The current US Environmental Protection Agency (USEPA) maximum contaminant level (MCL) for total chromium of 100 ppb is under revision to consider a specific level for Cr(VI), which has a proposed MCL of 10 ppb in California. Cr(VI) is a suspected carcinogen, and interconverts with the other most commonly found chromium species, Cr(III). To regulate and further understand the behavior of Cr(VI) in water systems, appropriate sample preservation methods are essential for accurate measurements. The ammonia buffer (recommended by EPA) was proven to be the most effective preservation when a holding time of 14 days is considered. Apart from proper Cr(VI) preservation, sampling at an appropriate site is important for determining the public's exposure to Cr(VI). The proposed MCL for Cr(VI) in the state of California will be monitored at the entry point of distribution systems. To the extent that Cr(VI) is formed in the distribution system or in water contacting plumbing, measurements at the treatment plant might not reflect consumer exposure at the tap. Cr(VI) can be released to drinking water from Cr present in stainless steel alloys. At the maximum residual disinfectant level (MRDL), Cr(VI) formation decreased in the order chlorine dioxide > chlorine > chloramine. Less Cr(VI) was released from stainless steel at lower pH in the presence of chlorine, but the opposite trend was observed for chlorine dioxide. Stainless steels with a higher chromium content tended to release more Cr(VI). / Master of Science

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In order to identify hexavalent chromium (Cr6) sources, behavior, and treatability, this thesis has profiled Cr6 in seven full-scale drinking water treatment plants and six distribution systems. Bench-scale jar tests assessed the treatment efficacy of coagulation and developed strategies to remove ultra-low level (0.01- 1.0 ~tg/L) Cr6. All water sources measured in this project contained dissolved Cr6 greater than or equal to the California Public Health Goal (0.02 ~g/L Cr6). The investigated coagulation plants did not remove Cr6; in fact, four of the seven treatment plants inadvertently added Cr6 to the treated waters. Thirteen types of drinking water treatment chemicals were evaluated as a potential non-water source of chromium. Amongst these, only iron-based coagulants contained trace levels of chromium sufficient to account for the observed increases at the full-scale plants. Other discussed non-water sources include leaching of chromium-bearing infrastructure or oxidation of Cr3. One of the treatment systems showed chlorine oxidized Cr3 to Cr6 and raised the finished concentration, in less than seven hours. One suggested improvement strategy was to use ferrous iron to reduce and remove Cr6 during coagulation. Bench-scale tests showed ferrous iron and a cationic polymer improved removal of both Cr6 and Total Cr. Chlorine interfered with that reduction. The full-scale test of this reduction-coupled coagulation treatment successfully decreased the finished Cr6 concentration when 40% ferrous iron was used and the point of chlorination was moved downstream from the coagulation process.

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Hexavalent Chromium (Cr(VI) induces malignant cell transformation in normal bronchial epithelial (BEAS-2B) cells. Cr(VI)-transformed cells exhibit increased level of antioxidants, are resistant to apoptosis, and are tumorigenic. RNAseq analysis in Cr(VI)-transformed cells showed that expression of transcripts associated with mitochondrial oxidative phosphorylation is reduced, and the expression of transcripts associated with pentose phosphate pathway, glycolysis, and glutaminolysis are increased. Sirtuin-3 (SIRT3) regulates mitochondrial adaptive response to stress, such as metabolic reprogramming and antioxidant defense mechanisms. SIRT3 was upregulated and it positively regulated mitochondrial oxidative phosphorylation in Cr(VI)-transformed cells. Our results suggests that SIRT3 plays an important role in mitophagy deficiency of Cr(VI)-transformed cells. Furthermore, SIRT3 knockdown suppressed cell proliferation and tumorigenesis of Cr(VI)-transformed cells. Nrf2 is a transcription factor that regulates oxidative stress response. This study investigated the role of Nrf2 in regulating metabolic reprogramming in Cr(VI)-transformed cells. We observed that in Cr(VI)-transformed cells p-AMPKthr172 was increased, when compared to normal BEAS-2B cells. Additionally, Nrf2 knockdown reduced p-AMPKthr172. Our results suggest that Nrf2 regulated glycolytic shift via AMPK regulation of PFK1/PFK2 pathway. Furthermore, our results showed that Nrf2 constitutive activation in Cr(VI-transformed cells increased cell proliferation and tumorigenesis. Overall this dissertation demonstrated that Cr(VI)-transformed cells undergo metabolic reprogramming. We demonstrated that Nrf2 constitutive activation plays decisive role on metabolic reprogramming induction, and SIRT3 activation contributing to increased cancer cell proliferation and tumorigenesis.

In order to assess the benefit or toxicity of chromium in dietary supplements, trivalent chromium and hexavalent chromium must be measured and verified with mass balance (sum of both species equaling total chromium). This is necessary because dietary supplements report trivalent chromium, an essential trace element, as an ingredient, but hexavalent chromium, a toxic carcinogen, may also be present. Because trivalent chromium is stable in acidic conditions and hexavalent chromium in alkaline conditions, interconversions between species occur and increase the difficulty of quantification. Therefore, EPA Method 3060A was first performed to extract hexavalent chromium. Then, EPA Method 3052 was performed on the residue to digest the remaining trivalent chromium. Speciated Isotope Dilution Mass Spectrometry (SIDMS) with Ion-Exchange Chromatography-Inductively Coupled Plasma-Mass Spectrometry (IC-ICP-MS) was used to account for interconversions as well as determination of trivalent and hexavalent chromium concentrations in the studied samples. Mass balance indicated that the analyzed supplements contained hexavalent chromium ranging from 0 to 16% of the total chromium content. / Bayer School of Natural and Environmental Sciences / Environmental Science and Management (ESM) / MS / Thesis

In order to assess the benefit or toxicity of chromium in dietary supplements, trivalent chromium and hexavalent chromium must be measured and verified with mass balance (sum of both species equaling total chromium). This is necessary because dietary supplements report trivalent chromium, an essential trace element, as an ingredient, but hexavalent chromium, a toxic carcinogen, may also be present. Because trivalent chromium is stable in acidic conditions and hexavalent chromium in alkaline conditions, interconversions between species occur and increase the difficulty of quantification. Therefore, EPA Method 3060A was first performed to extract hexavalent chromium. Then, EPA Method 3052 was performed on the residue to digest the remaining trivalent chromium. Speciated Isotope Dilution Mass Spectrometry (SIDMS) with Ion-Exchange Chromatography-Inductively Coupled Plasma-Mass Spectrometry (IC-ICP-MS) was used to account for interconversions as well as determination of trivalent and hexavalent chromium concentrations in the studied samples. Mass balance indicated that the analyzed supplements contained hexavalent chromium ranging from 0 to 16% of the total chromium content. / Bayer School of Natural and Environmental Sciences; / Environmental Science and Management (ESM) / MS; / Thesis;

Orientador: Meuris Gurgel Carlos da Silva / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química / Made available in DSpace on 2018-08-23T11:03:55Z (GMT). No. of bitstreams: 1 Bertagnolli_Caroline_D.pdf: 3477463 bytes, checksum: df8d9fab006a696fa5d027c25e848099 (MD5) Previous issue date: 2013 / Resumo: O cromo é um dos metais pesados que causa mais danos à saúde e ao meio ambiente. É utilizado em uma grande variedade de processos industriais podendo provocar contaminação dos recursos hídricos devido ao descarte de resíduos industriais. Neste trabalho a bioadsorção de cromo total e trivalente pela alga marinha Sargassum filipendula, pelo alginato extraído dessa alga e pelo resíduo da extração, assim como a bioadsorção das espécies de cromo por uma amostra de alginato comercial, foram estudados por meio de ensaios em sistema de batelada e em coluna. Os experimentos envolveram preparo e caracterização dos bioadsorventes, o estudo cinético e de equilíbrio, além de testes em sistema contínuo. Os bioadsorventes foram caracterizados antes e após a bioadsorção por microscopia eletrônica de varredura e o cromo presente no bioadsorvente foi mapeado. As técnicas de espectroscopia na região do infravermelho e espectroscopia de fotoelétrons excitados por raios-X foram utilizadas para compreensão dos mecanismos de ligação cromo+adsorvente e para avaliar o estado de oxidação do cromo adsorvido. O processo de extração do alginato a partir da alga brasileira foi estudado e os produtos da extração caracterizados. Os resultados mostraram capacidades máximas de adsorção obtidas pelo ajuste de Langmuir entre 0,411 e 2,493 mmol/g, com destaque para o resíduo da extração do alginato que se mostrou como uma boa alternativa de bioadsorvente, pois apresentou capacidade de adsorção máxima próxima à da alga e superior à dos alginatos para ambas as espécies de cromo, possibilitando o reaproveitamento de um rejeito do processo e comercialização do alginato extraído. Observou-se a ocorrência de diferentes mecanismos de adsorção simultaneamente, com formação de complexos de ambas as espécies de cromo com grupos sulfônico, amino e carboxila do adsorvente e a contribuição de mecanismos de troca iônica. No estudo da adsorção do cromo hexavalente foi verificada sua redução a cromo trivalente na superfície do adsorvente / Abstract: Chromium is one of the heavy metals that pose the greatest damages to health and to the environment. It is used in a great range of industrial processes, and it might even generate the contamination of water resources due to the disposal of industrial residues. In this study, hexavalent and trivalent chromium biosorption by Sargassum filipendula, alginate extracted from this seaweed, extraction residue and a commercial alginate were studied by means of batch and fixed-bed column. The experiments involved preparation and characterization of biosorbents, kinetic and equilibrium studies. The biosorbents were characterized before and after the biosorption process by scanning electron microscopy and the chromium present in the biosorbent has been mapped. The X-ray photoelectron spectroscopy and infrared spectroscopy have been used to evaluate the chromium oxidation state and the biosorbent group to which the metal is bound after the biosorption process. The process of alginate extraction from Brazilian seaweed has been studied and the extraction products characterized. The results showed the maximum adsorption capacities by Langmuir adjustment between 0.411 and 2.493 mmol/g and the alginate extraction residue as an alternative bioadsorbent. The residue has adsorption capacity near to seaweed and better than the alginates for both chromium species. Different mechanisms were observed for the adsorption of different chromium species as complexation of chromium with sulfonic, amino and carboxyl groups of the adsorbent and ion exchange mechanisms. In the adsorption of hexavalent chromium was verified reduction to trivalent chromium at the surface of the adsorbent / Doutorado / Engenharia de Processos / Doutora em Engenharia Quimica

The production of ferrochrome (FeCr) from chromite ore is a reducing process, whereby the Cr(III) and Fe(II) in the ore are reduced to metallic chromium (Cr) and iron (Fe) in the final product. FeCr is mostly used for the production of stainless steel, which is a vital alloy in modern society. It is, however, impossible to exclude oxygen completely from all the high temperature steps during the production process and very small amounts of Cr(VI) are therefore formed, although not intended. The formed Cr(VI) is mostly associated with the off-gas of the high temperature processes, which are cleaned before it is released into the atmosphere by means of venturi scrubbers or bag filter systems. Certain Cr(VI) species are regarded as carcinogenic, with specifically airborne exposure to these Cr(VI) species being associated with cancer of the respiratory system. FeCr smelter facilities generate three main types of waste materials, i.e. slag, venturi sludge and bag filter dust (BFD). Most of the Cr in the waste materials consists mostly of Cr(III). However, BFD generated during the cleaning of the off-gas of open/semi-closed furnaces, could contain more significant levels of Cr(VI) than the slag and sludge. The aim of this study was to determine the solubility of different Cr(VI) species present in BFDs. This would allow that the Cr(VI) in BFD is categorised as water soluble Cr(VI), sparingly soluble and insoluble Cr(VI). These solubility categories can then be related to groups of Cr(VI) compounds, therefore taking the first step in better characterisation of Cr(VI) present in BFD. Four different BFD samples from FeCr producers in South Africa were characterised in detail. Analytical methods such as scanning electron microscope (SEM), SEM with energy-dispersive X-ray spectroscopy (SEM-EDS), particle size analysis, trace metal analysis with inductively coupled plasma with a mass spectrometer detector (ICP-MS) and Cr(VI) analysis with ion chromatography (IC) were utilised in order to characterise and categorise the samples. The results indicated that more Cr(VI) leached with an increase in pH. This was in contrast with the trend for most heavy metals. This was also an indication that not only soluble, but also sparingly- and insoluble Cr(VI) compounds occur in the BFD samples evaluated. Further analysis showed that approximately one third of the Cr(VI) species was insoluble and the remainder consisted of sparingly insoluble and soluble Cr(VI) compounds. The most significant finding was that the current leaching procedures applied by FeCr producers, prior to the chemical reduction of Cr(VI), do not effectively extract the sparingly water insoluble compounds. This results in Cr(VI) leaching from waste facilities at later stages, even if seemingly effective Cr(VI) treatment was applied. Therefore, it should be considered as an extremely important future perspective to develop economically feasible Cr(VI) extraction procedures that will ensure complete extraction of sparing water soluble Cr(VI) compounds together with the water soluble fraction, prior to chemical reduction of Cr(VI) and subsequent storage of the residue on a waste facility. / MSc (Chemistry), North-West University, Potchefstroom Campus, 2015