Journal of Environmental Management最新文献

Climatic and anthropogenic pressures have caused significant changes in ocean ecosystems, but the long-term impacts on phytoplankton and underlying mechanisms in the continental shelf areas remain inadequately quantified. In this study, we reconstructed century-long records of phytoplankton productivity (PP) and community structure on the northern South China Sea (SCS) shelf using a combination of sedimentary lipid biomarkers (sterols and long-chain alkyl diols) and bulk geochemical proxies. The results revealed that diatoms and dinoflagellates predominated, with PP showing a consistent increasing trend over the past century, particularly accelerating after the 1980s. However, community structure exhibited divergent spatial trajectories. The relative abundance of dinoflagellates increased in the nearshore area, whereas diatoms increased offshore in recent decades. Statistical analyses identified the 1980s as a critical transition period, which was attributed to changes in sea surface temperature (SST) and nutrient levels. The Generalized Additive Model (GAM) results further demonstrated SST and nitrogen exerted cumulative and synergistic effects on promoting PP in the anthropogenically impacted nearshore region. This synergy, characterized by ocean warming coupled with elevated nitrogen loading and N/P ratios, favored the proliferation of dinoflagellates. The findings underscore that under ongoing climate change, proactive measures to control anthropogenic nitrogen inputs are crucial to mitigate the expanding frequency and geographical coverage of dinoflagellate blooms in coastal shelf ecosystems.

The overuse of ceftriaxone has resulted in its widespread occurrence in aquatic environments, posing ecological and health risks. An anaerobic membrane bioreactor (AnMBR) was operated for 128 days to systematically investigate the anaerobic microbial transformation of CTX. The AnMBR exhibited stable and efficient performance, maintaining chemical oxygen demand removal above 90% and achieving an average CTX removal efficiency of 65.0 ± 15.2%. Several potential degradation pathways are proposed, involving β-lactam ring hydrolysis, C-S bond cleavage, and decarboxylation reactions. Toxicity assessments using ADMETlab 3.0 platform reveal that although most TPs showed reduced ecotoxicity and dermal toxicity compared to the parent compound, several intermediates exhibited elevated risks of nephrotoxicity and genotoxicity. Metagenomic analysis indicates that long-term CTX exposure reshaped the microbial community, enriching methanogens such as Methanothrix soehngenii and Methanosarcina mazei, though these taxa might not directly participate in CTX degradation. Several archaeal and bacterial MAGs carrying functional genes, including lactam hydrolase, thioesterase, and decarboxylase, were identified, suggesting a collaborative and functionally diverse microbial network involved in CTX transformation. This study offers mechanistic insights and technical foundations for advancing anaerobic biotechnologies in the treatment of antibiotic-contaminated wastewater, while highlighting the need for ongoing monitoring of potential long-term risks associated with TPs.

Vegetation in Karst regions is highly sensitive to climate change, yet vegetation-climate relationships remain poorly quantified across spatial scales in these complex landscapes. Using 2000-2022 MODIS data, we apply kernel Normalized Difference Vegetation Index (kNDVI)-which reduces soil/rock background effects-to examine climate-vegetation dynamics at pixel, vegetation-type, and regional scales in Southwest China Karst Typical Region (SWCKTR). Multi-method correlation analyses (Pearson, detrended, and moving-window partial correlations) reveal scale-dependent patterns. Regional analysis shows persistent greening (0.0048 yr^-1) despite warming (0.028 °C/year) and drying (-5.19 mm/year), with temperature as the dominant driver (R = 0.3289, p < 0.01). At the pixel scale, 61.32% of areas show positive temperature correlations, while 92.65% show negative precipitation correlations, reflecting karst hydrological constraints. Vegetation-type analysis reveals divergent sensitivities: Northern Tropical Humid Semi-Evergreen Seasonal Rainforest exhibits the fastest spring greening (0.0086 yr^-1, p < 0.01) and positive autumn precipitation correlation (0.3705, p < 0.01), while Subtropical Mountain Coniferous Forest shows negative precipitation responses across all seasons (summer: 0.5808, p < 0.01) and autumn degradation (-0.0014 yr^-1). Seasonally, spring shows the fastest regional greening (0.0069 yr^-1, p < 0.01) with positive climate correlations, while summer exhibits the slowest growth (0.0039 yr^-1) despite strongest warming. Residual analysis indicates climate factors dominate (>80% of pixels), though human activities contribute significantly near urban centers (>10% positive residuals). Multi-scale integration reveals hierarchical climate-vegetation coupling, with temperature effects consistent across scales while precipitation effects vary by scale, season, and vegetation type.

Mycorrhizal associations drive plants absorb water and nutrients, thereby promoting plant community diversity and carbon (C) stock. However, the relationship between the mycorrhizal dominance and tree diversity and C stock remains unclear. Additionally, it is important to explore whether these relationships will change with spatial scale. Using observations from 456 field plots (each 0.1 ha) in a large natural temperate forest region, this study presents new evidence about the effects of the dominance of ectomycorrhizal (EcM) plants on tree diversity and C stock, and how these relationships change with the spatial scale. We found that the relationship between EcM-dominance, tree diversity, and C stock aligns with the mycorrhizal mixture hypothesis. Basal area promotes diversity and C stock. Diameter variation enhances diversity but reduces C stock. The explanatory power of EcM proportion for diversity and C stock significantly increases with spatial scale, along with the strengthening of structural variables' mediating effects. Our findings suggest that mycorrhizal dominance significantly influences forest carbon sequestration and biodiversity conservation. By exploring the cross-scale regulatory mechanisms of mycorrhizal dominance on forest structure-functioning relationships, our study provides important theoretical support for sustainable forest management.

Soil-Aquifer Treatment (SAT) systems are a sustainable option for improving wastewater quality and addressing freshwater scarcity. This study assessed how recharge operation (continuous vs. pulsed) and reactive barriers of natural organic materials influence contaminants of emerging concern (CECs) removal from treated wastewater effluents. Our results demonstrate that continuous recharge enhances SAT system performance, achieving CECs removal efficiencies up to 58% in woodchip barriers and 35% in compost barriers, compared to 20-25 % under pulsed recharge. Reactive barriers promoted microbial activity by releasing labile DOC, generating redox gradients, and supporting both adsorption and biodegradation processes. Pulsed recharge led to temporary CECs release although further removal occurred along the aquifer. Low molecular weight, polar, aromatic and readily biodegradable CECs were efficiently removed, while nonpolar and chemically stable compounds showed lower removal or accumulation. Physicochemical factors such as pH (6.8-7.8), oxygen availability, and ionic composition strongly influenced treatment outcomes. The use of locally available, low-cost materials such as woodchips and vegetable compost as reactive barriers, combined with passive SAT operation, supports the system's cost-effectiveness.

Mackinawite (FeS) can effectively activate peroxydisulfate (PDS) for pollutant degradation via synergistic radicals (SO₄^•- and HO•), yet the role of nonradical species (Fe(IV)) has been overlooked. PDS activation by FeS was investigated on the basis of operating parameters, reactive species, the quantitative structure-activity relationship (QSAR), and environmental applications. Compared with radicals, Fe(IV) played a secondary role in contaminant degradation. The radical and Fe(IV) contributions were assessed: the Fe(IV) contribution became more distinct with decreasing [PDS]/[FeS] ratio, initial pH, and operating temperature. A QSAR model regarding degradation rate (k) and molecular descriptors of fifteen organic compounds was developed and assessed. The PDS activation capability suffered kinetic retardation with coexisting natural matters (e.g., humic acid and anions) and solvent exchange with real water matrices. The repetition test showed that the treatment efficiency started to decrease after the first three runs then gradually declined when the catalytic cycle increased, which was ascribed to the Fe(II)-to-Fe(III) and S(-II)-to-SO₄^2- conversions on the surface of FeS during PDS activation. The binding energy of PDS on FeS was -9.471 eV based on density functional theory (DFT) method. These findings provide both meaningful insights into nonradical reactive species produced during persulfate activation and a QSAR model for predicting contaminant removal.

The Three Gorges Dam, as the largest hydropower project in the world, has created a relatively static water environment that promotes the frequent occurrence of algal blooms in the backwater area, thereby exerting negative impacts on the ecological environment and socio-economic benefits of the reservoir. The triple oxygen isotope technique builds upon the capabilities of conventional hydrogen and oxygen isotopes for tracking water exchange processes between different water bodies, while enhancing the unique advantage of δ¹⁷O in resisting equilibrium fractionation effects induced by temperature variations. This innovative approach is applied to the Three Gorges Reservoir specifically to explore the interactions between hydrodynamics and algal bloom formation. The results show that the triple oxygen isotope composition of the mainstream is lower than that of its tributaries, with higher isotope values observed in upstream tributaries. End-member mixing analysis indicates that the average contribution of mainstream water to individual tributaries increases progressively as the river approaches the dam. Furthermore, based on the Ward's classification method, tributary sampling sites with isotope values similar to those of the mainstream exhibit significantly higher frequencies of algal blooms than local rain-fed rivers, demonstrating that channels characterized by long water residence times and low flow velocities provide favorable conditions for algal bloom outbreaks. This study highlights the influence of reservoir-induced hydrological alterations on algal dynamics and provides scientific guidance for the effective management of ecological environments in backwater regions.

Rain gardens can effectively manage stormwater runoff. However, existing hydrological models cannot accurately evaluate rain garden performance, hampering informed decision-making. This study improved the simulation of rain garden's key processes in the Soil and Water Assessment Tool (SWAT), including implementation area, surface runoff distribution, bypass and orifice flows, percolation dynamics, and sub-daily temporal resolution. The improved SWAT was calibrated/validated using field-scale observed rain garden data, which showed good model performance. And then the model was demonstrated in Brentwood watershed (Austin, TX) to assess the long-term impacts of various rain garden designs. Increasing the fraction of runoff from pervious/impervious areas draining to rain garden significantly reduced discharge volume (37.41%-65.02%), peak discharge (e.g., 43.62%-57.32%), and combined sewer overflow (CSO) (e.g., 42.81%-63.53%). Deeper amended soil layers of rain gardens only marginally reduced discharge volume (64.86%-65.08%), peak discharge (e.g., 57.11%-57.39%), and CSO (e.g., 63.35%-63.59%). A larger ratio of rain garden's surface storage area to the pervious area substantially decreased discharge volume (56.81%-74.56%), peak discharge (e.g., 48.56%-67.55%), and CSO (e.g., 54.87%-72.80%). Increasing the depth of rain garden's surface storage and height of the orifice from the bottom of the rain garden's surface storage slightly reduced discharge volume (63.63%-67.75%), moderately decreased peak discharge (e.g., 55.83%-60.32%), and slightly lessened CSO (e.g., 62.35%-65.95%). Among different types of amended soil from sand, loamy sand, sandy loam, to loam exhibited slightly lower effectiveness in reducing discharge volume (65.61%-63.34%), peak discharge (e.g., 57.87%-56.17%), and CSO (e.g., 64.19%-61.86%). Therefore, the improved SWAT can provide valuable decision-support for optimizing rain garden design.

Transboundary aquifers (TBAs) are shared by different political entities, and their management often requires multilateral efforts. However, despite their strategic importance in sustaining ecosystems and human communities, the level of cooperation over TBAs remains generally low. Lack of awareness and political willingness are often cited for this. This paper further demonstrates the need for and relevance of TBA cooperation through an overview of real cases of cross-border groundwater impacts and joint management interventions across the world. The product of an extensive review of academic and grey literature, this study provides key insights into the types of cross-border groundwater impacts and joint management interventions, as well as the TBA settings where cases have been identified. This allows for important lessons on the scope of TBA cooperation to be drawn. Notably, the evidence-base suggests that in large TBAs, joint management interventions could often be prioritized over the border area. It also shows the need for proactive cooperation mechanisms to develop joint management interventions, not only to mitigate or remediate cross-border groundwater impacts, but also to prevent them.

Nitrogen fertilizer is essential for increasing forage productivity but often comes at the cost of higher greenhouse gas (GHG) emissions, which raises concerns about long-term sustainability. To address this challenge, the present study evaluated an integrated nitrogen fertilizer management by combining organic and chemical nitrogen sources, aimed to improve forage yield and nutritive quality while mitigating GHG emissions in alfalfa-grass mixed grassland. A two-year field experiment (2023-2024) was conducted in arid grassland to evaluate the effects of litter (LT), sheep excreta (SE), and chemical nitrogen fertilizer (CF) applied individually or in combination (CF + LT, LT + SE, CF + SE) on hay yield, forage quality, soil mineral nitrogen, and GHG fluxes. The results revealed that combined applications, particularly CF + SE, improved forage quality, reflected a decrease in neutral detergent fiber (37.7-37.2%) and acid detergent fiber (37.7-34.83%) and an increase in crude protein (115.0-143.8%) and hay yield (108.8-91.1%) in 2023 and 2024 compared to unfertilized control (CK). Soil nitrate and ammonium varied significantly, with CF + LT showing the highest nitrate contents. In both years, the highest N₂O emissions were evident with CF, while CF + SE reduced cumulative N₂O emissions by 45.5-39.2% compared to CF. Global warming potential and greenhouse gas emissions intensity were highest under CF, while CF + SE reduced them by 47.6-41.3% and 51.8-47.6% compared to CF in 2023-2024, respectively. Integrated fertilizer treatments effectively balanced the increase in forage yield with lower global warming potential and greenhouse gas emission intensity. Overall, results demonstrated that integrated nitrogen fertilizer management can improve productivity while minimizing environmental concerns, offering a sustainable management practice for cultivated grasslands in arid regions.