The environment of deposition of the Ohio Shale of the Appalachian Basin has been studied extensively using various geochemical proxies for each of its members. The accumulation of organic matter (OM) and its preservation in the Late Devonian-Early Mississippian black shales of central Kentucky have been studied extensively, especially the possible correlations between trace metal contents and water-column oxygenation. Previous work has centered on geochemical, petrographic, and isotopic analysis of samples collected throughout the central Appalachian Basin. Mechanisms for OM preservation include high productivity, enhanced preservation due to dysoxic or anoxic bottom waters, and a feedback loop due to high productivity that creates enhanced preservation through the periodic cycling and scavenging of essential nutrients. Usually, a combination of these factors results in the accumulation of enough OM to produce these black shales. This research shows the relationships between trace metal data and the environment of deposition of several cores taken along the eastern side of the Cincinnati Arch in the central Appalachian Basin. Whereas the indices do not all agree in every instance across the breadth of the study area, analyzed together a predominant environment of deposition has been inferred for the shales. The Sunbury Shale and upper part of the Cleveland Member of the Ohio Shale were deposited under euxinic conditions, the lower part of the Cleveland Member was likely euxinic in the northern study region and anoxic throughout the central and southern study areas, whereas the Huron Member of the Ohio Shale was deposited under a range of conditions, from oxic, to dysoxic, to anoxic.

A preocupaÃÃo com a contaminaÃÃo de metais traÃo na carcinicultura tem levado a realizaÃÃo de estudos com o propÃsito de medir as concentraÃÃes de metais em espÃcies comerciais, avaliar nÃveis potencialmente perigosos para nutriÃÃo humana e fornecer suporte para monitoramento ambiental. A produÃÃo do camarÃo Litopenaeus vannamei vem crescendo em ritmo acelerado no Estado do CearÃ. Dessa forma, o objetivo desse trabalho foi caracterizar a origem e a distribuiÃÃo de Cu e Zn em trÃs fazendas produtoras de camarÃo, localizadas no litoral leste do Estado do CearÃ, e o efeito da concentraÃÃo desses metais no desempenho zootÃcnico dos camarÃes. A concentraÃÃo de Cu e Zn em raÃÃes, outros insumos, sedimento, material em suspensÃo e camarÃo foi determinada por espectrofotometria de absorÃÃo atÃmica de chama convencional. Para a anÃlise da Ãgua utilizou-se a absorÃÃo atÃmica com forno de grafite. Nas raÃÃes as concentraÃÃes variaram de 13,1 a 79 μg/g e de 63,2 a 145,9 μg/g para Cu e Zn, respectivamente. A concentraÃÃo de Cu e Zn nos outros insumos variou de 0,7 a 3,3 μg/g e de 0,12 a 45,7 μg/g, respectivamente. Nos sedimentos dos viveiros as concentraÃÃes mÃdias de Cu foram de 16,5 e 10,3 μg/g e as de Zn foram 41,1 e 35,1 μg/g. No material em suspensÃo a concentraÃÃo de Cu variou de 38,4 a 66,8 μg/g e a de Zn nÃo foi detectÃvel. Na Ãgua a concentraÃÃo de Cu variou de 6,62 a 7,38 μg/l. No camarÃo as concentraÃÃes mÃdias de Cu variaram de 33,4 a 42,2 μg/g e de 74,0 a 87,2 μg/g no mÃsculo e no exoesqueleto, respectivamente, enquanto as concentraÃÃes de Zn variaram de 41,8 a 43,1 μg/g no mÃsculo e de 52,7 a 55,5 μg/g no exoesqueleto. O sistema de cultivo intensivo do L. vannamei pode funcionar como um acumulador de metais no sedimento provenientes da alimentaÃÃo, outros insumos e exÃvias. As concentraÃÃes de Cu e Zn nos camarÃes estÃo abaixo das concentraÃÃes mÃximas permitidas pela legislaÃÃo brasileira para consumo humano. Entretanto, foi observado que mecanismos de detoxificaÃÃo podem estar atuando nesses organismos, levando a crer que as concentraÃÃes a que estÃo expostos jà ultrapassam as necessidades de Cu para o metabolismo dos animais, podendo levar a uma diminuiÃÃo na taxa de crescimento desses camarÃes. / The concern with the contamination of heavy metals in farmed shrimp has led to studies with the purpose of measuring the concentration of heavy metals in commercial species, assess potentially hazardous levels from the human health and to supply support for environmental monitoring programs. The production of the shrimp Litopenaeus vannamei is growing fast in the Ceara State. In that way, the objective of is work is to characterize the origin and the distribution of Cu and Zn in three shrimp farms, located at the east coast of the State of Ceara, and the effect of the concentration of these metals in permorfance shrimp. The concentration of Cu and Zn in fertilizers, feed, sediment, suspended material and shrimp was determined by conventional flame atomic absorption spectrophotometry. The concentration of Cu and Zn in fertilizers and chemical additives varied from 0.7 to 3.3 μg/g and from 0.12 to 45.7 μg/g, respectively. In the feed concentrations varied from 13.1 to 79.0 μg/g and from 63.2 to 145.9 μg/g for Cu and Zn, respectively. In pond sediments the average concentrations of Cu varied from 10.3 to 16.5 μg/g and of Zn from 35.1 to 41.1 μg/g. In the suspended material the concentration of Cu varied from 38.4 to 66.8 μg/g whereas Zn was not detectable. In the water the concentration of Cu varied from 6.62 to 7.38 μg/l. In the shrimp the average concentrations of Cu varied from 33.4 to 42.2 μg/g and from 74.0 to 87.2 μg/g in the muscle and the exoskeleton, respectively, while the concentrations of Zn varied from 41.8 to 43.1 μg/g in the muscle and from 52.7 to 55.5 μg/g in the exoskeleton. The intensive farming system of L. vannamei can work as an accumulator of metals in sediments from feeding, chemicals and exuviae. The concentrations of Cu and Zn in the shrimps are below the limits established by the Brazilian legislation for human consumption. However, it was observed that detoxification mechanisms can be acting in those organisms, suggesting that the concentrations animals metabolism at least for Cu already surpass the needs of Cu and could resulting in a decrease in the growth rate the shrimps.

A espécie de cianobactéria Cylindrospermopsis raciborskii vem se destacando na literatura atual devido à sua presença e dominância em lagos e reservatórios em diversas regiões do planeta e a principal preocupação deste cenário é por ela ser potencialmente tóxica. Estudos revelaram que o crescimento e a síntese de toxinas em espécies de microrganismos fitoplanctônicos estão atrelados à limitação ou excesso de micronutrientes, porém, ainda são desconhecidos os efeitos desta variação na produção de saxitoxina (STX) por C. raciborskii. Para contribuir com o esclarecimento desta questão, investigou-se o efeito de diferentes concentrações dos micronutrientes Fe, Zn, Cu, Mn, Co e B no crescimento e na produção de STX de uma linhagem de C. raciborskii. Em salas climatizadas, culturas desta linhagem foram expostas durante 20 dias a 5 concentrações de cada micronutriente, com alteração do meio de cultura ASM-1. As respostas fisiológicas de C. racibosrkii a estas modificações foram verificadas através da velocidade máxima de crescimento (μmáx), rendimento do biovolume, tempo de duplicação (Td), concentração de clorofila a, assimilação de nitrato e ortofosfato e síntese de STX total (intra e extracelular). As maiores concentrações de STX por biovolume (STX/biovolume) foram obtidas nos tratamentos com baixa concentração de Fe (0,4 μM) e elevada concentração de Cu (0,8 μM). Nos micronutrientes Zn, Co e B, houve uma tendência de redução da síntese de STX nas maiores concentrações destes metais. Enquanto as concentrações extremas de Fe e Mn inibiram o crescimento (Fe: 0,4 e 400 μM e Mn: 0,7 e 600 μM), as concentrações centrais favoreceram (Fe: 4 a 60 μM e Mn: 7 a 200 μM). Elevada concentração de Cu (0,8 μM) causou aumento de 2,6 vezes (160%) do volume celular e redução na síntese de clorofila a, sem alterações significativas em μmáx e rendimento. O aumento da concentração dos micronutrientes Fe, Zn, Mn e B no meio de cultura causaram maior assimilação de ortofosfato por biovolume (P/biovolume). Estes principais resultados demonstraram que os micronutrientes afetam a síntese de STX e o crescimento de C. raciborskii, podendo ser associados aos diversos mecanismos de captura e detoxificação de metais que as cianobactérias possuem. Embora as extrapolações dos resultados laboratoriais para o ambiente devam ser realizadas com prudência, estudos relacionados à ecofisiologia de cianobactérias como este, são fundamentais para análise criteriosa de cada variável podendo ser utilizado como ferramenta de diagnóstico e prevenção de florações tóxicas. / Cylindrospermopsis raciborskii has been highlighted in several researches due to the dominance in many lakes and reservoirs around the world, the main concern about it due to the ability to produce toxins. Studies have revealed that growth and toxins production in phytoplankton species are linked to micronutrients limitation or excess. Nevertheless, micronutrient variation effects on saxitoxin (STX) production by C. raciborskii are still unknown. To contribute to clarify this issue, we investigated the effect of different micronutrients concentration, such as Fe, Zn, Cu, Mn, Co and B, on the growth and saxitoxin production of C. raciborskii strain. In climatized growth room, the cultures of C. raciborskii strain were exposed to 5 different concentration of each micronutrient, present in ASM-1 medium, during 20 days. The C. racibosrkii physiological responses was detected through maximum growth rate (μmáx), biovolume yield, doubling time (Td), chlorophyll-a, nitrate and orthophosphate assimilation and the total STX production (intra and extracellular). The higher concentrations of STX per biovolume (STX/biovolume) were observed in treatments with low Fe concentration (0.4 μM) and high Cu concentrations (0.8 μM). Higher concentrations of Zn, Co and B lead to low STX production. While the Fe and Mn extreme concentrations inhibited the growth (Fe: 0.4 and 400 μM and Mn: 0.7 to 600 μM), the central concentrations favored (Fe: 4 to 60 μM, and Mn: 7-200 μM). A high Cu concentration (0,8 μM) leads to 2,6 fold increase (160%) in cellular volume and decrease the chlorophyll-a content, however máx and biovolume yield did not change. Increasing the Fe, Zn, Mn and B concentration in the culture caused higher assimilation of orthophosphate per biovolume (P/biovolume). These results indicated that micronutrients affected C. raciborskii growth and STX production, and may be associated with the diverse cyanobacterial mechanisms of metals capture and detoxification. Cyanobacteria ecophysiology studies, as this research, are fundamental to careful analysis of each variable, which could be used as diagnostic and a tool to prevention of toxic blooms.

The mineralogic associations of arsenic (As) and antimony (Sb) were investigated for the Avon Park Formation (APF) in central Florida to determine its viability for aquifer storage and recovery (ASR). Rock samples were taken from fourteen different cores and samples were taken according to core length, interval samples, and based on areas suspected to contain high levels of arsenic and antimony, such as molds, dissolution fractures, pyrite, clays, and organic matter, targeted samples. Permeable samples were also taken from high permeability zones. In total 373 samples were described in hand specimen and analyzed for bulk rock chemistry. Inductively coupled plasma optical emission spectrometry and hydride generation atomic fluorescence spectrometry were used to determine Fe, Al, Si, Mg, Ca, S, P, Mn, Sr, Mo, As, and Sb in bulk samples, while electron-probe microanalysis was used to analyze Sb, As, Fe, S, Zn, Ca, Mo in discrete minerals. The mineralogic and geochemical investigation showed: (1) bulk As and Sb concentrations within the APF are low; (2) As values range from < 0 .1 to 30.8 mg/kg and Sb from < 0.1 to 6.76 mg/kg; (3) average values are 2.24 mg/kg As and 0.28 mg/kg Sb; (4) pyrite is present as framboids, hollow framboid rings, "honeycomb" pseudo-framboids, small irregularly shaped pieces with topography, and euhedral crystals; it is typically associated with oxidized organic laminations, fractures, and molds; (5) the framboid rings may have been precipitated by a bacteria making them biogenic; (6) euhedral pyrites contain significantly less As than other morphologies while irregular pyrites have the most; (7) individual pyrites range from < 0.1 to 5820 mg/kg As while Sb ranges from < 0.1 to 2470 mg/kg; (8) the samples from zones of high permeability have lower As and Sb averages than those of the other samples: 1.02 mg/kg As and 0.15 mg/kg Sb versus 1.32 mg/kg As and 0.19 mg/kg Sb for interval and 3.16 mg/kg As and 0.37 mg/kg Sb for targeted samples; (9) As is found mainly in pyrite but is possibly from organic matter and clay; (10) overall As concentrations and correlations may be low but individual cores and zones have high values; (11) the APF has appropriately permeable zones for ASR; (12) the success of ASR in the APF formation depends on the degree of geochemical alterations, presence of competing anions and simple organic ligands, and the amount of trace metals sorbed to surfaces versus coprecipitated.

>Magister Scientiae - MSc / This work reports the use of a pencil graphite electrode (PGE) as inexpensive and sensitive electrochemical sensing platform fabricated by using electrochemically reduced graphene oxide (ERGO) in conjunction with an in-situ plated thin mercury film. For the first time the ERGOHgF-PGE sensor is proposed for simultaneous detection of cadmium (Cd2+), copper (Cu2+), lead (Pb2+) and zinc (Zn2+) using N-Nitroso-N-phenylhydroxylamine (cupferron) as complexing agent by square-wave adsorptive cathodic stripping voltammetry (SW-AdCSV). The technique is based on the adsorption of cupferron- metal ion complexes onto the surface of the ERGO-HgFPGE at 0.1 V for 60 s carried out in 0.1 M acetate buffer solution (pH 4.6). The synthesized graphene oxide (GO) and graphene nanosheets (GNs) were characterized using different analytical techniques such as FT-IR which confirms the presence of oxygen moieties embedded in the graphitic structure and further demonstrated by UV-Vis, validating the synthesis of GO / 2023

The current urban infrastructure and demographic development of Uganda and in particular of Kampala city is rapid and does not correspond to the planned socio-economic and industrial infrastructure. This project was justified by the existence of numerous peri-urban areas with unplanned and no monitored san-itary as well as water supply systems. The unsanitary handling and disposal, of domestic and industrial solid waste, sewerage and small car related industries pose a serious threat to the quality of the groundwater resources. Field studies were conducted at different occasions between February and March 2012. These included soil and water sampling in and around five protected springs for analysis of the concentrations of four trace metals: Cu, Pb, Cd and Zn. The method used for leaching tests of the soil samples was the European Standard ISO/TS21268-1, and the samples produced were analyzed in a ICP-MS. Addi-tionally, metal concentrations and dissolved organic content of water samples were analyzed. The ICP-MS results showed that the concentration of the trace metals in the waters were below guideline values stated by the WHO, which implies that the residents are not exposed to notable trace metal contamination in the drinking water. As the total metal content in the soils were below the Swedish Environmental Protection Agency (Swedish EPA) guidelines, it was assumed that trace metal contamination was not of significance under the pre-vailing circumstances. However, the leachable metal contents in a number of the soils were high, which may pose a future risk to groundwaters.

<p> A method for the simultaneous preconcentration by solvent extraction of a group of trace metal ions from natural waters has been developed. The procedure makes use of a proprietary "liquid cation-exchanger", Kelex 100, the primary component of which is an alkylated oxine (8-quinolinol) derivative, 7-(4-ethyl-1-methyloctyl)-8-quinolinol (HL). After purification of HL from the commercial mixture, the extraction of ten environmentally-significant trace metal ions from artificial seawater into toluene solution was studied as a function of pH. From these investigations, the optimal conditions for the extraction of Cd(II), Co(II), Cu(II), Mn(II), Ni(II), Pb(II) and Zn(II) from natural waters were established. The conditions for quantitative back-extraction of the metal ions were then investigated. With the exception of cobalt, the metal ions were quantitatively back-extracted into a small volume of nitric acid, simplifying the matrix and providing additional analyte enrichment. The optimized forward- and back-extraction technique was subsequently applied to the determination of total (soluble) Cd, Cu, Mn, Ni and Pb in a coastal seawater reference standard by graphite-furnace atomic absorption spectroscopy (GFAAS). The quantitative recovery of the analytes and the uncomplicated matrix of analysis enabled quantitation to be carried out by external calibration. Compared to the method of standard additions, external calibration has advantages in overall analysis time and sample consumption. Satisfactory agreement was obtained between the experimental and reference values, although Cu(II) blanks were high due to trace Cu(II) contamination of HL and the stability of the Cu(II)-HL chelate.</p> <p> The lipophilicity of HL and its metal chelates provided high metal chelate distribution ratios which, in turn, permitted preconcentration factors of up to 500 in a single batch-extraction. Additionally, studies on the recovery of radiotracer spikes from lakewater and seawater suggested that HL is an effective extractant for stripping metal ions from variously-bound forms from natural waters.</p> / Thesis / Master of Science (MSc)

<p> In this study a combined field and laboratory approach was used to identify the bio-geochemical processes that control trace metal (Ni, Co, Cr) reactive transport within natural acid rock drainage (ARD) biofilms, over both diel and seasonal timescales. Results indicated that metal (Mn, Ni, Co and Cr) scavenging by these biological solids is stable on a seasonal time frame. Metal scavenging occurs within two key solids, the organic constituents of the biofilm (Ni, Co) and associated biogenic hydrous Mn oxyhydroxides (HMO; Ni, Co and Cr), and not in association with Fe-oxyhydroxysulphates which dominate the mineralogy of the biofilm samples by mass. On a diel basis, cycling of HMO and associated trace metal dynamics appear to be contingent on the vertical migration of the biofilm oxic-anoxic boundary, a microbially controlled process. </p> <p> The reactivity and sorptive capacities of synthetic HMO analogs for Ni were further examined under well-characterized laboratory conditions. Analysis of the local chemical environment of Ni sorbed to HMO by synchrotron-based X-ray absorption spectroscopy was integrated with a bulk geochemical model of the acid-base characteristics of HMO and a theoretical model of the HMO structure. The synergistic use of these techniques allowed unique insight into the structural reactivity of HMO for Ni and is the first study to mechanistically demonstrate why bulk surface complexation models (SCM) are not accurate for HMO metal uptake. </p> <p> Overall, the results of this thesis highlight the utility of combined field and laboratory investigation to characterize relevant processes for reactive metal transport and underscore the need to: (1) consider microscale microbial-geochemical linkages in geochemical behaviour; (2) use caution when applying results derived from synthetic analogs to interpret natural system behaviour; and (3) examine processes at the appropriate scale e.g. microscale, to evaluate the mechanisms involved in metal reactions with solids. </p> / Thesis / Doctor of Philosophy (PhD)

No description available.

Relationships between trace metals and nanoparticles were investigated using analytical transmission electron microscopy (aTEM) and asymmetric flow field flow fractionation (aFlFFF) coupled to both multi-angle laser light scattering (MALLS) and high resolution-inductively coupled plasma mass spectroscopy (HR-ICPMS). Riverbed sediment samples were taken from the Clark Fork River in Montana, USA where a large-scale dam removal project has released reservoir sediment contaminated with toxic trace metals (namely Pb, Zn, Cu and As) which accumulated from one and a half centuries of mining activities upstream. An aqueous extraction method was used to attempt to separate the nanoparticles from the bulk sediment. After analysis of initial results, it was found that low density clays were being selected for in this process and made up a major portion of the particles within the extracts. However, it was also realized that the metals of interest were associated almost exclusively with nano-sized Fe and Ti oxides. In order to more fully examine these relationships, a density separation method, using sodium polytungstate (2.8g/cm3), was developed to separate these higher density oxides from the lower density clays. The heavy fraction was then subjected to an aqueous extraction routine to extract the nanoparticulate fraction. FFF results indicated a smaller size distribution and more ideal fractionation with this method. The aFlFFF-HR-ICPMS profiles for Fe and Ti also matched strongly with the data for the trace metals. The majority of particles analyzed with the TEM were nano-sized Fe and Ti oxides (most commonly goethite, ferrihydrite and brookite), which typically had trace metals associated with them. In many cases, it was aggregates of these nano oxides that were found hosting trace metals. Nanoparticles and aggregates are known to behave differently than their bulk mineral phases or constituent particles, respectively. Nanoparticles are also capable of extended transport in the environment. For these reasons, it is important that their associations with toxic trace metals be extensively evaluated, as they will affect the bioavailability and toxicity of these metals with implications for any type of contaminant sediment relocation, dam removal or metal contaminated site. / Ph. D.