Journal of contaminant hydrology最新文献

{"title":"Ensemble surrogate modeling of advective-dispersive transport with intraparticle diffusion model for column-leaching test","authors":"Amirhossein Ershadi,&nbsp;Michael Finkel,&nbsp;Binlong Liu,&nbsp;Olaf A. Cirpka,&nbsp;Peter Grathwohl","doi":"10.1016/j.jconhyd.2024.104423","DOIUrl":"10.1016/j.jconhyd.2024.104423","url":null,"abstract":"<div><div>Column-leaching tests are a common approach for assessing the leaching behavior and resulting environmental risks of contaminated soils and waste materials, which are frequently reused for various construction purposes. The observed breakthrough curves of the contaminants are influenced by the complex dynamics of solute transport and kinetic inter-phase mass transfer. Disentangling these interactions necessitates numerical models. However, inverse modeling and sensitivity analysis can be time-consuming, especially when sorption kinetics are explicitly described by intraparticle diffusion, which requires discretizing the domain both in the flow direction along the column axis and inside the grains. To circumvent the need for such computationally intensive models, we have developed two different ensemble surrogate models. These models employ two separate ensemble methods: random forest stacking and inverse-distance weighted interpolation. Each method is applied to base surrogate models that cover different parts of the parameter space. The base surrogate models use the method of Extremely randomized Trees (ExtraTrees). The defined parameter range is based on the German standard for column-leaching tests. To optimize the base surrogate models, we utilized adaptive-sampling methods based on three distinct infill criteria: maximizing the expected improvement, staying within a certain Mahalanobis distance to the best estimate (both for exploitation), and maximizing the standard deviation (for exploration). The ensemble surrogate model demonstrates excellent performance in emulating the behavior of the original numerical model, with a relative root mean squared error of 0.09. We applied our proposed ensemble surrogate model to estimate the complete posterior parameter distribution using Simulation-Based Inference, specifically Neural Posterior Estimation, to determine the full parameter distribution conditioned on copper-leaching data from two different soils. Samples drawn from the posterior distribution align perfectly with the observed data for both the surrogate and original models.</div></div>","PeriodicalId":15530,"journal":{"name":"Journal of contaminant hydrology","volume":null,"pages":null},"PeriodicalIF":3.5,"publicationDate":"2024-09-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S016977222400127X/pdfft?md5=6d4cab59d29b967fe9ea34b7771fa9f3&pid=1-s2.0-S016977222400127X-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142312782","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Low-temperature Aquifer Thermal Energy Storage combined with in situ bioremediation of chlorinated ethenes: Pilot-scale observations and model-based interpretation","authors":"Henning Wienkenjohann ,&nbsp;Klaus Mosthaf ,&nbsp;Line Mørkebjerg Fischer ,&nbsp;Lars Bennedsen ,&nbsp;John Flyvbjerg ,&nbsp;Mette Christophersen ,&nbsp;Massimo Rolle","doi":"10.1016/j.jconhyd.2024.104421","DOIUrl":"10.1016/j.jconhyd.2024.104421","url":null,"abstract":"<div><p>Microbial reductive dechlorination is a key process in aquifers contaminated with chlorinated ethenes and results in a net mass reduction of organic pollutants. Biodegradation rates in the subsurface are temperature-dependent and may be enhanced by increased groundwater temperatures. This study explores the potential of combining the temperature increase from low-temperature Aquifer Thermal Energy Storage with In Situ Bioremediation (ATES-ISB). The effects of highly dynamic groundwater flow and heat transport on microbial degradation rates were examined in a contaminated aquifer based on a pilot-scale experiment and a comprehensive process-based modeling analysis. The low-temperature ATES-ISB pilot test was carried out in Birkerød (Denmark), in an aquifer contaminated with trichloroethene by implementing a groundwater flow dipole, injecting heated groundwater, biostimulating the system with lactate and bioaugmenting it with a <em>Dehalococcoides</em> containing culture. Solute concentrations were monitored in four observation wells over the course of the test and a non-isothermal reactive transport model, solved in a two-dimensional heterogeneous domain, was developed to quantitatively interpret the experimental observations. The process-based numerical model also allowed evaluating the evolution of chlorinated ethenes concentrations considering different hydraulic, thermal, and operational scenarios. The results demonstrate the beneficial combination of ATES with in situ contaminant bioremediation, showing enhancement of contaminant mass reduction and more complete reductive dechlorination. The developed process-based model can be instrumental for the design and parameterization of pilot and full scale low-temperature ATES-ISB remediation in shallow aquifer systems.</p></div>","PeriodicalId":15530,"journal":{"name":"Journal of contaminant hydrology","volume":null,"pages":null},"PeriodicalIF":3.5,"publicationDate":"2024-09-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0169772224001256/pdfft?md5=a777b0396720df7811ea5ce0dc56eb2f&pid=1-s2.0-S0169772224001256-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142229318","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Non-Fickian transport processes accelerate the movement of PFOS in unsaturated media: An experimental and modelling study","authors":"John F. Stults ,&nbsp;Christopher P. Higgins ,&nbsp;Tissa H. Illangasekare ,&nbsp;Kamini Singha","doi":"10.1016/j.jconhyd.2024.104424","DOIUrl":"10.1016/j.jconhyd.2024.104424","url":null,"abstract":"<div><p>The transport of <em>per</em>- and polyfluoroalkyl substances (PFASs) through unsaturated source-zone soils is a critical yet poorly understood aspect of their environmental behavior. To date, most experimental studies have only focused on the equilibrium or non-equilibrium partitioning of PFASs to the air-water interface, or solid-phase based equilibrium or non-equilibrium transport. Currently, there are discrepancies between air-water interfacial partitioning (<em>K</em>_<em>ia</em>) results measured using a drainage-based column method (which supports a Langmuir isotherm) when compared to measurements from alternative experimental methods (which support a Freundlich isotherm). We hypothesize that this discrepancy is the result of non-Fickian transport conditions developing during column tests using the drainage method, which reduces the magnitude of the apparent <em>K</em>_<em>ia</em> (<em>K</em>_{<em>ia,app</em>}) when estimated using the retardation factor correlation from breakthrough curve experiments. To test the validity of this hypothesis, the drainage method was implemented using PFOS in a sand column and compared with prior data collected using a quasi-saturated column method. Results demonstrate that the apparent <em>K</em>_<em>ia</em> was reduced by 3 to 123-fold, resulting in up to 123-fold faster breakthrough of PFOS than predicted with the assumption of equilibrium adsorption to the air-water interface. A novel mobile-immobile model (MIM) of PFAS fate and transport was developed, incorporating a term for anomalously adsorbed solute in the mobile zone to explain highly anomalous data. The modelling results using a modified HYDRUS-1D software show that anomalous air-water interfacial adsorption and/or flowpath channelization are plausible mechanisms for accelerated transport of PFOS and support the application of a Freundlich isotherm for PFOS. Overall, non-Fickian transport mechanisms demonstrate the potential to accelerate PFOS transport through the vadose zone by up to a factor of 123 under specific circumstances. This work demonstrates the assumption of equilibrium adsorption to air-water interfaces, even for homogeneous laboratory experiments, is not necessarily valid.</p></div>","PeriodicalId":15530,"journal":{"name":"Journal of contaminant hydrology","volume":null,"pages":null},"PeriodicalIF":3.5,"publicationDate":"2024-09-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142162004","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":"Application and innovation of artificial intelligence models in wastewater treatment","authors":"Wen-Long Xu,&nbsp;Ya-Jun Wang,&nbsp;Yi-Tong Wang,&nbsp;Jun-Guo Li,&nbsp;Ya-Nan Zeng,&nbsp;Hua-Wei Guo,&nbsp;Huan Liu,&nbsp;Kai-Li Dong,&nbsp;Liang-Yi Zhang","doi":"10.1016/j.jconhyd.2024.104426","DOIUrl":"10.1016/j.jconhyd.2024.104426","url":null,"abstract":"<div><p>At present, as the problem of water shortage and pollution is growing serious, it is particularly important to understand the recycling and treatment of wastewater. Artificial intelligence (AI) technology is characterized by reliable mapping of nonlinear behaviors between input and output of experimental data, and thus single/integrated AI model algorithms for predicting different pollutants or water quality parameters have become a popular method for simulating the process of wastewater treatment. Many AI models have successfully predicted the removal effects of pollutants in different wastewater treatment processes. Therefore, this paper reviews the applications of artificial intelligence technologies such as artificial neural networks (ANN), adaptive network-based fuzzy inference system (ANFIS) and support vector machine (SVM). Meanwhile, this review mainly introduces the effectiveness and limitations of artificial intelligence technology in predicting different pollutants (dyes, heavy metal ions, antibiotics, etc.) and different water quality parameters such as biochemical oxygen demand (BOD), chemical oxygen demand (COD), total nitrogen (TN) and total phosphorus (TP) in wastewater treatment process, involving single AI model and integrated AI model. Finally, the problems that need further research together with challenges ahead in the application of artificial intelligence models in the field of environment are discussed and presented.</p></div>","PeriodicalId":15530,"journal":{"name":"Journal of contaminant hydrology","volume":null,"pages":null},"PeriodicalIF":3.5,"publicationDate":"2024-09-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142171636","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":"PFOA remediation from kaolinite soil by electrokinetic process coupled with activated carbon/iron coated activated carbon - permeable reactive barrier","authors":"Namuun Ganbat ,&nbsp;Ali Altaee ,&nbsp;Faris M. Hamdi ,&nbsp;John Zhou ,&nbsp;Mahedy Hasan Chowdhury ,&nbsp;Syed Javaid Zaidi ,&nbsp;Akshaya K. Samal ,&nbsp;Raed Almalki ,&nbsp;Marie Joshua Tapas","doi":"10.1016/j.jconhyd.2024.104425","DOIUrl":"10.1016/j.jconhyd.2024.104425","url":null,"abstract":"<div><p>This study applied electrokinetic (EK) in situ soil remediation for perfluorooctanoic acid (PFOA) removal from kaolinite soil. The kaolinite soil was spiked with 10 mg/kg PFOA for the EK treatment using Sodium Cholate bio-surfactant coupled with Activated Carbon (AC) or iron-coated Activated Carbon (FeAC) permeable reactive barrier (PRB). The study also evaluated the impact of AC and FeAC PRBs' position on the EK process performance. In the EK with the PRB in the middle section, PFOA removal from kaolinite was 52.35 % in the AC-EK tests and 59.55 % in the FeAC-EK. Experimental results showed the accumulation of PFOA near the cathode region in FeAC PRB tests, hypothesising that Fe from the PRB formed a complex with PFOA ions and transported it to the cathode region. Spent PRBs were regenerated with methanol for PFOA extraction and reuse in the EK experiments. Although FeAC PRB achieved better PFOA removal than AC PRB, the EK tests with regenerated AC-EK and FeAC-EK PRBs achieved 40.37 % and 20.62 % PFOA removal. For EK with FeAC PRB near the anode, PFOA removal was 21.96 %. Overall, using PRB in conjunction with the EK process can further enhance the removal efficiency. This concept could be applied to enhance the removal of various PFAS compounds from contaminated soils by combining a suitable PRB with the EK process. It also emphasizes the feasibility of in-situ soil remediation technologies for forever chemical treatment.</p></div>","PeriodicalId":15530,"journal":{"name":"Journal of contaminant hydrology","volume":null,"pages":null},"PeriodicalIF":3.5,"publicationDate":"2024-09-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0169772224001293/pdfft?md5=22fcb0b9bc9e3b03836cf77a13641899&pid=1-s2.0-S0169772224001293-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142148738","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Effect of waste rock particle size on acid mine drainage generation: Practical implications for reactive transport modeling","authors":"Junghyun Lim ,&nbsp;Karine Sylvain ,&nbsp;Thomas Pabst ,&nbsp;Eunhyea Chung","doi":"10.1016/j.jconhyd.2024.104427","DOIUrl":"10.1016/j.jconhyd.2024.104427","url":null,"abstract":"<div><p>Mine waste rock poses significant environmental challenges. Evaluating management and reclamation options is particularly complex because of the wide particle size distribution, the non-uniform distribution of acid-generating and buffering minerals, and the variable contribution of the different particle size fractions to acid mine drainage (AMD) generation. Reactive transport simulations can be useful to complement and overcome the limitations of laboratory and field experiments. However, predicting field-scale and long-term geochemical behavior of waste rock requires a better understanding of numerical parameters scale-up. In this study, three waste rocks, with different mineral composition and particle size distribution, were separated into different fractions and tested in the laboratory. Kinetic tests were used to calibrate numerical models and adjust minerals' effective kinetic rate constants to match measured pH and metal concentrations. Calibrated reactive transport simulations were able to reproduce accurately the effect of particle size on pH and sulfate and calcium production rates. Experimental and numerical results confirmed that waste rock oxidation and neutralization rates tended to decrease with increasing particle sizes. Several models were tested and the weighted geometric mean of the effective kinetic rate constants as a function of the proportion of each fraction provided the most accurate estimation of the whole specimen kinetic rate constants. A novel approach to predict waste rock geochemical behavior from a single laboratory test also showed promising results. Overall, these results should contribute to improving the extrapolation of laboratory kinetic test results to field predictions.</p></div>","PeriodicalId":15530,"journal":{"name":"Journal of contaminant hydrology","volume":null,"pages":null},"PeriodicalIF":3.5,"publicationDate":"2024-09-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0169772224001311/pdfft?md5=9d7c032aa0b61be6d7637d8cb5f4886c&pid=1-s2.0-S0169772224001311-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142167713","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Contaminant mass discharge estimation of a sulfonamide plume by use of hydraulic profiling tool (HPT) and fluorescence techniques","authors":"G.G. Lemaire ,&nbsp;M.M. Broholm ,&nbsp;U. Wünsch ,&nbsp;M. Hirsch ,&nbsp;C.F. Ottosen ,&nbsp;B.B. Thrane ,&nbsp;J.K. Pedersen ,&nbsp;L. Dissing ,&nbsp;P.L. Bjerg","doi":"10.1016/j.jconhyd.2024.104422","DOIUrl":"10.1016/j.jconhyd.2024.104422","url":null,"abstract":"<div><p>The contaminant mass discharge is a relevant metric to evaluate the risk that a groundwater plume poses to water resources. However, this assessment is often vitiated by a high uncertainty inherent to the assessment method and often limited number of measurement points to carry out the assessment. Direct-Push techniques in combination with profiling tools and dedicated sampling can be an interesting alternative to increase the measurement point density and hence reduce the mass discharge uncertainty. The main objective of our study was to assess if DP logging and sampling could be employed to get a reasonable estimate of contaminant mass discharge in a large sulfonamide contaminant plume (&gt; 1500 m wide), compared to a more traditional approach based on monitoring wells. To do so, an Hydraulic Profiling Tool (HPT) logging with a dedicated site calibration was used to estimate the hydraulic conductivity field. The sulfonamide concentrations were inferred from the compound fluorescence properties measured by laboratory spectrofluorometry (λ_Ex / λ_Em = 255/340 nm) and a dedicated log-log linear regression model. Our results show that HPT-derived hydraulic conductivity values are in good agreement with the monitoring well results, and within the order of magnitude reported in similar studies or indirect geophysical techniques. Fluorescence appears as a powerful proxy for the sulfonamide concentration levels. Ultimately, the contaminant mass discharge estimate from HPT and fluorescence techniques lies within a factor 2 from the estimate by monitoring wells, with 549 [274–668] and 776 [695–879] kg/yr respectively. Overall, this study highlights that DP logging tools combined with indirect methods (correlation with fluorescence) could provide a relevant contaminant mass discharge estimate for some optically active substances, given that a proper calibration phase is carried out.</p></div>","PeriodicalId":15530,"journal":{"name":"Journal of contaminant hydrology","volume":null,"pages":null},"PeriodicalIF":3.5,"publicationDate":"2024-09-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0169772224001268/pdfft?md5=43c39e4f0184ca250e9de9c2b689b0e5&pid=1-s2.0-S0169772224001268-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142162124","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Hydrogeochemical evolution patterns of diverse water bodies in mining area driven by large-scale open-pit combined underground mining-taking Pingshuo Mining Area as an example","authors":"Wenrui Zhang ,&nbsp;Limin Duan ,&nbsp;Yinglan A ,&nbsp;Baolin Xue ,&nbsp;Guoqiang Wang ,&nbsp;Tingxi Liu","doi":"10.1016/j.jconhyd.2024.104420","DOIUrl":"10.1016/j.jconhyd.2024.104420","url":null,"abstract":"<div><p>Large-scale open-pit combined underground mining activities (OUM) not only reshape the original topography, geomorphology, and hydrogeochemical environment of the mining area, but also alter the regional water cycle conditions. However, due to the complexity arising from the coexistence of two coal mining technologies (open-pit and underground mining), the hydrological environmental effects remain unclear. Here, we selected the Pingshuo Mining Area in China, one of the most modernized open-pit combined underground mining regions, as the focus of our research. We comprehensively employed mathematical statistics, Piper diagram, Gibbs model, ion combination ratio, principal component analysis and other methods to compare the hydrochemistry and isotope data of different water bodies before (2006) and after (2021) large-scale mining. The changing patterns of hydrochemical characteristics of different water bodies and their main controlling factors in mining area driven by OUM were analyzed and identified, revealing the water circulation mechanism under the background of long-term coal mining. The results showed that: (1) The chemical composition of water has changed greatly due to large-scale coal mining. The hydrochemical types of Quaternary and Permian-Carboniferous aquifers shifted from predominantly HCO₃-Ca·Mg before intensive mining to primarily HCO₃·SO₄-Ca·Mg, HCO₃-Na, HCO₃·SO₄-Na·Mg, and HCO₃·SO₄-Ca·Mg, HCO₃-Ca·Na, HCO₃·SO₄-Mg·Ca post-mining. Variations in the hydrochemical types of surface water were found to be complex and diverse. (2) Coal mining activities promote the dissolution of silicate rock and sodium-bearing evaporites, enhancing the strength and scale of positive alternating adsorption of cations. The oxidation of pyrite, dissolution of silicate weathering, and the leaching of coal gangue were identified as the main reasons for the significant increase of SO₄²⁻, while decarbonation in confined aquifers led to a decrease in HCO₃⁻. (3) Results from the principal component analysis and stable isotopes demonstrated the hydraulic connection among surface water, Quaternary aquifers, and Permian-Carboniferous aquifers induced by long-term OUM. The research findings provide a reference basis for the coordinated development of coal and water in the Pingshuo Mining Area and other open-pit combined underground mining areas.</p></div>","PeriodicalId":15530,"journal":{"name":"Journal of contaminant hydrology","volume":null,"pages":null},"PeriodicalIF":3.5,"publicationDate":"2024-09-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142167715","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":"Stream salinity prediction in data-scarce regions: Application of transfer learning and uncertainty quantification","authors":"Kasra Khodkar ,&nbsp;Ali Mirchi ,&nbsp;Vahid Nourani ,&nbsp;Afsaneh Kaghazchi ,&nbsp;Jeffrey M. Sadler ,&nbsp;Abubakarr Mansaray ,&nbsp;Kevin Wagner ,&nbsp;Phillip D. Alderman ,&nbsp;Saleh Taghvaeian ,&nbsp;Ryan T. Bailey","doi":"10.1016/j.jconhyd.2024.104418","DOIUrl":"10.1016/j.jconhyd.2024.104418","url":null,"abstract":"<div><p>Scarcity of stream salinity data poses a challenge to understanding salinity dynamics and its implications for water supply management in water-scarce salt-prone regions around the world. This paper introduces a framework for generating continuous daily stream salinity estimates using instance-based transfer learning (TL) and assessing the reliability of the synthetic salinity data through uncertainty quantification via prediction intervals (PIs). The framework was developed using two temporally distinct specific conductance (SC) datasets from the Upper Red River Basin (URRB) located in southwestern Oklahoma and Texas Panhandle, United States. The instance-based TL approach was implemented by calibrating Feedforward Neural Networks (FFNNs) on a source SC dataset of around 1200 instantaneous grab samples collected by United States Geological Survey (USGS) from 1959 to 1993. The trained FFNNs were subsequently tested on a target dataset (1998-present) of 220 instantaneous grab samples collected by the Oklahoma Water Resources Board (OWRB). The framework's generalizability was assessed in the data-rich Bird Creek watershed in Oklahoma by manipulating continuous SC data to simulate data-scarce conditions for training the models and using the complete Bird Creek dataset for model evaluation. The Lower Upper Bound Estimation (LUBE) method was used with FFNNs to estimate PIs for uncertainty quantification. Autoregressive SC prediction methods via FFNN were found to be reliable with Nash Sutcliffe Efficiency (NSE) values of 0.65 and 0.45 on in-sample and out-of-sample test data, respectively. The same modeling scenario resulted in an NSE of 0.54 for the Bird Creek data using a similar missing data ratio, whereas a higher ratio of observed data increased the accuracy (NSE = 0.84). The relatively narrow estimated PIs for the North Fork Red River in the URRB indicated satisfactory stream salinity predictions, showing an average width equivalent to 25 % of the observed range and a confidence level of 70 %.</p></div>","PeriodicalId":15530,"journal":{"name":"Journal of contaminant hydrology","volume":null,"pages":null},"PeriodicalIF":3.5,"publicationDate":"2024-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142098435","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":"Factors influencing residual air saturation during consecutive imbibition processes in an air-water two-phase fine sandy medium – A laboratory-scale experimental study","authors":"Weile Huang ,&nbsp;Yan Li ,&nbsp;Yijin Du ,&nbsp;Xinya He ,&nbsp;Chengfeng Li ,&nbsp;Jingya Xi ,&nbsp;Yihang Yang ,&nbsp;Xiaoyi Wu ,&nbsp;Weiliang Liu","doi":"10.1016/j.jconhyd.2024.104416","DOIUrl":"10.1016/j.jconhyd.2024.104416","url":null,"abstract":"<div><p>The residual air saturation plays a crucial role in modeling hydrological processes of groundwater and the migration and distribution of contaminants in subsurface environments. However, the influence of factors such as media properties, displacement history, and hydrodynamic conditions on the residual air saturation is not consistent across different displacement scenarios. We conducted consecutive drainage-imbibition cycles in sand-packed columns under hydraulic conditions resembling natural subsurface environments, to investigate the impact of wetting flow rate, initial fluid state, and number of imbibition rounds (NIR) on residual air saturation. The results indicate that residual air saturation changes throughout the imbibition process, with variations separated into three distinct stages, namely, unstable residual air saturation (S_gr-u), momentary residual air saturation (S_gr-m), and stable residual air saturation (S_gr). The results also suggest that the transition from S_gr-u to S_gr is driven by changes in hydraulic pressure and gradient; the calculated values followed the following trend: S_gr &gt; S_gr-u &gt; S_gr-m. An increase in capillary number, which ranged from 1.46 × 10⁻⁷ to 3.07 × 10⁻⁶, increased S_gr-u and S_gr-m in some columns. The increase in S_gr ranged from 0.034 to 0.117 across all the experimental columns; this consistent increase can be explained by water film expansion at the primary wetting front along with a strengthening of the hydraulic gradient during water injection. Both the pre-covered water film on the sand grain surface and a pore-to-throat aspect ratio of up to 4.42 were identified as important factors for the increased residual air saturation observed during the imbibition process. Initial air saturation (S_ai) positively influenced all three types of residual air saturation, while initial capillary pressure (P_ci) exhibited a more pronounced inhibitory effect on residual air saturation, as it can partly characterized the initial connectivity of the air phase generated under different drying flow rates. Under identical wetting flow rate conditions, S_gr was higher during the second imbibition than during the first imbibition due to variations in initial fluid state, involving both fluid distribution and the concentration of dissolved air in the pore water. In contrast, NIR did not have an obvious effect on the three types of residual air saturation. This work aims to provide empirical evidences and offer further insights into the capture of non-wetting phases in groundwater environments, as well as to put forward some potential suggestion for future investigations on the retention and migration of contaminants that involves multiphase interface interactions in subsurface environments.</p></div>","PeriodicalId":15530,"journal":{"name":"Journal of contaminant hydrology","volume":null,"pages":null},"PeriodicalIF":3.5,"publicationDate":"2024-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142137393","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}