employed to conduct an in-depth investigation into the dynamic variations in karst water levels in the Huaibei region from the perspective of groundwater recharge–discharge relationships. The results provide a scientific underpinning for the remediation of karst water over-exploitation and the optimal allocation of water resources. Specifically, pumping and artificial recharge schemes can be proactively adjusted based on periodicity forecasts. Zoned management strategies for water resources are put forward: artificial regulation and storage are recommended for zones with sensitive hydrological responses, while preventive protection is prioritized for zones with sluggish responses. By incorporating periodic characteristics and lag durations, targeted pumping strategies for dry and wet seasons can be developed, and a coupled water level–rainfall–pumping early warning system can be established to realize the long-term sustainable regulation of karst water resources. Full article

The groundwater resources are increasingly stressed in the Islamabad–Rawalpindi metropolitan area of Pakistan due to unplanned urbanization, growth of industries, and inadequate waste management. In this study, the aquifer vulnerability was evaluated in the productive alluvial zone of Islamabad Watershed using a Geographic Information System (GIS)-based DRASTIC model and critically comparing it with independent measured contamination of groundwater, which is a common weakness in many machine-learning-based DRASTIC studies considering the vulnerability index as the model input. The data from 21 boreholes supplied by the Capital Development Authority (CDA) were used to map seven hydrogeological parameters in ArcGIS Pro at a 30 m resolution. The DRASTIC Index values ranged from 69 to 188, with 12.9% of the mapped watershed (209.3 km²) being rated as Very High vulnerability, mainly in the shallow western urban alluvium where water tables are below 5 m. Single-parameter sensitivity analysis showed that the most influential factors of the index were impact of the vadose zone (S_i = 1.14) and depth to water table (S_i = 1.09). A Random Forest model was trained on independently measured nitrate instead of the DRASTIC Index, but had a poor predictive skill (cross-validated R² = 0.08), and the SHapley Additive exPlanations (SHAP) analysis suggested that increased vulnerability (shallow water table and high recharge) was correlated with lower nitrate concentrations. The inverse relationship between groundwater intrinsic vulnerability and measured nitrate was statistically significant when compared to 233 groundwater samples collected at the same locations during two different campaigns (2018 and 2024) (pooled Pearson r = −0.27, p < 0.001; Spearman ρ = −0.19, p = 0.007; Kruskal–Wallis H = 14.10, p = 0.003). Levels of nitrate in both Low and Moderate vulnerability zones (6.0 and 7.7 mg/L, respectively) were higher than in Very High zones (3.4 mg/L). The inverse direction was consistent across both campaigns and robustly significant in the 2024 dataset (ρ = −0.33, p < 0.001), which covered a wider contamination gradient; in the 2018 dataset, only the parametric test was significant. Nitrate showed no significant difference between land-use classes (H = 7.23, p = 0.065) and was found as a few individual high concentrations, suggesting that these were not diffuse loading issues or intrinsic susceptibility, but were likely influenced by point sources. These results show that intrinsic DRASTIC vulnerability is useful to identify areas vulnerable to potential future contamination, but does not explain the current distribution of contamination in this aquifer, which is influenced by point-source loading and residence-time effects. To provide effective groundwater protection, intrinsic vulnerability assessment must be complemented with specific monitoring of point sources. Full article

Historic water infrastructure has often been treated primarily as a technical system, while its relationships with urban form, architectural organization, and everyday life have received less attention. Focusing on the old city of Mardin, this study examines historic water infrastructure, including partially accessible underground routes and their above-ground interfaces, as a constitutive component of spatial organization in a settlement shaped by arid climatic conditions and steep topography. A multi-scalar spatial-decoding approach combines Quantum Geographic Information System (QGIS)-based mapping, morphological and sectional analysis, Light Detection and Ranging (LiDAR)-based three-dimensional documentation, archival research, field observation, and oral testimony. The findings reveal a decentralized configuration of largely independent gravity-fed source-to-outlet routes embedded across urban and architectural scales. Water access, maintenance requirements, and architectural integration contributed to the organization of public nodes, institutional buildings, domestic spaces, and everyday practices without independently determining them. The transition to centralized modern supply disrupted these embedded relationships and transformed the visibility, accessibility, use, and situated knowledge of water. Methodologically, the study offers a transferable cross-scalar approach for reconstructing relationships between partially concealed infrastructure and visible urban form. Full article