Indiana University-Purdue University Indianapolis (IUPUI) / Colonial settlement of Indiana changed the environment in significant ways; the aim of this study is to quantify the impacts of settlement through the use of geochemical proxies including: % lithics; the carbon (δ13C), nitrogen (δ15N), and sulfur (δ34S) isotope composition of organic matter; the elemental composition of carbon (TOC) and nitrogen (Ntot) in organic matter and their ratio (C/N); the δ34S of mineral sulfides (pyrite and acid volatile sulfides); and iron redox proxies. Lakes are a great recorder of aquatic-terrestrial linkages on both local and global scales. Martin lake’s watershed, in northeastern Indiana, was settled in 1840 by Euro-Americans, and since then clear shifts in lake chemistry are recorded in its sediments. A core spanning roughly the last 300 years taken from Martin Lake is the basis of this study. The impacts of settlement can be seen through the lenses of all the proxies that were used in this study. 1) Post-settlement deforestation increased erosion in Martin Lake’s watershed, increasing sedimentation rates and % lithics. 2) δ13C of organic matter reveals a pattern of deforestation and partial regrowth and agricultural use of land. 3) A pronounced increase in δ15N timed with the change in population at the time of settlement is consistent with the increased input of human or animal waste into Martin Lake. 4) TOC and C/N show an overall increase in the amount of organic matter within the lake caused by deforestation, and that the increased nutrient supply may have stimulated more in-lake productivity. 5) δ34S of mineral sulfides show that deforestation lead to an increase in the available sulfate pool of Martin Lake, which in combination with 6) an increase in FeHR created redox conditions in which pyrite formation was more favorable. These factors culminated in a transition in Martin Lake chemistry and redox cycling within the sediments.

Internal loading of phosphorus (P) from lake sediments can delay the recovery of lakes from eutrophication for years to decades following decreases in external nutrient inputs. While internal P loading is a pervasive problem in freshwater systems, molecular speciation of P in benthic sediments of these systems remains poorly characterized. As different P species will exhibit different responses to changing sediment-water interface (SWI) geochemistry, quantifying P speciation in sediments is a critical step in understanding P dynamics in sediment-water systems. Here, various synchrotron-based techniques were employed to directly probe the bonding environments of P and iron (Fe) in natural and experimentally manipulated lake sediments in order to link chemical speciation to chemical behavior and to identify the geochemical drivers that mediate this linkage. We manipulated SWI redox conditions in mesocosm experiments to investigate the impacts of prolonged anoxia and redox oscillations on P mobility and speciation in sediments. Mesocosm experiments demonstrate that oscillating redox conditions near the SWI may drive accelerated P release from sediments relative to uninterrupted reducing conditions. Sediment P is found to be predominantly associated with Fe oxyhydroxides, calcium carbonate, and apatite minerals in three shallow hyper/eutrophic lakes in northern Vermont. In Missisquoi Bay and Lake Carmi, Fe redox cycling controls P mobility via precipitation and dissolution of Fe oxyhydroxides. In the hypereutrophic Shelburne Pond, the presence of Fe sulfides precludes redox-driven P cycling and P mobility is instead dominated by organic matter mineralization. Our results demonstrate that internal P loading can manifest differently in similar shallow lake systems due to differences in lake configuration, sediment P and Fe speciation, and organic content of sediments. This work demonstrates the potential utility, as well as the limitations, of P K- edge X-ray absorption near edge structure spectroscopy in determining sediment P speciation in freshwater lakes.

Iron (Fe) minerals and ferrous iron (Fe(II)) play an important role in the several natural elemental cycles, including the carbon cycle, nutrient cycles, and the cycling of metals. In this work we have characterized the reactivity structural Fe(II) in several Fe minerals and in natural soil with uranium. We have studied the reactivity of Fe(II) in solution with the Fe oxide goethite conditions relevant to many natural systems. Green rusts are widely recognized as an intermediate phase in the Fe cycle. Here we investigate the reactivity of green rusts containing different structural anions with uraniumVI (UVI). We have also investigated the effect of aqueous bicarbonate on UVI sorption and reduction by green rusts. Our findings indicate that green rusts reduce UVI to UIV, and that environmentally relevant carbonate concentrations have little effect the rate and extent on this reaction. We have also investigated UVI reduction by structural Fe(II) in magnetite. Magnetite with varying stoichiometry (x = Fe2+/Fe3+) was reacted with UVI. Results from x-ray absorption spectroscopy indicate that the redox properties of magnetite dictate whether magnetite reduces UVI. In addition, magnetite reactivity can be "recharged" by electron transfer from aqueous Fe(II). There is little evidence of the reactivity of structural Fe(II) towards UVI in natural materials. We have characterized a naturally reduced soil and found it contains structural Fe(II) in clay minerals and a possible green rust-like phase. When this soil is exposed to UVI we find that Fe(II) reduces a portion of the U added. Our work highlights the potential for abiotic reduction of UVI by Fe(II) in reduced, Fe-rich environments. We have used 57Fe Mössbauer spectroscopy to study redox reactions of Fe(II) with goethite under biogeochemical conditions relevant to natural systems. When Fe(III) in goethite is substituted with aluminum or anions such as phosphate, silicate, carbonate, and natural organic matter are sorbed onto the surface of goethite, interfacial electron transfer occurs between sorbed Fe(II) and goethite. These results indicate that electron transfer between Fe(II) and Fe oxides occurs under environmentally relevant conditions. Electron transfer was blocked by phospholipids, however, suggesting electron transfer may be inhibited under eutrophic conditions.

No description available.

Oxidation of sulfidic mine waste is of significant environmental concern due to the consequent formation of acid rock drainage (ARD), deteriorating the water quality of natural water systems. Iron (Fe) and sulfur (S) are two major redox elements involved in these reactions and typically the major redox-sensitive elements (whose solubility, speciation, and mobility are affected by pH and Eh) in water affected by ARD. Measurements of Fe and S species concentrations may reveal valuable information about geochemical processes in mine waste but are typically included when analyzing the chemical composition of ARD. In this study, robust and portable methods for the determination of Fe and S species concentrations in leachate water affected by sulfidic mine waste were tested and evaluated. The leachate water resulting from interaction with high-  and low-sulfide waste rock was collected from three leaching columns, each reflecting different geochemical environments that could occur during mine waste management: (1) fully oxidized conditions (reference column), (2) gradual oxygen depletion from atmospheric level to <1% (anoxic column), (3) treatment with alkaline industrial residual material (alkaline column). The leachate water was analyzed for its pH, Eh, electric conductivity (EC), and major and trace elements. UV-Vis spectrophotometric ferrozine method was tested and applied for Fe speciation and concentration analysis, allowing determination of Fe(II) and Fetot and further calculation of Fe(III) as a difference. The method was found to achieve accurate and reliable results. Turbidimetry was tested and evaluated for dissolved sulfate analysis, and even though the analytical precision was poorer, ca. ±20%, the method provides useful semi-quantitative estimations of dissolved sulfate concentrations. Both spectrophotometry and turbidimetry are easy to perform and utilizes robust, cheap and portable instrumentation. Leachate water from the high and low sulfide experiments had pH and Eh in the range of pH 2.6 – 12 and Eh 200 – 720 mV and pH 3.5 – 4 and Eh 550 – 700 mV, respectively. Measurements of iron species and sulfate concentrations revealed that sulfate was the dominating S species and during the background leachate Fe(II) was the predominant Fe oxidation state. Upon decreasing oxygen saturation and pH in the anoxic column, Fe speciation in the reference and anoxic column differed, with the relative importance of Fe(III) increasing in the anoxic column. Total Fe, pH and Eh potential measured in the leachate water did not respond to decreasing oxygen saturation, but changes in the Fe redox speciation coincided with this decrease. Under alkaline conditions, total Fe and sulfate concentrations decreased in the alkaline environment, indicating their immobilization in the solid phase. Geochemical calculations were carried out to gain further understanding of the dominant reactions in the columns. Theoretical values of Fe(II) and Fe(III) concentrations were calculated from the measured redox potential, and these were found to deviate from the measured concentrations. Therefore, estimation of Fe species distribution from redox measurements using a Pt-electrode is not considered sufficient in these systems. Mineral saturation indices of common secondary minerals associated with ARD indicated dissolution of ferrihydrite, jarosite and schwertmannite in the leachate water from the anoxic column. This suggests that these minerals are the probable source of the Fe and sulfate, as well as As and Cu released to the leachate water.

Master of Science / Department of Agronomy / Michel D. Ransom / Factors governing potassium fixation and release are poorly understood. This study was conducted to investigate the effects of clay mineralogy and structural iron oxidation state on potassium fixation. Five reference clays and two soil clays were used to capture a range in mineralogical compositions and potassium behaviors. Reference clays used were illite (IMt-1), kaolinite (KGa-1b), montmorillonite (STx-1b), nontronite (NAu-2), and vermiculite (VTx-1). Soil clays used were from the upper 15 cm of a Belvue loam (BEL) and a Cherokee silt (CHE). Potassium fixation capacities were measured on unaltered as well as sodium dithionite reduced forms of each clay. Ferrous and total iron contents were determined photometrically using 1, 10-phenanthroline. Potassium fixation was measured by potassium saturating the clays and washing off exchangeable and solution potassium with solutions of magnesium chloride; samples were then acid digested and the amount fixed was calculated as the amount of potassium in the acid digestion minus the amount originally in the sample. BEL released potassium rather than fixed it while CHE tended to release potassium in the unaltered form and fix potassium in the reduced form. Structural iron reduction significantly impacted the amounts of potassium fixed by VTx-1 and NAu-2, which had the highest total iron contents of all the clays evaluated. NAu-2 and VTx-1 both on average fixed less than 1 mg K g clay[superscript]-1 in the unaltered form and an average of 6 and 11 mg K g clay[superscript]-1, respectively, in the reduced form. Regardless of being in the unaltered or reduced form, KGa-1b fixed essentially no potassium and IMt-1 and STx-1b fixed intermediate amounts of potassium—2 to 4 mg K g clay[superscript]-1 on average. The effects of clay mineralogy and structural iron oxidation state on potassium fixation can largely be explained through an understanding of layer type, layer charge, and charge distribution. In order for potassium fixation to occur, interlayer sites need to be accessible and available. Generally, the greater the negative layer charge the greater the amounts of fixation, with tetrahedral layer charge favoring fixation more than octahedral layer charge, and layer charge being a function of structural iron oxidation state.

Multicomponent silicate and borosilicate glasses find wide technological applications ranging from optical fibers, biomedicine to nuclear waste disposal. As a common component of earth's mantle and nuclear waste, iron is a frequent encounter in silicate and borosilicate melts and glasses. The redox ratio in glass matrix defined by the ratio of ferrous and ferric ions is dependent on factors such as temperature, pressure, and oxygen fugacity. Understanding their roles on the short- and medium-range structure of these glasses is important in establishing the structure-property relationships which are important for glass composition design but usually difficult to obtain from experimental characterization techniques alone. Classical molecular dynamics simulations were chosen in this dissertation to study iron containing glasses due to challenges in experimental techniques such as NMR spectroscopy originated from the paramagnetic nature of iron. Magnesium is also a common element in the oxide glass compositions and its effect on the structure of boroaluminosilicate glasses were also investigated. Magnesium ion (Mg2+) has relatively higher cation field strength than other modifier cations and its structural role in oxide glasses is still under debate. Therefore, investigating the effects of cation field strength of modifier cations in light of MgO in boroaluminosilicate glasses is also an important goal of this dissertation. Overall, through detailed and systematic molecular dynamics simulations with effective interatomic potentials, the structures of iron and magnesium containing complex boroaluminosilicate glasses were obtained and used to interpret properties and their changes with glass composition for nuclear waste disposal and other applications.

In the copper smelting processes, the viscosity of the matte and the slag is an important factor for establishing efficiency. Impurities in the concentrates affect the viscosity not only by changing the melt structure but also by promoting precipitation of solid phase which sharply rises it. In this master thesis, a comprehensive methodology was established to study the MgO effects on the properties of a copper smelting slag. Thus, glassy samples were obtained and after confirmation of the composition and the glassy structure with EDS, SEM, and XRD analysis, they were examined through Ramanspectroscopy to study their glassy structure. Moreover, Mössbauer spectroscopy was used to determine the amount of Fe3+ in the samples. Models from the literature were compared to the experimental data. Coherence with the literature was found with the effect of MgO as a network modifier of the oxide melt structure and a promoter of high coordinated structures. Estimations through models were performed to study the iron redox equilibria of the melt and were compared with experimental data, but it was not possible to find the limit of Fe3+ at which precipitation of solid phase initiates. / I kopparsmältningsprocesserna är mattans och slaggens viskositet en viktig faktor för att uppnå effektivitet. Föroreningar i koncentraten påverkar viskositeten inte bara genom att ändra smältstrukturen utan också genom att främja utfällning av fast fas som kraftigt höjer den. I denna magisteruppsats fastställdes en omfattande metod för att studera MgO-effekterna på egenskaperna hos en kopparsmältningsslagg. Således erhölls glasiga prover och efter bekräftelse av kompositionen och den glasiga strukturen med EDS-, SEM- och XRD-analys undersöktes de genom Ramanspektroskopi för att studera deras glasstruktur. Dessutom användes Mössbauerspektroskopi för att bestämma mängden Fe3+ i proverna. Modeller från litteraturen jämfördes med experimentella data. Överensstämmelse med litteraturen hittades med effekten av MgO som ett nätverksmodifierare av oxidsmältstrukturen och en promotor för högkoordinerade strukturer. Uppskattningar genom modeller utfördes för att studera smältans järnredoxjämvikter och dessa jämfördes med experimentella data, men det var inte möjligt att hitta gränsen för Fe3+ vid vilken utfällning av fast fas initierades.

The available antiretroviral compounds can effectively suppress the replication of HIV-1 and block the disease progression. However it is impossible to eradicate the virus from the organism as the HIV-1 integrated in the genome is not affected by the existing anti-HIV-1 drugs. Therefore, new latency reversing agents are being actively developed as part of "shock and kill" therapy to reactivate the provirus and clear the reservoir. Normosang (heme arginate; HA) is a human hemin- containing compound used to treat acute porphyria. Heme is physiologically catabolised by heme oxygenases to form iron (Fe2+ ), carbon monoxide (CO) and biliverdin that is further converted to bilirubin by biliverdin reductase. In this study, we have demonstrated that HA inhibited HIV-1 replication during the acute infection, which was accompanied by the inhibition of reverse transcription. On the other hand, HA synergised with phorbol myristyl acetate (PMA) and reactivated the HIV-1 provirus in ACH-2 cells and the HIV-1 "mini-virus" in Jurkat cell clones A2 and H12. HIV-1 ''mini-virus'' was reactivated also by HA-alone. Further, we have studied the effects of heme degradation products on latent HIV-1 reactivation when added individually. We employed addition of ascorbate to generate Fe2+ , resulting in an increased...

The available antiretroviral compounds can effectively suppress the replication of HIV-1 and block the disease progression. However it is impossible to eradicate the virus from the organism as the HIV-1 integrated in the genome is not affected by the existing anti-HIV-1 drugs. Therefore, new latency reversing agents are being actively developed as part of "shock and kill" therapy to reactivate the provirus and clear the reservoir. Normosang (heme arginate; HA) is a human hemin- containing compound used to treat acute porphyria. Heme is physiologically catabolised by heme oxygenases to form iron (Fe2+ ), carbon monoxide (CO) and biliverdin that is further converted to bilirubin by biliverdin reductase. In this study, we have demonstrated that HA inhibited HIV-1 replication during the acute infection, which was accompanied by the inhibition of reverse transcription. On the other hand, HA synergised with phorbol myristyl acetate (PMA) and reactivated the HIV-1 provirus in ACH-2 cells and the HIV-1 "mini-virus" in Jurkat cell clones A2 and H12. HIV-1 ''mini-virus'' was reactivated also by HA-alone. Further, we have studied the effects of heme degradation products on latent HIV-1 reactivation when added individually. We employed addition of ascorbate to generate Fe2+ , resulting in an increased...