Journal of contaminant hydrology最新文献

{"title":"Microplastic surge in the Ariyankuppam river, Puducherry, India: A study on abundance, characterization, and pollution load index","authors":"Cheena Joshi ,&nbsp;Saoo Wan Emi Phyllei ,&nbsp;Sunidhi Bhatt ,&nbsp;Subhankar Chatterjee","doi":"10.1016/j.jconhyd.2025.104669","DOIUrl":"10.1016/j.jconhyd.2025.104669","url":null,"abstract":"<div><div>The increasing rate of microplastic (MP) pollution in the aquatic environment poses an escalating threat to marine ecosystems and several health concerns to humans. Ocean and Sea MP pollution has been a grave concern in recent decades, and rivers are considered one of the main channels that carry MP to the sea. Here, we investigated the MP abundance in the Ariyankuppam River, which flows through the Puducherry region in South India and merges with the Bay of Bengal. The water and sediment samples were collected from ten locations along the river over three months, from January to March 2024, coinciding with the post-monsoon phase in Puducherry, to understand the impact of seasonal variations on MP abundance. The average MP abundance of sediments and water was found to be 136.33 ± 24.75 particles/Kg and 124.83 ± 22.44 particles/L, respectively. A total of 7837 MP particles were detected, with approximately 52.2 % and 47.8 % originating from sediment and water samples. Fibers were major polymer forms, with an abundance of 79.4 % in sediment and 87.9 % in water samples. The classification of MP (0–3000 μm) reveals predominance of smaller particles, mainly within 0–500 μm and 500–1000 μm. High-density polyethylene (HDPE) and Low-Density Polyethylene (LDPE) were the dominant polymer types in sediments and water samples collected from ten sites along the river. Our results found not much of a significant difference in MP abundances across the months in both sediment and water samples. The Pollution Load Index (PLI) assessment indicated a Hazard Level I (&lt;10), a minimal risk level. These data will help the local government and other agencies take necessary measures for mitigation strategies to safeguard these vital water bodies.</div></div>","PeriodicalId":15530,"journal":{"name":"Journal of contaminant hydrology","volume":"274 ","pages":"Article 104669"},"PeriodicalIF":3.5,"publicationDate":"2025-07-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144595798","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Consequences of variations in flow magnitude and duration on water quality of the Apalachicola River floodplain","authors":"Love Kumar ,&nbsp;Matthew J. Deitch ,&nbsp;William K. Jones PE ,&nbsp;Lauren Williams ,&nbsp;Todd Z. Osborne ,&nbsp;Ramna Kumari","doi":"10.1016/j.jconhyd.2025.104668","DOIUrl":"10.1016/j.jconhyd.2025.104668","url":null,"abstract":"<div><div>Large coastal plain river systems are often characterized by complex networks of secondary channels and sloughs that support wetland forests and estuarine productivity. These sloughs have exceptional ecological importance but have been impacted by hydrologic alterations such as upstream water withdrawals, dam operations, dredging, and channel modifications. These changes reduce hydrologic connectivity between the river and its floodplain, primarily through sediment accumulation and morphological degradation at slough inlets. This study examines the effects of reduced flow and disconnection on water quality in three sloughs connected to a major floodplain river. Water monitoring stations were installed upstream and downstream in each slough to collect water level and water quality data. Streamflow records were developed using regular in-situ discharge measurements. The data was collected from June 2021 to December 2023. The results show that as streamflow in the main river recedes, flow through each slough often recedes to intermittence. This affects water chemistry in the slough, lowering dissolved oxygen (DO) to 0–3 mg/L, effects on electrical conductivity (EC) and pH were less consistent. Principal component analysis identified flow as a key driver of seasonal variation in water quality parameters such as conductivity and temperature. The findings of this research indicate that mitigating stagnation and hypoxia in these sloughs can be achieved by extending the duration for which river water freely flows within the slough channels.</div></div>","PeriodicalId":15530,"journal":{"name":"Journal of contaminant hydrology","volume":"274 ","pages":"Article 104668"},"PeriodicalIF":3.5,"publicationDate":"2025-07-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144595802","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Experimental evaluation of the impact of CO2/N2 mixture on residual water saturation during CO2 storage in saline aquifer","authors":"Yi Li ,&nbsp;Wendong Dan ,&nbsp;Jiaqi Zhao ,&nbsp;Zhikai Hu ,&nbsp;Ruiting Suo ,&nbsp;Liang Xue ,&nbsp;Li He ,&nbsp;Qingchun Yu","doi":"10.1016/j.jconhyd.2025.104674","DOIUrl":"10.1016/j.jconhyd.2025.104674","url":null,"abstract":"<div><div>Residual water critically constrains CO₂ geological storage efficiency, yet we discover that elevated CO₂ concentration in gas mixtures systematically reduces its saturation. By revealing that N₂ co-injection paradoxically enhances storage safety despite increasing residual water, this work provides transformative strategies for optimizing carbon sequestration with impurities. Specifically, in this study, nine sets of core-flooding experiments were conducted using three different ratios of a CO₂/N₂ gas mixture (50 % CO₂ + 50 % N₂, 75 % CO₂ + 25 % N₂, and 99.99 % CO₂). The experimental results indicate that an increase in the ratio of CO₂ within the gas mixture leads to a progressive reduction in residual water saturation, with the order of saturation being 50 % CO₂ + 50 % N₂ &gt; 75 % CO₂ + 25 % N₂ &gt; 99.99 % CO₂. Furthermore, a detailed mathematical relationship that delineates the connection between residual water saturation and drainage duration is presented, with coefficients <em>a</em> and <em>b</em> examined thoroughly. The incorporation of N₂ into the CO₂ mixture raises residual water saturation, as lower concentrations of CO₂ correlate with increased residual water saturation. However, the presence of N₂ effectively extends the CO₂ breakthrough time, making it more difficult for CO₂ to penetrate the rocks and thereby enhancing storage safety. As the concentration of CO₂ in the gas mixture increases, a reduction in contact angle values and interfacial tension (IFT) occurs. This variation results in a decrease in capillary pressure, which facilitates the displacement or migration of fluids within the core pore space. Concurrently, the viscosity ratio of the gas phase to the liquid phase reduces the viscous resistance in the pores and improves displacement efficiency. Furthermore, the experimental results are primarily influenced by capillary forces. This study enhances the theoretical understanding of CO₂ storage, and provides valuable insights for evaluating the feasibility of CO₂ storage projects that include impurities.</div></div>","PeriodicalId":15530,"journal":{"name":"Journal of contaminant hydrology","volume":"274 ","pages":"Article 104674"},"PeriodicalIF":3.5,"publicationDate":"2025-07-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144589158","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Harnessing deep learning for fusion-based heavy metal contamination index prediction in groundwater","authors":"Ali Asghar Rostami ,&nbsp;Zahra Sedghi ,&nbsp;Ata Allah Nadiri ,&nbsp;Rahim Barzegar ,&nbsp;Natasha T. Dimova ,&nbsp;Venkatramanan Senapathi ,&nbsp;Abu Reza Md. Towfiqul Islam","doi":"10.1016/j.jconhyd.2025.104672","DOIUrl":"10.1016/j.jconhyd.2025.104672","url":null,"abstract":"<div><div>Groundwater contamination by heavy metals presents a major environmental threat with serious implications for public health and resource sustainability. This study proposes a novel deep learning-based data fusion framework to predict heavy metal contamination index in groundwater, focusing specifically on Manganese (Mn), Iron (Fe), Arsenic (As), and Lead (Pb)—elements found to exceed World Health Organization (WHO) permissible limits in the Gultepe-Zarrinabad sub-basin, Zanjan, Iran. Five widely used water contamination indices (e.g., EHCI, HPI, HEI, MI, and CI) were integrated into a unified composite metric using a customized root-based data fusion and normalization approach. This fused index was modeled using a Deep Neural Network (DNN) and benchmarked against traditional machine learning models—Decision Tree (DT), k-Nearest Neighbors (KNN), and Artificial Neural Network (ANN). The DNN model achieved superior predictive accuracy (R² = 0.98), with minimal error (RMSE and MAE = 0.01) and excellent generalization capacity, outperforming all other models. This study marks a successful application of a fusion-based DNN approach for comprehensive groundwater heavy metal assessment, demonstrating its strong potential to support AI-enabled environmental monitoring and sustainable water resource management.</div></div>","PeriodicalId":15530,"journal":{"name":"Journal of contaminant hydrology","volume":"274 ","pages":"Article 104672"},"PeriodicalIF":3.5,"publicationDate":"2025-07-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144654200","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Health risk assessment of water resources within the lignite series of Obomkpa and environs, southern Nigeria","authors":"G.E. Odesa,&nbsp;P.N. Okanigbuan,&nbsp;M.O. Eyankware,&nbsp;C.S. Ngozi-Chika,&nbsp;Efetobo Oghenetega","doi":"10.1016/j.jconhyd.2025.104665","DOIUrl":"10.1016/j.jconhyd.2025.104665","url":null,"abstract":"<div><div>The study evaluated the quality of the surface water overflowing the lignite seams and groundwater in Obomkpa and its vicinity to ascertain its pollution status. Nineteen groundwater samples were collected and tested following APHA standards to assess physicochemical properties, including Cl, HCO3, SO4, Fe, Mn, Pb, Zn, Cr, Ca, Mg, and Na (mg/l). Additionally, six surface water samples were analyzed for polycyclic aromatic hydrocarbons (PAHs) alongside the physicochemical parameters. In a novel, integrated approach, the study simultaneously assessed both heavy metals and PAHs using a suite of advanced pollution and health risk indices such as Contamination Factor (CF), Pollution Index of Groundwater (PIG), Nemerow Pollution Index (NPI), Geoaccumulation Index (Igeo), and Entropy Water Quality Index (EWQI), as well as indices for PAHs such as Carcinogenic Toxic Equivalence (TEQs) and Excess Cancer Risk (ECR), were employed to determine the suitability of the water for domestic use. The results revealed a predominant Ca-Mg-HCO3 water type, with the evaluated PIG indicating that approximately 31.5 % of the groundwater samples fell within the low pollution categories. While EWQI showed that 20 % of the total samples fell within the good water quality categories, NPI indicated that 20 % of the samples were slightly polluted. The evaluated CF and Igeo revealed that the groundwater quality ranged from slightly polluted to significantly contaminated due to iron contamination. PAH content was minimal, ranging from 0 to 1 × 10–5 mg/L, which falls within the WHO (2015) acceptable limit for water consumption. An in-depth evaluation of the health hazards stemming from the cancer-causing properties of PAH-polluted water using TEQs and ECR further confirms that the water meets the standards for domestic use. Inferences from the principal component analysis suggested that the dissolution of ferruginous sandstone was the major influence on groundwater quality, highlighting the need for ongoing monitoring.</div></div>","PeriodicalId":15530,"journal":{"name":"Journal of contaminant hydrology","volume":"274 ","pages":"Article 104665"},"PeriodicalIF":3.5,"publicationDate":"2025-07-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144569917","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A Bayesian Maximum Entropy Fusion model for enhanced prediction and risk assessment of fluoride and arsenic contamination in groundwater","authors":"Jiang Zhang ,&nbsp;Changlai Xiao ,&nbsp;Xiujuan Liang ,&nbsp;Weifei Yang ,&nbsp;Linzuo Zhang ,&nbsp;Rongkun Dai ,&nbsp;Weifeng Li ,&nbsp;Heshan Ni","doi":"10.1016/j.jconhyd.2025.104664","DOIUrl":"10.1016/j.jconhyd.2025.104664","url":null,"abstract":"<div><div>In the central and western regions of Jilin Province, excessive groundwater extraction has resulted in elevated levels of fluoride (F⁻) and arsenic (As) in drinking water. Prolonged exposure to these contaminants is linked to endemic health issues, including dental and skeletal fluorosis as well as chronic arsenic poisoning, posing significant risks to both environmental integrity and public health. Since traditional models lack prediction accuracy, this study aimed to construct a Bayesian Maximum Entropy Fusion (BMEF) integrating hard and soft data for improved prediction of F⁻ and As concentrations and probabilistic estimations of contamination risk. This was accomplished by combining the spatial heterogeneity modeling of Geographically Weighted Regression (GWR), the probabilistic forecasting strength of Gaussian Process Regression (GPR), and the uncertainty quantification framework of Bayesian Maximum Entropy (BME). The BMEF model provided predictions of F⁻ with improvements in accuracy (R²) over GWR, GPR, and BME of 60.8 %, 112 %, and 26.9 %, respectively; improvements in As prediction were 456 %, 84.4 %, and 58.5 %, respectively. The model was able to identify high-risk F⁻ zones spanning 3208 km², 3650 km², and 5240 km² at 95 %, 90 %, and 75 % confidence levels, respectively; those for As were 3884 km², 4573 km², and 6490 km². The model effectively addressed the limitations of individual models in prediction accuracy and uncertainty quantification by integrating water quality sampling data with regression-based predictions. However, it faced challenges such as high computational complexity, sensitivity to data quality, and a lack of consideration for temporal variability.</div></div>","PeriodicalId":15530,"journal":{"name":"Journal of contaminant hydrology","volume":"274 ","pages":"Article 104664"},"PeriodicalIF":3.5,"publicationDate":"2025-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144562905","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Propensity and repercussion of microplastics in the soil-water-urban continuum","authors":"Manish Kumar ,&nbsp;Priyansha Gupta ,&nbsp;Shiwangi Dogra ,&nbsp;Dibyendu Sarkar ,&nbsp;Abrahan Mora ,&nbsp;Nancy Ornelas-Soto ,&nbsp;Jürgen Mahlknecht","doi":"10.1016/j.jconhyd.2025.104663","DOIUrl":"10.1016/j.jconhyd.2025.104663","url":null,"abstract":"<div><div>Despite consistently increasing efforts to reduce legacy and emerging pollutants like microplastic (MP), agro-ecosystems, particularly soil carbon is alarmingly threated to be replaced by plastic carbon, endangering the one health. While MPs have witnessed unprecedented research focus and frequency spike, the hydro-biological aspects in connection to urbanization, agricultural practices and ecosystem services are not explicitly discussed. Hence, we provide a comprehensive examination of MP sources, transport, and factors influencing their migration in soil and groundwater, with specific emphasis on urbanization, surface-groundwater interactions, and flooding, its interactions with organic and inorganic pollutants, antibiotic resistance genes, and potential routes exposure to humans, and toxicity augmentation. The investigation explicitly establishes the fact that flood-prone countries exhibit higher MPs infiltration into the greater depth of soil profile. However, plastic mobilization during undefended flood events varies significantly across the globe. Notably, China stands out with the highest MP concentrations in both agricultural soil and groundwater samples compared to other countries. MPs are found to be heterogeneously distributed across different soil depths, from shallow (0–5 cm) layers to deeper ones (up to 40 cm). On the other hand rapid urban development increases plastic waste on streets and other urban areas, and thus the influence of hydro(<em>bio</em>)logy-urbanization-agro-ecosystems nexus become highly significant. As MPs migrate through vadose zone via both vertical and horizontal transport mechanisms, it is imperative that interdisciplinary collaboration of experts from environmental science, hydrogeology, microbiology, material science, and engineering to understand and mitigate MPs contamination to achieve sustainable development goals.</div></div>","PeriodicalId":15530,"journal":{"name":"Journal of contaminant hydrology","volume":"274 ","pages":"Article 104663"},"PeriodicalIF":3.5,"publicationDate":"2025-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144589122","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Diffusive transport properties of seawater in calcite nanopores: A molecular dynamics study","authors":"Juan C. Burgos ,&nbsp;Sergio Bustamante ,&nbsp;Jairo A. Aviles ,&nbsp;Edgar Quiñones-Bolaños ,&nbsp;Mehrab Mehrvar","doi":"10.1016/j.jconhyd.2025.104631","DOIUrl":"10.1016/j.jconhyd.2025.104631","url":null,"abstract":"<div><div>Classical molecular dynamics (MD) simulations were used to explore the diffusive transport properties of seawater through porous media of different calcite structures. Two different calcite surfaces constituted the pore slit models with a size of 1.5 nm; seawater with a 3.5 wt% of salinity occupied the free volume between calcite surfaces at the corresponding average seawater density. The SPC/E water model was employed to describe the water molecules’ interactions, while a Buckingham-type potential modeled the calcite. All cross-interactions were modeled using the Lennard-Jones potential and Ewald sums electrostatics. The simulations demonstrated that calcite surfaces reduce the diffusivity of Na⁺ and Cl^{protect relax special {t4ht=−}} ions, and the magnitude of the diffusivity reduction depends on the structure of the calcite surface. The topology and charge distribution features of the energetically most stable calcite (104) surface led to a slight reduction in the electrolyte diffusivity. On the contrary, density profiles evidenced that the least stable calcite surface (100) favored preferential adsorption of Na⁺, leading to significant differences in ionic diffusion coefficients. Finally, the ionic-specific diffusion coefficients obtained from molecular dynamics simulations were loaded into an advection–dispersion model to simulate a seawater intrusion into coastal aquifers scenario, with parameters associated with a predominantly diffusive transport through the most stable calcite pore. The concentration profiles showed that minor differences between Na⁺ and Cl^{protect relax special {t4ht=−}} diffusivities result in Na⁺/Cl^{protect relax special {t4ht=−}} concentration disparities a few meters away from the coastline after years of seawater shifting the dispersion zone.</div></div>","PeriodicalId":15530,"journal":{"name":"Journal of contaminant hydrology","volume":"274 ","pages":"Article 104631"},"PeriodicalIF":3.5,"publicationDate":"2025-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144595799","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Association of toxic effects and the quality of surface water and wastewater: Application under environmental conditions and literature overview by CiteSpace","authors":"Sara Šariri ,&nbsp;Želimira Cvetković ,&nbsp;Tatjana Mijošek Pavin ,&nbsp;Zorana Kljaković-Gašpić ,&nbsp;Damir Valić ,&nbsp;Tomislav Kralj ,&nbsp;Amalia Brkić ,&nbsp;Zuzana Redžović ,&nbsp;Vlatka Filipović Marijić","doi":"10.1016/j.jconhyd.2025.104667","DOIUrl":"10.1016/j.jconhyd.2025.104667","url":null,"abstract":"<div><div>Monitoring of wastewaters is crucial for the protection of surface waters and should contain quality and toxicity analyses to ensure safety of aquatic organisms. In this study, the impacts of industrial and municipal wastewaters were assessed by examining the responses of organisms from different trophic levels, <em>Pseudokirchneriella subcapitata</em> (microalgae) and <em>Daphnia magna</em> (crustaceans), together with physical and chemical water parameters and total metal(loid) concentrations, separately in wastewater lagoons and four nearby sites in the karst Krka River in spring, summer and autumn. The sites in close proximity to the inappropriately treated wastewaters exhibited diminished ecological status, especially regarding COD, nutrients, turbidity, mineral oils, and elevated concentrations of metals (Cd, Co, Cu, Fe, Na, Ni, and Zn). Toxicity effects were confirmed for surface river water near the municipal wastewater outlet (hazard class III) and for basins with industrial wastewater (hazard class IV). Although such approach enabled determination of the toxic hazard of complex mixtures in aquatic environments, literature overview by CiteSpace showed that data in this field are limited and that European countries dominate in this area of research. In addition, multivariate statistical analysis confirmed association of water quality data and toxic effects and the importance of microbiotests in assessment of ecologically relevant risks for aquatic organisms.</div></div>","PeriodicalId":15530,"journal":{"name":"Journal of contaminant hydrology","volume":"274 ","pages":"Article 104667"},"PeriodicalIF":3.5,"publicationDate":"2025-07-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144563412","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Stable carbon and hydrogen isotope analysis applied to follow the anaerobic biodegradation of trimethylbenzenes in groundwater","authors":"Ouassim Boukaroum,&nbsp;Carine Demelas,&nbsp;Laurent Vassalo,&nbsp;Patrick Höhener","doi":"10.1016/j.jconhyd.2025.104666","DOIUrl":"10.1016/j.jconhyd.2025.104666","url":null,"abstract":"<div><div>Trimethylbenzene (TMB) isomers (1,2,3-TMB, 1,2,4-TMB, 1,3,5-TMB) are used as conservative tracers of alkylbenzenes in contaminated aquifers, but their resistance to anaerobic biodegradation remains uncertain. In this study, TMB degradation was investigated using enrichment cultures in microcosms under denitrifying, iron-, manganese- and sulfate-reducing conditions. Evidence for TMB biodegradation was gathered using concentration measurements, metabolites identification and multi-elemental compound specific isotope analysis (ME-CSIA). Degradation was &gt;80 % under all anaerobic conditions and followed first-order reactions, after fluctuating lag phases depending on the condition and compound. In a mixture, a selective degradation pattern was observed with 1,2,4-TMB degradation starting almost immediately, whereas 1,3,5-TMB and 1,2,3-TMB degradation began only after 1,2,4-TMB was fully consumed. First-order biodegradation rates ranged from 0.03 ± 0.00 to 0.16 ± 0.02 day⁻¹ for 1,2,3-TMB, from 0.16 ± 0.01 to 0.32 ± 0.05 day⁻¹ for 1,2,4-TMB and from 0.02 ± 0.00 to 0.11 ± 0.02 day⁻¹ for 1,3,5-TMB. Dimethylbenzoic acid isomers were detected, which are signature metabolic intermediates formed during the anaerobic degradation of TMBs via the fumarate addition pathway. Low carbon and hydrogen fractionation, associated with their strong variability, tends to suggest that non-fractionating steps provoke isotope fractionation masking. ME-CSIA permitted to reveal that TMB biodegradation is a complex multi-step process, with Λ ranging from 14 ± 9 to 107 ± 91 for 1,2,3-TMB, from 29 ± 6 to 120 ± 70 for 1,2,4-TMB and from 14 ± 6 to 58 ± 23 for 1,3,5-TMB. The results will allow to identify non-conservative behaviors of TMBs during reactive transport in groundwater.</div></div>","PeriodicalId":15530,"journal":{"name":"Journal of contaminant hydrology","volume":"274 ","pages":"Article 104666"},"PeriodicalIF":3.5,"publicationDate":"2025-06-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144534857","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}