The ability of supersaturated water injection (SWI) to recover non-aqueous phase liquids (NAPLs) was studied at the field scale as part of an ongoing program to evaluate its applicability to groundwater remediation. SWI uses Gas inFusionTM technology to efficiently dissolve gases into liquids at elevated pressures. SWI has been shown to both volatilize and mobilize residual NAPL ganglia (Li, 2004). During SWI pressurized water containing high concentrations of CO2 is injected into the subsurface below the zone of contamination. Once the injected water is in the aquifer the pressure drops substantially and the concentration of CO2 is no longer in equilibrium with the water and as a result CO2 bubbles nucleate. These bubbles then migrate upwards through the contaminated zone towards the water table. As they move they come into contact with residual NAPL ganglia and they either volatilize this NAPL, resulting in a bubble comprised of CO2 and gaseous NAPL, or mobilize this NAPL, resulting in a film of NAPL surrounding the bubble. In either case the bubbles continue to rise until they reach the water table at which point they are removed by a dual phase extraction system. In this work, a known amount of NAPL was emplaced below the water table at residual concentrations to represent a residual source of weathered gasoline. The source was created in a hydraulically isolated cell in an unconfined sand aquifer at CFB Borden, Ontario. After the source was emplaced SWI was used to remove as much of the contaminant mass as possible in 22.25 days of operation over three months. The goal of this project was to determine if SWI was capable of removing residual NAPL at a field site. It was successful in removing volatile NAPL but not non-volatile NAPL. 64% of the volatile compounds were removed but contaminant mass was still being removed when the system was shut down so with continued operation more mass would have been removed. There is no way of knowing how much more would have been removed had the project continued. These results indicate that continued development of the technology is warranted.

La contamination des ressources en eaux souterraines par une phase organique non miscible à l'eau couramment appelée NAPL (Non Aqueous Phase Liquid) constitue aujourd'hui un défi scientifique majeur compte tenu de la durée de vie d'un tel polluant. Bien que l'activité bactérienne (généralement présente sous forme de biofilm) joue un rôle crucial dans le devenir à long terme de ces effluents, peu d'études existent à l'heure actuelle sur son impact dans des conditions multiphasiques (i.e., à proximité de la source). En effet, dans la zone saturée, sous l'action des forces capillaires, le NAPL se retrouve souvent piégé, en effet, sous forme de «gouttelettes» au niveau des pores. Ce comportement spécifique au polluant modifie la dynamique du système biofilm/milieu poreux saturé et d'importantes questions restent encore ouvertes : accessibilité du polluant, modification de la tension interfaciale, production de biosurfactant, effet de toxicité (inhibition de la croissance bactérienne). Pour tenter de répondre à ces questions, nous avons adopté une approche aussi bien théorique qu'expérimentale. L'approche théorique porte sur le développement d'un modèle macroscopique décrivant le transport multiphasique en milieu poreux pour un système eau/NAPL/biofilm. Elle repose sur la méthode de prise de moyenne volumique, appliqué aux équations décrivant le couplage écoulement/transport à l'échelle du pore, permettant d'effectuer le changement d'échelle et dériver un modèle à deux équations. Le modèle est établit sous les hypothèses d'équilibre de masse local à l'interface fluide/biofilm et les contraintes associées à ces hypothèses ont étés définies. L'influence des caractéristiques microscopiques (arrangement des grains, fraction volumique du biofilm, distribution des blobs de NAPL, mouillabilité) sur les propriétés effectives du milieu (coefficient de dispersion, coefficient d'échange de masse) est discutée au travers des résultats issus des simulations. Ensuite, le modèle macroscopique a été comparé avec succès à la simulation numérique direct à l'échelle du pore pour la géométrie 2D complexe considérée. Quant à l'approche expérimentale, elle consiste à étudier le transport et la biodégradation du toluène en présence des bactéries Pseudomonas Putida F1 à l'aide d'un milieu poreux transparent 2D (micromodèle). Premièrement, nous avons étudié la dissolution du toluène résiduel sans bactéries et des courbes de dissolution du toluène ont été obtenues. Les résultats de dissolution du toluène en condition abiotique ont été comparés avec succès aux résultats du modèle théorique. Ensuite, l'étude expérimentale en micromodèle a porté sur la dissolution du toluène en condition biotique. Les résultats de ces études (courbes de dissolution et évolution de la saturation résiduelle) ont montré un impact significatif de la présence des bactéries sur les processus de dissolution par comparaison au cas abiotique. / Contamination of groundwater resources by an immiscible organic phase commonly called NAPL (Non Aqueous Phase Liquid) represents a major scientific challenge considering the residence time of such a pollutant. Although bacterial activity (usually in the form of biofilm) plays a crucial role in the long term fate of these effluents, very few works are focused on the study of such processes in multiphase conditions (oil/water/biofilm systems). The NAPL often gets trapped, in fact, under the action of capillary forces in the saturated zone in the form of «droplets» within the pores. This specific pollutant behavior changes the dynamics of biofilm /saturated porous medium system where important questions remain open: accessibility of the pollutant, changes in interfacial tension, biosurfactant production, toxicity effect (inhibition of bacterial growth). Modeling the transport of chemical species in the presence of bacteria is an extremely complex issue in terms of scale. We will use an experimental and theoretical approach to address these questions. In this thesis, we developed a macroscopic model describing multiphase transport in porous media for a water/NAPL/biofilm system. A volume averaging method has been applied here to the equations at the pore scale to make the upscaling and derive the model. This two-equation model is established under the assumptions of local mass equilibrium at the fluid/biofilm interface and the constraints associated with these assumptions were defined. The effect of microscopic features (arrangement of grains, volume fraction of the biofilm, distribution of NAPL blobs, wettability) on the effective properties of the media (dispersion coefficient, mass exchange coefficient) is discussed through some results from simulations. Subsequently, the macroscopic model has been successfully compared with the direct numerical simulation at pore scale for a 2D complex geometry. The experimental approach consists of studying transport and biodegradation of toluene in the presence of bacteria Pseudomonas Putida F1 using a flowcell. First, we studied the dissolution of toluene in abiotic conditions and toluene dissolution curves were obtained. The results of toluene dissolution in abiotic conditions were compared with success the results of the theoretical model. Finally, an experimental study in flowcell on the dissolution of toluene under biotic conditions was performed. The results of these studies (dissolution curve and evolution of toluene saturation) showed a significant impact of the presence of bacteria on the dissolution process compared to the abiotic case.

As more sites containing contaminated sediments are remedied with sediment caps, so grows the interest among site managers and engineers in the benefits afforded by active capping. While traditional sediment caps can effectively manage strongly solid-associated contaminants in many situations, under certain conditions active caps or amendments may be needed to effectively reduce risk to an acceptable level. This research assessed the predicted and observed breakthrough of dissolved organic contaminants in two newly developed geotextiles; one designed to sorb non-aqueous–phase liquids (NAPLs), the other dissolved-phase contaminants. The performance of the geotextiles was then compared to that of another remediation technology that has been deployed in the field for two years. All active materials were then evaluated based on their sorption capacity and their predicted life under field conditions. The sorbent containing geotextiles designed for active capping applications were tested in columns to simulate field conditions, where upwelling groundwater would be contaminated by impacted sediments, thereby transporting contaminants to the water column. The contaminants of interest in these studies were three polycyclic aromatic hydrocarbons (PAHs) of varying hydrophobicity. Breakthrough curves for the materials vii of interest were constructed for the three PAHs and were fit to an advection-dispersion model to predict the mass of contaminants sorbed onto them. This mass was then compared and verified to be similar to values found in literature. The performance of the geotextiles was compared to that of organoclay deployed in Portland, OR, at the McCormick & Baxter Creosoting Company Superfund Site. In 2004, over 22 acres of sediment at the site were remedied with both passive and active caps to mitigate the effects of decades worth of contamination. In certain portions of the site, a 12 inch thick layer of organoclay was employed, while at other portions of the site, conventional sand or a thin reactive core mat with the equivalent of approximately 1 cm of organoclay were employed. The continued effectiveness of these sediment caps was evaluated using a variety of laboratory techniques, including measuring samples’ hexane extractable material, which is a proxy for NAPL contamination, as well as their PAH bulk concentrations. These analyses performed on core samples allowed for the generation of vertical profiles critical to cap evaluation. Despite possessing a significantly greater specific sorption capacity, the geotextiles could not offer the same protection for the extended period of time that the bulk organoclay could. The greater mass of organoclay deployed in bulk at the McCormick & Baxter site allowed a much greater sorption capacity to be placed. It would take over sixty stacked layers of the one of the geotextiles evaluated in these studies to achieve the same capacity for dissolved-phase contaminants as the 1 ft organoclay cap. However, no significant penetration of NAPL into the bulk organoclay has been noted, and thus even the thin layer within a geotextile might have been sufficient at the site, despite its significantly lower overall capacity. The data generated provides information as to the expected capacity of the various sorbent placement approaches and can help guide decisions at other sites. / text

Immiscible liquids, including chlorinated solvents, have proven to be a lasting source of subsurface contamination at many hazardous waste sites. Continued improvement of site characterization and determination of applicable remediation technologies can be achieved by further understanding of the transport and fate of these contaminants. The transport and fate of trichloroethene (TCE) was investigated through miscible displacement and dissolution experiments. Miscible displacement experiments were conducted using homogeneously packed columns with several porous media encompassing a range of particle size distributions. Immiscible liquid dissolution was investigated using homogeneously packed columns containing a residual saturation of trichloroethene. The same porous media were used for immiscible liquid dissolution experiments. Mathematical modeling of miscible displacement and dissolution experiments was conducted using a one-dimensional single region or multi-region model. Imaging of immiscible liquid dissolution was also conducted, using Synchrotron X-ray Microtomography imaging at Argonne National Laboratory, Argonne, IL. Dissolution experiments exhibited nonideal dissolution behavior that was apparent in observed effluent data and in collected imaging data. Nonideal behavior was manifested as secondary regions of relatively constant aqueous concentrations occurring for a number of pore volumes. This behavior was observed to increase in magnitude as particle size distribution of the porous media increased. During imaging, immiscible liquid blobs were observed to dissolve throughout the column during dissolution. This behavior is also indicative of nonideal dissolution, as it would be expected that dissolution would first occur for the blobs nearest the inlet and then proceed upward through the column as dissolution progressed. In many cases, a multi-region modeling approach was necessary to successfully represent the nonideal behavior observed. Comparisons were made between the natural porous media used for this research and a well-sorted sand. Nonideal dissolution was not observed in the well-sorted sand.

The ability of supersaturated water injection (SWI) to recover non-aqueous phase liquids (NAPLs) was studied at the field scale as part of an ongoing program to evaluate its applicability to groundwater remediation. SWI uses Gas inFusionTM technology to efficiently dissolve gases into liquids at elevated pressures. SWI has been shown to both volatilize and mobilize residual NAPL ganglia (Li, 2004). During SWI pressurized water containing high concentrations of CO2 is injected into the subsurface below the zone of contamination. Once the injected water is in the aquifer the pressure drops substantially and the concentration of CO2 is no longer in equilibrium with the water and as a result CO2 bubbles nucleate. These bubbles then migrate upwards through the contaminated zone towards the water table. As they move they come into contact with residual NAPL ganglia and they either volatilize this NAPL, resulting in a bubble comprised of CO2 and gaseous NAPL, or mobilize this NAPL, resulting in a film of NAPL surrounding the bubble. In either case the bubbles continue to rise until they reach the water table at which point they are removed by a dual phase extraction system. In this work, a known amount of NAPL was emplaced below the water table at residual concentrations to represent a residual source of weathered gasoline. The source was created in a hydraulically isolated cell in an unconfined sand aquifer at CFB Borden, Ontario. After the source was emplaced SWI was used to remove as much of the contaminant mass as possible in 22.25 days of operation over three months. The goal of this project was to determine if SWI was capable of removing residual NAPL at a field site. It was successful in removing volatile NAPL but not non-volatile NAPL. 64% of the volatile compounds were removed but contaminant mass was still being removed when the system was shut down so with continued operation more mass would have been removed. There is no way of knowing how much more would have been removed had the project continued. These results indicate that continued development of the technology is warranted.

In situ capping is a remediation alternative for contaminated sediments which has been implemented to contain contaminants in sediments in rivers, lakes and ponds. One concern with in situ capping is that the additional load due to the in situ cap may cause consolidation-induced mobilization of non aqueous phase liquids (NAPL). Therefore, it is important to understand the consolidation behavior of NAPL contaminated soils. The difficulties of testing river-bed sediments are that these sediments usually are very soft, have very high porosities, and are very compressible. In addition, the contaminants in these sediments should be contained during testing. The primary objective of this research is to investigate the behavior of NAPL contaminated sediments under anisotropic consolidation. A modified triaxial testing system was developed to simulate the consolidation of very soft sediment specimens along with a reconstituted NAPL contaminated specimen preparation procedure. Kaolinite and Anacostia River sediments were used for the sediments’ solids phase. A low viscosity mineral oil, Soltrol 130, was used to represent the NAPL phase. Tap water was used as the water phase. PM199TM, a type of organophilic clay manufactured by CETCO, was used as well to study its effectiveness in containing expelled NAPL. Two sets of consolidation tests were performed: 1) tests on sediment specimens at various NAPL contents and porosities; and 2) tests on specimens contaminated with NAPL with organophilic clays either placed as a layer on top or mixed within the sediment. The results showed that NAPL mobilization was negligible below a threshold NAPL content. Hydraulic conductivities increased with increasing NAPL content up to four orders of magnitude. The tests with organophilic clay showed that when large enough amounts are used, NAPL expulsion can be completely stopped. Organophilic clay reached its full capacity independent of the NAPL content of the underlying sediment. / text

Multicomponent nonaqueous phase liquids (NAPL) contaminating the subsurface can significantly inhibit remediation. One method of enhancing the rate of remediation of NAPL constituents, compared to pump-and-treat, involves source zone treatment with enhanced solubilization agents (ESAs) including cyclodextrins. Equilibrium cyclodextrin enhanced solubilization of simple 1, 2, and 3 component NAPL mixtures was examined to evaluate the applicability of Raoult's Law. The results suggest that Raoult's Law may be used to estimate equilibrium and early-time dynamic concentrations in contact with ideal NAPL mixtures, and Raoult's Law may be used to estimate cyclodextrin enhanced groundwater concentrations for ideal NAPL mixtures. Solubility enhancement of NAPL compounds was dependent on the cyclodextrin concentration and independent of NAPL composition. Column experiments and numerical modeling were used to evaluate the dissolution behavior of the NAPL mixtures in water and a cyclodextrin solution to estimate mass transfer rates. The aqueous multicomponent dissolution followed Raoult's Law, and the model-estimated lumped rate coefficients were independent of the NAPL composition. Addition of the cyclodextrin enhanced the dissolution and removal of compounds from residual NAPL due to an increase in the driving force (i.e. concentration gradient) and the mass transfer coefficient. The model results suggest that Raoult's Law is applicable for ideal NAPL mixture dissolution in water, but potential nonideality was observed and caused the model simulation to deviate from the dissolution behavior for NAPL mixture cyclodextrin experiments. The cyclodextrin dissolution experiments were less rate-limited than aqueous dissolution, and the mass transfer coefficients were quantified with the model. The results of the model suggest that NAPL mixture nonideality and intra-NAPL diffusion may also impact enhanced dissolution behavior. Additionally, the importance of NAPL mixture characterization was illustrated by evaluation of a mixture of PCE (tetrachloroethene) and diesel fuel collected from a site in Tucson, Arizona. A sample from the site was used to create mixtures with increasing PCE in the NAPL. Chemical evaluation of the complex NAPL was conducted, and physical property and phase partitioning testing was performed, which demonstrated the effect of NAPL composition on its distribution, interphase mass transfer, and potential mobilization.

Dissolving multicomponent NAPL as a source of contamination in subsurface water is considered. In particular, two processes are analyzed with regard to how they alter inter-species concentration ratios at remote monitoring locations relative to inter-species molar ratios in the NAPL: nonlinear dissolution governed by Raoult’s Law and differential sorption during subsurface transport. An analytic solution for Raoult’s Law-governed dissolution is presented. Separately, it is shown how a variety of 1D analytic transport models for simple boundary conditions may be adapted to use arbitrary time-varying concentrations by use of some properties of Laguerre series. This is combined with the analytic solution so that Raoult’s Law-governed multicomponent NAPL dissolution may be employed as the boundary condition for analytic transport models. A new computer model implementing this technique in an environment of discrete, parallel fractures is presented, and its accuracy verified for specific conditions against an existing code. The new code is applied to a parametric study on the plume separation of PAH and phenolic compounds from the dissolution of creosote. Narrow fracture spacing as well as significant values of matrix organic carbon are seen as particularly conducive to separation of these types of plumes, which in some circumstances may be entirely disjoint. Concentration ratios downgradient are shown largely unrelated to concentration ratios at the source. Finally, a study of PCB speciation is undertaken in fractured rock with known parameters, for which a rigorous, least squares speciation approach is developed. Even at distances of 5 m from the source, given perfect information about the subsurface, it is found not possible to chemically fingerprint a source PCB mixture from a list of three absent a model of the weathering of the NAPL. Both the PCB and creosote studies demonstrate that forensic inference of source compositions from field data is unreliable and the need for coupled dissolution and transport models like the one developed here. / Thesis (Ph.D, Civil Engineering) -- Queen's University, 2012-09-25 21:43:29.04

学位授与大学：京都大学 ; 取得学位: 博士(工学) ; 学位授与年月日: 2007-09-25 ; 学位の種類: 新制・課程博士 ; 学位記番号: 工博第2845号 ; 請求記号: 新制/工/1419 ; 整理番号: 25530 / Multiphase flows are governed by three-dimensional Navier Stokes equations for each involved phase. Therefore, solution of these equations for given boundary and initial conditions, in principle, would determine the flow field in time and space. Generally, boundaries between involved phases are not known a priory, but are part of the, solution; or in the case of flows in a porous medium, these boundaries have too complicated geometry to be resolved mathematically. This resulted into development of simplified models, where the level of simplifications determines the model applicability. However, in order to represent simulated flows accurately, the model should include as much as possible relevant mechanisms and fluid properties. In this study, a numerical model is developed based on finite volume method, in which the volume averaged governing equations are solved. In contrary to the simplified models. a full momentum equations for each involved phase is considered. Such model is utilized in the study to investigate commonly adopted simplifications, and their effects on the model applicability. Namely, for the flows in porous media, the effects of acceleration terms in momentum equations are investigated; first for the saturated groundwater flow, and then; for the air/water flow during air injection into initially saturated soil. It is revealed that in the case of saturated flow in homogeneous, incompressible, low permeable soils, the pressure adapts the new imposed boundary conditions instantaneously, while the velocities reach the quasi-steady conditions extremely fast. In the case of heterogeneous soil, pressure and velocity field have transient nature, but quickly reach the quasi-steady conditions. Only during this onset of flow, the inertia terms play a role. In the case of air/water flow during air sparging, it is revealed that acceleration becomes important for porous medium with average grain size larger than 2 rum. This implies that simulations of such flow in coarse sands and gravels should include acceleration. It is explicitly shown that phenomena of flow pulsation, manifesting as steady pulsation at the constant air-injection flow rate, can be modeled only by inclusion of acceleration terms in governing equations. Theoretical analysis; conducted by application of one-dimensional stability analysis, revealed that inertial effects promote the instability, while the capillary forces oppose it. Ratio of these forces determines the onset of instability. It is showed that for materials with average grain size smaller than 2 mm, instability can not be expected. In order to apply the model for simulation of contaminant removal during air sparging, the contaminant transport model is supplied. Mechanistic numerical models inherently assume that involved phases are completely mixed, and by now reported models commonly assume the local equilibrium of contaminant between the air and water phase. As reported by many investigators, this leads toward an overestimated contaminant removal. Therefore, in this model a channel air flow pattern is considered, where transfer of contaminant between the water and the air phase is modeled according to two film theory. Diffusive process of contaminant transport toward the air phase is modeled by a first order kinetic process between two water compartments: a immobile compartment in contact with the air phase and mobile compartment which has no contact with the air phase. Application of the developed model to reported two-dimensional experiment, showed a good agreement between simulated and measured transient change of dissolved contaminant in the water. This study also showed that single numerical model, through the minor refinements, can be applied to wide variety of hydraulic engineering problems. By inclusion of gas compressibility, and mass exchange between the gas and the water phase in continuity equations, with adapting the drag term in momentum equations, a bubble phone model is proposed which can be utilized for simulation of lake amelioration by gas (air or pure oxygen) injection. Model is qualitatively and quantitatively validated by comparison with reported experiments from the literature. Hypothetical simulation of pure oxygen injection into 50 in deep lake showed that, due to ambient water entrainment into the gas plume, a significant spreading of dissolved oxygen can not be expected. Therefore, a optional gas injection strategy should be considered. Developed model can be utilized in order to propose an optimal gas injection design. Finally.. the same numerical model is proposed for simulation of flow in complex flow domains, consisting of bulk water and flow in porous medium with free surface boundary. Model is formulated in generalized curvilinear coordinates, in order to provide adequate representation of irregular boundaries. In contrast to earlier proposed boundary conditions at the two domain interface, in this model a continuity of velocities and stresses is assumed; for both regions a single set of governing equations is solved. Model application is illustrated by simulation of embankment overflow and its effect on effective stresses in the porous medium. It is showed that coupled, bulk water and groundwater flow, significantly influence the slope failure potential, here quantified by the Coulomb failure coefficient for non cohesive soils. / Kyoto University (京都大学) / 0048 / 新制・課程博士 / 博士(工学) / 甲第13374号 / 工博第2845号 / 新制||工||1419(附属図書館) / 25530 / UT51-2007-Q775 / 京都大学大学院工学研究科都市社会工学専攻 / (主査)教授 細田 尚, 准教授 牛島 省, 准教授 後藤 仁志 / 学位規則第4条第1項該当

As áreas contaminadas por NAPL (Non-Aqueous Phase-Liquids ou fase líquida não aquosa ou ainda fase livre) podem causar riscos à saúde humana e aos ecossistemas, restrições para o desenvolvimento urbano e diminuição do valor imobiliário das propriedades. Este trabalho utilizou o gás radônio como um indicador para a análise de gás subsuperficial do solo, uma vez que este gás nobre apresenta boa solubilidade em uma ampla gama de NAPL, sendo parcialmente retido na contaminação NAPL. Portanto, uma diminuição da atividade de gás radônio no solo contaminado pode ser esperada, devido à elevada capacidade de particionamento do radônio em NAPL, o que permite que o NAPL retenha uma parte do radônio anteriormente disponível nos poros do solo. O levantamento foi realizado em uma indústria abandonada, contaminada por NAPL pouco volátil, localizada na zona sudeste da cidade de São Paulo, entre junho de 2014 e maio de 2015. A concentração de radônio foi avaliada pela metodologia de detecção passiva com detectores sólidos de traços nucleares (SSNTD) tipo CR-39 em dez estações de monitoramento instaladas na área contaminada investigada e nomeadas de A até J. A média das concentrações de atividade de radônio para as oito estações de monitoramento em locais supostamente não contaminados variou de (22 ± 4) kBq.m-3 a (39 ± 4) kBq.m-3. Para as duas estações de monitoramento supostas como locais contaminados, as concentrações de radônio foram (1,4 ± 0,4) kBq.m-3 e (13 ± 9) kBq.m-3. Os resultados demonstraram que o método utilizado foi consistente com as técnicas convencionais de investigação ambiental para a maioria das estações de monitoramento em diferentes estações do ano. Resultados obtidos com CR-39 variam ao longo dos períodos de exposição, devido à sazonalidade. Não foi observada relação entre as oscilações das concentrações de atividade de radônio e o volume de chuva acumulada nos diferentes períodos de exposição dos detectores CR-39. As menores concentrações de atividade do 222Rn ocorreram nas estações de monitoramento G e H e verificou-se por espectrometria gama, que a baixa atividade não está relacionada à concentração de atividade de seu pai 226Ra na série do decaimento radioativo do 238U, reforçando a teoria de retenção do gás radônio nos locais contaminados por NAPL. Resultados da etapa de remediação comprovaram que a técnica utilizada neste trabalho foi mais eficiente que as técnicas convencionais de investigação ambiental, especialmente para as estações de monitoramento D e G na área contaminada investigada. / Contaminated sites by NAPL (Non-Aqueous Phase-Liquids) may lead to safety risks to human health and to ecosystems, restrictions to urban development and decrease of real estate value. This work used the radon gas as an indicator for the analysis of subsurface soil gas, once this noble gas presents good solubility in a wide range of NAPL, being partially retained in the NAPL contamination. Therefore, a decrease of the activity of radon in the contaminated soil gas can be expected, due to the high capacity of partitioning of radon in NAPL, which allows that the NAPL retain part of the radon previously available in the soil pores. The survey was carried out at a disused industry, contaminated by low volatile NAPL, located at southeast of São Paulo city, from June/14 to May/15. Radon was evaluated by passive detection methodology with CR-39 solid state nuclear track detectors (SSNTD) in ten monitoring stations installed in the contaminated area investigated and named \"A\" to \"J\". Radon concentrations average for the eight monitoring stations at non-contaminated locations varied from (22 ± 4) kBq.m-3 to (39 ± 4) kBq.m-3. For the two monitoring stations assumed as contaminated locations, radon concentrations average were (1.4 ± 0.4) kBq.m-3 and (13 ± 9) kBq.m-3. The results have shown good agreement between the used method and the conventional environmental investigation techniques, for the majority of the monitoring stations in different seasons. Results obtained with CR-39 detectors varied over the exposure time due to the different seasons. No relation was observed between radon activity concentrations and rain volume accumulated over the different CR-39 exposure times. The lowest 222Rn activity concentrations occurred in G and H monitoring stations, also verifying by gamma-ray spectrometry, that the low activities are not related to the activity concentration of its father 226Ra from the 238U decay chain, reinforcing the theory that radon gas is retained in sites where NAPL contamination is present. Results obtained during environmental remediation proved that the methodology employed in this study was more efficient than the conventional investigation techniques, specially for the D and G monitoring stations to the investigated site.