acase@tulane.edu / Redox-sensitive trace metals tend to be more soluble under oxidizing conditions and less soluble under reducing conditions resulting in authigenic enrichments in oxygen-depleted sedimentary facies (Algeo and Rowe, 2012; P Ho et al., 2017; Tribovillard et al., 2006). Because of that, redox sensitive trace elements are used as paleoredox proxies to reconstruct redox status of the environment (Tribovillard et al., 2006). Unfortunately, we lack the quantitative understanding of many of these trace elements. One of the most important trace elements is tungsten. To contribute a better understanding of the biogeochemistry of tungsten to our community, I utilize laboratory experiments, geochemical modeling, and statistical methods to investigate the speciation, kinetics, and adsorption of tungsten in the environment. This thesis includes three major chapters. In the first major chapter, I performed a series of chemical experiments to explore the particle reactivity of tungstate and tetrathiotungstate in sulfidic solutions. I found that pyrite is a strong scavenger of W in aquatic environments. Our results indicate that the difference of specific adsorption between WO42– and WS42– may be attributed to their different inner-sphere complexation on the pyrite surface. Our results also show that WS42– is less particle reactive with respect to pyrite than MoS42–. In the second major chapter, I examined effect of acid on tungsten (W) sulfidation process as well as developed the Brønsted acid relationship, which provides a tool to predict the effect of acids on the kinetics of the thiolation reaction of W in natural waters. The results of laboratory experiments show that thiotungstate formation is first order with respect to both H2S and WO42- concentrations, and is catalyzed by acids. Therefore, low pH and high H2S concentrations both favor W thiolation. However, compared to molybdenum (Mo), thiolation of W is kinetically “sluggish”. The modeling results show that full thiolation of Mo requires ca. 110 days, whereas full thiolation of W requires ca. 50 years under a persistent euxinic condition such as the Black Sea. Our results indicate that the longer the period of euxinia, the higher chance of WS42- species in solutions and subsequently be incorporated into euxinic sediments as W-S species. In the last chapter, I successfully tested whether protonated mineral surfaces also catalyze the hydrolysis of tetrathiotungstate anions. Our results show that kaolin (Al2Si2O5[OH]4), aluminum oxide (γ-Al2O3), and titanium dioxide (TiO2) exert an appreciable catalytic effect on tetrathiotungstate hydrolysis. The data suggest that the pH dependent hydrolysis rate of WS42- for kaolin, γ-Al2O3, and TiO2 fall into two distinct groups, which consist two reaction pathways. The pH dependence of the mineral-catalyzed reactions suggest that acid surface sites on the mineral surfaces promote WS42- hydrolysis reactions. In the presence of UV-light, TiO2 substantially enhanced the hydrolysis rate of WS42- compared to identical experiments that were conducted in the absence of UV-light, we suggest the increased hydrolysis rate of WS42- in the presence of UV-light reflects the production of reactive oxygen species by TiO2. Due to the rapid development of nanotechnology, more engineered nanomaterials like TiO2 are introduced into the environment, which can impact the speciation and mobility of trace elements. Combined, the results in this thesis advance our understanding of mechanisms for W biogeochemistry in euxinic systems and will allow to facilitate reconstruction of paleodepositional conditions, paleoproductivity, and paleoredox. / 1 / Minming Cui

Chromosomal evolution has long been linked with the process of organismal speciation, and many different theories have been suggested over the years to explain why this would be so. These theories can be loosely grouped into two eras. Classical chromosomal speciation models focused on negative heterosis of chromosomal rearrangements causing malsegregation and germ cell death in hybrids. More recent models examine the effects of reduced recombination around rearrangements and the impact this can have on sequence evolution, specifically the accumulation of genetic incompatibilities.¶ The huntsman spider Delena cancerides is known to be highly chromosomally variable, and to have reduced recombination near fusions. However, this species has previously only been interpreted with reference to the classical models of chromosomal speciation, the expectations of which it does not fit well. Broad-scale sampling of this spider has revealed extensive chromosomal diversity and complexity. Twenty one chromosomally differentiated populations (karyomorphs) of this spider have now been described, including those with the putatively ancestral configuration of all telocentric bivalents at meiosis (tII), and many that are saturated for Robertsonian fusions. These include up to six different karyomorphs with metacentric bivalents (mII), eight karyomorphs that form a chain of chromosomes at male meiosis, and six karyomorphs that form two separate but co-segregating chains.¶ A computer simulation was used to test hypotheses regarding the evolution of this chromosomal diversity, which indicated that fusions are likely to have accumulated gradually, possibly due to meiotic drive. Historical phylogeographic analyses have shown that deep cryptic divisions exist which are concordant with the chromosomal diversity.¶ Hybridization experiments have suggested that many hybrid zones between karyomorphs of this species are tension zones, and that genetic incompatibilities are likely to play an important role in generating partial reproductive isolation of karyomorphs. Furthermore, several hybrid zones appear to have been modified by staggered clines. The staggering of clines is thought to ameliorate reproductive isolation mechanisms that are dependent on epistatic fitness interactions, and so may prevent diverging populations progressing towards speciation. ¶Therefore, on the basis of the available evidence, D. cancerides may fit the recombination suppression model of chromosomal speciation, although it may be unlikely that the karyomorphs will progress towards full species status. Hence, this species may in the future make a highly informative model organism for investigating the early stages of genetic reproductive isolation associated with chromosomal rearrangements.

Two related techniques, based upon ion-exchange solid phase extraction, have been developed for the determination of arsenic speciation. The inorganic arsenic species arsenite (As(III)) and arsenate (As(V)) are separated by anion-exchange and detected with graphite furnace atomic absorption spectrophotometry (GFAAS) with a nickel matrix modifier. The first separation technique, which is based on a published method, utilizes a strong anion-exchange resin in a column format. The method was refined to achieve a cleaner and more rapid separation of the As species. In the second separation technique, the recently available Empore[superscript TM] anion-extraction disks are used. In both cases, rapid separations of several samples are achieved with the use of a vacuum manifold. The simplicity of the separation techniques allows them to be applied in the field which eliminates potential problems due to sample storage. In the pH range of most natural water samples (5-9), As(III) exists as a neutral species which is not retained by the resin, while As(V) exists as a monovalent or divalent species which are subsequently retained by the resin. The two arsenic species are collected in 3 to 4 fractions with As(III) appearing in the first two fractions. The As(V) species is eluted from the resin with 0.1 M HCl and collected in the last one or two fractions. Percent recoveries for each species range from 94 to 99%. The detection limit for each species with GFAAS is 2 ��g/L. The speciation techniques were used successfully in several applications. First, the resin technique was used to monitor the oxidation of As(III) by 0���, H���0���, and ��-Mn0���. The technique was also used to monitor the reduction of As(V) by Fe(II) and in solutions containing combinations of Fe(II), Fe(III), and a scorbic acid. Second, the resin technique was used to monitor the redox behavior of arsenic in soil slurries in bio-reactor systems. Upon spiking the soil slurry to a level of 500 ��g/L As(V), 80 to 90% of the As(V) was immediately adsorbed, presumably to hydrous Fe(III) oxides. In general, as conditions became more reducing, total soluble arsenic increased as a result of either abiotic or biotic reduction of the As(V) to the more soluble As(III). Third, the disk technique was applied in the field to determine arsenic speciation in creek water at Sutter Creek, Ca., where homes are built upon a large pile of mine tailings containing arsenic. In the creek water, no As(III) was detected but As(V) was detected at a level of 8 ��g/L. Fourth and finally, the resin technique was used to determine arsenic speciation when a sample of the mine tailings was placed in a reactor and combined with a soil slurry thus simulating a flooded condition. As conditions became more reducing, up to 800 ��g/L As was detected in solution with As(III) accounting for almost 90% of total soluble species. Also presented here is an investigation of zinc amalgam as a reducing agent for Cr(III) and selected redox indicators. Zinc amalgam, in a column format, also known as the classic Jones Reductor, provides an efficient means for production of Crap and reduced forms of various redox indicators. Finally, the reduction capabilities of Ti(III) citrate and zinc amalgam were compared. / Graduation date: 1996

A study of the phyletic relationships among five species of tragopans and an outgroup, the Blood Pheasant (Ithaginis cruentus), was conducted from 1987 to 1991. Biochemical, behavioral, and external morphologic characteristics were compared. A cladistic approach was used to compare the behavioral, biochemical, and external morphologic data collectively, as different phyletic relationships were obtained when each area of investigation was analyzed separately. Although unlike other pheasant species the genera Tragopan and Ithaginis molt their tail feathers centrifugally, study results did not indicate that these two groups were closely related. Based on a compilation of 25 characters, seven possible phylogenetic trees were generated. I rejected six of the seven trees based on current geographical distribution, morphology (size and complexity of lappet in males), behavior (wing coordination during the frontal display of male tragopans), and electrophoretic (number of unique alleles among the different species of tragopans) data. I accepted the tree that grouped Satyr and Western as closely related species and grouped Temminck's, Blyth's, and Cabot's tragopans together, with Temminck's and Cabot's being more closely related to each other than either was to Blyth's. I proposed that the prototype of tragopans probably had their origin in the eastern Himalayas. There were probably two major dispersal events; one population dispersed into central and south-east China and the Himalayas provided a corridor for the dispersal of a second population. Due to geological events in the Himalayas and China, these populations further split and eventually evolved into the extant forms. / Graduation date: 1992

The major goal of this research is the development of a competitive ligand equilibration-solvent solvent extraction (CLE-SSE) method to determine organically complexed mercury species in estuarine water. The method was applied to estuarine surface waters of Galveston Bay and the water column of Offatts Bayou. Thermodynamic equilibrium modeling estimated organically complexed mercury species in estuarine water using the conditional stability constants of mercury-organic complexes and the concentrations of organic ligands determined by CLE-SSE. Two competing ligands, chloride and thiosalicylic acid (TSA), were used for CLE-SSE. Chloride ion competition determined conditional stability constants for 1 : 1 mercury-ligand complexes ranging from ~1023 to ~1024 with concentrations of organic ligands at low nM levels. TSA competition determined stronger mercury-binding ligands by manipulating the TSA concentration such that a higher binding strength was achieved than that for the mercury-chloride complex. TSA competition determined conditional stability constants for 1 : 1 mercury-ligand complexes ranging from ~1027 to ~1029, with ligand concentrations ranging from 10 to 100 pM. Mercury-organic binding strengths in these ranges are consistent with bidentate mercury complexation by low molecular weight organic thiols. A linear relationship was observed between log stability constants for the mercury-ligand complex and log ligand concentrations, supporting the hypothesis that there is a continuum of mercury binding site strengths associated with dissolved organic matter. In Galveston Bay, organically complexed mercury accounted for > 95 % of the total dissolved mercury in surface water. Organic complexation of mercury coupled with mercury dissolution from particulate phases controls the filter-passing mercury distribution in surface waters of Galveston Bay. The estuarine distributional features of mercury-complexing organic ligands were similar to those of glutathione, supporting mercury complexation by a thiol binding group. In Offatts Bayou, a seasonally anoxic bayou on Galveston Bay, thermodynamic equilibrium modeling suggests that the speciation of dissolved mercury in anoxic systems is dominated by sulfide complexation rather than organic complexation.

The hybridizing Daphnia mendotae and D. dentifera (Crustacea: Cladocera) are sympatric throughout much of North America, and are considered a cryptic species complex due to their lack of phylogenetically informative morphological characters. They appear to have no biological mating barriers: hybrids may dominate or coexist with either or both parental species, and are sexually competent, forming both F2 hybrids and back-crosses. Nevertheless, the two species remain distinct. There is observational evidence that separation may be enforced by adaptation to different predation regimes: D. mendotae, with its greater anti-predator morphological plasticity, may out-compete D. dentifera under intense invertebrate predation, while the smaller D. dentifera may be better adapted to avoid predation by visually feeding fish. We tested this idea by examining whether D. mendotae and D. dentifera differ in ecologically relevant life history and morphological traits. We performed a replicated life history experiment involving 6 replicates of 6 clones within each species, and measured time until first reproduction, fecundity, and juvenile and population growth rates. In parallel, we examined whether these species differed in morphological traits predicted to arise from adaptation to different predator types, and tested the ecological relevance of these traits by exposing Daphnia to predation by the invasive cladoceran Bythotrephes longimanus. Finally, we examined the plasticity of life history, morphology, and susceptibility to predation by rearing Daphnia under exposure to Bythotrephes chemical cues for two generations. D. mendotae and D. dentifera differed across almost all measured life history and morphological traits in directions that accord with our hypotheses, strongly suggesting that their species boundaries are maintained by adaptation to different predation regimes. Plastic reaction to Bythotrephes, however, was weak and inconsistent, suggesting that these species either do not detect or respond to this recent invader, or that their responses are manifested in other ways. / Thesis (Master, Biology) -- Queen's University, 2011-12-23 20:31:14.76

A three-part study of the vocal and visual cues important for species recognition in six species of Darwin's Finches (Geospiza) in the Galapagos is presented. Part I quantifies structure and species-specificity of advertising song. Part II describes experiments on song function and recognition. Part III examines the role of morphology in mate recognition and reproductive isolation. Geospiza song is variable and lacks species-specificity, due to intrapopulation song polymorphism, dialect divergence, song parallelism and interspecific song overlap. Song functions in conspecific territorial communication. Much intraspecific song variation apparently has little functional significance, although vocal confusion between syntopic G. fuliginosa and G. fortis may exist. Visual recognition involves morphological (non-plumage) stimuli of both head and body. Male recognition of potential mates functions in reproductive isolation, and character displacement in recognition ability occurs. Visual cues appear to override vocal ones in short-range communication. Lack's (1945) hypothesis that Geospiza use characters specialized for feeding as mate identification cues is confirmed. Low interspecific song divergence is probably related to the evolution of visual species recognition.

Precipitation reactions of phosphorus (P) with Ca decrease the P fertilizer efficiency in calcareous soils. The hypothesis was that anion competition of sulphate with phosphate to precipitate with Ca will increase P solubility in calcareous soils. Initial experiments were conducted to investigate the effect of co-application of K2SO4, (NH4)2SO4, MgSO4 and (NH4)2CO3 on the solubility of monopotassium phosphate (MPP) and monoammonium phosphate (MAP) in different Manitoba soils. Co-application of sulphate salts enhanced P solubility by a factor that ranged from 6% to 44% in soils with greater exchangeable Ca and smaller acid-extractable Ca content (i.e. Osborne, Red River, Balmoral and St. Claude soil series). Solubility and solid-state speciation of P were investigated when MPP was banded with sulphate salts in both model and natural (Dezwood Loam soil series, DL) calcareous soils. The results of S K-edge X-ray absorption near edge structure spectroscopy (XANES) showed that CaSO4•2H2O was formed in DL soil when either K2SO4, (NH4)2SO4 or MgSO4 was applied with MPP. Phosphorus-31 magic-angle spinning nuclear magnetic resonance (MAS NMR) analysis showed that dicalcium phosphate dihydrate (DCPD) was formed in both soils, but the relative proportion of DCPD decreased in the presence of sulphate salts due to the formation of a new P compound. The results also showed that decreasing Ca saturation on the cation exchange complex increased the solubility and mobility of MAP in model calcareous soils and Ca played a more dominant role in forming P precipitates than Mg. According to 31P MAS NMR results, DCPD was the dominant P species in soils with 100% to 50% Ca saturation on the cation exchange complex while poorly ordered magnesium phosphate trihydrate was the prominent P phase with 70% to 100% Mg saturation. This study has demonstrated that the combination of solid state NMR and XANES provided complimentary information concerning anion competition and changes in P speciation due to the co-application of sulphate salts in fertilizer bands. Application of sulphate salts is a promising agronomic practice to enhance P solubility in soils with greater exchangeable Ca content due to the anion competition by sulphates with phosphate to precipitate with Ca.

This thesis is directed towards the development of the diffusive gradients in thin films (DGT) technique for the measurement of total dissolved As, and for As speciation measurements. In addition, a preliminary investigation of a novel laboratory-based method for measuring labile metal species was carried out; this method involved the coupling of a microcolumn of adsorbent with a standard electrothermal atomic absorption spectrometer. An iron-oxide adsorbent was utilized for As measurements by DGT. The diffusion coefficients of inorganic Asv and AsIII> were measured through the polyacrylamide diffusive gel using both a diffusion cell and DGT devices. A variety of factors that may affect the measurement of total As by DGT were investigated. These factors, which included pH, anions, cations, fulvic acid, FeIII-fulvic acid complexes, and colloidal Fe, may affect the adsorption of the As species to the iron-oxide, or may affect the diffusion coefficients of the individual As species. The DGT method was further developed to selectively accumulate the AsIII species in the presence of Asv. This was achieved by the placement of a negatively charged Nafion membrane at the front of the DGT device which slowed the diffusion of the negatively charged Asv species (H₂AsO₄₂ ⁻) considerably, relative to the uncharged AsIII species (H₃AsO₃). The effect that pH, anions, and cations may have on the selective accumulation of AsIII, in the presence of Asv, was investigated. DGT devices without a Nafion membrane and with a Nafion membrane were deployed in natural waters to determine the total inorganic As and AsIII> concentrations, and to evaluate its performance. A preliminary investigation of the coupling of a microcolumn of Chelex-100 resin with a standard electrothermal atomic absorption spectrometer was undertaken to establish its value as a laboratory-based speciation method. This involved the examination of various microcolumn materials to accommodate the Chelex-100 resin, and finding an appropriate buffer that could be used to buffer the Chelex-100 resin without interfering with the ETAAS measurement. Furthermore, factors that may affect the uptake of metal by the Chelex-100 resin, such as concentration of buffer in solution, ionic strength, and conditioning of the Chelex-100 resin, were investigated.

Paleoanthropology has been beset by controversies concerning the number of hominid species at any given time. This thesis examines the case for one or more species from the time of early H. erectus using the biological and evolutionary species concepts as frames of reference. To accomplish this task, measurements were made on casts of African and Asian fossil hominid skulls with previously published data used as both a control and a supplement. Due to the fragmentary nature of the data and the small sample size, principle components analysis was used to create a usable data set. Linear regression was then used to calculate mean differences between the African and Asian fossil samples for PC 1 (a derived factor denoted overall cranial size) and XCB (maximum cranial breadth). This data was then compared to that of 28 pair-wise comparisons of eight modem human populations from the same general regions as the fossils. Since a number of these comparisons had mean differences greater or equal to that of the fossils, the finding are suggestive of the fossils all being from the same species, Homo erectus. / Department of Anthropology