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Enzyme-linked immunosorbent assay (ELISA) is the gold standard technique for measuring protein biomarkers due to its high sensitivity, specificity, and throughput. Despite its success, continuous advancements in ELISA and immunoassay formats are crucial to meet evolving global challenges and to address new analytical needs in diverse applications. To expand the capabilities and applications of immunoassays, we introduce a novel ELISA-like assay that we call Bioluminescent-bacteria-linked immunosorbent assay (BBLISA). BBLISA is an enzyme-free assay that utilizes the inner filter effect between the bioluminescent bacteriaAllivibrio fischeriand metallic nanoparticles (gold nanoparticles and gold iridium oxide nanoflowers) as molecular absorbers. Functionalizing these nanoparticles with antibodies induces their accumulation in wells upon binding to molecular targets, forming the classical immune-sandwich complex. Thanks to their ability to adsorb the light emitted by the bacteria, the nanoparticles can suppress the bioluminescence signal, allowing the rapid quantification of the target. To demonstrate the bioanalytical properties of the novel immunoassay platform, as a proof of principle, we detected two clinically relevant biomarkers (human immunoglobulin G and SARS-CoV-2 nucleoprotein) in human serum, achieving the same sensitivity and precision as the classic ELISA. We believe that BBLISA can be a promising alternative to the standard ELISA techniques, offering potential advancements in biomarker detection and analysis by combining nanomaterials with a low-cost, portable bioluminescent platform.

As the current pandemic has shown, lateral flow assays (LFAs) are a prime example of point-of-care devices enabling quick testing at an affordable price. However, their ease of use undeniably affects their sensitivity, making them less sensitive than other multi-step and time-consuming diagnostic assays, such as polymerase chain reactions and enzyme-linked immunosorbent assays. A possible solution to overcome this lack of sensitivity is the exploitation of bottom-up approaches to synthesize nanomaterials with outstanding properties for use as colorimetric labels in LFAs, that is, using nanoparticles with better optical capabilities to improve the generation of the colorimetric signal and the overall sensitivity of LFAs. Following this strategy, we rationally optimized the synthesis of gold and iridium oxide nanoflowers (Au-IrO2 NFs) to enhance their physical-chemical properties as colorimetric labels in LFAs. Specifically, we were able to rationally control their size (from 155 to 53 nm in diameter) in order to guarantee an optimal flow along the different pads of a LFA. Moreover, thanks to their superior plasmonic behavior (compared to standard AuNPs), we could achieve an 8.5-fold lower limit of detection (down to 1.2 ng/mL) for human immunoglobulin G (HIgG) than standard LFAs (10.1 ng/mL). Therefore, due to their optical and redox properties, bioconjugation capabilities, and synergic combination of the individual components, Au-IrO2 NFs appear as potential candidates for the next generation of optical LFAs.

This manuscript aims at raising the attention of the scientific community to the need for better characterised bioreceptors for fast development of point-of-care diagnostic devices able to support mass frequency testing. Particularly, we present the difficulties encountered in finding suitable antibodies for the development of a lateral flow assay for detecting the nucleoprotein of SARS-CoV-2.

As the current pandemic has shown, lateral flow assays (LFAs) are a prime example of point-of-care devices enabling quick testing at an affordable price. However, their ease of use undeniably affects their sensitivity, making them less sensitive than other multi-step and time-consuming diagnostic assays, such as polymerase chain reactions and enzyme-linked immunosorbent assays. A possible solution to overcome this lack of sensitivity is the exploitation of bottom-up approaches to synthesize nanomaterials with outstanding properties for use as colorimetric labels in LFAs, that is, using nanoparticles with better optical capabilities to improve the generation of the colorimetric signal and the overall sensitivity of LFAs. Following this strategy, we rationally optimized the synthesis of gold and iridium oxide nanoflowers (Au–IrO2 NFs) to enhance their physical–chemical properties as colorimetric labels in LFAs. Specifically, we were able to rationally control their size (from 155 to 53 nm in diameter) in order to guarantee an optimal flow along the different pads of a LFA. Moreover, thanks to their superior plasmonic behavior (compared to standard AuNPs), we could achieve an 8.5-fold lower limit of detection (down to 1.2 ng/mL) for human immunoglobulin G (HIgG) than standard LFAs (10.1 ng/mL). Therefore, due to their optical and redox properties, bioconjugation capabilities, and synergic combination of the individual components, Au–IrO2 NFs appear as potential candidates for the next generation of optical LFAs.

The quantitative detection of different molecular targets is of utmost importance for a variety of human activities, ranging from healthcare to environmental studies. Bioanalytical methods have been developed to solve this and to achieve the quantification of multiple targets from small volume samples. Generally, they can be divided into two different classes: point of care (PoC) and laboratory-based approaches. The former is rapid, low-cost, and user-friendly; however, the majority of the tests are semiquantitative, lacking in specificity and sensitivity. On the contrary, laboratory-based approaches provide high sensitivity and specificity, but the bulkiness of experimental instruments and complicated protocols hamper their use in resource-limited settings. In response, here we propose a smartphone-based device able to support laboratory-based optical techniques directly at the point of care. Specifically, we designed and fabricated a portable microplate reader that supports colorimetric, fluorescence, luminescence, and turbidity analyses. To demonstrate the potential of the device, we characterized its analytical performance by detecting a variety of relevant molecular targets (ranging from antibodies, toxins, drugs, and classic fluorophore dyes) and we showed how the estimated results are comparable to those obtained from a commercial microplate reader. Thanks to its low cost (<$300), portability (27 cm [length] × 18 cm [width] × 7 cm [height]), commercially available components, and open-source-based system, we believe it represents a valid approach to bring high-precision laboratory-based analysis at the point of care.

Centrifuge modeling technique appears to be a powerful experimental tool to study the geo-environmental problems such as pollutant migration in soils and the infiltration of gasoline in subsurface systems. However, centrifuge modeling of light non-aqueous phase liquids (LNAPLs) migration in a porous medium has yet to be validated. In this study, centrifugal model tests were conducted to examine the gasoline migration and distribution in unsaturated soil. The technique of modeling of models was used to validate the feasibility of using geotechnical centrifuge for modeling LNAPLs transport at 50, 75 and 100 g-levels. All the experiments were performed to simulate a 3-D spill of gasoline and its subsequent subsurface migration. When centrifuge gravity reached the desired g-level, the LNAPLs leaked out from the underground storage tank and migrated in soils corresponding to a prototype time equivalent to I year. After the centrifuge tests, soil was collected using sampling tubes and extracted by chloroform prior to gas chromatograph analysis. Results obtained from centrifuge tests at different g-levels show that the migration patterns of BTEX, which represents the main components of LNP ALs, in porous media are reasonably close indicating that the models are correctly scaled. In addition, the transport behavior of BTEX is somewhat related to their water solubility. The infiltration of xylene in CDG soil is slower than that in fine sand, which leads to a faster spreading in lateral direction and a wider plume.

Biomarkers are nucleic acids, peptides, proteins, lipids metabolites, or other small molecules in human tissues or biological fluids whose accurate detection contributes to the prediction and determination of diseases and their status. In recent years, platforms that allow the detection of important biomarkers at the point-of-care (PoC) are moving the field of diagnostics towards personalized medicine. In order to comply with the REASSURED criteria stated by the WHO, the most efficient solution is to integrate PoC devices with smartphones. Without a doubt the smartphone camera is a “smart detector,” and almost all the optical-based methods have been integrated, including absorbance, fluorescence, microscopic bio-imaging, surface plasmon resonance, chemiluminescence, bioluminescence, and photoluminescence. In this chapter, we explain how smartphones can be used as smart detectors in diagnostic devices and we will provide an overview of recent developments of smartphone-based optical PoC devices.

The mobility of nano zero-valent iron (nZVI) will greatly affect its practical application as a remediation material for contaminated groundwater. One-dimensional (1D) column tests are commonly used in previous work to study its migration behavior, but the two-dimensional (2D) test is still very limited. This study reports a novel research system to study the 2D transport and retention behavior of colloids and solutes, which includes a 2D model test setup and the corresponding image analysis method. The transport behaviors of methyl orange (MO), nZVI, and phosphate-loaded nZVI (PnZVI) are studied using this system. The results show that the research system can reasonably describe the tempo-spatial concentration distribution of colloids and solutes. After phosphate adsorption, the mobility of nZVI is enhanced due to the increase in negative surface charge, which implies a potential environmental risk of nZVI to facilitate contaminant transport. The migration of PnZVI is not significantly influenced by its density, which is faster than MO in the longitudinal direction. The range of the plume of PnZVI in the longitudinal direction is larger than that of MO, which implies that PnZVI has a stronger longitudinal dispersion than MO. © 2022 American Chemical Society. All rights reserved.

Colloid transport and retention in porous media is a common phenomenon in nature. However, retention mechanisms are not fully revealed based on macroscale experimental observations. The pore-network model (PNM) is an effective method to account for the pore structure of a porous medium and provides a direct connection between pore-scale retention mechanisms and macroscale phenomenon. In this study, PNMs with cylindrical pore throats and spherical pore bodies are used to upscale water flow and colloid transport from pore- to macro-scales, taking into consideration surface deposition, hydrodynamic bridging, and straining. Numerical experiments were conducted to investigate the effect of colloid size, initial concentration, and flow velocity of pore water on colloid transport and retention behavior. Results show that hydrodynamic bridging and straining produce hyper-exponential retention profiles, whereas surface deposition due to nanoscale roughness and charge heterogeneity yields exponential or uniform retention profiles. Hydrodynamic bridging will not happen when the colloid size, initial concentration and flow velocity are lower than some threshold value (rp ≤ 500 nm, C0 ≤ 7.1 × 1014 Nc/m3, U0 ≤ 0.1 m/d under the conditions of this study). The relative importance of hydrodynamic bridging in comparison to surface deposition increases with an increase in the colloid size, initial concentration, and flow velocity. The PNM is a useful tool to discriminate different retention mechanisms and to predict colloid transport and retention behavior in porous media. © 2021 Elsevier B.V.

Colloid transport and retention in porous media is a common phenomenon in both nature and industry. However, many questions remain on how to obtain colloid transport and retention parameters. Previous work usually assumed constant transport parameters in a medium under a given physicochemical condition. In this study, pore-network modeling is employed to upscale colloid transport and retention from the pore-scale to the macro-scale. The pore-scale transport parameters including the collection efficiency (eta), the sticking efficiency (alpha), and the fraction of the solid-water interface that contributes to the colloid attachment (S-f) are obtained using numerical simulation and probability analysis for each pore throat. The influence of roughness and charge heterogeneity on the distribution of pore-scale parameters is discussed. Breakthrough curves and the retention profiles under different roughness and charge heterogeneity conditions are also analyzed. Results show that pore-scale parameters eta, alpha, and S-f have various distributions in porous media that may not be accurately described using single-valued effective parameters. The value of eta decreases with velocity and exhibits a wide distribution under low-velocity conditions. The parameter alpha tends to decrease with the colloid size and the pore water velocity and increased with the charge heterogeneity fraction. Nanoscale roughness alters alpha in a non-monotonic fashion but tends to increase for lower roughness fractions and zeta potential. Microscopic roughness increases values of alpha for colloids that would otherwise be susceptible to hydrodynamic removal. Breakthrough curves and retention profiles show that more retention occurs for smaller particles, which reflects the influence of blocking.

Nano zero-valent iron (nZVI) has been used for in situ groundwater remediation due to its strong adsorption and reaction characteristics. However, oxyanion contaminants in groundwater can ready adsorbed onto the surface of nZVI. This can potentially alter the mobility of nZVI and create a secondary pollution source, but these issues have not yet been systematically investigated. In this study, polyaniline-supported nZVI (PnZVI) and phosphate-sorbed PnZVI (PS-PnZVI) were synthesized in the laboratory. The sedimentation and transport behavior of these two nZVI particles were investigated, compared, and mathematically modeled to better understand the impact of phosphate adsorption on these processes. Results showed that phosphate adsorption can enhance the stability and mobility of PnZVI. Interaction energy calculations that considered van der Waals and magnetic attraction, electrostatic double layer and Born repulsion, and the influence of nanoscale roughness and binary charge heterogeneity were conducted to better infer mechanisms causing nZVI particle sedimentation and retention. Nanoscale roughness and binary charge heterogeneity were found to significantly decrease the energy barrier, but not to low enough levels to explain the observed behavior. The rapid settling of PnZVI was attributed to strong magnetic attraction between particles, which produced rapid aggregation and retention due to straining and/or hydrodynamic bridging. Phosphate adsorption enhanced the mobility of PS-PnZVI in comparison with PnZVI due to a decrease in particle size and aggregation, and an increase in the energy barrier with the porous media. A potential risk of nZVI particles to facilitate oxyanion contaminant transport was demonstrated for phosphate. © 2021 The Authors. Vadose Zone Journal published by Wiley Periodicals LLC on behalf of Soil Science Society of America

Altres ajuts: CERCA Programme/Generalitat de Catalunya, Altres ajuts: Consejo Superior de Investigaciones Científicas (CSIC) for the project "COVID19-122", The COVID-19 pandemic made clear how our society requires quickly available tools to address emerging healthcare issues. Diagnostic assays and devices are used every day to screen for COVID-19 positive patients, with the aim to decide the appropriate treatment and containment measures. In this context, we would have expected to see the use of the most recent diagnostic technologies worldwide, including the advanced ones such as nano-biosensors capable to provide faster, more sensitive, cheaper, and high-throughput results than the standard polymerase chain reaction and lateral flow assays. Here we discuss why that has not been the case and why all the exciting diagnostic strategies published on a daily basis in peer-reviewed journals are not yet successful in reaching the market and being implemented in the clinical practice.

Colloid transport and retention in porous media is a common phenomenon in nature. However, retention mechanisms are not fully revealed based on macroscale experimental observations. The pore-network model (PNM) is an effective method to account for the pore structure of a porous medium and provides a direct connection between pore-scale retention mechanisms and macroscale phenomenon. In this study, PNMs with cylindrical pore throats and spherical pore bodies are used to upscale water flow and colloid transport from pore- to macro-scales, taking into consideration surface deposition, hydrodynamic bridging, and straining. Numerical experiments were conducted to investigate the effect of colloid size, initial concentration, and flow velocity of pore water on colloid transport and retention behavior. Results show that hydrodynamic bridging and straining produce hyper-exponential retention profiles, whereas surface deposition due to nanoscale roughness and charge heterogeneity yields exponential or uniform retention profiles. Hydrodynamic bridging will not happen when the colloid size, initial concentration and flow velocity are lower than some threshold value (rp ≤ 500 nm, C0 ≤ 7.1 × 1014 Nc/m3, U0 ≤ 0.1 m/d under the conditions of this study). The relative importance of hydrodynamic bridging in comparison to surface deposition increases with an increase in the colloid size, initial concentration, and flow velocity. The PNM is a useful tool to discriminate different retention mechanisms and to predict colloid transport and retention behavior in porous media. © 2021 Elsevier B.V.

Colloid transport and retention in porous media is a common phenomenon in both nature and industry. However, many questions remain on how to obtain colloid transport and retention parameters. Previous work usually assumed constant transport parameters in a medium under a given physicochemical condition. In this study, pore-network modeling is employed to upscale colloid transport and retention from the pore-scale to the macro-scale. The pore-scale transport parameters including the collection efficiency (eta), the sticking efficiency (alpha), and the fraction of the solid-water interface that contributes to the colloid attachment (S-f) are obtained using numerical simulation and probability analysis for each pore throat. The influence of roughness and charge heterogeneity on the distribution of pore-scale parameters is discussed. Breakthrough curves and the retention profiles under different roughness and charge heterogeneity conditions are also analyzed. Results show that pore-scale parameters eta, alpha, and S-f have various distributions in porous media that may not be accurately described using single-valued effective parameters. The value of eta decreases with velocity and exhibits a wide distribution under low-velocity conditions. The parameter alpha tends to decrease with the colloid size and the pore water velocity and increased with the charge heterogeneity fraction. Nanoscale roughness alters alpha in a non-monotonic fashion but tends to increase for lower roughness fractions and zeta potential. Microscopic roughness increases values of alpha for colloids that would otherwise be susceptible to hydrodynamic removal. Breakthrough curves and retention profiles show that more retention occurs for smaller particles, which reflects the influence of blocking.

Nano zero-valent iron (nZVI) has been used for in situ groundwater remediation due to its strong adsorption and reaction characteristics. However, oxyanion contaminants in groundwater can ready adsorbed onto the surface of nZVI. This can potentially alter the mobility of nZVI and create a secondary pollution source, but these issues have not yet been systematically investigated. In this study, polyaniline-supported nZVI (PnZVI) and phosphate-sorbed PnZVI (PS-PnZVI) were synthesized in the laboratory. The sedimentation and transport behavior of these two nZVI particles were investigated, compared, and mathematically modeled to better understand the impact of phosphate adsorption on these processes. Results showed that phosphate adsorption can enhance the stability and mobility of PnZVI. Interaction energy calculations that considered van der Waals and magnetic attraction, electrostatic double layer and Born repulsion, and the influence of nanoscale roughness and binary charge heterogeneity were conducted to better infer mechanisms causing nZVI particle sedimentation and retention. Nanoscale roughness and binary charge heterogeneity were found to significantly decrease the energy barrier, but not to low enough levels to explain the observed behavior. The rapid settling of PnZVI was attributed to strong magnetic attraction between particles, which produced rapid aggregation and retention due to straining and/or hydrodynamic bridging. Phosphate adsorption enhanced the mobility of PS-PnZVI in comparison with PnZVI due to a decrease in particle size and aggregation, and an increase in the energy barrier with the porous media. A potential risk of nZVI particles to facilitate oxyanion contaminant transport was demonstrated for phosphate. © 2021 The Authors. Vadose Zone Journal published by Wiley Periodicals LLC on behalf of Soil Science Society of America

The COVID-19 pandemic made clear how our society requires quickly available tools to address emerging healthcare issues. Diagnostic assays and devices are used every day to screen for COVID-19 positive patients, with the aim to decide the appropriate treatment and containment measures. In this context, we would have expected to see the use of the most recent diagnostic technologies worldwide, including the advanced ones such as nano-biosensors capable to provide faster, more sensitive, cheaper, and high-throughput results than the standard polymerase chain reaction and lateral flow assays. Here we discuss why that has not been the case and why all the exciting diagnostic strategies published on a daily basis in peer-reviewed journals are not yet successful in reaching the market and being implemented in the clinical practice.

Colloid transport and retention in porous media is a common phenomenon in nature. However, retention mechanisms are not fully revealed based on macroscale experimental observations. The pore-network model (PNM) is an effective method to account for the pore structure of a porous medium and provides a direct connection between pore-scale retention mechanisms and macroscale phenomenon. In this study, PNMs with cylindrical pore throats and spherical pore bodies are used to upscale water flow and colloid transport from pore- to macro-scales, taking into consideration surface deposition, hydrodynamic bridging, and straining. Numerical experiments were conducted to investigate the effect of colloid size, initial concentration, and flow velocity of pore water on colloid transport and retention behavior. Results show that hydrodynamic bridging and straining produce hyper-exponential retention profiles, whereas surface deposition due to nanoscale roughness and charge heterogeneity yields exponential or uniform retention profiles. Hydrodynamic bridging will not happen when the colloid size, initial concentration and flow velocity are lower than some threshold value (rp ≤ 500 nm, C0 ≤ 7.1 × 1014 Nc/m3, U0 ≤ 0.1 m/d under the conditions of this study). The relative importance of hydrodynamic bridging in comparison to surface deposition increases with an increase in the colloid size, initial concentration, and flow velocity. The PNM is a useful tool to discriminate different retention mechanisms and to predict colloid transport and retention behavior in porous media. © 2021 Elsevier B.V.

Colloid transport and retention in porous media is a common phenomenon in both nature and industry. However, many questions remain on how to obtain colloid transport and retention parameters. Previous work usually assumed constant transport parameters in a medium under a given physicochemical condition. In this study, pore-network modeling is employed to upscale colloid transport and retention from the pore-scale to the macro-scale. The pore-scale transport parameters including the collection efficiency (eta), the sticking efficiency (alpha), and the fraction of the solid-water interface that contributes to the colloid attachment (S-f) are obtained using numerical simulation and probability analysis for each pore throat. The influence of roughness and charge heterogeneity on the distribution of pore-scale parameters is discussed. Breakthrough curves and the retention profiles under different roughness and charge heterogeneity conditions are also analyzed. Results show that pore-scale parameters eta, alpha, and S-f have various distributions in porous media that may not be accurately described using single-valued effective parameters. The value of eta decreases with velocity and exhibits a wide distribution under low-velocity conditions. The parameter alpha tends to decrease with the colloid size and the pore water velocity and increased with the charge heterogeneity fraction. Nanoscale roughness alters alpha in a non-monotonic fashion but tends to increase for lower roughness fractions and zeta potential. Microscopic roughness increases values of alpha for colloids that would otherwise be susceptible to hydrodynamic removal. Breakthrough curves and retention profiles show that more retention occurs for smaller particles, which reflects the influence of blocking.

Nano zero-valent iron (nZVI) has been used for in situ groundwater remediation due to its strong adsorption and reaction characteristics. However, oxyanion contaminants in groundwater can ready adsorbed onto the surface of nZVI. This can potentially alter the mobility of nZVI and create a secondary pollution source, but these issues have not yet been systematically investigated. In this study, polyaniline-supported nZVI (PnZVI) and phosphate-sorbed PnZVI (PS-PnZVI) were synthesized in the laboratory. The sedimentation and transport behavior of these two nZVI particles were investigated, compared, and mathematically modeled to better understand the impact of phosphate adsorption on these processes. Results showed that phosphate adsorption can enhance the stability and mobility of PnZVI. Interaction energy calculations that considered van der Waals and magnetic attraction, electrostatic double layer and Born repulsion, and the influence of nanoscale roughness and binary charge heterogeneity were conducted to better infer mechanisms causing nZVI particle sedimentation and retention. Nanoscale roughness and binary charge heterogeneity were found to significantly decrease the energy barrier, but not to low enough levels to explain the observed behavior. The rapid settling of PnZVI was attributed to strong magnetic attraction between particles, which produced rapid aggregation and retention due to straining and/or hydrodynamic bridging. Phosphate adsorption enhanced the mobility of PS-PnZVI in comparison with PnZVI due to a decrease in particle size and aggregation, and an increase in the energy barrier with the porous media. A potential risk of nZVI particles to facilitate oxyanion contaminant transport was demonstrated for phosphate. © 2021 The Authors. Vadose Zone Journal published by Wiley Periodicals LLC on behalf of Soil Science Society of America

Recently, many bioluminescence-based applications have arisen in several fields, such as biosensing, bioimaging, molecular biology, and human health diagnosis. Among all bioluminescent organisms, Aliivibrio fischeri (A. fischeri) is a bioluminescent bacterium used to carry out water toxicity assays since the late 1970s. Since then, several commercial A. fischeri-based products have been launched to the market, as these bacteria are considered as a gold standard for water toxicity assessment worldwide. However, the aforementioned commercial products rely on expensive equipment, requiring several reagents and working steps, as well as high-trained personnel to perform the assays and analyze the output data. For these reasons, in this work, we have developed for the first time a mobile-phone-based sensing platform for water toxicity assessment in just 5 min using two widespread pesticides as model analytes. To accomplish this, we have established new methodologies to enhance the bioluminescent signal of A. fischeri based on the bacterial culture in a solid media and/or using graphene oxide. Finally, we have addressed the biocompatibility of graphene oxide to A. fischeri, boosting the sensitivity of the toxicity assays and the bacterial growth of the lyophilized bacterial cultures for more user-friendly storage.

Nano zero-valent iron (nZVI) has been considered as a promising material for groundwater remediation in the past few decades. The size distribution of nZVI is one of the main factors that influences its transport capability and remediation capacity. However, studies on the size distribution of nZVI under different environmental conditions are still limited. In this study, the influence of the pH (pH = 5, 7, 9) and ionic strength (IS = 0, 15, 30, 45 mM) on the size distribution of nZVI are investigated. The dynamic light scattering (DLS) method is used to study the variation of the size distribution of nZVI aggregate with time, and batch tests are performed to evaluate the efficiency of phosphate removal. Meanwhile, the phosphate removal capacity of nZVI with different size distribution was examined. Experimental results show that under low IS and high pH conditions, nZVI aggregate exhibited a stable, narrow and one-peak size distribution. By contrast, under high IS and low pH conditions, nZVI exhibited a wide and complicated size distribution with multiple peak values. This different pattern in size distribution was further explained by the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory. The phosphate removal rate of nZVI under acidic and neutral conditions is higher than 98% but is only 68% under alkaline conditions. The phosphate removal capacity is insensitive to the variation of IS since the removal rate is higher than 97% for different IS conditions. Favorable environmental conditions for colloidal stability and removal capacity of nZVI can be different, which needs comprehensive consideration in the application.

Nano zero-valent iron (nZVI) has been considered as a promising material for groundwater remediation in the past few decades. The size distribution of nZVI is one of the main factors that influences its transport capability and remediation capacity. However, studies on the size distribution of nZVI under different environmental conditions are still limited. In this study, the influence of the pH (pH = 5, 7, 9) and ionic strength (IS = 0, 15, 30, 45 mM) on the size distribution of nZVI are investigated. The dynamic light scattering (DLS) method is used to study the variation of the size distribution of nZVI aggregate with time, and batch tests are performed to evaluate the efficiency of phosphate removal. Meanwhile, the phosphate removal capacity of nZVI with different size distribution was examined. Experimental results show that under low IS and high pH conditions, nZVI aggregate exhibited a stable, narrow and one-peak size distribution. By contrast, under high IS and low pH conditions, nZVI exhibited a wide and complicated size distribution with multiple peak values. This different pattern in size distribution was further explained by the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory. The phosphate removal rate of nZVI under acidic and neutral conditions is higher than 98% but is only 68% under alkaline conditions. The phosphate removal capacity is insensitive to the variation of IS since the removal rate is higher than 97% for different IS conditions. Favorable environmental conditions for colloidal stability and removal capacity of nZVI can be different, which needs comprehensive consideration in the application.

Nano zero-valent iron (nZVI) has been considered as a promising material for groundwater remediation in the past few decades. The size distribution of nZVI is one of the main factors that influences its transport capability and remediation capacity. However, studies on the size distribution of nZVI under different environmental conditions are still limited. In this study, the influence of the pH (pH = 5, 7, 9) and ionic strength (IS = 0, 15, 30, 45 mM) on the size distribution of nZVI are investigated. The dynamic light scattering (DLS) method is used to study the variation of the size distribution of nZVI aggregate with time, and batch tests are performed to evaluate the efficiency of phosphate removal. Meanwhile, the phosphate removal capacity of nZVI with different size distribution was examined. Experimental results show that under low IS and high pH conditions, nZVI aggregate exhibited a stable, narrow and one-peak size distribution. By contrast, under high IS and low pH conditions, nZVI exhibited a wide and complicated size distribution with multiple peak values. This different pattern in size distribution was further explained by the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory. The phosphate removal rate of nZVI under acidic and neutral conditions is higher than 98% but is only 68% under alkaline conditions. The phosphate removal capacity is insensitive to the variation of IS since the removal rate is higher than 97% for different IS conditions. Favorable environmental conditions for colloidal stability and removal capacity of nZVI can be different, which needs comprehensive consideration in the application.

Lateral-flow assays (LFAs) are quick, simple and cheap assays to analyze various samples at the point of care or in the field, making them one of the most widespread biosensors currently available. They have been successfully employed for the detection of a myriad of different targets (ranging from atoms up to whole cells) in all type of samples (including water, blood, foodstuff and environmental samples). Their operation relies on the capillary flow of the sample throughout a series of sequential pads, each with different functionalities aiming to generate a signal to indicate the absence/presence (and, in some cases, the concentration) of the analyte of interest. To have a user-friendly operation, their development requires the optimization of multiple, interconnected parameters that may overwhelm new developers. In this tutorial, we provide the readers with: (i) the basic knowledge to understand the principles governing an LFA and to take informed decisions during lateral flow strip design and fabrication, (ii) a roadmap for optimal LFA development independent of the specific application, (iii) a step-by-step example procedure for the assembly and operation of an LF strip for the detection of human IgG and (iv) an extensive troubleshooting section addressing the most frequent issues in designing, assembling and using LFAs. By changing only the receptors, the provided example procedure can easily be adapted for cost-efficient detection of a broad variety of targets.

The ease of use, low cost and quick operation of lateral flow assays (LFA) have made them some of the most common point of care biosensors in a variety of fields. However, their generally low sensitivity has limited their use for more challenging applications, where the detection of low analytic concentrations is required. Here we propose the use of soluble wax barriers to selectively and temporarily accumulate the target and label nanoparticles on top of the test line (TL). This extended internal incubation step promotes the formation of the immune-complex, generating a 51.7-fold sensitivity enhancement, considering the limit of quantification, and up to 96% signal enhancement compared to the conventional LFA for Human IgG (H-IgG) detection.

Malaria is a life-threatening disease affecting millions. Microscopy-based assessment of thin blood films is a standard method to (i) determine malaria species and (ii) quantitate high-parasitemia infections. Full automation of malaria microscopy by machine learning (ML) is a challenging task because field-prepared slides vary widely in quality and presentation, and artifacts often heavily outnumber relatively rare parasites. In this work, we describe a complete, fully-automated framework for thin film malaria analysis that applies ML methods, including convolutional neural nets (CNNs), trained on a large and diverse dataset of field-prepared thin blood films. Quantitation and species identification results are close to sufficiently accurate for the concrete needs of drug resistance monitoring and clinical use-cases on field-prepared samples. We focus our methods and our performance metrics on the field use-case requirements. We discuss key issues and important metrics for the application of ML methods to malaria microscopy., Comment: 16 pages, 13 figures

Gasoline type contaminants are a serious threat to soil and groundwater quality as well as health and welfare of general public. Most constituents of gasoline are volatile organic compounds. Soil vapor extraction and air sparging (SVE/AS) are the most efficient techniques to remediate soils and groundwater contaminated with volatile organic compounds. Hence in this state-of-the-art review paper the transport of gasoline-type contaminants in subsurface system and subsequent remediation process are introduced, discussed and summarized. First the mechanism of contaminant transport in subsurface system is briefly introduced, and the mass transport equations, fluid flow equations, and the constitutive model of relative permeability — saturation — capillary pressure are discussed. Then the numerical method is introduced to simulate the process of multiphase flow and contaminate transport in porous media, and the tempo-spatial distribution of contaminants. Then the geotechnical centrifuge modeling, a convenient and efficient physical modeling technique is introduced. Centrifuge model tests were conducted to study transport behavior of gasoline during contamination and remediation process, as well as air flow patterns during sparging process. The test results showed that gasoline infiltrated the vadose zone and moved downwards, forming a high concentration zone above the water table and then spreading out laterally. The water solubility and soil property influence gasoline transport behavior. The vapor pressure of contaminant seems to be an important factor affecting the efficiency of SVE. The zone of influence (ZOI) for air sparging is cone-shaped, and a stable ZOI can be maintained by the sparging pressure higher that a critical value. Based in the presentation it can be concluded that a combination of numerical simulation and centrifuge modeling can be a used to understand the subsurface transport of LNAPLs and their remediation

Gasoline type contaminants are a serious threat to soil and groundwater quality as well as health and welfare of general public. Most constituents of gasoline are volatile organic compounds. Soil vapor extraction and air sparging (SVE/AS) are the most efficient techniques to remediate soils and groundwater contaminated with volatile organic compounds. Hence in this state-of-the-art review paper the transport of gasoline-type contaminants in subsurface system and subsequent remediation process are introduced, discussed and summarized. First the mechanism of contaminant transport in subsurface system is briefly introduced, and the mass transport equations, fluid flow equations, and the constitutive model of relative permeability — saturation — capillary pressure are discussed. Then the numerical method is introduced to simulate the process of multiphase flow and contaminate transport in porous media, and the tempo-spatial distribution of contaminants. Then the geotechnical centrifuge modeling, a convenient and efficient physical modeling technique is introduced. Centrifuge model tests were conducted to study transport behavior of gasoline during contamination and remediation process, as well as air flow patterns during sparging process. The test results showed that gasoline infiltrated the vadose zone and moved downwards, forming a high concentration zone above the water table and then spreading out laterally. The water solubility and soil property influence gasoline transport behavior. The vapor pressure of contaminant seems to be an important factor affecting the efficiency of SVE. The zone of influence (ZOI) for air sparging is cone-shaped, and a stable ZOI can be maintained by the sparging pressure higher that a critical value. Based in the presentation it can be concluded that a combination of numerical simulation and centrifuge modeling can be a used to understand the subsurface transport of LNAPLs and their remediation

The transport of non-aqueous phase liquids ( NAPLs) in unsaturated soils and groundwater is an important research topic in geo-environmental engineering. In this paper, the mechanism of light NAPLs (LNAPLs) transport in subsurface system is briefly introduced, and the mass transport equations, fluid flow equations, and the constitutive model of relative permeability - saturation - capillary pressure are discussed. Then the numerical method is introduced to simulate the multiphase flow problems in porous media, and the tempo-spatial distribution of LNAPLs is obtained. Moreover, different boundary conditions are employed in numerical simulation to investigate its effect on transport behavior. To verify the numerical data, centrifugal tests are conducted to model the LNAPLs migration in unsaturated soils and groundwater. The calculation results are agreeable with the experimental findings of centrifugal modeling, which indicates that LNAPLs from leaking point move downwards due to gravity force, and form a high concentration zone above the capillary fringe, and then spread out laterally along the groundwater table. Some LNAPL enters groundwater system to further migrate. The combination of numerical simulation and centrifuge modeling can be a Useful means to study the transport behavior of LNAPLs in subsurface system.

Centrifuge modeling appears to be a useful experimental tool to study geoenvironmental problems, such as pollutant migration in subsurface systems. In this paper, the migration process of light nonaqueous phase liquids (LNAPLs) in unsaturated soils and thereafter soil vapor extraction (SVE) was simulated using the geotechnical centrifuge technique. Two series of centrifuge experiments were conducted to simulate a gasoline spill from a leaking underground storage tank (UST) and the subsequent subsurface migration of the gasoline along with soil remediation techniques. When centrifuge gravity reached the desired g level, the gasoline was released from the UST. It migrated into the unsaturated soil corresponding to a prototype time equivalent to 1 year. In soil remediation tests, after the LNAPLs migration occurred for 1 year, compressed air was injected into the soil mass for periods of 2 and 4 months to extract LNAPLs into the air phase from the contaminated soil. After each centrifuge test, the soil samples were collected using sampling tubes and the concentrations of the individual constituents in LNAPLs were measured by means of gas chromatograph analysis. The spatial distributions of contaminant concentrations were obtained to investigate the transport behavior of contaminants. Centrifuge tests results shown that the concentrations of LNAPLs were remarkably reduced by means of SVE. After SVE for 2 months, 47% of benzene, toluene, ethylbenzene, and o-xylene was removed from the soil; after 4 months of SVE, nearly 68% of contaminant was extracted from the contaminated area. It is demonstrated that SVE could be an effective soil remediation technology. Moreover, the vapor pressure of each contaminant component seems to be an important factor affecting the efficiency of SVE remediation technology. © 2006 ASCE.

Centrifuge modeling appears to be a useful experimental tool to study geoenvironmental problems, such as pollutant migration in subsurface systems. In this paper, the migration process of light nonaqueous phase liquids (LNAPLs) in unsaturated soils and thereafter soil vapor extraction (SVE) was simulated using the geotechnical centrifuge technique. Two series of centrifuge experiments were conducted to simulate a gasoline spill from a leaking underground storage tank (UST) and the subsequent subsurface migration of the gasoline along with soil remediation techniques. When centrifuge gravity reached the desired g level, the gasoline was released from the UST. It migrated into the unsaturated soil corresponding to a prototype time equivalent to 1 year. In soil remediation tests, after the LNAPLs migration occurred for 1 year, compressed air was injected into the soil mass for periods of 2 and 4 months to extract LNAPLs into the air phase from the contaminated soil. After each centrifuge test, the soil samples were collected using sampling tubes and the concentrations of the individual constituents in LNAPLs were measured by means of gas chromatograph analysis. The spatial distributions of contaminant concentrations were obtained to investigate the transport behavior of contaminants. Centrifuge tests results shown that the concentrations of LNAPLs were remarkably reduced by means of SVE. After SVE for 2 months, 47% of benzene, toluene, ethylbenzene, and o-xylene was removed from the soil; after 4 months of SVE, nearly 68% of contaminant was extracted from the contaminated area. It is demonstrated that SVE could be an effective soil remediation technology. Moreover, the vapor pressure of each contaminant component seems to be an important factor affecting the efficiency of SVE remediation technology. © 2006 ASCE.

The transport of non-aqueous phase liquids ( NAPLs) in unsaturated soils and groundwater is an important research topic in geo-environmental engineering. In this paper, the mechanism of light NAPLs (LNAPLs) transport in subsurface system is briefly introduced, and the mass transport equations, fluid flow equations, and the constitutive model of relative permeability - saturation - capillary pressure are discussed. Then the numerical method is introduced to simulate the multiphase flow problems in porous media, and the tempo-spatial distribution of LNAPLs is obtained. Moreover, different boundary conditions are employed in numerical simulation to investigate its effect on transport behavior. To verify the numerical data, centrifugal tests are conducted to model the LNAPLs migration in unsaturated soils and groundwater. The calculation results are agreeable with the experimental findings of centrifugal modeling, which indicates that LNAPLs from leaking point move downwards due to gravity force, and form a high concentration zone above the capillary fringe, and then spread out laterally along the groundwater table. Some LNAPL enters groundwater system to further migrate. The combination of numerical simulation and centrifuge modeling can be a Useful means to study the transport behavior of LNAPLs in subsurface system.

Centrifuge modeling appears to be a useful experimental tool to study geoenvironmental problems, such as pollutant migration in subsurface systems. In this paper, the migration process of light nonaqueous phase liquids (LNAPLs) in unsaturated soils and thereafter soil vapor extraction (SVE) was simulated using the geotechnical centrifuge technique. Two series of centrifuge experiments were conducted to simulate a gasoline spill from a leaking underground storage tank (UST) and the subsequent subsurface migration of the gasoline along with soil remediation techniques. When centrifuge gravity reached the desired g level, the gasoline was released from the UST. It migrated into the unsaturated soil corresponding to a prototype time equivalent to 1 year. In soil remediation tests, after the LNAPLs migration occurred for 1 year, compressed air was injected into the soil mass for periods of 2 and 4 months to extract LNAPLs into the air phase from the contaminated soil. After each centrifuge test, the soil samples were collected using sampling tubes and the concentrations of the individual constituents in LNAPLs were measured by means of gas chromatograph analysis. The spatial distributions of contaminant concentrations were obtained to investigate the transport behavior of contaminants. Centrifuge tests results shown that the concentrations of LNAPLs were remarkably reduced by means of SVE. After SVE for 2 months, 47% of benzene, toluene, ethylbenzene, and o-xylene was removed from the soil; after 4 months of SVE, nearly 68% of contaminant was extracted from the contaminated area. It is demonstrated that SVE could be an effective soil remediation technology. Moreover, the vapor pressure of each contaminant component seems to be an important factor affecting the efficiency of SVE remediation technology. © 2006 ASCE.

The transport of non-aqueous phase liquids ( NAPLs) in unsaturated soils and groundwater is an important research topic in geo-environmental engineering. In this paper, the mechanism of light NAPLs (LNAPLs) transport in subsurface system is briefly introduced, and the mass transport equations, fluid flow equations, and the constitutive model of relative permeability - saturation - capillary pressure are discussed. Then the numerical method is introduced to simulate the multiphase flow problems in porous media, and the tempo-spatial distribution of LNAPLs is obtained. Moreover, different boundary conditions are employed in numerical simulation to investigate its effect on transport behavior. To verify the numerical data, centrifugal tests are conducted to model the LNAPLs migration in unsaturated soils and groundwater. The calculation results are agreeable with the experimental findings of centrifugal modeling, which indicates that LNAPLs from leaking point move downwards due to gravity force, and form a high concentration zone above the capillary fringe, and then spread out laterally along the groundwater table. Some LNAPL enters groundwater system to further migrate. The combination of numerical simulation and centrifuge modeling can be a Useful means to study the transport behavior of LNAPLs in subsurface system.

Centrifuge modeling appears potentially useful for studying geo-environmental problems such as pollutant migration in subsurface systems. In this study, the "modeling of models" technique was used to validate the feasibility of using a geotechnical centrifuge to model the transport behavior of light non-aqueous phase liquids (LNAPLs) in unsaturated soils. All the experiments were conducted to simulate a gasoline spill from a leaking underground storage tank (UST) and the subsequent subsurface migration of the gasoline. When the gravity in the centrifuge reached the desired g-level, the gasoline was released from the UST and then it migrated in the unsaturated soil corresponding to a prototype time equivalent of one year After the centrifuge tests, soil samples were collected using sampling tubes and the concentrations of individual constituent in the LNAPL were directly measured by means of gas chromatograph analysis. Results obtained from the centrifuge tests at different g-levels show that similar migration patterns are found for LNAPL transport in unsaturated porous media. The location of the peak concentration and the behavior of lateral spreading can be adequately described. In addition, centrifuge test data show that the migration pattern of LNAPLs is related to the soil type and the physical properties of individual constituents in the LNAPLs.

Researchers recently have come to recognize that geotechnical centrifuge can provide a powerful experimental tool for investigating the flow and transport of inorganic contaminants in soils. Inert, non-adsorptive inorganic compounds (e.g., sodium ions) rather than adsorptive heavy metals are often used as the chemicalfor the investigation of pollutant transport behavior in most centrifuge modeling. To overcome the shortcomings of this approach, centrifuge tests for the study of one-dimensional pollutant migration in both saturated and unsaturated soils were designed using an adsorptive pollutant (i.e., cadmium) and conducted at two centrifugal accelerations. In this study, the concentration profile of adsorptive cadmium along the depth of soil, the moisture content varying with the soil depth and the transport behavior of the cadmium in soils were investigated. The centrifuge results show that the cadmium concentration profiles are found to be similar for the centrifuge models performed at 15 g and 20 g and the one-dimensional moisture movement in the unsaturated soil can be reproducible. The validity of centrifuge modeling of adsorptive pollutants might be affected by the g-level that, in turn, determines the centrifuge testing time and affects the sorption equilibrium.

Centrifuge modeling appears potentially useful for studying geo-environmental problems such as pollutant migration in subsurface systems. In this study, the "modeling of models" technique was used to validate the feasibility of using a geotechnical centrifuge to model the transport behavior of light non-aqueous phase liquids (LNAPLs) in unsaturated soils. All the experiments were conducted to simulate a gasoline spill from a leaking underground storage tank (UST) and the subsequent subsurface migration of the gasoline. When the gravity in the centrifuge reached the desired g-level, the gasoline was released from the UST and then it migrated in the unsaturated soil corresponding to a prototype time equivalent of one year After the centrifuge tests, soil samples were collected using sampling tubes and the concentrations of individual constituent in the LNAPL were directly measured by means of gas chromatograph analysis. Results obtained from the centrifuge tests at different g-levels show that similar migration patterns are found for LNAPL transport in unsaturated porous media. The location of the peak concentration and the behavior of lateral spreading can be adequately described. In addition, centrifuge test data show that the migration pattern of LNAPLs is related to the soil type and the physical properties of individual constituents in the LNAPLs.

Researchers recently have come to recognize that geotechnical centrifuge can provide a powerful experimental tool for investigating the flow and transport of inorganic contaminants in soils. Inert, non-adsorptive inorganic compounds (e.g., sodium ions) rather than adsorptive heavy metals are often used as the chemicalfor the investigation of pollutant transport behavior in most centrifuge modeling. To overcome the shortcomings of this approach, centrifuge tests for the study of one-dimensional pollutant migration in both saturated and unsaturated soils were designed using an adsorptive pollutant (i.e., cadmium) and conducted at two centrifugal accelerations. In this study, the concentration profile of adsorptive cadmium along the depth of soil, the moisture content varying with the soil depth and the transport behavior of the cadmium in soils were investigated. The centrifuge results show that the cadmium concentration profiles are found to be similar for the centrifuge models performed at 15 g and 20 g and the one-dimensional moisture movement in the unsaturated soil can be reproducible. The validity of centrifuge modeling of adsorptive pollutants might be affected by the g-level that, in turn, determines the centrifuge testing time and affects the sorption equilibrium.

Centrifuge modeling appears potentially useful for studying geo-environmental problems such as pollutant migration in subsurface systems. In this study, the "modeling of models" technique was used to validate the feasibility of using a geotechnical centrifuge to model the transport behavior of light non-aqueous phase liquids (LNAPLs) in unsaturated soils. All the experiments were conducted to simulate a gasoline spill from a leaking underground storage tank (UST) and the subsequent subsurface migration of the gasoline. When the gravity in the centrifuge reached the desired g-level, the gasoline was released from the UST and then it migrated in the unsaturated soil corresponding to a prototype time equivalent of one year After the centrifuge tests, soil samples were collected using sampling tubes and the concentrations of individual constituent in the LNAPL were directly measured by means of gas chromatograph analysis. Results obtained from the centrifuge tests at different g-levels show that similar migration patterns are found for LNAPL transport in unsaturated porous media. The location of the peak concentration and the behavior of lateral spreading can be adequately described. In addition, centrifuge test data show that the migration pattern of LNAPLs is related to the soil type and the physical properties of individual constituents in the LNAPLs.

Researchers recently have come to recognize that geotechnical centrifuge can provide a powerful experimental tool for investigating the flow and transport of inorganic contaminants in soils. Inert, non-adsorptive inorganic compounds (e.g., sodium ions) rather than adsorptive heavy metals are often used as the chemicalfor the investigation of pollutant transport behavior in most centrifuge modeling. To overcome the shortcomings of this approach, centrifuge tests for the study of one-dimensional pollutant migration in both saturated and unsaturated soils were designed using an adsorptive pollutant (i.e., cadmium) and conducted at two centrifugal accelerations. In this study, the concentration profile of adsorptive cadmium along the depth of soil, the moisture content varying with the soil depth and the transport behavior of the cadmium in soils were investigated. The centrifuge results show that the cadmium concentration profiles are found to be similar for the centrifuge models performed at 15 g and 20 g and the one-dimensional moisture movement in the unsaturated soil can be reproducible. The validity of centrifuge modeling of adsorptive pollutants might be affected by the g-level that, in turn, determines the centrifuge testing time and affects the sorption equilibrium.

The transport process of LNAPLs in subsurface system was simulated by use of centrifuge technology, and thereafter soil vapor extraction process was modeled to remediate the contaminated soils. The groundwater samples soil samples were collected and contaminant concentrations were detected through gas chromatograph analysis. Test results show that there formed a contaminant plume in unsaturated soils, which can be efficiently removed by SVE remediation technology.

Centrifuge modeling appears useful for studying geo-environmental problems such as pollutant migration in subsurface systems. In this study, centrifuge tests were conducted to simulate a gasoline spill from a leaking underground storage tank (UST) and the subsequent subsurface migration of the gasoline. When the centrifugal acceleration reached the desired g level, the gasoline was released from the UST and then it migrated in the unsaturated soil for a prototype time equivalent to 1 year. After the centrifuge tests, soil samples C were collected using sampling tubes and the concentrations of individual constituents in the light nonaqueous phase liquids (LNAPLs) were directly measured by means of gas chromatograph analysis. Two types of unsaturated soils were used to study the migration patterns of LNAPLs in unsaturated porous media. Centrifuge test data show that the migration pattern of LNAPLs is related to the soil type and the physical properties of individual constituents in the LNAPLs.

Centrifuge modeling of the long-term migration of light nonaqueous-phase liquids (LNAPLs unsaturated soils has been accomplished at a gravitational acceleration of 75g. When centrifugal gravity reached the desired g-level, synthetic gasoline was released from an underground storage tank and migrated into the unsaturated soils following a prototype time equivalent of 1, 5, and 10 years. After termination of the centrifuge test, soil samples were gathered using sampling tubes to determine the spatial distribution of various constituents of the gasoline through gas chromatograph analysis. The centrifuge tests adequately simulated gasoline migration processes in subsurface systems. The test results show that gasoline infiltrated the vadose zone and moved downwards, forming a high concentration zone above the water table and then spreading out laterally. The concentrations of benzene, toluene, ethylbenzene, and xylenes (BTEX), which represent the main components of gasoline, decrease with time, and gradually extend to a further distance. The water solubilities of BTEX affect their individual migration patterns and concentration distributions in unsaturated soil. In addition, soil properties influence gasoline transport behavior. © ASCE.

Centrifuge modeling of the long-term migration of light nonaqueous-phase liquids (LNAPLs unsaturated soils has been accomplished at a gravitational acceleration of 75g. When centrifugal gravity reached the desired g-level, synthetic gasoline was released from an underground storage tank and migrated into the unsaturated soils following a prototype time equivalent of 1, 5, and 10 years. After termination of the centrifuge test, soil samples were gathered using sampling tubes to determine the spatial distribution of various constituents of the gasoline through gas chromatograph analysis. The centrifuge tests adequately simulated gasoline migration processes in subsurface systems. The test results show that gasoline infiltrated the vadose zone and moved downwards, forming a high concentration zone above the water table and then spreading out laterally. The concentrations of benzene, toluene, ethylbenzene, and xylenes (BTEX), which represent the main components of gasoline, decrease with time, and gradually extend to a further distance. The water solubilities of BTEX affect their individual migration patterns and concentration distributions in unsaturated soil. In addition, soil properties influence gasoline transport behavior. © ASCE.

Centrifuge modeling appears useful for studying geo-environmental problems such as pollutant migration in subsurface systems. In this study, centrifuge tests were conducted to simulate a gasoline spill from a leaking underground storage tank (UST) and the subsequent subsurface migration of the gasoline. When the centrifugal acceleration reached the desired g level, the gasoline was released from the UST and then it migrated in the unsaturated soil for a prototype time equivalent to 1 year. After the centrifuge tests, soil samples C were collected using sampling tubes and the concentrations of individual constituents in the light nonaqueous phase liquids (LNAPLs) were directly measured by means of gas chromatograph analysis. Two types of unsaturated soils were used to study the migration patterns of LNAPLs in unsaturated porous media. Centrifuge test data show that the migration pattern of LNAPLs is related to the soil type and the physical properties of individual constituents in the LNAPLs.

The transport process of LNAPLs in subsurface system was simulated by use of centrifuge technology, and thereafter soil vapor extraction process was modeled to remediate the contaminated soils. The groundwater samples soil samples were collected and contaminant concentrations were detected through gas chromatograph analysis. Test results show that there formed a contaminant plume in unsaturated soils, which can be efficiently removed by SVE remediation technology.

Centrifuge modeling of the long-term migration of light nonaqueous-phase liquids (LNAPLs unsaturated soils has been accomplished at a gravitational acceleration of 75g. When centrifugal gravity reached the desired g-level, synthetic gasoline was released from an underground storage tank and migrated into the unsaturated soils following a prototype time equivalent of 1, 5, and 10 years. After termination of the centrifuge test, soil samples were gathered using sampling tubes to determine the spatial distribution of various constituents of the gasoline through gas chromatograph analysis. The centrifuge tests adequately simulated gasoline migration processes in subsurface systems. The test results show that gasoline infiltrated the vadose zone and moved downwards, forming a high concentration zone above the water table and then spreading out laterally. The concentrations of benzene, toluene, ethylbenzene, and xylenes (BTEX), which represent the main components of gasoline, decrease with time, and gradually extend to a further distance. The water solubilities of BTEX affect their individual migration patterns and concentration distributions in unsaturated soil. In addition, soil properties influence gasoline transport behavior. © ASCE.

Centrifuge modeling appears useful for studying geo-environmental problems such as pollutant migration in subsurface systems. In this study, centrifuge tests were conducted to simulate a gasoline spill from a leaking underground storage tank (UST) and the subsequent subsurface migration of the gasoline. When the centrifugal acceleration reached the desired g level, the gasoline was released from the UST and then it migrated in the unsaturated soil for a prototype time equivalent to 1 year. After the centrifuge tests, soil samples C were collected using sampling tubes and the concentrations of individual constituents in the light nonaqueous phase liquids (LNAPLs) were directly measured by means of gas chromatograph analysis. Two types of unsaturated soils were used to study the migration patterns of LNAPLs in unsaturated porous media. Centrifuge test data show that the migration pattern of LNAPLs is related to the soil type and the physical properties of individual constituents in the LNAPLs.