Compositonal Analysis of Potentially harmful Elements in Soils: Implications for Epidemiology and Kidney Disease

A substantial proportion of aetiological risks for many cancers and chronic diseases remain unexplained. Using geochemical soil and stream water samples collected as part of the Tellus Project studies, current research is investigating naturally occurring background levels of potentially toxic elements (PTEs) in soils and stream sediments and their possible relationship with progressive chronic kidney disease (CKD). The Tellus geological mapping project, Geological Survey Northern Ireland, collected soil sediment and stream water samples on a grid of one sample site every 2 km2 across the rural areas of Northern Ireland resulting in an excess of 6800 soil sampling locations and more than 5800 locations for stream water sampling. Accumulation of several PTEs including arsenic, cadmium, chromium, lead and mercury have been linked with human health and implicated in renal function decline. The hypothesis is that long-term exposure will result in cumulative exposure to PTEs and act as risk factor(s) for cancer and diabetes related CKD and its progression. The ‘bioavailable’ fraction of total PTE soil concentration depends on the ‘bioaccessible’ proportion through an exposure pathway. Recent work has explored this bioaccessible fraction for a range of PTEs across Northern Ireland. In this study the compositional nature of the multivariate geochemical PTE variables and bioaccessible data is explored to augment the investigation into the potential relationship between PTEs, bioaccessibility and disease data.

Arsénio em águas subterrâneas em Portugal

Da totalidade da água existente na Terra, somente 1% diz respeito à água subterrânea, recurso finito e essencial para a sobrevivência do Homem. A composição química das águas subterrâneas é influência não só pela actividade humana, mas também pelas características químicas do substrato geológico. As rochas e os sedimentos funcionam como meio de transporte e armazém desse tipo de águas e a presença de certos minerais pode originar a contaminação natural das águas subterrâneas em elementos prejudiciais para o Homem. Um desses elementos é o arsénio. Uma vez que a concentração máxima admitida de arsénio para água consumo humano diminuiu dos anteriores 50 mg.l-1 para os actuais 10 mg.l-1,a probabilidade de encontrar concentrações naturais em arsénio em águas subterrâneas acima desse limite aumentou. Este trabalho visa estudar e compreender, através de ensaios laboratoriais, a interacção água/rocha em termos químicos e a mobilidade/comportamento do arsénio em seis zonas de Portugal Continental com contextos geológicos diferentes (Vila Flor – Formação Filito-Quartzítica, Baião – granitos, Cacia – sedimentos do Cretácico, Mamodeiro – sedimentos do Neogénico, Escusa – calcários dolomíticos e Beja - gabros). Para o efeito, nas zonas de estudo mencionadas foram colhidas amostras de rocha ou sedimento e de água subterrânea que foram analisadas para 36 e 76 elementos, respectivamente. A componente mineralógica e as fases suporte do As foram estudadas recorrendo à análise por difracção de raios X, microssonda electrónica e à aplicação da extracção química selectiva sequencial. A mobilização do As foi avaliada através da realização de ensaios de coluna e de agitação com hidrocarbonetos derivados do petróleo. No primeiro ensaio, a circulação de diferentes soluções com diferentes velocidades lineares no interior de colunas de vidro cheias de rocha moída, avaliou a presença de As associado a fases hidrossolúveis e biodisponíveis. No segundo, a agitação de rocha moída com água e hidrocarbonetos derivados do petróleo pretendeu avaliar o comportamento do As quando um aquífero apresenta uma contaminação com aquele tipo de hidrocarbonetos.

Aplicação de cortiça em dois tipos de reatores para tratamento de água

A qualidade da água degradou-se de forma relevante nas últimas décadas e os processos de sorção têm vindo a ser investigados como métodos promissores para o tratamento de águas contaminadas. Neste trabalho avaliou-se a capacidade de dois tipos de cortiça para a remoção de diversos contaminantes, em reatores de vaso fechado e de leito fixo. Os ensaios realizados em reatores de vaso fechado permitiram (i) avaliar o efeito do pH e da granulometria na eficiência dos sorventes na remoção de mercúrio e (ii) avaliar a afinidade dos sorventes para outros contaminantes, nomeadamente arsénio, cádmio, níquel e chumbo. Estruturalmente as duas cortiças estudadas aparentam ser semelhantes, com uma pequena diferença de comportamento ácido-base e não apresentam diferenças estatisticamente significativas na remoção de mercúrio. Os resultados obtidos permitiram constatar que o processo de remoção é independente do pH, tendo-se obtido percentagens de remoção da ordem dos 80% e de concentrações de mercúrio na cortiça na ordem dos 117 μg/g. As cortiças estudadas revelaram-se menos eficazes no tratamento de água com os restantes contaminantes, atingindo percentagens de remoção máximas de 0% para As, 11% para Cd, 35% para Ni e 69% para Pb. Os ensaios em leito fixo, mesmo sem terem sido otimizados, revelam que é possível obter uma eficácia de remoção de mercúrio superior a 90% nas primeiras 40 horas de trabalho, sendo a concentração de mercúrio no leito de 680 μg/g. Relativamente aos mecanismos de sorção, os resultados experimentais indicam que estes são possivelmente de natureza química e que as interações eletrostáticas têm pouca importância.

New oxomolybdenum(VI) hybrid materials

In this thesis, 2,2’-bipyridine (bipy), di-tert-butyl-2,2’-bipyridine (di-t-Bubipy), 2,2’-bipyridine-5,5’-dicarboxylic acid (H2bpdc), 2-[3(5)-pyrazolyl]pyridine (pzpy) and 2-(1-pentyl-3-pyrazolyl)pyridine (pent-pp) ligands were used as the N,N-chelate ligands in the formation of discrete [MoO2Cl2L]-type complexes. These complexes were employed as precursors for the preparation in aqueous media of oxomolybdenum(VI) products with a wide range of structural diversity. Three distinct heating methods were studied: hydrothermal, reflux or microwave-assisted synthesis. An alternative reaction with the inorganic molybdenum(VI) trioxide (MoO3) and the ligands di-t-Bu-bipy, H2bpdc and pzpy was also investigated under hydrothermal conditions. The distinct nature of the N,N-chelate ligands and/or the heating method employed promoted the isolation of a series of new oxomolybdenum(VI) hybrid materials that clearly reflected the strong structure-directing influence of these ligands. Thus, this thesis describes the synthesis and characterization of the discrete mononuclear [MoO2Cl2(pent-pp)], the dinuclear [Mo2O6(di-t-Bu-bipy)2] and the octanuclear [Mo8O22(OH)4(di-t-Bu-bipy)4] complexes as well as the highly unique polymeric materials {[MoO3(bipy)][MoO3(H2O)]}n, (DMA)[MoO3(Hbpdc)]·nH2O, [Mo3O9(pzpy)]n and [Mo2O6(pent-pp)]n (fine structural details of compound [Mo2O6(pent-pp)]n are presently unknown; however, characterization data strongly pointed toward a polymeric oxide hybrid compound). The catalytic behaviour of the discrete complexes and the polymeric compounds was tested in olefin epoxidation reactions. Compounds [Mo3O9(pzpy)]n and [Mo2O6(pent-pp)]n acted as sources of soluble active species that where identified as the oxodiperoxido complexes [MoO(O2)2(pzpy)] and [MoO(O2)2(pent-pp)], respectively. The majority of the compounds here presented were fully characterized by using solid-state techniques, namely elemental analyses, thermogravimetry, FT-IR, solid-state NMR, electron microscopy and powder X-ray diffraction (both from laboratory and/or synchrotron sources).

Metais em águas e sedimentos da plataforma dos Açores

A presente tese tem por objetivo principal contribuir para o conhecimento da geoquímica sedimentar da zona oceânica da crista da Terceira e montanhas submarinas a sul (região entre 29-39ºN e 27-32ºW), integrando também a caraterização dos metais e nutrientes na coluna de água e propondo concentrações para servirem de referência nesta região do Atlântico Central. Para o efeito foram realizadas amostragens na coluna de água em sete locais e de sedimento em cinco locais, durante a campanha oceanográfica designada por EMEPC/AÇORES/G3/2007 a bordo do navio SV Kommandor Jack, no âmbito do projeto da Estrutura de Missão para a Extensão da Plataforma Continental (EMEPC). Os perfis de CTD da coluna de água na região estudada revelam a presença de massas de água distintas: a Western North Atlantic Central Water (WNACW), a Eastern North Atlantic Central Water tropical (ENACWt), a Eastern North Atlantic Central Water polar (ENACWp), a Mediterranean Overflow Water (MOW), a Deep Mediterranean Water (DMW) e a North Eastern Atlantic Deep Water (NEADW). Observou-se nos perfis de temperatura e salinidade, referentes aos primeiros 200 m da coluna de água, um gradiente meridional negativo entre as estações localizadas na crista da Terceira e as estações localizadas mais a sul. Observou-se nas águas superficiais valores de oxigénio dissolvido de 93% e de pH de 8,1, assim como que as concentrações dos nutrientes NOx, PO4 e SiO2 variam de acordo com a atividade biológica, tendo-se registado concentrações medianas mais baixas, respetivamente de 6,5, 0,23 e 1,3 mol L-1, que aumentam com a profundidade devido à ausência de produção primária (respetivamente 31, 1,4 e 22 mol L-1). As concentrações de NH4 e de SO4 não variam significativamente nas massas de água, sendo os valores medianos mínimos e máximos de 0,69 a 0,79 mol L-1 para o NH4 e de 30 a 32 mol L-1 para o SO4. São propostas concentrações de referência para as massas de água, para os elementos cobre, cádmio, chumbo e arsénio. Os perfis de sedimento analisados permitem distinguir os sedimentos na crista da Terceira (core A) dos restantes (cores B a E). A grande variabilidade textural encontrada no core A, que contrasta com os outros cores analisados, deve-se a importantes contribuições terrígenas, originadas pela erosão sub-aérea e pela atividade vulcânica das ilhas próximas. iv resumo (continuação) A análise mineralógica, efetuada à fração areia e à fração fina (< 63 μm), confirma que os sedimentos do core A derivam de rochas vulcânicas formadas maioritariamente por piroxenas, olivinas, anfíbolas, biotite, alterites e ainda calcite, plagióclase e magnetite, tendo-se identificado ao microscópio a glauconite e o vidro vulcânico. De acordo com a composição química destes minerais o core A apresenta valores mais elevados de Al, Fe, K, P, Mg, Si, Na, Zn, V, Cr e Mn relativamente aos cores B a E. Os cores B a E apresentam grandes quantidades de calcite (>80%) formada maioritariamente por foraminíferos e nanoplâncton calcário (cocolitóforos). A fração areia confirma a composição maioritariamente carbonatada com grande abundância de material biogénico formado por oozes de foraminíferos (planctónicos e bentónicos) com raras espículas de espongiários e restos de conchas. Os cores B a E apresentam valores muito mais elevados que o core A para os elementos Ca e Sr. Os resultados para o Al, Fe, K, P, Si, Na, As, Cu, Ni, Zn, V, Cr, Li, Pb, Cd e Co presentes nos locais B, C, D e E sugerem que estes cores são comparáveis aos sedimentos de fundo carbonatados. Propõe-se concentrações de referência para a região do Atlântico compreendida entre 29-39ºN e 27-32ºW considerando a primeira camada colhida em cada core. Para o core A as concentrações são normalizadas a 5% de Al e CaCO3, enquanto que para os cores B a E são normalizadas a 2% de Al e CaCO3. Assim as concentrações de referência para o core A são: As – 18 mg kg-1, Cr – 91 mg kg-1, Cu – 127 mg kg-1, Ni – 84 mg kg-1, Pb – 41 mg kg-1, Hg – 41 ng g-1 e Zn – 482 mg kg-1. Para os cores B a E as concentrações de referência são: As – 3 mg kg-1, Cr – 10 mg kg-1, Cu – 36 mg kg-1 Ni – 12 mg kg -1, Hg – 3 ng g-1 e Zn – 20 mg kg-1. Para os restantes metais as concentrações de referência para o core A são: Al – 9%, Si – 25%, Fe – 6%, Ca – 13%, K – 2%, Mg – 2%, Na – 3%, P – 0,4%, Sr – 900 mg kg-1, Li – 10 mg kg-1, Mn – 1200 mg kg-1, Ba – 700 mg kg-1 e V – 140 mg kg-1. Para os cores B a E as concentrações de referência são: Al – 0,9%, Si – 2%, Fe – 0,2%, Ca – 95%, K – 0,3%, Mg – 0,4%, Na – 0,3%, P – 0,04%, Sr – 2600 mg kg-1, Li – 5 mg kg-1, Mn – 240 mg kg-1, Ba – 345 mg kg-1, Co – 2 mg kg-1 e V – 6 mg kg-1. Os resultados da presente tese constituem um contributo para a caraterização geoquímica da região e podem servir de referência à monitorização futura do mar dos Açores e montes submarinos a sul.

Sources and transport of surface sediment and metals in B.C. fjord, Tahsis Inlet

Senior thesis written for Oceanography 445

Assessment of heavy metals in the surroundings of coal-fired power plant

This paper aims to survey metal concentrations in soils in the vicinity of a coal-firedpower plant located in southwest of Portugal. Two annual sampling campaigns were carried out to measure a hypothetical soil contamination around the coal plant. The sampling area was divided into two subareas, both centered in the emission source, delimited by two concentric circles with radius of 6 km and 20 km. About 40 samplings points were defined in the influence area. Metals measurements were performed with a portable analytical X-ray dispersive energy fluorescence spectrometer identifying about 20 different elements in each sampling point. The most relevant elements measured included As, Cu, Fe, Hg, Pb, Ti and Zn in both sampling areas. Considering the results obtained in the first sampling campaign, arsenic is predominantly higher within the 6-20 km sampling area. The second sampling campaign showed that both sampling areas presented relatively similar metal concentrations except for Fe, Mn, Sr and Zn which concentration is higher within the 6-20 km sampling area. Also, As, Fe, Mn and Ti concentrations decreased significantly from the first to the second sampling campaign and their concentration were predominately higher in the NE-E and E-SE directions.

Multiple linear and principal component regressions for modelling ecotoxicity bioassay response

The ecotoxicological response of the living organisms in an aquatic system depends on the physical, chemical and bacteriological variables, as well as the interactions between them. An important challenge to scientists is to understand the interaction and behaviour of factors involved in a multidimensional process such as the ecotoxicological response.With this aim, multiple linear regression (MLR) and principal component regression were applied to the ecotoxicity bioassay response of Chlorella vulgaris and Vibrio fischeri in water collected at seven sites of Leça river during five monitoring campaigns (February, May, June, August and September of 2006). The river water characterization included the analysis of 22 physicochemical and 3 microbiological parameters. The model that best fitted the data was MLR, which shows: (i) a negative correlation with dissolved organic carbon, zinc and manganese, and a positive one with turbidity and arsenic, regarding C. vulgaris toxic response; (ii) a negative correlation with conductivity and turbidity and a positive one with phosphorus, hardness, iron, mercury, arsenic and faecal coliforms, concerning V. fischeri toxic response. This integrated assessment may allow the evaluation of the effect of future pollution abatement measures over the water quality of Leça River.

Trace Elements in Ambient Air at Porto Metropolitan Area—Checking for Compliance with New European Union (Eu) Air Quality Standards

Because of the scientific evidence showing that arsenic (As), cadmium (Cd), and nickel (Ni) are human genotoxic carcinogens, the European Union (EU) recently set target values for metal concentration in ambient air (As: 6 ng/m3, Cd: 5 ng/m3, Ni: 20 ng/m3). The aim of our study was to determine the concentration levels of these trace elements in Porto Metropolitan Area (PMA) in order to assess whether compliance was occurring with these new EU air quality standards. Fine (PM2.5) and inhalable (PM10) air particles were collected from October 2011 to July 2012 at two different (urban and suburban) locations in PMA. Samples were analyzed for trace elements content by inductively coupled plasma–mass spectrometry (ICP-MS). The study focused on determination of differences in trace elements concentration between the two sites, and between PM2.5 and PM10, in order to gather information regarding emission sources. Except for chromium (Cr), the concentration of all trace elements was higher at the urban site. However, results for As, Cd, Ni, and lead (Pb) were well below the EU limit/target values (As: 1.49 ± 0.71 ng/m3; Cd: 1.67 ± 0.92 ng/m3; Ni: 3.43 ± 3.23 ng/m3; Pb: 17.1 ± 10.1 ng/m3) in the worst-case scenario. Arsenic, Cd, Ni, Pb, antimony (Sb), selenium (Se), vanadium (V), and zinc (Zn) were predominantly associated to PM2.5, indicating that anthropogenic sources such as industry and road traffic are the main source of these elements. High enrichment factors (EF > 100) were obtained for As, Cd, Pb, Sb, Se, and Zn, further confirming their anthropogenic origin.

Effects of sodium arsenite on neurite outgrowth and glutamate AMPA receptor expression in mouse cortical neurons.

There has been broad concern that arsenic in the environment exerts neurotoxicity. To determine the mechanism by which arsenic disrupts neuronal development, primary cultured neurons obtained from the cerebral cortex of mouse embryos were exposed to sodium arsenite (NaAsO2) at concentrations between 0 and 2μM from days 2 to 4 in vitro and cell survival, neurite outgrowth and expression of glutamate AMPA receptor subunits were assessed at day 4 in vitro. Cell survival was significantly decreased by exposure to 2μM NaAsO2, whereas 0.5μM NaAsO2 increased cell survival instead. The assessment of neurite outgrowth showed that total neurite length was significantly suppressed by 1μM and 2μM NaAsO2, indicating that the lower concentration of NaAsO2 impairs neuritogenesis before inducing cell death. Immunoblot analysis of AMPA receptor subunit expression showed that the protein level of GluA1, a specific subunit of the AMPA receptor, was significantly decreased by 1μM and 2μM NaAsO2. When immunocytochemistry was used to confirm this effect by staining for GluA1 expression in neuropeptide Y neurons, most of which contain GluA1, GluA1 expression in neuropeptide Y neurons was found to be significantly suppressed by 1μM and 2μM NaAsO2 but to be increased at the concentration of 0.5μM. Finally, to determine whether neurons could be rescued from the NaAsO2-induced impairment of neuritogenesis by compensatory overexpression of GluA1, we used primary cultures of neurons transfected with a plasmid vector to overexpress either GluA1 or GluA2, and the results showed that GluA1/2 overexpression protected against the deleterious effects of NaAsO2 on neurite outgrowth. These results suggest that the NaAsO2 concentration inducing neurite suppression is lower than the concentration that induces cell death and is the same as the concentration that suppresses GluA1 expression. Consequently, the suppression of GluA1 expression by NaAsO2 seems at least partly responsible for neurite suppression induced by NaAsO2.

Investigations into the determinations of hydride-forming elements

Analytical methods for the determination of trace amounts of germanium, tin and arsenic were established using hydride generation coupled with direct current plasma atomic emission spectrometry. A continuous gas flowing batch system for the hydride generation was investigated and was applied to the determination of germanium(Ge), tin(Sn), antimony(Sb) and lead(Pb) (Preliminary results suggest that it is also applicable to arsenic)As) ). With this system, the reproducibility of signals was improved and the determination was speeded up, compared with the conventional batch type hydride generation system. Each determination was complete within one minute. Interferences from a number of transition metal ions, especially from Pd(II), Pt(IV), Ni(II), Cu(II), Co(II), and Fe(II, III), have proven to be very serious under normal conditions, in the determination of germanium, tin, and arsenic. These interference effects were eliminated or significantly reduced in the presence of L-cystine or L-cysteine. Thus, a 10-1000 fold excess of Ni(II), Cu(II), Co(II), Fe(II), Pt(IV), Pd(II), etc. can be tolerated without interference, In the presence of L-cystine or L-cysteine, compared with absence of interference reducing agent. The methods for the determination of Ge, Sn, and As were examined by the analyses of standard reference materials. Interference effects from the sample matrix, for example, in transition metal-rich samples, copper, iron and steel, were eliminated by L-cystine (for As and Sn) and by LI cysteine (for Ge). The analysis of a number of standard reference materials gave excellent results of As and Sn contents in agreement with the certified values, showing there was no systematic interference. The detection limits for both germanium and tin were 20 pg ml- I . Preliminary studies were carried out for the determination of antimony and lead. Antimony was found to react with NaBH4, remaInIng from the previous determinations, giving an analytical signal. A reversed injection manner, i.e., injection of the NaBH4 solution prior to the analyte solution was used to avoid uncertainty caused by residual NaBH4 present and to ensure that an excess of NaB H4 was available. A solution of 0.4% L-cysteine was found to reduce the interference from selected transition metal ions, Co(II), Cu(II), Ni(II) and Pt(IV). Hydrochloric acid - hydrogen peroxide, nitric acid - ammonium persulphate, and potassium dichromate malic acid reaction systems for lead hydride generation were compared. The potassium dichromate - malic acid reaction medium proved to be the best with respect to reproducibility and minimal interference. Cu(II), Ni(II), and Fe(II) caused strong interference In lead determinations, which was not reduced by L-cysteine or Lcystine. Sodium citrate, ascorbic acid, dithizone, thiosemicarbazide and penicillamine reduced interferences to some extent. Further interference reduction studies were carried out uSIng a number of amino acids, glycine, alanine, valine, leucine and histidine, as possible interference reducing agents in the determination of germanium. From glycine, alanine, valine to leucine, the interference reduction effect in germanium determinations decreased. Histidine II was found to be very promising In the reduction of interference. In fact, histidine proved more efficient than L-cystine and L-cysteine In the reduction of interference from Ni(II) in the determination of germanium. Signal enhancement by easily ionized elements (EIEs), usually regarded as an interference effect in analysis by DCP-AES, was studied and successfully applied to advantage in improving the sensitivity and detection limit in the determination of As, Ge, Sn, Sb, and Pb. The effect of alkali and alkaline-earth elements on the determination of the above five hydride forming elements was studied. With the appropriate EIE, a signal enhancement of 40-115% was achieved. Linear calibration and good reproducibility were also obtained in the presence of EIEs. III

Mass spectral studies of some pentafluorophenyl derivatives of group V /|nby Andrew Tanner Rake. -- 260 St. Catharines, Ont. : [s. n.],

The mass spectra of compounds of t he series (C6F5 )3-n MP~ (n = 1,2,3, M = P and As ), (C6F5>3Sb, Ph) Sb and (C6F5 )2SbPh have been studied in detail and the important modes of fragmentation were e1ucidated, a ided by metastable ions. Various trends attributed to the central atom and or the . substituent groups have been noted and, where applicable, compared to recent studies on related phenyl and pentafluorophenyl compounds of groups IV and V. The mass spectra of fluorine containing organometallic compounds exhibit characteristic migrations of fluorine to t he central atom, giving an increasing abundance of MF+, MF2+' and RMF+ (R = Ph or C6F5) ions on descending the group_ The mass spectra of pentafluorophenyl , antimony, and arsenic compounds show a greater fragmentation of the aromatic ring than those of phosphorus. The mixed phenyl pentafluorophenyl derivatives show a characteristic pattern depending on the number of phenyl grm.lps present but show t he general characteristics of both the tris(phenyl) and tris(pentafluorophenyl) compounds. The diphenyl pentafluorophenyl der ivatives show the loss of biphenyl ion as the most import ant step, the los s of phenyl t o give the i on PhMC6F5 + being of secondary importance. The ,bis(pentafluorophenyl) phenyl derivatives fragment primarily by loss of PhC6F5 to give C6F5M+ ions, the abundance of t hese increasing r apidly from phosphorus to arsenic. This species then, exhibits a characteristic fragmentation observed in the tris(penta- fluorophenyl ) compounds. However, the abundance of (C6F5)2M+ species in these compounds i s small. I ons of the type C6H4MC6F4 + and tetrafluorobiphenylene ions C6H4C6F4 + also are observed on substitution of a phenyl group for a penta- fluorophenyl group. The fully fluorinated species (C6F4)2M+ is not observed, although octafluorobiphenylene ions , (C6F4)2+' are evident in several spectra . The appearance potentials of the major ions were obtatned from the ionisation efficiency curves. Attempts were made to correlate these to the effect of the central atom in substituent groups, but the large errors involved prevented the reaching of quantitative conclusions, although it would appear that the electron is removed from the ligand in the ionisation of t he parent molecule .

Application of thermal ion-molecule reactions in tackling spectroscopic inferences in inductively coupled plasma mass spectrometry

Part I: Ultra-trace determination of vanadium in lake sediments: a performance comparison using O2, N20, and NH3 as reaction gases in ICP-DRC-MS Thermal ion-molecule reactions, targeting removal of specific spectroscopic interference problems, have become a powerful tool for method development in quadrupole based inductively coupled plasma mass spectrometry (ICP-MS) applications. A study was conducted to develop an accurate method for the determination of vanadium in lake sediment samples by ICP-MS, coupled with a dynamic reaction cell (DRC), using two differenvchemical resolution strategies: a) direct removal of interfering C10+ and b) vanadium oxidation to VO+. The performance of three reaction gases that are suitable for handling vanadium interference in the dynamic reaction cell was systematically studied and evaluated: ammonia for C10+ removal and oxygen and nitrous oxide for oxidation. Although it was able to produce comparable results for vanadium to those using oxygen and nitrous oxide, NH3 did not completely eliminate a matrix effect, caused by the presence of chloride, and required large scale dilutions (and a concomitant increase in variance) when the sample and/or the digestion medium contained large amounts of chloride. Among the three candidate reaction gases at their optimized Eonditions, creation of VO+ with oxygen gas delivered the best analyte sensitivity and the lowest detection limit (2.7 ng L-1). Vanadium results obtained from fourteen lake sediment samples and a certified reference material (CRM031-040-1), using two different analytelinterference separation strategies, suggested that the vanadium mono-oxidation offers advantageous performance over the conventional method using NH3 for ultra-trace vanadium determination by ICP-DRC-MS and can be readily employed in relevant environmental chemistry applications that deal with ultra-trace contaminants.Part II: Validation of a modified oxidation approach for the quantification of total arsenic and selenium in complex environmental matrices Spectroscopic interference problems of arsenic and selenium in ICP-MS practices were investigated in detail. Preliminary literature review suggested that oxygen could serve as an effective candidate reaction gas for analysis of the two elements in dynamic reaction cell coupled ICP-MS. An accurate method was developed for the determination of As and Se in complex environmental samples, based on a series of modifications on an oxidation approach for As and Se previously reported. Rhodium was used as internal standard in this study to help minimize non-spectral interferences such as instrumental drift. Using an oxygen gas flow slightly higher than 0.5 mL min-I, arsenic is converted to 75 AS160+ ion in an efficient manner whereas a potentially interfering ion, 91Zr+, is completely removed. Instead of using the most abundant Se isotope, 80Se, selenium was determined by a second most abundant isotope, 78Se, in the form of 78Se160. Upon careful selection of oxygen gas flow rate and optimization ofRPq value, previous isobaric threats caused by Zr and Mo were reduced to background levels whereas another potential atomic isobar, 96Ru+, became completely harmless to the new selenium analyte. The new method underwent a strict validation procedure where the recovery of a suitable certified reference material was examined and the obtained sample data were compared with those produced by a credible external laboratory who analyzed the same set of samples using a standardized HG-ICP-AES method. The validation results were satisfactory. The resultant limits of detection for arsenic and selenium were 5 ng L-1 and 60 ng L-1, respectively.

Les grelots mésoaméricains : sons et couleurs du pouvoir?

Ce mémoire prend la forme d’une réflexion critique sur le modèle proposé par Hosler afin d’expliquer les taux quantifiés d’étain et d’arsénique dans des objets de statut métalliques Mésoaméricains provenant principalement de l’Occident mésoaméricain et couvrant les deux phases de développement de la métallurgie mésoaméricaine. Ces objets font partie de la collection du Museo Regional de Guadalajara. Plus particulièrement, ce mémoire s’intéresse aux grelots mésoaméricains puisqu’ils représentent un élément important de la métallurgie préhispanique en Mésoamérique. Cette réflexion critique soulève plusieurs considérations techniques, méthodologiques, étymologiques, iconographiques, ethnohistoriques et logiques du modèle de Hosler relativement à la couleur des alliages constituant les grelots mésoaméricains. Les paramètres sur lesquels Hosler base son modèle sont questionnables à plusieurs niveaux. Ainsi, le fait que les niveaux d’arsenic ou d’étain observés dans les alliages cupriques de biens utilitaires sont généralement inférieurs à ceux quantifiés dans les alliages cupriques usités pour la fabrication de biens de statut de la Période 2 pourrait s’expliquer par le fait qu’il s’agit de deux méthodes de fabrication distinctes ayant des contraintes techniques différentes ou que ces artéfacts ont des paramètres et des fonctions distinctes. Les limites de l’association soleil-or, lune-argent y sont également exposées et un chapitre est consacré à la sonorité.

Caractérisation phénotypique et génotypique de Campylobacter jejuni et évaluation d’une stratégie de contrôle de la colonisation du poulet de chair par ce pathogène alimentaire

Campylobacter jejuni est l’agent causal de la campylobactériose, infection bactérienne importante en santé publique. Un des vecteurs de transmission de C. jejuni pour l’humain est le poulet via la chaîne alimentaire. Les mécanismes impliqués dans colonisation caecale commensale des oiseaux par C. jejuni sont toujours peu caractérisés, bien qu’une meilleure compréhension de ces mécanismes puisse apporter des solutions pour le contrôle du pathogène à la ferme. Cette étude avait pour buts de caractériser les propriétés phénotypiques et les facteurs génétiques impliqués dans la colonisation du poulet par C. jejuni et d’identifier de nouveaux mécanismes impliqués dans cette association. Des souches, issues d’élevages conventionnels échantillonnés en 2003 et en 2008 ainsi que d’élevages biologiques, ont été caractérisées afin d’obtenir leur profil de résistance aux antibiotiques, leur autoagglutination et leur chimiotactisme. Les souches des élevages conventionnels ont de plus été caractérisées pour leur capacité à adhérer et envahir une culture primaire de cellules caecales de poulet. Une puce à ADN a été développée pour détecter la présence de 254 gènes et variants associés à la colonisation des poulets ainsi qu’à la résistance aux antibiotiques chez les souches issues d’élevages conventionnels. Les propriétés phénotypiques et la présence de certains gènes chez les souches ont par la suite été comparées. Finalement, des souches ayant des caractéristiques différentes ont été utilisées dans un modèle de colonisation du poulet pour évaluer l’efficacité d’un nouvel additif alimentaire à base d’acides organiques et d’huiles essentielles sur le contrôle de C. jejuni. Les propriétés phénotypiques des souches étaient très variées et n’étaient pas corrélées entre elles, à l’exception de l’adhésion et de l’invasion. L’analyse génétique a révélé que le contenu en gènes des souches était variable, notamment au niveau des gènes de l’enveloppe bactérienne, au flagelle, aux récepteurs du chimiotactisme et à la résistance à l’arsenic. Les souches de 2003 et de 2008 étaient semblables lorsque leur contenu en gènes ainsi que leurs propriétés phénotypiques étaient comparés. Des gènes possiblement associés à un fort ou un faible potentiel de colonisation ont été identifiés. L’additif alimentaire a diminué la contamination des carcasses bien qu’une augmentation de la colonisation intestinale ait été observée pour certaines souches. La moitié des lots de poulets d’origine biologique étaient positifs pour C. jejuni. Les souches issues de ce type d’élevage étaient peu résistantes aux antibiotiques et possédaient des phénotypes variés. Cette étude a permis de mieux définir les caractéristiques importantes de C. jejuni qui sont associées à la colonisation intestinale du poulet. Elle a établi pour la première fois au Canada la présence du pathogène dans les élevages de poulets biologiques. Cette étude fait partie des quelques études qui décrivent la présence des gènes de colonisation et de résistance aux antibiotiques dans une collection de souches issues uniquement du poulet. Elle a également remis en doute l’importance de certains gènes dans la colonisation. La caractérisation exhaustive des souches a également permis d’identifier de nouveaux gènes possiblement associés à la colonisation de poulet par C. jejuni. Finalement, elle a indiqué que l’utilisation d’un mélange d’huiles essentielles et d’acide organique encapsulés pouvait être efficace pour réduire la contamination des carcasses de poulet par C. jejuni et que son effet était souche-dépendant.