Quantitative analysis of the reactivity of formate species seen by DRIFTS over a Au/Ce(La)O2 water–gas shift catalyst: First unambiguous evidence of the minority role of formates as reaction intermediates

The reactivity of the species formed at the surface of a Au/Ce(La)O2 catalyst during the water������¢���¯���¿���½���¯���¿���½gas shift (WGS) reaction were investigated by operando diffuse reflectance Fourier transform spectroscopy (DRIFTS) at the chemical steady state during isotopic transient kinetic analyses (SSITKA). The exchanges of the reaction product CO2 and of formate and carbonate surface species were followed during an isotopic exchange of the reactant CO using a DRIFTS cell as a single reactor. The DRIFTS cell was a modified commercial cell that yielded identical reaction rates to that measured over a quartz plug-flow reactor. The DRIFTS signal was used to quantify the relative oncentrations of the surface species and CO2. The analysis of the formate exchange curves between 428 and 493 K showed that at least two levels of reactivity were present. ������¢���¯���¿���½���¯���¿���½Slow formates������¢���¯���¿���½���¯���¿���½ displayed an exchange rate constant 10- to 20-fold slower than that of the reaction product CO2. ������¢���¯���¿���½���¯���¿���½Fast formates������¢���¯���¿���½���¯���¿���½ were exchanged on a time scale similar to that of CO2. Multiple nonreactive readsorption of CO2 took place, accounting for the kinetics of the exchange of CO2(g) and making it impossible to determine the number of active sites through the SSITKA technique. The concentration (in mol g������¢���¯���¿���½���¯���¿���½1) of formates on the catalyst was determined through a calibration curve and allowed calculation of the specific rate of formate decomposition. The rate of CO2 formation was more than an order of magnitude higher than the rate of decomposition of formates (slow + fast species), indicating that all of the formates detected by DRIFTS could not be the main reaction intermediates in the production of CO2. This work stresses the importance of full quantitative analyses (measuring both rate constants and adsorbate concentrations) when investigating the role of adsorbates as potential reaction intermediates, and illustrates how even reactive species seen by DRIFTS may be unimportant in the overall reaction scheme.

Long-term ecology of native pinewood communities in East Glen Affric, Scotland

Fossil pollen, stomata and charcoal were examined from a lake sedimentary sequence in the Glen Affric National Nature Reserve, one of the largest areas of remnant native pine woodland in Scotland, in order to assess ecosystem dynamics over the last 11 000 years. Results reveal that pinewood communities have been continuously present in East Glen Affric for the last 8300 years. Pinus sylvestris fi rst arrived in the area around 9900 cal. BP, but occurred in only low abundance for the subsequent 1600 years. Pine populations expanded around 8300 cal. BP and remained in relatively constant abundance throughout the remainder of the Holocene. There is no evidence of a hypothesized regional mid-Holocene ‘ pine decline ’ at the site. Charcoal results reveal that pinewood communities in East Glen Affric do not appear to have been dependent on fire for either their establishment or their maintenance as has previously been suggested.

Impacts of climate change on species, populations and communities: palaeobiogeographical insights and frontiers

Understanding climate change and its potential impact on species, populations and communities is one of the most pressing questions of twenty-fi rst-century conservation planning. Palaeobiogeographers working on Cenozoic fossil records and other lines of evidence are producing important insights into the dynamic nature of climate and the equally dynamic response of species, populations and communities. Climatic variations ranging in length from multimillennia to decades run throughout the palaeo-records of the Quaternary and earlier Cenozoic and have been shown to have had impacts ranging from changes in the genetic structure and morphology of individual species, population sizes and distributions, community composition to large-scale bio-diversity gradients. The biogeographical impacts of climate change may be due directly to the effects of alterations in temperature and moisture on species, or they may arise due to changes in factors such as disturbance regimes. Much of the recent progress in the application of palaeobiogegraphy to issues of climate change and its impacts can be attributed to developments along a number of still advancing methodological frontiers. These include increasingly finely resolved chronological resolution, more refi ned atmosphere-biosphere modelling, new biological and chemical techniques in reconstructing past species distributions and past climates, the development of large and readily accessible geo-referenced databases of biogeographical and climatic information, and new approaches in fossil morphological analysis and new molecular DNA techniques.

Differences in composition of macroinvertebrate communities with invasive and native Gammarus spp. (Crustacea : Amphipoda)

1. Assessing the effects on communities of invasive species is often confounded by environmental factors. In Irish rivers, the introduced amphipod Gammarus pulex replaces the native G. duebeni celticus in lowland stretches. The two amphipods are associated with different macroinvertebrate communities, which may in part be the result of natural longitudinal physicochemical change. However, this hinders assessment of any direct community impacts of the invasive as compared with the native species. Here, we report on a fortuitous circumstance that allowed us to uncouple the community effects of Gammarus species from environmental differences.

Non-indigenous marine macroalgae in native communities: a case study in the British Isles

It has traditionally been considered that areas with high natural species richness are likely to be more resistant to non-indigenous species than those with lower numbers of species. However, this theory has been the subject of a debate over the last decade, since some studies have shown the opposite trend. In the present study, a macroalgal survey was carried out at 24 localities in Northern Ireland and southern England, using a quadrat approach in the lower littoral. The two opposing hypotheses were tested (negative versus positive relationship between native and non-indigenous species richness) in this marine environment. The effect of the presence of 'impacts', potential sources of disturbance and species introduction (e.g. marina, harbour or aquaculture), was also tested. A positive relationship was found between the number of non-indigenous species and the native species richness at the three different scales tested (quadrats, sites and localities). At no scale did a richer native assemblage appear to restrict the establishment of introduced species. The analyses revealed greater species richness and different community composition, as well as more non-indigenous species, in southern England relative to Northern Ireland. The presence of the considered impacts had an effect on the community composition and species richness in southern England but not in Northern Ireland. Such impacts had no effect on the non-indigenous species richness in either area.

Are Northern Ireland’s communities dividing? Evidence from geographically consistent Census of Population data, 1971–2001

There is an extensive literature on various aspects of segregation in Northern Ireland (NI). However, there are no census-based analyses of population change and residential segregation that cover the entire 1971 – 2001 period using consistent geographical units through time for all NI. This shortcoming is addressed in this paper by an analysis of changes in (ihs1) the spatial distribution of population and (iihs1) residential segregation between 1971 and 2001 using the NI Grid-Square Product comprising data for a set of 1 rm km2 cells that cover all populated areas in NI. The substantive issue of whether NI has become more segregated through time is addressed as are questions about measuring change through time using the census and the importance of spatial scale. One important conclusion is that NI indeed became more residentially segregated between 1971 and 2001, but that residential segregation in 2001 remained approximately at its 1991 level according to most indicators.

Housing Rural Communities: Connecting Rural Dwellings to Rural Development in Ireland

This paper explores the interaction between rural development policy and spatial planning policies for rural housing within the context of the island of Ireland. It draws on research commissioned by the Northern Ireland Housing Executive for a high level review of its rural housing policy. The paper highlights issues of wider relevance comprising a strained relationship between rural communities and rural planning, and argues for the adoption of cultural, environmental and community values within the rural planning policy arena.