abstract: Mineral weathering and industrial activities cause elevated concentration of hexavalent chromium (Cr(VI)) in groundwater, and this poses potential health concern (>10 ppb) to southwestern USA. The conversion of Cr(VI) to Cr(III) – a fairly soluble and non-toxic form at typical pH of groundwater is an effective method to control the mobility and carcinogenic effects of Cr(VI). In-situ chemical reduction using SnCl2 was investigated to initiate this redox process using jar testing with buffered ultrapure water and native Arizona groundwater spiked with varying Cr(VI) concentrations. Cr(VI) transformation by SnCl2 is super rapid (<60 seconds) and depends upon the molar dosage of Sn(II) to Cr(VI). Cr(VI) removal improved significantly at higher pH while was independent on Cr(VI) initial concentration and dissolved oxygen (DO) level. Co-existing oxyanions (As and W) competed with Cr(VI) for SnCl2 oxidation and adsorption sites of formed precipitates, thus resulted in lower Cr(VI) removal in the challenge water. SnCl2 reagent grade and commercial grade behaved similarly when freshly prepared, but the reducing strength of the commercial product decreased by 50% over a week after exposing to atmosphere. Equilibrium modeling with Visual MINTEQ suggested redox potential < 400 mV to reach Cr(VI) treatment goal of 10 ppb. Kinetics of Cr(VI) reduction was simulated via the rate expression: r=-k[H+]-0.25[Sn2+]0.5[Cr2O72-]3 with k = 0.146 uM-2.25s-1, which correlated consistently with experimental data under different pH and SnCl2 doses. These results proved SnCl2 reductive treatment is a simple and highly effective method to treat Cr(VI) in groundwater. / Dissertation/Thesis / Masters Thesis Civil, Environmental and Sustainable Engineering 2019

Grande parte das áreas contaminadas conhecidas atualmente advém de práticas passadas onde os cuidados com a proteção à saúde humana e ao meio ambiente eram desconhecidos ou ignorados. O uso indiscriminado de produtos solventes clorados fez com que tais compostos se tornassem uma das principais fontes de contaminação no setor industrial. Por serem compostos de alta toxicidade, quando presentes na água subterrânea, mesmo em baixas concentrações, a tornam imprópria para o consumo. Técnicas de remediação como atenuação natural, ou que envolvam bombeamento e tratamento de água subterrânea contaminada por solventes clorados, vêm sendo substituídas por metodologias químicas destrutivas, por apresentarem resultados satisfatórios em um período de tempo inferior às técnicas utilizadas anteriormente. Este trabalho objetiva apresentar os resultados obtidos em duas áreas industriais onde foram aplicadas técnicas de remediação, envolvendo a redução química in situ, através da injeção de polisulfeto de cálcio e a oxidação química in situ, com a injeção de permanganato de potássio. Em ambas as áreas, os contaminantes organoclorados são os principais compostos de interesse presentes na água subterrânea. A redução química in situ é uma metodologia que utiliza um agente químico para reduzir óxidos de ferro III, presentes naturalmente no aquífero sedimentar, e transformá-los em ferro II que, por sua vez reduzirá contaminantes organoclorados. A principal característica desta metodologia é a eliminação contígua de dois átomos de cloro das moléculas dos contaminantes, o que tende e diminuir ou eliminar o acúmulo de subprodutos tóxicos como cloreto de vinila. Na oxidação química in situ, o agente promove a transferência de elétrons, onde os íons Cl- das moléculas dos contaminantes são substituídos por H+. Devido à baixa reatividade entre o permanganato de potássio e a matriz do aquífero durante as reações de oxidação química, este oxidante pode ser transportado pelos processos advectivo e dispersivo juntamente com o fluxo da água subterrânea e persistir por um período maior de tempo, reagindo com os contaminantes orgânicos. Ensaios de bancada com solo saturado contaminado de uma das áreas de estudo mostraram excelentes resultados na utilização do polisulfeto de cálcio, mas o mesmo não foi observado no teste piloto realizado em campo. Embora tenha sido observada dispersão do produto nas proximidades de pelo menos um dos pontos onde a solução foi injetada, notou-se que não houve redução significativa dos contaminantes, evidenciando que o ferro II não foi eficaz no processo de degradação. Isto pode ter sido ocasionado por uma série fatores, como possíveis reações, características hidráulicas, ou geológicas do meio. Portanto, o prosseguimento desta metodologia como alternativa de remediação para toda a área impactada foi descontinuado, tornando necessário novos estudos para avaliar a melhor técnica aplicável na área. Quanto à área onde foi aplicada a oxidação química, a remediação foi considerada eficiente. Ao longo do período de vinte e dois meses, quando foram realizadas atividades de monitoramento da água subterrânea, observou-se a presença do permanganato de potássio nas áreas mais impactadas das plumas de contaminação, fato que permitiu o processo de transferência de elétrons e consequentemente a oxidação dos contaminantes. Vinte e dois meses após as atividades de injeção, o principal contaminante identificado na área, o 1,-1-dicloroeteno, foi detectado em apenas um ponto com concentração superior a meta de remediação obtida anteriormente à injeção. Considerando que durante a sequência das atividades relacionadas à remediação, este contaminante sofreu alterações em seus valores toxicológicos estabelecidos pela Agência de Proteção Ambiental dos Estados Unidos, e passou a ser considerado um composto não carcinogênico, todos os poços apresentaram-se com concentrações inferiores a nova meta de remediação calculada. Como efeito colateral, foi observado o aumento das concentrações de metais dissolvidos, como: alumínio, bário, cromo e ferro. Tal mobilização de metais para a água subterrânea pode ser considerada temporária. Após o total consumo do permanganato de potássio pelos contaminantes ainda presentes no meio, as características físico-químicas do aquífero retornarão à situação identificada naturalmente, permitindo a precipitação dos metais. / Most of the currently known contaminated areas are the result of past practices, where precautions regarding protection of human health and the environment were either unknown or ignored. The indiscriminate use of chlorinated solvents is the driving factor that has led to such compounds becoming one of the main sources of contamination in the industrial sector. Chlorinated solvents are highly toxic and, when present at even low concentrations in groundwater, they make this resource unfit for human consumption. Such remediation techniques as natural attenuation, or that involve pumping and treatment of groundwater contaminated by chlorinated solvents, are currently being replaced by destructive chemical methods, as they show satisfactory results in a shorter period of time than previously used techniques. This study has the objective of showing the results obtained at two industrial sites where remediation techniques have been used involving in-situ chemical reduction, through injection of calcium polysulfide, and in-situ chemical oxidation, with injection of potassium permanganate. At both sites, organochlorine contaminants are the main compounds of concern present in groundwater. In-situ chemical reduction is a methodology that uses a chemical agent in order to reduce iron III oxides, naturally present in the sedimentary aquifer, and transform them into iron II which, in turn, reduces the organochlorine contaminants. The principal characteristic of this methodology is that of contiguous elimination of two chlorine atoms from contaminant molecules, which tends to reduce or eliminate accumulation of such toxic byproducts as vinyl chloride. In in-situ chemical oxidation, the chemical agent brings about a transfer of electrons, where the Cl- ions of contaminant molecules are replaced by H+ ions. Due to the low degree of reactivity between potassium permanganate and the aquifer matrix during chemical oxidation reactions, this oxidizing agent can be transported via groundwater flow, by advective and dispersive processes, and persist for a longer period of time, reacting with organic contaminants. Bench tests performed with contaminated saturated soil from one of the sites under study showed excellent results through the use of calcium polysulfide; however, the same results were not observed during a pilot test performed in the field. Although product dispersion was observed in the vicinity of at least one of the points where the solution had been injected, it was found that there was no significant reduction of contaminants, showing that iron II was not effective in enhancing the degradation process. This could have been the result of a series of factors, for example, possible reactions or the hydraulic or geological characteristics of the medium. Therefore, it was decided not to continue with use of this methodology as a remediation alternative for the whole impacted area, making it necessary for further studies in order to assess the best technique applicable at the site. With respect to the site where a chemical oxidation approach was adopted, remediation was considered to be effective. Over a period of twenty-two months, during which groundwater monitoring activities were performed, the presence of potassium permanganate was observed in the most impacted areas of the contamination plumes, a fact that allowed for the electron transfer process and, consequently, contaminant oxidation. Twenty-two months after initiation of injection activities, the main contaminant identified at the site (1,1-dichloroethene) was only detected at one point at a concentration exceeding the post-remediation target value established prior to commencing these activities. Considering that, during the sequence of activities related to the remediation process, this contaminant underwent changes in its toxicological values established by the United States Environmental Protection Agency, and came to be considered a non-carcinogenic compound, all wells showed concentrations below the new calculated post-remediation target. As a collateral effect, there was found to be an increase in concentrations of such dissolved metals as aluminum, barium, chromium and iron. Such mobilization of metals to groundwater can be considered a temporary effect. Following complete consumption of potassium permanganate by contaminants still present in the medium, the physical-chemical characteristics of the aquifer will return to the situation occurring naturally, allowing for the precipitation of these metals.

Grande parte das áreas contaminadas conhecidas atualmente advém de práticas passadas onde os cuidados com a proteção à saúde humana e ao meio ambiente eram desconhecidos ou ignorados. O uso indiscriminado de produtos solventes clorados fez com que tais compostos se tornassem uma das principais fontes de contaminação no setor industrial. Por serem compostos de alta toxicidade, quando presentes na água subterrânea, mesmo em baixas concentrações, a tornam imprópria para o consumo. Técnicas de remediação como atenuação natural, ou que envolvam bombeamento e tratamento de água subterrânea contaminada por solventes clorados, vêm sendo substituídas por metodologias químicas destrutivas, por apresentarem resultados satisfatórios em um período de tempo inferior às técnicas utilizadas anteriormente. Este trabalho objetiva apresentar os resultados obtidos em duas áreas industriais onde foram aplicadas técnicas de remediação, envolvendo a redução química in situ, através da injeção de polisulfeto de cálcio e a oxidação química in situ, com a injeção de permanganato de potássio. Em ambas as áreas, os contaminantes organoclorados são os principais compostos de interesse presentes na água subterrânea. A redução química in situ é uma metodologia que utiliza um agente químico para reduzir óxidos de ferro III, presentes naturalmente no aquífero sedimentar, e transformá-los em ferro II que, por sua vez reduzirá contaminantes organoclorados. A principal característica desta metodologia é a eliminação contígua de dois átomos de cloro das moléculas dos contaminantes, o que tende e diminuir ou eliminar o acúmulo de subprodutos tóxicos como cloreto de vinila. Na oxidação química in situ, o agente promove a transferência de elétrons, onde os íons Cl- das moléculas dos contaminantes são substituídos por H+. Devido à baixa reatividade entre o permanganato de potássio e a matriz do aquífero durante as reações de oxidação química, este oxidante pode ser transportado pelos processos advectivo e dispersivo juntamente com o fluxo da água subterrânea e persistir por um período maior de tempo, reagindo com os contaminantes orgânicos. Ensaios de bancada com solo saturado contaminado de uma das áreas de estudo mostraram excelentes resultados na utilização do polisulfeto de cálcio, mas o mesmo não foi observado no teste piloto realizado em campo. Embora tenha sido observada dispersão do produto nas proximidades de pelo menos um dos pontos onde a solução foi injetada, notou-se que não houve redução significativa dos contaminantes, evidenciando que o ferro II não foi eficaz no processo de degradação. Isto pode ter sido ocasionado por uma série fatores, como possíveis reações, características hidráulicas, ou geológicas do meio. Portanto, o prosseguimento desta metodologia como alternativa de remediação para toda a área impactada foi descontinuado, tornando necessário novos estudos para avaliar a melhor técnica aplicável na área. Quanto à área onde foi aplicada a oxidação química, a remediação foi considerada eficiente. Ao longo do período de vinte e dois meses, quando foram realizadas atividades de monitoramento da água subterrânea, observou-se a presença do permanganato de potássio nas áreas mais impactadas das plumas de contaminação, fato que permitiu o processo de transferência de elétrons e consequentemente a oxidação dos contaminantes. Vinte e dois meses após as atividades de injeção, o principal contaminante identificado na área, o 1,-1-dicloroeteno, foi detectado em apenas um ponto com concentração superior a meta de remediação obtida anteriormente à injeção. Considerando que durante a sequência das atividades relacionadas à remediação, este contaminante sofreu alterações em seus valores toxicológicos estabelecidos pela Agência de Proteção Ambiental dos Estados Unidos, e passou a ser considerado um composto não carcinogênico, todos os poços apresentaram-se com concentrações inferiores a nova meta de remediação calculada. Como efeito colateral, foi observado o aumento das concentrações de metais dissolvidos, como: alumínio, bário, cromo e ferro. Tal mobilização de metais para a água subterrânea pode ser considerada temporária. Após o total consumo do permanganato de potássio pelos contaminantes ainda presentes no meio, as características físico-químicas do aquífero retornarão à situação identificada naturalmente, permitindo a precipitação dos metais. / Most of the currently known contaminated areas are the result of past practices, where precautions regarding protection of human health and the environment were either unknown or ignored. The indiscriminate use of chlorinated solvents is the driving factor that has led to such compounds becoming one of the main sources of contamination in the industrial sector. Chlorinated solvents are highly toxic and, when present at even low concentrations in groundwater, they make this resource unfit for human consumption. Such remediation techniques as natural attenuation, or that involve pumping and treatment of groundwater contaminated by chlorinated solvents, are currently being replaced by destructive chemical methods, as they show satisfactory results in a shorter period of time than previously used techniques. This study has the objective of showing the results obtained at two industrial sites where remediation techniques have been used involving in-situ chemical reduction, through injection of calcium polysulfide, and in-situ chemical oxidation, with injection of potassium permanganate. At both sites, organochlorine contaminants are the main compounds of concern present in groundwater. In-situ chemical reduction is a methodology that uses a chemical agent in order to reduce iron III oxides, naturally present in the sedimentary aquifer, and transform them into iron II which, in turn, reduces the organochlorine contaminants. The principal characteristic of this methodology is that of contiguous elimination of two chlorine atoms from contaminant molecules, which tends to reduce or eliminate accumulation of such toxic byproducts as vinyl chloride. In in-situ chemical oxidation, the chemical agent brings about a transfer of electrons, where the Cl- ions of contaminant molecules are replaced by H+ ions. Due to the low degree of reactivity between potassium permanganate and the aquifer matrix during chemical oxidation reactions, this oxidizing agent can be transported via groundwater flow, by advective and dispersive processes, and persist for a longer period of time, reacting with organic contaminants. Bench tests performed with contaminated saturated soil from one of the sites under study showed excellent results through the use of calcium polysulfide; however, the same results were not observed during a pilot test performed in the field. Although product dispersion was observed in the vicinity of at least one of the points where the solution had been injected, it was found that there was no significant reduction of contaminants, showing that iron II was not effective in enhancing the degradation process. This could have been the result of a series of factors, for example, possible reactions or the hydraulic or geological characteristics of the medium. Therefore, it was decided not to continue with use of this methodology as a remediation alternative for the whole impacted area, making it necessary for further studies in order to assess the best technique applicable at the site. With respect to the site where a chemical oxidation approach was adopted, remediation was considered to be effective. Over a period of twenty-two months, during which groundwater monitoring activities were performed, the presence of potassium permanganate was observed in the most impacted areas of the contamination plumes, a fact that allowed for the electron transfer process and, consequently, contaminant oxidation. Twenty-two months after initiation of injection activities, the main contaminant identified at the site (1,1-dichloroethene) was only detected at one point at a concentration exceeding the post-remediation target value established prior to commencing these activities. Considering that, during the sequence of activities related to the remediation process, this contaminant underwent changes in its toxicological values established by the United States Environmental Protection Agency, and came to be considered a non-carcinogenic compound, all wells showed concentrations below the new calculated post-remediation target. As a collateral effect, there was found to be an increase in concentrations of such dissolved metals as aluminum, barium, chromium and iron. Such mobilization of metals to groundwater can be considered a temporary effect. Following complete consumption of potassium permanganate by contaminants still present in the medium, the physical-chemical characteristics of the aquifer will return to the situation occurring naturally, allowing for the precipitation of these metals.

This master thesis is focused on groundwater remediation of chlorinated ethylenes and methanes in the area of chemical factory Spolchemie in the Czech Republic, Ústí nad Labem city. For these purposes nano zero valent iron particles were used. For the remediation two separate applications of different types of particles together in suspension with tracer (lithium chloride), were carried out. The results from the first application were evaluated by the supervisor of this thesis and are briefly summarized and discussed together with the second application which was evaluated by the author of this thesis. Second application of particles was carried out in October 2015 and observed for 424 days. Observation consisted of monitoring of groundwater level, physical-chemical parameters and collection of water samples for the analysis of concentrations of chlorinated hydrocarbons, their degradation products and several chosen ions. Nanoiron particles had the assumed effect onto the physical-chemical parameters and reduction of contamination. The application of tracer had proven the expected groundwater flow and made a possibility to distinguish between the process of reductive dehalogenation and dilution caused by the injected water, the dilution did not exceeded 5 % in most monitored points. Other...

[pt] Esta dissertação apresenta os resultados obtidos no processo de remediação de uma área contaminada por cromo hexavalente por meio da técnica de remediação química in situ (ISCR). A área de estudo localiza-se na cidade do Rio de Janeiro e foi ocupada por uma fábrica de vidros por cerca de quarenta anos e comprada para construção de condomínios residenciais. A área de estudo passou um processo de gerenciamento ambiental que contemplou diversos estudos ambientais para aquisição de dados e delimitar a contaminação, horizontal e verticalmente. O teste de bancada realizado com o reagente químico polissulfeto de cálcio demonstrou ser eficiente para reduzir as concentrações de cromo hexavalente em solo e água subterrânea. Com base nos dados adquiridos neste teste foi possível calcular a dose de injeção do polissulfeto de cálcio. Foram realizados setenta pontos de sondagem, pela técnica direct push, para injetar duzentos e cinquenta e dois mil e trinta litros de solução de polissulfeto de cálcio e água, sendo aproximadamente três mil e quinhentos litros por ponto de injeção. Os resultados após a injeção demonstraram que o polissulfeto de cálcio conseguiu remover o cromo hexavalente que estava adsorvido ao solo e reduziu a concentração de cromo hexavalente na água subterrânea entre quarenta e seis e sessenta e sete e noventa e nove e noventa e cinco por cento , após dezenove meses da injeção. Dessa forma, comprovou a eficiência deste reagente químico para remediação de áreas contaminadas por cromo hexavalente, assim como foi observado nos artigos técnicos de estudos de casos nos Estados Unidos e Europa. / [en] This dissertation presents the results obtained in the remediation process remediation of a contaminated area by hexavalent chromium applying the technology in situ chemical remediation (ISCR). The study area is located in the Rio de Janeiro city and was occupied by a glass factory for forty years and purchased for construction of residential condominiums. This dissertation presents the results obtained in the remediation process remediation of a contaminated area by hexavalent chromium applying the technology in situ chemical remediation (ISCR). The study area is located in the Rio de Janeiro city and was occupied by a glass factory for forty years and purchased for construction of residential condominiums. Chromium is an important metal for the industry and is used in various products and processes, such as electroplating, leather treatment, pulp, wood preservation, and refractory manufacturing. The trivalent chromium is essential from a nutritional point of view, non-toxic and poorly absorbed in the body, acting in the maintenance of some functions. Cr(III) is the most common being found and occurs naturally, since the element Cr(VI) can occur naturally, but in low concentrations, if the groundwater has geochemical conditions the Cr (III) can be oxidize to Cr (VI). The hexavalent chromium is the most dangerous valence state and, according to ATSDR (two thousand and twelve), have greater mobility in the groundwater, being carcinogenic by inhalation of high doses of soluble chromate salts. The mobility of hexavalent chromium is high in soil and groundwater because it is not adsorbed by the soil in that valence state, on the other hand when it is in trivalent form is strongly adsorbed by the soil, forming insoluble precipitates, having low mobility in soil and groundwater. The hexavalent chromium remediation by in situ chemical reduction using calcium polysulfide has been the subject of several field studies documented in the literature, both for soil and groundwater from the Chromite Ore Processing Residue (COPR) (Storch, et al., two thousand and two; Graham, et al., two thousand and six ; Charboneau, et al., two thousand and six ; Wazne, et al., two thousand seven a; Wazne, et al., two thousand seven b; Chrysochoou, et al., two thousand and ten ; Chrysochoou & Ting, two thousand and eleven ; Pakzadeh & Batista, two thousand and eleven ; Chrysochoou, et al., two thousand and twelve ). Calcium polysulfide is a fertilizer to soil and commercially available and has been used in some remediation studies cases for reducing hexavalent chromium in soil and groundwater. Being commercially available and used as fertilizer, it is a relatively cheap chemical reagent in comparison with other chemical compounds exclusively developed for this purpose. The stoichiometric demand and the chemical kinetics of the reduction of Cr (VI) by the calcium polysulfide in aqueous solution was studied by Graham et al. (two thousand and six) from the chromite ore processing residue (COPR). With this study it was reported that a molar ratio of a point sixty-six is required (close to the theoretical value of one point five) and a first-order kinetics with an initial concentration of twenty-six eight point mg/L and pH of the CPS solution around eleven point five, with the presence of oxygen. Thus, the hexavalent chromium is reduced to chromium hydroxide, slightly water soluble compound which is precipitated to the soil. The trivalent chromium has low solubility, toxicity, mobility, reactivity and is considered stable. There are various application techniques of chemical reagents in the underground environment, and choosing the most appropriate method for each area depends on the type of contaminant, geological environment, groundwater and surface interference, depth, thickness and size of the contaminated area. As described by Suthersan (mil novecentos ninety-six), the injection of chemical reagents has to achieve two objectives: (one) creating and maintaining an ideal redox environment and other parameters such as pH, presence or absence of dissolved oxygen, etc.; and (two) the delivery and distribution of the necessary reagents for a homogeneous way throughout the injection area, both horizontally and vertically. Thus, it is essential that the conceptual model of the study area is very detailed, so there is no doubt in the choice of chemical reagent application methodology. Although there are numerous laboratory studies on hexavalent chromium remediation using calcium polysulfide, there are few reports in the literature on the field application, especially case studies in Brazil, therefore, this case study becomes a demonstration applying calcium polysulfide as a remediation technique for hexavalent chrome, with geochemical data, which are important for monitoring chemical reduction. This case study shows the effectiveness, dosage and concentration of the study area, and may apply to other hexavalent chromium remediation projects. Materials and Methods A former glass factory (the Site ) operated in the North Zone of Rio de Janeiro / RJ, Brazil from the mid-thousand nine hundred and fifty s to two thousand and five. A portion of the facility was used to store raw material to produce glass, including arsenic oxide, and another portion of the Site was used to conduct industrial plating using hexavalent chromium (Cr(VI)) in the glass molds. In two thousand and nine, the Site was purchased for mixed use redevelopment, demanding an environmental assessment and subsequent remediation. Between two thousand and nine and two thousand and twelve several phases of site investigation was conducted. The results of the investigation indicated that Cr(VI) was present in soil at concentrations up to approximately twenty one mg/kg and in groundwater at concentrations up to approximately thirty mg/L. These concentrations exceeded regulatory criteria of three hundred mg/Kg for soil and zero point zero five mg/L for groundwater. A phased remedial approach was developed consisting of the following: (a) excavation and off-site disposal of two and four hundred ton of Cr(VI) impacted soil from the source area, performed in the unsaturated and saturated zone soils in the Cr(VI) source area; (b) post-excavation monitoring of the groundwater conditions; and (c) groundwater treatment following the excavation program. Hexavalent chromium concentrations in groundwater decreased significantly following the excavation, however, additional reduction of concentrations of Cr(VI) contaminant in groundwater was required. Then was designed and implemented a set of bench-scale treatability tests in order to evaluate groundwater remediation alternatives. Several proprietary and non-proprietary reductants for co-treatment of Cr(VI) were evaluated. Calcium polysulfide were selected to treat Cr(VI). To reduce residual Cr(VI) concentrations in the groundwater plume located downgradient of the former excavated source area, dois e seven hundred cubic meters were targeted for active treatment. The groundwater remediation approach consisted of the injection of thirty liters of CPS (twenty nine percent) diluted in two hundred and twenty liters of water, yielding a total of two hundred and fifty liters of solution injected using direct push technology into seventy two locations. Groundwater Monitoring As part of chemical reagent injection stage was performed the baseline monitoring with collection of soil and groundwater samples. The soil sampling was performed by direct push technique using PVC liner with two inches in diameter, to analyze the total and hexavalent chromium concentrations. Six months after the injection were installed sixteen monitoring wells, eight shallow wells (five meters) and eight deep wells (nine meters) spread upstream, side, middle and downstream of the injection area. Groundwater geochemical parameters (i.e., temperature, total solids dissolved, specific conductance, pH, oxidation-reduction potential, and temperature) were measured at the time groundwater samples were collected. Groundwater samples were collected and analyzed for total and dissolved chromium, hexavalent chromium, iron, arsenic, manganese, calcium, sulfate, and sulfide. Samples were field-filtered with disposable zero point forty-five μm polyethylene filter capsules prior to collecting samples for dissolved metals. Results and Discussion Dose calculations for the reduction of hexavalent chromium have been performed with the data obtained in the bench-scale treatability test and resulted in a stoichiometric demand of four mlCPS/kg soil to the treatment of the study area. Therefore thirty liters of solution was used containing twenty-nine percent calcium polysulfide and approximately two hundred and twenty two liters to perform their mixture, totaling two hundred and fifty-two thousand and thirty liters of solution. For solution injection were performed seventy two soil borings with eight point five meters deep, and the product was injected range between two point five and eightpoint five meters. The depth of injection was from two point five mbgl covered any change in water level due to seasonal variation. In each soil boring was injected chemical reagent solution comprised four hundred and seventeen liters of calcium polysulfide diluted in tree and eighty-three liters of water for a total volume of tree and a half liters of solution injected per point. The comparative analysis results of the third monitoring campaign ( eighteen months post-injection) with the baseline campaign (september/two thousand and twelve) indicated reduction of hexavalent chromium concentrations between forty-six point sixty-seven and ninety-nine and ninety-five percent. Regarding the second monitoring campaign (twelve months post-injection), the hexavalent chromium concentrations reduced between twenty-three point ninety-nine and ninety nine point seventy-nine percent in five of the fifteen monitoring wells that were sampled. In three of the fifteen monitoring wells the hexavalent chromium concentrations remained below the quantitation limit used by the analytical laboratory method. There was no increase in hexavalent chromium concentration, compared the results of the third and second monitoring campaign. The evaluation of the Eh and pH values measured in the monitoring campaigns showed that the pH value was in the acidic range (about four ) and after removal of contaminated soil with hexavalent chromium pH raised to between five and six, after the chemical reagent injection pH increased to the basic range (above seven point five). In the second and third campaign the pH reduced to acid range (below six point five), which can be regarded as the pH value of the area background. The Eh has inversely proportional behavior, increasing between the first and third campaign, and in the third campaign the measured values are in the ranges considered as moderately reducing (hundred to four hundred mV) and oxidizer (> four hundred mV). The pH variation also showed a relationship between increased concentrations of calcium, iron, manganese and sulfate (in some monitoring wells). There were also reductions in hexavalent chromium concentrations in monitoring wells. Conclusion This case study indicates that the use of different remediation techniques when applied together (excavation and chemical reduction), reducing the time required for remediation of a contaminated site without impacting the final cost of remediation. The chemical reduction of hexavalent chromium using calcium polysulfide was effective to reduce the concentration to less than the quantification limit of the analytical method used. Therefore, as presented it is necessary to carry out several studies to detail the hexavalent chromium concentration in the site, as well as understand the geochemistry of groundwater and performing bench-scale tests to evaluate the effectiveness of the chemical reagent in the site study hydrogeological environment and calculate the required dose. The treatability test with calcium polysulfide demonstrated the feasibility of using this chemical reagent by In Situ Chemical Reduction (ISCR) to reduce the hexavalent chrome concentration in soil and groundwater. The test resulted in a stoichiometric demand of four mlCPS /kg soil to the treatment of the study area. Soil samples collected six months after injection showed that the calcium polysulfide could desorb hexavalent chromium from the soil, since, contaminant concentrations were not detected in the samples. neteen months after the injection of the chemical reagent the groundwater concentrations of hexavalent chromium reduced from forty-six point sixty-seven to ninety-nine and ninety-five percent in relation to baseline campaign. And, of the fifteen monitoring wells in just three wells hexavalent chromium concentrations were detected. This demonstrates the effectiveness of using calcium polysulfide to remediate hexavalent chromium in soil and groundwater, confirming the studies by Storch et al. (two thousand and two), Graham et al (two thousand and six), Charboneau et al. ( two thousand and six), Wazne et al. (two thousand and seven a), Wazne et al. (two thousand and seven b), Chrysochoou et al. (two thousand and ten), Chrysochoou & Ting (two thousand and eleven), Pakzadeh & Batista (two thousand and eleven), Chrysochoou et al (2012) in several areas in United States and Europe.

Vojtěch Stejskal - Diplomová práce 2014 - Přírodovědecká fakulta UK v Praze 4 ABSTRACT The thesis describes pilot applications of combined method - combination of sodium lactate and nanoparticles of zero-valent iron and their synergic effect. Two applications of combined method are described onto two geologically different sites - in Rožmitál pod Třemšínem and Spolchemie in Ústí nad Labem. First site is contaminated by polychlorinated biphenyls; contamination is situated in hydraulically well conducted porous media formed by weathered granodiorite. Main contaminants of Spolchemie site are trichloroethylene and tetrachloroethylene, contamination is situated in geologically heterogenous quaternary terrace of Bílina river. Effects of combined method on two different sites were compared and recommendations and conclusions were done. Part of the thesis is research of scientific articles and literature on topics: polychlorinated biphenyls, chlorinated ethylenes, in situ chemical reduction by sodium lactate and nanoiron, natural conditions of both sites, history of sites. In the thesis are also processed and evaluated results of geophysical investigation, changes of groundwater level and results of groundwater monitoring in view of the application of combined method on both sites.