A comparison of a range of models for dispersion in a partially stratified room

A comparative study of models used to predict contaminant dispersion in a partially stratified room is presented. The experiments were carried out in a ventilated test room, with an initially evenly dispersed pollutant. Air was extracted from the outlet in the ceiling of the room at 1 and 3 air changes per hour. A small temperature difference between the top and bottom of the room causes very low air velocities, and higher concentrations, in the lower half of the room. Grid-independent CFD calculations were compared with predictions from a zonal model and from CFD using a very coarse grid. All the calculations show broadly similar contaminant concentration decay rates for the three locations monitored in the experiments, with the zonal model performing surprisingly well. For the lower air change rate, the models predict a less well mixed contaminant distribution than the experimental measurements suggest. With run times of less than a few minutes, the zonal model is around two orders of magnitude faster than coarse-grid CFD and could therefore be used more easily in parametric studies and sensitivity analyses. For a more detailed picture of internal dispersion, a CFD study using coarse and standard grids may be more appropriate.

Quantitative DRIFTS investigation of possible reaction mechanisms for the water-gas shift reaction on high-activity Pt- and Au-based catalysts

The present work emphasizes the importance of including a full quantitative analysis when in situ operando methods are used to investigate reaction mechanisms and reaction intermediates. The fact that some surface species exchange at a similar rate to the reaction product during isotopic transients is a necessary but not sufficient criterion for participation as a key reaction intermediate. This is exemplified here in the case of highly active low-temperature water-gas shift (WGS) catalysts based on gold and platinum. Operando DRIFTS data, isotopic exchanges, and DRIFTS calibration curves relating the concentration of formate species to the corresponding DRIFTS band intensity were combined to obtain a quantitative measure of the specific rate of formate decomposition. Despite displaying a rapid isotopic exchange rate (sometimes as fast as that of the reaction product CO2), the concentration of formates seen by DRIFTS was found to account for at most only 10% of the CO2 produced under the experimental conditions reported herein. These new results obtained on Au/CeZrO4 and Pt/CeO2 preparations (which are among the most active low-temperature WGS catalysts reported to date), led to the same conclusions regarding the minor role of IR-observable formates as those obtained in the case of less active Au/Ce(La)O-2 and Pt/ZrO2 catalysts. (c) 2007 Elsevier Inc. All rights reserved.

Factors That Impact Technology Innovation Adoption Among Irish Professional Service Sector SMEs

This paper disseminates the findings from a study into the factors impacting technological innovation adoption and diffusion specific to the deployment of electronic-commerce strategies within professional service sector SMEs in Ireland. Confirmatory factor analysis was performed and seven factors relating to a firm's external/internal environment were found to underpin adoption. These are: electronic-commerce capability; willingness to change/rate of response to new technologies; technological opportunity recognition; customer orientation; sensitivity to competitive/customer environments; perceptions of technology feasibility; and e-skills development mechanisms. t-tests revealed differences between adopters and non-adopters, and forward stepwise logistic regression is used to assess the extent to which these seven factors actually predict electronic-commerce adoption. It was found that electronic-commerce capability and the willingness to change/rate of response to new technologies are the two most important factors affecting adoption behaviours. © Imperial College Press.

Isotopic composition of inorganic carbon as an indicator of benzoate degradation by Pseudomonas putida: temperature, growth rate and pH effects.

Degradation experiments of benzoate by Pseudomonas putida resulted in enzymatic carbon isotope fractionations. However, isotopic temperature effects between experiments at 20 and 30 °C were minor. Averages of the last three values of the CO2 isotopic composition (δ13CCO2(g)) were more negative than the initial benzoate δ13C value (−26.2‰ Vienna Pee Dee Belenite (VPDB)) by 3.8, 3.4 and 3.2‰ at 20, 25 and 30 °C, respectively. Although the maximum isotopic temperature difference found was only 0.6‰, more extreme temperature variations may cause larger isotope effects. In order to understand the isotope effects on the total inorganic carbon (TIC), a better measure is to calculate the proportions of the inorganic carbon species (CO2(g), CO2(aq) and HCO3−) and to determine their cumulative δ13CTIC. In all three experiments δ13CTIC was more positive than the initial isotopic composition of the benzoate at a pH of 7. This suggests an uptake of 12C in the biomass in order to match the carbon balance of these closed system experiments.

Isotopic Assessment of Sources of Surface Water Nitrate within the Oldman River Basin, Southern Alberta, Canada

Concentrations and isotopic compositions of NO-3 from the Oldman River (OMR) and some of its tributaries (Alberta, Canada) have been determined on a monthly basis since December 2000 to assess temporal and spatial variations of riverine NO-3 sources within the OMR basin. For the OMR sites, NO-3 -N concentrations reached up to 0.34 mg L-1, d15N-NO-3 values varied between –0.3 and +13.8‰, and d18O-NO-3 values ranged from –10.0 to +5.7‰. For the tributary sites, NO-3 -N concentrations were as high as 8.81 mg L-1, d15N-NO-3 values varied between –2.5 and +23.4‰, and d18O-NO-3 values ranged from –15.2 to +3.4‰. Tributaries in the western, relatively pristine forested part of the watershed add predominantly NO-3 to the OMR with d15N-NO-3 indicative of soil nitrification. In contrast, tributaries in the eastern agriculturally-urban-industrially-used part of the basin contribute NO-3 with d15N-NO-3 values of about +16‰ indicative of manure and/or sewage derived NO-3. This difference in d15N-NO-3 values of tributaries was found to be independent of the season, but rather indicates a spatial change in the NO-3 source, which correlates with land use changes within the OMR basin. As a consequence of tributary influx, d15N-NO-3 values in the Oldman River increased from +6‰ in the downstream direction (W to E), although [NO-3 -N] increased only moderately (generally

Dissolved Argon Changes the Rate of Diffusion in Room Temperature Ionic Liquids: Effect of the Presence and Absence of Argon and Nitrogen on the Voltammetry of Ferrocene

This work explores the effects of argon and nitrogen, two electrochemically and chemically inert gases frequently used in sample preparation of room temperature ionic liquid (RTIL) solutions, on the eelectrochemical characterization of ferrocene (Fc) dissolved in the RTIL 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([C(2)mim][NTf2]). Remarkably, chronoamperometrically determined diffusion coefficients of Fc in [C(2)mim][NTf2] are found to increase from 4.8 (+/- 0.2) x 10(-11) m(2) s(-1) under vacuum conditions to 6.6 (+/- 0.5) x 10(-11) m(2) s(-1) in an atmosphere of 1 atm Ar. In contrast, exposing a vacuum-purified sample to an atmosphere of 1 atm N-2 resulted in no significant change in the measured diffusion coefficient of Fc. The effect of dissolved argon on diffusion transport is unexpected and has implications in electrochemistry and elsewhere. Fc was found to volatilize under vacuum conditions. We propose, however, that evacuation of the cell by vacuum prior to electrochemical measurements being carried out is the only way to ensure that no contamination of the sample occurs, and use of an in situ method of determining the diffusion coefficient and concentration of Fc dispells,any ambiguity associated with Fc depletion by vacuum.

Climate change-linked range expansion of Nathusius' pipistrelle bat, Pipistrellus nathusii (Keyserling & Blasius, 1839)

Aim To examine the effect of climate change on the occurrence and distribution of Pipistrellus nathusii (Nathusius' pipistrelle) in the United Kingdom (UK).Location We modelled habitat and climatic associations of P. nathusii in the UK and applied this model to the species' historical range in continental Europe.Methods A binomial logistic regression model was constructed relating the occurrence of P. nathusii to climate and habitat characteristics using historical species occurrence records (1940-2006) and CORINE land cover data. This model was applied to historical and projected climate data to examine changes in suitable range (1940-2080) of this species. We tested the predictive ability of the model with known records in the UK after 2006 and applied the model to the species' known range in Europe.Results The distribution of P. nathusii was related positively to the area of water bodies, woodland and small areas of urbanization, and negatively related to the area of peat/heathland. Species records were associated with higher minimum temperatures, low seasonal variation in temperature and intermediate rainfall. We found that suitable areas have existed in the UK since the 1940s and that these have expanded. The model had high predictive power when applied to new records after 2006, with a correct classification rate of 70%, estimated by receiver operating characteristic analysis. Based on climate projections, our model suggests a potential twofold increase in the area suitable for P. nathusii in the UK by 2050. The single most influential climate variable contributing to range increase was the projected increase in minimum temperature. When applied to Europe, the model predictions had best predictive capability of known records in western areas of the species' range, where P. nathusii is present during the winter.Main conclusions We show that a mobile, migratory species has adapted its range in response to recent climate change on a continental scale. We believe this may be the first study to demonstrate a case of range change linked to contemporary climate change in a mammal species in Europe.

Late Holocene climate change in central Sweden inferred from lacustrine stable isotope data

Stable isotopes (delta O-18 and delta C-13) of lacustrine carbonates (Chara spp. algae and Pisidium spp. molluscs) from a lake sedimentary sequence in central Sweden were analysed to infer changes in lake hydrology and climate during the late Holocene. Results from analysis of lake water isotopes (delta O-18 and delta H-2) show that Lake Blektjarnen water isotope composition is responsive to the balance between evaporation and input water (E/l ratio). A high E/l ratio results from a dry and probably warmer climate, decreasing the relative importance of precipitation input. Under such conditions evaporation and atmospheric equilibration probably enrich lake water in O-18 and C-13, respectively, which is reflected in the isotopic composition of the carbonates in the lake. From the relatively positive Chara delta O-18 values we infer that conditions were dry and warm between 4400 and 4000 cal. a BP, whereas more negative values indicate that conditions were wetter and probably cooler between 4000 and 3000 cal. a BP. A drier climate is inferred from more positive values between 2500 and 1000 cal. a BP. However, a successive depletion after ca. 1750 cal. a BP, also detected in several other delta O-18 records (carbonate and diatom), suggest increasingly wetter conditions in Scandinavia after that time, which is probably related to increased strength of the zonal flow.

Carbon Isotopic Fractionation of CFCs during Abiotic and Biotic Degradation

Carbon stable isotope ((13)C) fractionation in chlorofluorocarbon (CFC) compounds arising from abiotic (chemical) degradation using zero-valent iron (ZVI) and biotic (landfill gas attenuation) processes is investigated. Batch tests (at 25 °C) for CFC-113 and CFC-11 using ZVI show quantitative degradation of CFC-113 to HCFC-123a and CFC-1113 following pseudo-first-order kinetics corresponding to a half-life (t(1/2)) of 20.5 h, and a ZVI surface-area normalized rate constant (k(SA)) of -(9.8 ± 0.5) × 10(-5) L m(-2) h(-1). CFC-11 degraded to trace HCFC-21 and HCFC-31 following pseudo-first-order kinetics corresponding to t(1/2) = 17.3 h and k(SA) = -(1.2 ± 0.5) × 10(-4) L m(-2) h(-1). Significant kinetic isotope effects of e(‰) = -5.0 ± 0.3 (CFC-113) and -17.8 ± 4.8 (CFC-11) were observed. Compound-specific carbon isotope analyses also have been used here to characterize source signatures of CFC gases (HCFC-22, CFC-12, HFC-134a, HCFC-142b, CFC-114, CFC-11, CFC-113) for urban (UAA), rural/remote (RAA), and landfill (LAA) ambient air samples, as well as in situ surface flux chamber (FLUX; NO FLUX) and landfill gas (LFG) samples at the Dargan Road site, Northern Ireland. The latter values reflect biotic degradation and isotopic fractionation in LFG production, and local atmospheric impact of landfill emissions through the cover. Isotopic fractionations of ?(13)C ~ -13‰ (HCFC-22), ?(13)C ~ -35‰ (CFC-12) and ?(13)C ~ -15‰ (CFC-11) were observed for LFG in comparison to characteristic solvent source signatures, with the magnitude of the isotopic effect for CFC-11 apparently similar to the kinetic isotope effect for (abiotic) ZVI degradation.

Nineteenth and twentieth century sea-level changes in Tasmania and New Zealand

Positive deviations from linear sea-level trends represent important climate signals if they are persistent and geographically widespread. This paper documents rapid sea-level rise reconstructed from sedimentary records obtained from salt marshes in the Southwest Pacific region (Tasmania and New Zealand). A new late Holocene relative sea-level record from eastern Tasmania was dated by AMS(14)C (conventional, high precision and bomb-spike), Cs-137, Pb-210, stable Pb isotopic ratios, trace metals, pollen and charcoal analyses. Palaeosea-level positions were determined by foraminiferal analyses. Relative sea level in Tasmania was within half a metre of present sea level for much of the last 6000 yr. Between 1900 and 1950 relative sea level rose at an average rate of 4.2 +/- 0.1 mm/yr. During the latter half of the 20th century the reconstructed rate of relative sea-level rise was 0.7 +/- 0.6 mm/yr. Our study is consistent with a similar pattern of relative sea-level change recently reconstructed for southern New Zealand. The change in the rate of sea-level rise in the SW Pacific during the early 20th century was larger than in the North Atlantic and could suggest that northern hemisphere land-based ice was the most significant melt source for global sea-level rise. (C) 2011 Elsevier B.V. All rights reserved.

Comparative growth rates and internal banding periodicity of maerl species (Corallinales, Rhodophyta) from northern Europe

Maerl is a type of rhodolith, found in ecologically important beds of high conservation value; a major conservation objective is to establish growth rates. Maerl shows internal banding of controversial periodicity that may contain a high-resolution record of palaeoceanographic-palaeoclimatic data. To investigate growth rates and banding periodicity, we used the vital stain Alizarin Red in combination with scanning electron microscopy (SEM). Three maerl species, Phymatolithon calcareum, Lithothamnion corallioides and L. glaciale, were collected from maerl beds in Ireland. Following staining, maerl was grown in three controlled temperature treatments and at two depths in the field (P. calcareum only), with Corallina officinalis as a control for the stain. Alizarin Red was shown to be a suitable marker for growth in European maerl species and for C. officinalis. The average tip growth rate of P. calcareum from Northern Ireland at 10 m depth and under constant laboratory conditions was c. 0.9 mm yr(-1), double the rates observed at 5 m depth and in L. corallioides. Our measurements and re-examination of reported data allow us to conclude that the three most abundant maerl species in Europe grow about 1 (0.5-1.5) mm per tip per year under a wide range of field and artificial conditions. Internal banding in temperate European maerl revealed by SEM is a result of regular changes in wall thickness; the approximately monthly periodicity of bands in field-grown specimens is consistent with previous suggestions that they may be lunar. The potential for maerl banding to be a high-resolution record of palaeoclimatic and palaeoenvironmental change could be realized with this vital stain in conjunction with isotopic or microgeochemical analyses.

A comparison of nitogen fate and transport in catchments underlain by high and low permeability aquifers using chemical and isotopic tools.

Variability in nitrogen fate and transport in different catchments types is often not considered. This research considers the importance of such nitrogen processes within groundwater pathways in two agricultural catchments in Ireland; a well drained catchment, underlain by karstified Carboniferous limestone, and a poorly drained catchment, underlain by Silurian greywacke.
Depth specific low-flow groundwater sampling was used to evaluate the hydrochemical stratification in groundwater. Groundwater samples, as well as surface water samples, along river courses were analysed for nitrogen species (NO3, NH4 and NO2) and nitrate isotopes (d15N and d18O) as well as field parameters and major ions
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The dominant nitrate (NO3) groundwater pathway in the poorly drained greywacke catchment is through the shallow weathered bedrock, as indicated by transmissivity values and the ionic and isotopic signatures, and a clear reduction in NO3 concentration is observed with depth. A similar chloride trend would suggest dilution is a major factor, however d15N and d18O isotopic values producing an enrichment ratio of 1.8 indicate that denitrification is also an important process involved in the fate of the NO3 within the groundwater flow system. This consistent trend with depth is in contrast to the stratification pattern observed in the karstified catchment. NO3 was not detected in the shallow groundwater pathway; the dominant groundwater pathway is in the deeper groundwater where there is little change in the nitrate isotope values with depth (d15N values range between 4.1 and 4.6 ‰). This deeper groundwater contributes the dominant proportion of the river flow through a number of springs. As a result, the deeper groundwater, springs and river have a similar ionic signature and NO3 concentration range (23 ± 3 mg/l). Despite this pattern, the NO3 isotopes show a distinct difference in isotopic values between the deeper groundwater in the diffuse karst and the springs indicating some denitrification is occurring during groundwater discharge into the river. Furthermore the isotopes give an indication of the variability of the spatial extent of the springs and the complexities of the fissures through which they are fed. The results of this study clearly show the importance of the geology in the fate and transport of NO3 in agricultural catchments.

A millennial record of environmental change in peat deposits from the Misten bog (East Belgium)

In this study, palaeoenvironmental changes recorded in the top metre of a peat profile (Misten bog, East Belgium) were investigated using a multiproxy approach. Proxies include bulk density, Ti and Si content, pollen, macrofossils, d13C on specific Sphagnum stems, and d13C–d18O on Sphagnum leaves. A high-resolution chronology was generated using 210Pb measurements and 22 14C AMS dates on carefully selected Sphagnum macrofossils. d13C only records large change in mire surface wetness. This is partly due to the fact that the core was taken from the edge of a hummock, which may make it difficult to track small isotopic changes. The d13C signal seems to be dependent upon the Sphagnum species composition. For example, a change between Sphagnum section Cuspidata towards Sphagnum imbricatum causes a significant drop in the d13C values. On the whole, the C and O isotopes record two shallow pool phases during the 8th–9th and the 13th centuries. Pollen and atmospheric soil dust (ASD) fluxes records increased human occupation in the area. There may be some climatic signals in the ASD flux, but they are difficult to decipher from the increasing human impact (land clearance, agriculture) during the last millennium. The variations in the proxies are not always synchronous, suggesting different triggering factors (temperature, wetness, windiness) for each proxy. This study also emphasizes that, compared to studies dealing with pollution using geochemical proxies, palaeoclimatic inferences from peat bogs need as many proxies as possible, together with highly accurate and precise age-models, in order to better understand climate variability and their consequences during the Holocene.