Variations In Speciation Research Articles

Short-term temporal variations in speciation of Pb, Cu, Zn and Sb in a shooting range runoff stream

This study was designed to explore the changes in physico-chemical forms of Pb, Cu, Zn and Sb in a stream draining a contaminated shooting range, located at Steinsjøen in the South-Eastern part of Norway, during a period of 21 days. To obtain information on the element species distribution, an interphased size and charge fractionation system was applied, where membrane filtration (0.45 µm) and ultrafiltration using hollow fibre (nominal cut off 10 kDa) were performed prior to charge fractionation using chromatography (cationic and anionic exchange resins). The results show that Pb mainly was present as particulate and colloidal high molecular mass (HMM) species, Cu as colloidal (HMM) and low molecular mass (LMM) species, while Sb and Zn were mainly present as LMM species. The total element concentrations of Pb, Cu, Zn and Sb were positively correlated to water flow and dissolved organic carbon (DOC), suggesting these are important factors in controlling the run-off of the investigated elements in this catchment. During episodes of higher water flow, the increase in element concentration was mainly in the colloidal fraction. Partial redundancy analysis (pRDA) revealed that variations in pH, HMM organic carbon (HMM OC) and LMM organic carbon (LMM OC) explained 47% of the variation in size distribution of the elements, while variations in precipitation and water flow explained 48% of the variation in the charge distribution of the elements. The variation in concentrations during the period varied by a factor of 4, also stressing the importance of frequent sampling opposed to spot sampling in environmental surveys and risk assessments.

Karyo-morphological characterization of natural genetic variation in some threatenedCymbidiumspecies of Northeast India

Abstract Karyo-morphological studies have been carried out in three different species of the genus Cymbidium from North-eastern India. The somatic chromosome number (2n = 40) has been recorded in all the three species with distinct inter-specifi c variation in the arm ratio of few homologous pairs in the complements. The karyotypes of the species were more or less symmetrical. The significance of karyotypic variation in speciation of the genus Cymbidium has been discussed.

10.1007/s11476-008-3002-6

Based on the synthesis of hydrogeochemical materials on Sb occurrence in carbonate and thermal waters and thermodynamic simulations, genetic analysis was conducted of the transformations of probable Sb migration species (particularly oxygen-bearing and sulfide ones), and their transformations were calculated depending on the main parameters of hydrogeochemical systems (\( P_{CO_2 } \), T, R/W, Eh, and pH). The oxygen 2HSbO 02 + 3H2S = Sb2S3 + 4H2O (2SbO −2 + 3HS− + 5H+ = Sb2S3 + 4H2O) and sulfide HSb2S −4 + H+ = Sb2S3 cr + H2S (Sb2S 2−4 + 2H+ = Sb2S3cr + H2S) models for the genesis of hydrogenic Sb2S3(cr) were simulated. Information on occurrences of carbonate and thermal waters in various regions worldwide was generalized, and the reasons were identified for the geochemical separation of As and Sb in carbonate and thermal waters. The causes and conditions of an increase in Sb concentrations in thermal waters were revealed, and Sb migration species in carbonate and thermal waters were identified for various parameters of hydrogeochemical systems. Variations in Sb speciation were demonstrated for hydrogeochemical systems depending on their boundary conditions (\( P_{CO_2 } \), T, and R/W). Models were outlined responsible for the precipitation of Sb2S3(cr) from carbonate and thermal waters.

Genetics and ecological speciation

Species originate frequently by natural selection. A general mechanism by which this occurs is ecological speciation, defined as the evolution of reproductive isolation between populations as a result of ecologically-based divergent natural selection. The alternative mechanism is mutation-order speciation in which populations fix different mutations as they adapt to similar selection pressures. Although numerous cases now indicate the importance of ecological speciation in nature, very little is known about the genetics of the process. Here, we summarize the genetics of premating and postzygotic isolation and the role of standing genetic variation in ecological speciation. We discuss the role of selection from standing genetic variation in threespine stickleback (Gasterosteus aculeatus), a complex of species whose ancestral marine form repeatedly colonized and adapted to freshwater environments. We propose that ecological speciation has occurred multiple times in parallel in this group via a "transporter" process in which selection in freshwater environments repeatedly acts on standing genetic variation that is maintained in marine populations by export of freshwater-adapted alleles from elsewhere in the range. Selection from standing genetic variation is likely to play a large role in ecological speciation, which may partly account for its rapidity.

Iron solubility driven by speciation in dust sources to the ocean

Particulate aerosols are thought to be the primary source of iron to the oceans, but the factors determining their solubility, and thus bioavailability, are unclear. X-ray absorption analysis reveals that speciation controls the solubility of iron in three large sources of aerosol iron. Although abundant in the Earth’s crust, iron is present at trace concentrations in sea water and is a limiting nutrient for phytoplankton in approximately 40% of the ocean1,2. Current literature suggests that aerosols are the primary external source of iron to offshore waters, yet controls on iron aerosol solubility remain unclear3,4. Here we demonstrate that iron speciation (oxidation state and bonding environment) drives iron solubility in arid region soils, glacial weathering products (flour) and oil combustion products (oil fly ash). Iron speciation varies by aerosol source, with soils in arid regions dominated by ferric (oxy)hydroxides, glacial flour by primary and secondary ferrous silicates and oil fly ash by ferric sulphate salts. Variation in iron speciation produces systematic differences in iron solubility: less than 1% of the iron in arid soils was soluble, compared with 2–3% in glacial products and 77–81% in oil combustion products, which is directly linked to fractions of more soluble phases. We conclude that spatial and temporal variations in aerosol iron speciation, driven by the distribution of deserts, glaciers and fossil-fuel combustion, could have a pronounced effect on aerosol iron solubility and therefore on biological productivity and the carbon cycle in the ocean.

Identification of Uranyl Surface Complexes on Ferrihydrite: Advanced EXAFS Data Analysis and CD-MUSIC Modeling

Previous spectroscopic research suggested that uranium(VI) adsorption to iron oxides is dominated by ternary uranyl-carbonato surface complexes across an unexpectedly wide pH range. Formation of such complexes would have a significant impact on the sorption behavior and mobility of uranium in aqueous environments. We therefore reinvestigated the identity and structural coordination of uranyl sorption complexes using a combination of U LIII-edge extended X-ray absorption fine structure (EXAFS) spectroscopy and iterative transformation factor analysis, which enhances the resolution in comparison to conventional EXAFS analysis. A range of conditions (pH, CO2 partial pressure, ionic strength) made it possible to quantify the variations in surface speciation. In the resulting set of spectral data (N=11) the variance is explained by only two components, which represent two structurally different types of surface complexes: (1) a binary uranyl surface complexwith a bidentate coordination to edges of Fe(O,OH)6 octahedra and (2) a uranyl triscarbonato surface complex where one carbonate ion bridges uranyl to the surface. This ternary type B complex differs from a type A complex where uranyl is directly attached to surface atoms and carbonate is bridged by uranyl to the surface. Both surface complexes agree qualitatively and quantitatively with predictions by a charge distribution (CD) model. According to this model the edge-sharing uranyl complex has equatorial ligands (-OH2, -OH, or one -CO3 group) that point away from the surface. The monodentate uranyl triscarbonato surface complex (type B) is relevant only at high pH and elevated pC0O. At these conditions, however, it is responsible for significant uranyl sorption, whereas standard models would predict only weak sorption. This paper presents the first spectroscopic evidence of this ternary surface complex, which has significant implications for immobilization of uranyl in carbonate-rich aqueous environments.

Speciation variation of trace metals in coal gasification and combustion

Coal gasification is a very important aspect of coal use today. In this paper, the speciation of trace metals (Cu, Pb, Zn, Mo, Mn, V, Ba, and Be) in crude lignite, combustion ash and gasification ash is studied in order to understand the environmental impact of coal gasification on trace metal pollution. Results demonstrate that the trace metals are changed partly from the active (labile) fraction to the residual (non-labile) fraction in the processes of gasification and direct combustion. The metals bound to the active fraction in gasification ash are diminished in the process of lignite gasification more than in the process of lignite direct combustion: 73.1% for Cu, 86% for Pb, 74.1% for Zn, 46.3% for Mo, 35% for Mn, 29.8% for V, 1.9% for Ba, and 40.2% for Be. These facts suggest that the coal gasification is a reasonable method of coal utilization for the environment protection of trace metal pollution from coal ashes, as well as for resource economics.

Seasonal variations in nutrient concentrations and speciation in the Chena River, Alaska

To better understand the seasonal controls on nutrient abundances, speciation, and fluxes in a watershed underlain by discontinuous permafrost, we collected water samples biweekly from the Chena River during 2005–2006 to measure inorganic and organic N, P, and Si in dissolved and particulate phases. Nitrate concentrations were low (8–14 μM) during the winter and summer dry seasons but were elevated during the spring freshet (15–24 μM). Ammonium varied from 8 to 13 μM during the winter but dropped dramatically during the ice‐open season to 0.1–3 μM. Phosphate was very low throughout the year (ranging from 0.03 to 0.3 μM), reflecting the pristine condition of the watershed. Dissolved silica was high in the winter and reached its minimum during the spring freshet. DIN was the dominant species in the total N pool (60%), followed by DON (30%) and PN (10%). Most of the phosphorous was present in the particulate phase (74%), with phosphate and DOP only comprising 19% and 7%, respectively. Seasonal variations in nutrient concentrations and speciation were mostly controlled by the hydrological flow regime and biological activity in the river. Annual nutrient export fluxes from the Chena River during 2005–2006 were 51.1 × 106 mole‐N, 1.4 × 106 mole‐P, and 197 × 106 mole‐Si, corresponding to an annual yield of 9.8 × 103 mol‐N km−2, 0.28 × 103 mol‐P km−2, and 37.9 × 103 mol‐Si km−2, respectively. Within the annual export fluxes, the spring freshet contributed about 18% of TN, 27% of TP, and 10% of Si, while the winter season contributed 11% of TN, 12% of TP, and 20% of Si. Continued climatic warming in northern watersheds will likely increase the export of nutrient species from watersheds.

Short-time variation of mercury speciation in the urban of Göteborg during GÖTE-2005

Mercury species samples for gaseous elemental mercury (GEM) with a temporal resolution of 5 min, 5 h and 20 min integrated measurements of reactive gaseous mercury (RGM), and 24-h sampling of particulate mercury (HgP) at urban Femman and total gaseous mercury (TGM) at rural Rörvik were conducted during the measurement campaign GÖTE-2005 in Göteborg, Sweden. Results showed that average concentrations for GEM, RGM, HgP and TGM were 1.96 ± 0.38 ng m −3, 2.53 ± 4.09 pg m −3, 12.50 ± 5.88 pg m −3 and 1.63 ± 0.19 ng m −3, respectively. A reverse diurnal distribution pattern between GEM and RGM was observed, and early morning GEM concentration was elevated compared to daytime values which was likely due to activation of fossil fuel combustion, electric utilities, etc., by the formation of a nighttime inversion layer, less activity of GEM and reduced mixing. The subsequent decline and afternoon minimum were likely related to increase vertical mixing, photochemical reaction, and coupling with the coal combustion. However, the photochemical conversion from GEM during daytime and nocturnal behavior of “sticky” gases under higher relative humidity may result in strong diurnal cycles for RGM. Sampling site was heavily affected by anthropogenic sources from two distinguished wind sectors. One was ESE-SSW sector which was likely impacted by long distance transport from south highly industrialized region; the other was likely tied with local sources from N–NE sector.

Short-term temporal variations in iron concentration and speciation in a canal during a summer algal bloom

We conducted field investigations in a canal connected to Lake Kasumigaura (Japan) twice weekly during a summer algal bloom to understand the temporal variations in dissolved iron and its speciation, and the controlling factors. Dissolved iron (D-Fe), which is operationally defined as that passing through a 0.2-μm pore filter, acid-labile particulate iron (LP-Fe), and chemical speciation of dissolved iron were analyzed. LP-Fe was extracted from the suspended solids (SS) on 0.2-μm pore-size filters after a 2 h soak in 25% (4.5 M) acetic acid. The chemical speciation of dissolved iron was determined using cathodic stripping voltammetry. The concentration of D-Fe ranged from 72 to 1354 nM and that of filterable labile iron (FL-Fe) from 5 to 881 nM, and both increased markedly after two heavy rains. The increased D-Fe and FL-Fe appeared to be removed within a few days. The concentrations of LP-Fe ranged from 4.1 to 16.1 μM, were much higher than those of D-Fe, and did not increase after the rains. There was a significant correlation (|r| = 0.88, P < 0.01) between ln[D-Fe] and pH. This suggests that the dynamics of D-Fe in the canal depend upon the cycle of adsorptive removal onto the surface of SS at high pH and desorptive supply from the surface of SS at low pH. Moreover, D-Fe concentration would also be controlled by the formation of iron oxyhydroxides amorphous particles at high pH and dissolution at low pH. The percentage of organically complexed iron ranged from 35% to 99% and varied markedly at time scales of days to weeks. There was a significant correlation (|r| = 0.60, P < 0.01) between the percentage of organically complexed iron and the log of the cell density of Microcystis spp.. This suggests that the growth of specific algal species affects iron speciation in the canal.

The genic view of plant speciation: recent progress and emerging questions

The genic view of the process of speciation is based on the notion that species isolation may be achieved by a modest number of genes. Although great strides have been made to characterize 'speciation genes' in some groups of animals, little is known about the nature of genic barriers to gene flow in plants. We review recent progress in the characterization of genic species barriers in plants with a focus on five 'model' genera: Mimulus (monkey flowers); Iris (irises); Helianthus (sunflowers); Silene (campions); and Populus (poplars, aspens, cottonwoods). The study species in all five genera are diploid in terms of meiotic behaviour, and chromosomal rearrangements are assumed to play a minor role in species isolation, with the exception of Helianthus for which data on the relative roles of chromosomal and genic isolation factors are available. Our review identifies the following key topics as being of special interest for future research: the role of intraspecific variation in speciation; the detection of balancing versus directional selection in speciation genetic studies; the timing of fixation of alleles of major versus minor effects during plant speciation; the likelihood of adaptive trait introgression; and the identification and characterization of speciation genes and speciation gene networks.

Role of Aluminum Speciation in the Removal of Disinfection Byproduct Precursors by a Coagulation Process

Humic acid (HA) was extracted and separated into different molecular weight (MW) fractions, then coagulated by aluminum chloride and polyaluminum chloride (PACl). The removal of disinfection byproduct (DBP) precursors and the aluminum speciation variation of the coagulants were investigated in detail. In particular, the role of aluminum speciation in the removal of DBP precursors was discussed. During the coagulation process, AlCl3 hydrolyzed into dominating in situ Al13 species at pH 5.5. The in situ Al13 species exhibited better removal ability for haloacetic acid (HAA) precursors than PACl. At pH 7.5, in situ hydrolyzed Al13 species of AlCl3 decomposed into dimeric Al species. In this case, preformed Al13 of PACl had a high removal ability of HAA precursors. Specially, the greatest reduction of HAA precursors with a low MW (<30 kDa) was through charge neutralization at pH 5.5, and that of HAA precursors in high MW (> 30 kDa) fractions was through adsorption at pH 7.5. Different from HAA precursors, the in situ Al13 species did not have a high removal ability of trihalomethane (THM) precursors. Therefore, PACl exhibited a better removal ability of THM precursors than AlCl3 at different pH values. In the different MW fractions, the greatest reduction of THM precursors was through charge neutralization at pH 5.5.

Geochemical evolution of Sb migration species in carbonate and thermal waters in relation to Sb hydrogenic mineralization

Based on the synthesis of hydrogeochemical materials on Sb occurrence in carbonate and thermal waters and thermodynamic simulations, genetic analysis was conducted of the transformations of probable Sb migration species (particularly oxygen-bearing and sulfide ones), and their transformations were calculated depending on the main parameters of hydrogeochemical systems (\( P_{CO_2 } \), T, R/W, Eh, and pH). The oxygen 2HSbO 2 0 + 3H2S = Sb2S3 + 4H2O (2SbO 2 − + 3HS− + 5H+ = Sb2S3 + 4H2O) and sulfide HSb2S 4 − + H+ = Sb2S3 cr + H2S (Sb2S 4 2− + 2H+ = Sb2S3cr + H2S) models for the genesis of hydrogenic Sb2S3(cr) were simulated. Information on occurrences of carbonate and thermal waters in various regions worldwide was generalized, and the reasons were identified for the geochemical separation of As and Sb in carbonate and thermal waters. The causes and conditions of an increase in Sb concentrations in thermal waters were revealed, and Sb migration species in carbonate and thermal waters were identified for various parameters of hydrogeochemical systems. Variations in Sb speciation were demonstrated for hydrogeochemical systems depending on their boundary conditions (\( P_{CO_2 } \), T, and R/W). Models were outlined responsible for the precipitation of Sb2S3(cr) from carbonate and thermal waters.

Seasonal Variation of Iron Speciation in a Pearl-Raising Bay Sediment by Mössbauer Spectroscopy

Ago Bay in Mie Prefecture, central Japan, is world-famous for the site of Mikimoto pearl culture, but recently the production of pearls has considerably declined. Environmental deterioration of the bay is suspected of having caused the decline. The periodic investigation into iron speciation of the bay sediment by 57 Fe Mossbauer spectroscopy revealed its high pyrite (FeS2) content from the surface to the 20-cm depth. The pyrite in the surface sediment decreased only in spring, three months after the dissolved oxygen in the bottom water was at maximum. Such oxygen-consuming material as pyrite accumulated through long-term biotic activity is a most-likely explanation for the prolonged environmental deterioration of the bay, which appears in the high chemical oxygen demand (COD) of the sediment.

Investigation of Mercury Transformation by HBr Addition in a Slipstream Facility with Real Flue Gas Atmospheres of Bituminous Coal and Powder River Basin Coal

An investigation of speciated mercury transformation with the addition of hydrogen bromide (HBr) at elevated temperatures was conducted in a slipstream reactor with real flue gas atmospheres. A real flue gas atmosphere is composed of bituminous coal (with high sulfur and high chlorine contents) and Powder River Basin (PRB) coal (with lower sulfur and chlorine contents). The average sulfur, chlorine, and mercury contents in the tested bituminous coal were 1.31% and 1328 and 0.11 ppm and 0.61% and 170 and 0.08 ppm, respectively, for tested PRB coal. The average CaO, Fe2O3, and loss on ignition in collected fly ash contents of tested bituminous coal were 1.71, 17.51, and 7.13% and 22.95, 4.91, and 0.64%, respectively, for tested PRB coal. The different contents of coal chlorine, CaO, and Fe2O3 in fly ash can be attributed to the different mercury speciations at baseline tests for these two coals in this study. The addition of HBr concentrations into the flue gas was controlled in the 3−15 ppm range. Semi-continuous mercury emission monitors were used to check the variation of mercury speciation at sampling locations. The Ontario Hydro Method (ASTM D6784-02) was used for data validation or comparison. For both methods, a high temperature inertial sampling probe was used to minimize the interference between vapor phase mercury and fly ash. Its temperatures were controlled consistently with flue gas temperatures at their installation locations in the slipstream reactor. Test results indicated that adding HBr into the flue gas at several parts per million strongly impacted the mercury oxidation and adsorption, which were dependent upon temperature ranges. Higher temperatures (in the range of 300−350 °C) promoted mercury oxidation by HBr addition but did not promote mercury adsorption. Lower temperatures (in a range of 150−200 °C) enhanced mercury adsorption on the fly ash by adding HBr. Test results also verified effects of flue gas atmospheres on the mercury oxidation by the addition of HBr, which included concentrations of chlorine and sulfur in the flue gas. Chlorine species seemed to be involved in the competition with bromine species in the mercury oxidation process. With the addition of HBr at 3 ppm at a temperature of about 330 °C, the additional mercury oxidation could be reached by about 55% in a flue gas atmosphere by burning PRB coal in the flue gas and by about 20% in a flue gas by burning bituminous coal. These are both greater than the maximum gaseous HgBr2 percentage in the flue gas (35% for PRB coal and 5% for bituminous coal) by thermodynamic equilibrium analysis predictions under the same conditions. This disagreement may indicate a greater complexity of mercury oxidation mechanisms by the addition of HBr. It is possible that bromine species promote activated chlorine species generation in the flue gas, where the kinetics of elemental mercury oxidation were enhanced. However, SO2 in the flue gas may involve the consumption of the available activated chlorine species. Thus, the higher mercury oxidation rate by adding bromine under the flue gas by burning PRB coal may be associated with its lower SO2 concentration in the flue gas.

Evolution and the latitudinal diversity gradient: speciation, extinction and biogeography

A latitudinal gradient in biodiversity has existed since before the time of the dinosaurs, yet how and why this gradient arose remains unresolved. Here we review two major hypotheses for the origin of the latitudinal diversity gradient. The time and area hypothesis holds that tropical climates are older and historically larger, allowing more opportunity for diversification. This hypothesis is supported by observations that temperate taxa are often younger than, and nested within, tropical taxa, and that diversity is positively correlated with the age and area of geographical regions. The diversification rate hypothesis holds that tropical regions diversify faster due to higher rates of speciation (caused by increased opportunities for the evolution of reproductive isolation, or faster molecular evolution, or the increased importance of biotic interactions), or due to lower extinction rates. There is phylogenetic evidence for higher rates of diversification in tropical clades, and palaeontological data demonstrate higher rates of origination for tropical taxa, but mixed evidence for latitudinal differences in extinction rates. Studies of latitudinal variation in incipient speciation also suggest faster speciation in the tropics. Distinguishing the roles of history, speciation and extinction in the origin of the latitudinal gradient represents a major challenge to future research.

Transformations of γ-alumina in aqueous suspensions : 1. Alumina chemical weathering studied as a function of pH

Hydration of γ-Al 2O 3 is often reported to occur via the superficial transformation of the alumina surface into aluminum hydroxide-like layers. However, very little evidence has been given so far to support this hypothesis. It is demonstrated here by X-ray diffraction, TEM, electron diffraction, and solubility studies that a second process of hydration takes place that involves the dissolution of alumina and subsequent precipitation of well-shaped Al(OH) 3 particles from supersaturated alumina aqueous solution. This process can be observed on a macroscopic scale (XRD, TEM) for any pH ⩾ 5 , provided that the contact time between alumina and water exceeds 10 h. The least thermodynamically stable phase of aluminum hydroxide, bayerite, becomes favored compared with gibbsite when the pH of the solution is increased. It is assumed that the rate of formation of bayerite germs is greater than that of gibbsite due to variations in aluminum speciation in solution as a function of pH.

Temporal variability of mercury speciation in urban air

Semi-continuous measurements of ambient mercury (Hg) species were performed in Detroit, MI, USA for the calendar year 2003. The mean (±standard deviation) concentrations for gaseous elemental mercury (GEM), particulate mercury (HgP), and reactive gaseous mercury (RGM) were 2.2±1.3 ng m −3, 20.8±30.0, and 17.7±28.9 pg m −3, respectively. A clear seasonality in Hg speciation was observed with GEM and RGM concentrations significantly ( p<0.001) greater in warm seasons, while HgP concentrations were greater in cold seasons. The three measured Hg species also exhibited clear diurnal trends which were particularly evident during the summer months. Higher RGM concentrations were observed during the day than at night. Hourly HgP and GEM concentrations exhibited a similar diurnal pattern with both being inversely correlated with RGM. Multivariate analysis coupled with conditional probability function analysis revealed the conditions associated with high Hg concentration episodes, and identified the inter-correlations between speciated Hg concentrations, three common urban air pollutants (sulfur dioxide, ozone, and nitric oxides), and meteorological parameters. This analysis suggests that both local and regional sources were major factors contributing to the observed temporal variations in Hg speciation. Boundary layer dynamics and the seasonal meteorological conditions, including temperature and moisture content, were also important factors affecting Hg variability.

Study of Mercury Oxidation by a Selective Catalytic Reduction Catalyst in a Pilot-Scale Slipstream Reactor at a Utility Boiler Burning Bituminous Coal

One of the cost-effective mercury control technologies in coal-fired power plants is the enhanced oxidation of elemental mercury in selective catalytic reduction (SCR) followed by the capture of the oxidized mercury in the wet scrubber. To better understand Hg oxidation chemistry within a SCR, the Institute for Combustion Science and Environmental Technology at Western Kentucky University set up a pilot-scale SCR slipstream facility at a selected utility boiler burning bituminous coal. The greatest benefit of this scaled-down SCR slipstream test is the ability to investigate the effects of Hg oxidation in a SCR using actual flue gas with fly ash included and to isolate and control specific flue-gas compositions with spike gas additions. The average sulfur, chlorine, and mercury contents in the burned coal were 1.67% and 731 and 0.13 ppm, respectively. CaO and Fe2O3 and loss on ignition of the fly ash, which are reported to possibly affect Hg speciation, are approximately 1.65, 14.6, and 2.6% on average, respectively. The maximum concentrations of spike gases were 500, 25, 2000, 50, and 15 ppm for HCl, Cl2, SO2, SO3, and HBr, respectively. Semicontinuous mercury emission monitors were used to monitor the variation of mercury speciation at the inlet and outlet of the SCR slipstream reactor, and the American Society for Testing and Materials certified Ontario hydro method was used for data comparison and validation. This paper is the first in a series of two in which the validation of the SCR slipstream test and Hg speciation variation in runs with or without SCR catalysts inside the SCR slipstream reactor under special gas additions (HCl, Cl2, SO2, and SO3) are presented. Effects of HBr additions on mercury speciation within the SCR will be presented in the second part of the series. Tests indicate that the use of a catalyst in a SCR slipstream reactor can achieve greater than 90% NO reduction efficiency with a NH3/NO ratio of about 1. There is no evidence to show that the reactor material affects mercury speciation. Both SCR catalysts used in this study exhibited a catalytic effect on the elemental mercury oxidation but had no apparent adsorption effect. SCR catalyst 2 seemed more sensitive to the operational temperature. The spike gas tests indicated that HCl can promote Hg0 oxidation but not Cl2. The effect of Cl2 on mercury oxidation may be inhibited by higher concentrations of SO2, NO, or H2O in real flue-gas atmospheres within the typical SCR temperature range (300−350 °C). SO2 seemed to inhibit mercury oxidation; however, SO3 may have some effect on the promotion of mercury oxidation in runs with or without SCR catalysts.

GLOBAL BIODIVERSITY PATTERNS OF BENTHIC MARINE ALGAE

Species richness patterns are remarkably similar across many marine taxa, yet explanations of how such patterns are generated and maintained are conflicting. I use published occurrence data to identify previously masked latitudinal and longitudinal diversity gradients for all genera of benthic marine macroalgae and for species in the Order Bryopsidales. I also quantify the size, location, and overlap of macroalgal geographic ranges to determine how the observed richness patterns are generated. Algal genera exhibit an inverse latitudinal gradient, with biodiversity hotspots in temperate regions, while bryopsidalean species reach peak diversity in the tropics. The geographic distribution of range locations results in distinct clusters of range mid-points. In particular, widespread taxa are centered within tight latitudinal and longitudinal bands in the middle of the Indo-Pacific and Atlantic Oceans while small-ranged taxa are clustered in peripheral locations, suggesting that variation in speciation and extinction are important drivers of algal diversity patterns. Hypotheses about factors that regulate diversity contain underlying assumptions about the size and location of geographic ranges, in addition to predictions as to why species numbers will differ among regions. Yet these assumptions are rarely considered in assessing the validity of the prevailing hypotheses. I assess a suite of hypotheses, suggested to explain patterns of marine diversity, by comparing algal-richness patterns in combination with the size and location of algal geographic ranges, to the richness and range locations predicted by these hypotheses. In particular, the results implicate habitat areas and ocean currents as the most plausible drivers of observed diversity patterns.