Search Results (215)

Background: Drilling slurry, a waste material generated during natural gas extraction, requires careful chemical characterization to determine its environmental hazard classification and inform appropriate management strategies. Methods: This study characterizes the drilling fluid used as raw material and the resulting drilling slurry waste, using a case study sample from the Buzău extraction area (Well 1 Florica, S.N.G.N. Romgaz S.A.), including total composition analysis, three-stage leaching tests, linear regression of leaching kinetics, and standardized geoaccumulation indices (Igeo, CF, PLI). Results: Total composition analysis confirmed low heavy metal concentrations (Cd = 0.02, Cr = 0.05, Pb = 0.64, Zn = 2.82 mg/kg dry matter). All leachate parameters remained below non-hazardous waste thresholds (Order No. 95/2005), with safety factors of 20–100× for regulated metals and 1.2–2.7× for chlorides, sulphates, and dissolved organic carbon. Standardized pollution indices confirmed Class 0 (unpolluted) status for all five metals, with a composite Pollution Load Index of 0.0124. Leaching regression analysis revealed dissolution-controlled release for chlorides, sulphates, and zinc (R² > 0.93) versus matrix-retention behavior for copper, nickel, cadmium, and chromium. Comparative analysis showed horizontal drilling generates approximately 146% more waste volume than conventional vertical drilling (170 m³ versus 69 m³ at 2100 m depth). Conclusions: The analyzed drilling slurry meets non-hazardous waste classification with substantial safety margins, corroborated by three independent analytical frameworks. Waste minimization strategies and biodegradable fluid substitution offer practical pathways to reduce the environmental footprint of natural gas drilling operations. Full article

This critical perspective review first classifies glyphosate-sensing platforms and then evaluates their analytical applicability to agricultural runoff. Platforms are divided at the primary level into optical and electrochemical transduction, because these families measure different physical signals and have different sources of matrix interference. They are then grouped by the process that produces selectivity or signal change: direct interaction or metal coordination, affinity recognition by aptamers, antibodies, or molecularly imprinted polymers, catalytic modulation by enzymes or nanozymes, and separation or preconcentration before detection. This hierarchy distinguishes recognition chemistry from transduction method and device configuration. The review next defines four intended analytical applications—trace surveillance, runoff event screening, spill triage, and laboratory-adjacent confirmation—and compares them in terms of matrix, target concentration range, sample preparation, reporting metrics, and quality control requirements. Glyphosate occurs in dissolved and particle-associated forms, degrades mainly to AMPA, and coexists with phosphate, glufosinate, divalent cations, natural organic matter, and suspended sediment. Consequently, the lowest reported LOD is rarely the sole criterion for selecting a method. Matrix-matched calibration, spike recovery, selectivity, response time, storage stability, reader requirements, and invalid result rules determine whether an assay is suitable for a specified analytical application. The most defensible near-term approach combines matrix-specific sample preparation, platform-specific controls, and LC-MS/MS confirmation when results are regulatory, contested, or close to a decision threshold. Full article

Biogenic or microbial methane (CH₄) emissions, believed to be the main driver of the recent surge in global atmospheric CH₄ emissions, have altered monitoring, measurement, and mitigation of fossil-fuel emissions. As of 1981, over 20% of the world’s natural gas reserves were biogenic in origin. Additional biogenic CH₄ reserves from coal have been discovered since 1981 mixed (40–80%) with thermogenic CH₄. Biogenic CH₄ accumulates up to 100% in coal reservoirs in the Powder River Basin (PRB), USA. Biogenic CH₄ is generated by microbial breakdown of fossil organic matter as an early-stage (primary) type during burial over geologic time and is rarely preserved. Also, biogenic CH₄ is generated as a late-stage (secondary) type from recent geologic to present times and is commonly preserved. Late-stage biogenic CH₄ is sustained by nutrients and microbes in meteoric/surface waters discharged into coal aquifers. Groundwater is pumped from wells in coal aquifers to desorb and produce CH₄ and dewater coal mines. The co-produced water with dissolved CH₄ is discharged into diverse surface aquatic systems. The emission factors (EFs) of co-produced water are 2.0522 × 10⁻⁹ Gg CH₄/gal of water in the PRB and 2.0694 × 10⁻³ Gg CH₄/well in the Black Warrior Basin, U.S. Accurate data on biogenic CH₄ emissions from coal sources is a major gap in the accounting of current global groundwater-driven CH₄ whose average flux is estimated to be 3.9 ± 6.2 mmol/m²/day or accounting for up to 70% of CH₄ emissions from surface aquatic systems. Biogenic CH₄ emissions from coal mining and coalbed gas extractions and related infrastructures are overlooked because the focus has been on coalmine methane (CMM) emissions. CMM data from ground-based measurements is highly variable and used by the Intergovernmental Panel on Climate Change three-tier system to estimate EFs for national inventories. However, 90% of CMM emissions are attributable to a small group of the most coal-consuming-and-producing countries but fails to capture other coal sources worldwide. This created gaps and “blind spots” in “unstructured” low-concentration, diffused biogenic CH₄ emission data. These key “blind spots” include sources from flooded, abandoned coal mines; coalbed methane (CBM) co-produced water with dissolved CH₄ and infrastructures/facilities; and groundwater drawdown from water withdrawals during coal mining and CBM extraction. Also, a critical “blind spot” is the mixing of biogenic CH₄ emissions from subsurface coals with biogenic CH₄ generated at the surface from wetlands, agriculture, and landfills/wastes, which grew 85% from 2008 to 2020. Limited understanding of the mixing of biogenic CH₄ from diverse sources and their contributions to global methane requires accurate attribution of overlapping isotopic signatures (δ¹³C_CH4 and δD). This paper addresses knowledge gaps in coalbed biogenic CH₄ emissions by a systematic review of the literature and specific study cases, which provided insights on key “blind spots” in their mitigation. Full article

Leaf litter decomposition is a key pathway for carbon transfer from forest ecosystems to soils and surface waters. Dissolved organic matter (DOM) released during early-stage leaching represents a potentially reactive fraction of this carbon pool; however, its molecular composition and short-term reactivity remain insufficiently characterised. This study provides a comparative characterisation of DOM released from composite leaf litter samples representing five common deciduous tree species (Betula pendula, Carpinus betulus, Alnus glutinosa, Populus tremula, and Quercus robur) under controlled laboratory conditions. Leaf material collected from multiple trees per species was pooled to obtain a single composite sample; therefore, replicate leaching experiments represent procedural rather than biological replication. DOM was isolated using solid-phase extraction (SPE) and analysed by gas chromatography–mass spectrometry (GC–MS) following trimethylsilyl (TMS) derivatisation, while chemical oxygen demand (COD) and biochemical oxygen demand (BOD₅) were used as indicators of oxidative reactivity and short-term biodegradability. The applied analytical approach captures a selective and operationally defined fraction of DOM, primarily low-molecular-weight and derivatisable compounds; therefore, the results are interpreted as semi-quantitative compositional fingerprints. Carbohydrates, phenolic compounds, and low-molecular-weight organic acids dominated the detected fraction of DOM, with differences observed among composite samples. The composite samples representing A. glutinosa and P. tremula contained higher relative proportions of carbohydrate-related compounds, whereas the composite samples representing B. pendula and C. betulus showed higher relative contributions of aromatic compounds. Apparent differences in BOD₅ were observed among composite samples; however, these observations likely reflect procedural variability rather than independent biological effects. The results indicate variability in DOM composition and apparent reactivity among composite litter samples under controlled laboratory conditions. Due to the lack of biological replication and the selective nature of the analytical approach, the findings should be interpreted as exploratory and not as evidence of generalised tree-species effects. Full article

Acid mine drainage (AMD) is enriched with arsenite (As(III)), arsenate (As(V)), and jarosite. While jarosite can immobilize arsenic (As) through adsorption and other mechanisms, it dissolves and transforms into other minerals under near-neutral and reducing conditions via microbial mediation, thereby altering As fate. Fulvic acid (FA), a ubiquitous natural organic matter in the environment, has been proven to exhibit complex interactions with various iron minerals, Fe/S-metabolizing microorganisms, and As. However, the role of FA in the bioreduction and transformation of jarosite, as well as its subsequent impact on As mobility and fate, remains unclear. This study aims to elucidate the regulatory effect of FA on the biodissolution and transformation of jarosite, and the corresponding changes in As speciation. The results showed that FA exerted contrasting effects depending on arsenic speciation. In the As(III) treatments, FA intensified the inhibition of microbial dissimilatory sulfate reduction, suppressed sulfide production, and consequently limited orpiment formation. In contrast, in the As(V) treatments, FA enhanced the association of As(V) with jarosite surfaces, reduced aqueous As stress, and supported the persistence of As-tolerant sulfate-reducing populations. This promoted jarosite transformation toward mackinawite and facilitated As immobilization through orpiment precipitation. This study reveals the critical role of FA in the migration and transformation of As in mining areas, providing novel insights for optimizing AMD remediation strategies such as soil capping. Full article

Eutrophication remains a persistent water-quality problem in shallow lakes, where external inputs interact with internal loading and biogeochemical cycling. Although floating treatment wetlands (FTWs) are increasingly promoted as nature-based solutions for water remediation, their field-scale interpretation in hydrologically complex eutrophic lakes remains challenging. This study examined the spatial organization of water quality during the operation of a floating-island system in a eutrophic urban lake affected by polluted tributary inflow. The study was not designed to quantify isolated FTW removal efficiency, but to evaluate spatial water quality organization during FTW operation under real-use field conditions. Water quality was monitored over two growing seasons across six functionally defined zones, and spatial and temporal patterns were analyzed using descriptive statistics and linear mixed-effects models. The results showed parameter-specific spatial structuring rather than a uniform treatment response. The clearest inlet-lake contrasts were observed for electrical conductivity (EC), suspended matter (SM), and nitrate nitrogen (NO₃-N), whereas biochemical oxygen demand (BOD₅), ammonium nitrogen (NH₄-N), and total organic carbon (TOC) showed lower values at the inlet and higher values in downstream zones. Dissolved oxygen (DO), oxygen saturation (SO), chemical oxygen demand (COD), nitrite nitrogen (NO_2-N), and orthophosphate phosphorus (PO₄-P) showed moderate or non-robust zonal effects. These findings indicate that FTWs in shallow eutrophic lakes should be evaluated through functional zoning and parameter-specific interpretation rather than as isolated units with uniform removal responses. Full article

Ferrate(VI) has increasingly been proposed as an environmentally friendly oxidant due to its high reactivity and the relatively low toxicity of its by-products. However, its performance in degrading emerging pollutants (EPs) has not been systematically compared with conventional systems. This study presents a novel comparative assessment of three oxidation systems for the degradation of acetaminophen (APAP): (i) Fe⁰-activated hydrogen peroxide (HP), (ii) Fe⁰-activated persulfate (PS), and (iii) a commercial ferrate(VI)-based product, Envifer^® (Fe(VI)). Optimal conditions were determined based on degradation kinetics, pH dependence, and oxidant stability. Oxidant systems were then evaluated in realistic matrices, including tap water and synthetic wastewater. When UP water was used, the HP/Fe⁰ system achieved the highest APAP mineralization (i.e., 66%) with 1 mM of oxidant dosage, and PS/Fe⁰ was shown to be effective without pH adjustment. Nevertheless, these heterogeneous systems presented serious limitations when applied in more complex matrices. Fe(VI) instead achieved a rapid APAP degradation even in the presence of carbonates and natural organic matter without pH adjustment. This represents a key advantage over HP- and PS-based systems, enabling simpler implementation and lower chemical demand. Furthermore, Fe(VI) resulted in lower dissolved iron concentrations, potentially enabling less intensive post-treatment requirements. Overall, the results identify Fe(VI)-based AOPs as a potentially green alternative to conventional systems for wastewater treatment. Full article

Primary succession following glacier retreat provides a natural system for testing whether soil development simply shifts fine roots along a single acquisitive–conservative axis orinstead changes the nutrient-acquisition pathway that dominates at the community level. We hypothesized a stage-dependent sequence, from substrate-limited exploration, to transient morphological capture, and finally to rhizosphere-mediated biochemical mobilization. To test this idea, we quantified fine-root morphology, absorptive-transport partitioning, anatomy, phosphatase activity, exudation, community-scale belowground structure, and soil and rhizosphere properties across woody communities representing approximately 20, 40, and 90 years since deglaciation in the Hailuogou Glacier foreland. Across succession stages, bulk density and pH declined, whereas field capacity, soil carbon, and soil nitrogen increased, indicating rapid development of the belowground resource environment. Fine-root strategies did not fall along a single acquisitive–conservative continuum. Instead, morphological nutrient capture peaked at intermediate succession: the 40-year stage had the highest specific root length, specific root area, absorptive-to-transport root length ratio, and root nitrogen concentration. In contrast, the 90-year stage showed lower specific root length but higher dry matter content, thicker cortex, greater standing fine-root biomass, larger rhizosphere volume, higher phosphatase activity, and greater area-based carbon exudation. This late-successional syndrome coincided with stronger extracellular enzyme activity, larger dissolved organic carbon and nitrogen pools, and higher microbial biomass, despite negative net nitrogen mineralization. Species-level analyses showed that biochemical-input traits were jointly shaped by successional stage, species identity, and their interaction. Together, these results show that primary succession did not simply increase or decrease root acquisitiveness. Instead, as soils developed, it changed the nutrient-acquisition pathway that dominated, with direct implications for nutrient cycling and vegetation dynamics in rapidly developing glacier-foreland ecosystems. Full article

This study investigates the geochemical behavior and transport mechanisms of Rare Earth Elements (REEs), Yttrium (Y), Zirconium (Zr), and Hafnium (Hf) in three natural water systems under reducing conditions: the Santa Barbara and Occhio dell’Abisso mud volcanoes and a sulphureous spring at Villafranca Sicula. A comprehensive fractionation approach was applied to isolate the truly dissolved fraction (TDF < 10 kDa), the colloidal fraction (10 kDa < CF < 450 nm), the suspended particulate matter (SPM > 450 nm), and the associated bottom sediments. Analytical results reveal that REE distribution is significantly influenced by redox conditions and solid–liquid interface processes. The absence of negative Cerium (Ce) anomalies and the presence of pronounced positive Europium (Eu) anomalies in the Santa Barbara and Occhio dell’Abisso waters suggest strongly reducing environments where Eu²⁺ stability is enhanced. Shale-normalized patterns indicate that, while SPM and sediment fractions often exhibit Middle REE (MREE) enrichment, linked to Mn-bearing and Fe-oxyhydroxide phases, the dissolved phase reflects dissolution processes governed by a non-CHARAC (CHarge-and-RAdius-Controlled) behavior. Furthermore, the study highlights a significant decoupling in the Zr/Hf and Y/Ho pairs. While these pairs remain coherent during magmatic processes, they undergo mutual fractionation in aqueous systems due to differential reactivity toward colloidal surfaces and organic ligands. Specifically, Zr/Hf ratios in the colloidal and dissolved fractions deviate from chondritic values, driven by the preferential scavenging of Hf onto mineral surfaces. These findings underscore the utility of REE and Zr-Hf systematics as high-resolution tracers for reconstructing water–rock interaction processes and elemental cycling in complex hydrological environments. Full article

Three–dimensional excitation–emission matrix (3D–EEM) fluorescence spectroscopy is widely applied for the rapid characterization of dissolved organic matter (DOM) in aquatic environments. However, conventional decomposition based on parallel factor analysis (PARAFAC) requires multiple spectra and manual intervention, limiting its applicability for rapid analysis and future online implementation. The purpose of this study is to develop an efficient data–driven method capable of decomposing fluorescence components from a single 3D–EEM spectrum. We propose a conditional single–spectrum decomposition network (CSSD–Net) based on the encoder–decoder model. The encoder extracts fluorescence features from the input spectrum, while the decoder combines these features with conditional information on component count to generate up to five component maps. The component count can be automatically predicted by CSSD–Net or manually specified to support flexible application scenarios. CSSD–Net was trained using publicly available component spectra from the OpenFluor database without PARAFAC preprocessing. Validation on natural water samples demonstrates that the results obtained from CSSD–Net using a single sample are highly consistent with those from PARAFAC using multiple parallel samples, with a mean Tucker’s congruence coefficient (TCC) of 0.9615. These results show that CSSD–Net provides a fast and practical solution for decomposing single 3D–EEM spectra under constrained aquatic scenarios, and it has potential for future near–real–time and in situ applications. Full article

Removing trace amounts of dissolved organic matter (DOM) has always been a significant issue in the field of environmental science and engineering. Herein, a UV-coupled O₃ micro-nano bubble (O₃-MNB) system was constructed, demonstrating superior efficiency in eliminating DOM compared to bulk O₃-MNB oxidation and direct UV photolysis. Various advanced analytical techniques, including in situ electron paramagnetic resonance, Fourier transform infrared spectroscopy and three-dimensional excitation–emission matrix, were employed to reveal the mechanism of the reaction process. Benefiting from the abundant interfacial area and enhanced mass transfer efficiency provided by the micro-nano bubbles, along with the simultaneous generation of reactive oxygen species such as •OH through UV activation, the UV/O₃-MNB system demonstrates excellent performance in removing DOM, and more than 90% of the mineralization rate was achieved after 1 h reaction. Furthermore, the findings were verified using both municipal water and natural surface water, and the proposed system also shows advantages in energy consumption compared to direct UV irradiation and conventional O₃ treatment, with an energy consumption of 25 kWh/mg dissolved organic carbon. This study innovatively integrates UV light with O₃-MNB technology, offering novel insights for advanced water purification and providing valuable references for practical engineering applications. Full article

Methane (CH₄) emissions in urban areas remain a major source of uncertainty in greenhouse gas inventories, particularly in Eastern European cities, where observational studies are limited. This study presents a comprehensive, system-based assessment of CH₄ sources in Cluj-Napoca, Romania, based on high-resolution in situ measurements across five representative urban systems: aquatic environments (AQs), natural gas distribution end-use points (NG), sewer infrastructure (SE), building basements (BSs), and traffic emissions (TEs). Elevated CH₄ concentrations were consistently detected across all investigated systems, confirming the coexistence of both diffuse and point sources within the urban environment. Dissolved methane (dCH₄) in aquatic systems showed strong and persistent oversaturation relative to atmospheric equilibrium, reaching up to 3 × 10⁵% of air–water equilibrium, indicating active microbial methanogenesis enhanced by urban inputs of organic matter and nutrients. Measurements at natural gas end-use points revealed highly localized leaks with concentrations up to 482 ppmv. Sewer infrastructure exhibited extreme variability (up to 1222 ppmv), likely controlled by a combination of microbial production, hydraulic conditions, and potential interactions with adjacent gas distribution networks. Basement environments showed CH₄ accumulation up to 12 ppmv, reflecting the combined effects of gas leakage and limited ventilation. Measurements at vehicle exhausts identified transient CH₄ peaks reaching 162 ppmv during vehicle engine acceleration, with distinct ethane-to-methane ratios, indicative of pyrogenic sources. Overall, these results demonstrate that urban CH₄ emissions are spatially heterogeneous, temporally variable, and derived from multiple coexisting sources. The urban area should, therefore, be understood as a hybrid environment, with natural and anthropogenic CH₄ contributions. Full article

With the large-scale cultivation of transgenic Bacillus thuringiensis (Bt) crops, the Bt toxin released from Bt crops is continuously introduced into the soil. Its environmental fate represents a key indicator for assessing the ecological safety of transgenic crops. However, the persistence of Bt toxin in soil is influenced by both biotic and abiotic processes, and their respective contributions under natural conditions remain unclear. This study measured water-dissolved Bt toxin concentrations in paddy soil (PS) and red soil (RS) to compare the influence of biotic and abiotic factors on the dynamic retention of exogenous Bt toxin under different sterilization methods: no sterilization, heat sterilization (HT), and irradiation sterilization (IS). The water-dissolved Bt toxin exhibited a dynamic decrease–increase–decrease trend across all three treatments in both soil types during the 30 day experimental period. Bt toxin displayed rapid adsorption during the initial 2 h stage in RS, but subsequently showed a high desorption, whereas PS probably achieved more stable bonding through soil organic matter (SOM). Different sterilization methods significantly influenced the results by altering abiotic factors: Compared to CK, HT affected soil physicochemical properties and enhanced adsorption resilience, whereas IS caused minimal impact on the soil physicochemical properties, thereby providing a more accurate reflection of abiotic processes. And microbial, as biotic facters, also influence the reduction process of Bt toxin by participating in the adsorption–desorption–degradation equilibrium process. Therefore, we infer that over time, the concentration of water-soluble Bt proteins in the soil will tend toward zero. Additionally, the initial Bt toxin concentration influenced dynamic balance by adjusting adsorption site saturability, with more pronounced desorption reversibility at 500 ng/g concentrations. Overall, this study systematically reveals the effects of soil properties, microorganisms, and sterilization methods on Bt toxin persistence. The findings underscore the importance of selecting and justifying sterilization methods in related environmental behavior studies, while providing essential guidance for the scientific assessment of environmental risks posed by transgenic crops. Full article

Heavy metal pollution from mining activities and urban runoff poses a serious threat to public health and aquatic ecosystems in vulnerable communities around the Bolivia–Peru transboundary Lake Titicaca basin. This study evaluates the use of two abundant wetland plants—totora (Schoenoplectus californicus) and reed (Phragmites australis)—as low-cost, locally available biosorbents for the removal of dissolved iron (Fe²⁺) from the Pallina River, a major contaminant source to Cohana Bay. Monitoring data from Bolivia’s Ministry of Environment and Water (2019–2022) revealed Fe²⁺ concentrations exceeding the national legal limit (0.3 mg/L) by more than 20 times during the dry season. Laboratory experiments using synthetic Fe²⁺ solutions (20 mg/L) optimized biosorption conditions, identifying pH 5, 4–6 g/L biomass, fine particle size (0.15–0.212 mm), and a 3 h contact time as optimal. Both plants followed pseudo-second-order kinetics and Langmuir isotherms. Totora showed superior performance, achieving a maximum capacity of 7.8 mg/g compared to reed’s 2.9 mg/g. Continuous-flow column tests removed up to 95% of Fe²⁺ from synthetic water. When applied to real Pallina River water, totora achieved 50% Fe²⁺ removal despite reduced efficiency due to competing organic matter. The findings demonstrate the potential of totora-based biosorption as a scalable, nature-based solution for transboundary water management. The policy implications of this study are profound under the national and global water and wetland governance mechanisms and transboundary frameworks like the Binational Autonomous Authority of Lake Titicaca (ALT, est. 1996) and Ramsar Convention. Full article

Chemical coagulation is a highly important step of the conventional treatment processes, determination of the optimum coagulant dose to meet the demand of particulate materials and natural organic matters (NOMs) in raw water is crucial for good drinking water quality. WTC-Coag is a universal non-site-specific coagulant prediction model using three raw water quality parameters, UV₂₅₄, colour, and turbidity, as model inputs. The empirical model can determine the dose for maximum dissolved organic carbon (DOC) removal to achieve the conditions of enhanced coagulation; it also features an operator-selectable input—% setpoint (as % DOC removal)—to establish a dose for the desirable treated water quality. This hybrid modelling and control approach in practice is extremely useful for operators to be able to optimise the process by balancing between water quality and use of resources (chemical and sludge disposal costs) for sustainable operation. This paper discusses the practicality of this hybrid modelling approach via a long-term evaluation by comparing the plant dose against predicted dose using five years historical operations and water quality data. The assessment covered raw water quality change against treatment performance, predictability, usability and operator behaviour in response to the dose change situation. During the study period, five “black water” events were captured, and the performance of the predictability due to operational changes and operator’s response in these extreme events have been analysed. The comparison between the predicted enhanced dose and the plant dose indicated enhanced coagulation would not be always required. Furthermore, the selection of 50% setpoint from the targeted dose option matched well with the plant dose during which the lower-dose situation would be sufficient, with 90% of the predicted doses within ±10 mg/L of the plant dose and 95% of the predicted doses within ±15 mg/L of the plant dose during the normal period. The use of a correction factor to compensate for the particulate demand due to powdered activated carbon (PAC) dose during “black water” events has shown to be effective. The 50% setpoint matches with the plant alum dose over the entire period after accounting for the PAC dose, with 70% of the predicted doses within ±10 mg/L and 80% within ±15 mg/L of the plant dose. All the coagulation-related prediction functions have been evaluated and confirmed their non-site-specific nature. This study is unique in terms of using real operations data for an extended period to evaluate this novel hybrid modelling concept towards the sustainability goal. Full article