Monoaromatic compounds in ambient air of various cities: A focus on correlations between the xylenes and ethylbenzene

Speciation of o-xylene, m-xylene, p-xylene and ethylbenzene was performed by gas chromatography from ambient air and liquid fuel samples collected at various locations in 19 cities in Europe, Asia and South America. The xylene's mixing ratios were compared to each other from the various locations, which included urban air, traffic air and liquid fuel. For all samples, the xylenes exhibited robust correlations, and the slopes remained constant. The m-xylene/p-xylene ratio was found to be 2.33±0.30, and the m-xylene/o-xylene ratio was found to be 1.84±0.25. These ratios remain persistent even in biomass combustion experiments (in South America and South Africa). Comparing the xylenes to toluene and benzene indicate that combustion, but not fuel evaporation, is the major common source of the xylenes in areas dominated by automotive emissions. Although a wide range of combustion types and combustion efficiencies were encountered throughout all the locations investigated, xylenes and ethylbenzene ratios remained persistent. We discuss the implications of the constancies in the xylenes and ethylbenzene ratios on atmospheric chemistry

Influence of the public transportation system on the air quality of a major urban center. A case study: Milan, Italy

A sampling campaign was conducted in the city of Milan, Italy before and during a transportation strike in January 2004. This strike provided a unique opportunity to investigate the influence of public transportation on the air quality in a major metropolitan area. Twenty-four air samples were collected each day around the city on January 2nd, 7th and 9th. The samples were analyzed for methane, carbon monoxide, non-methane hydrocarbons (NMHCs), halocarbons and alkyl nitrates. Significant differences in the mixing ratios were observed among the three days of sampling, with January 2nd showing the lowest concentrations as a result of decreased activity in the city during the holiday season. January 9th showed the highest NMHC concentrations because of increased vehicular activity in the city due to a public transportation strike. This paper investigates the correlation between the increased number of vehicles and decreased air quality because of a reduction in public transportation. Computer simulations were able to reproduce measurements of ozone production during the January 2004 strike and a July 2005 strike. The measurements and simulations suggest that reduced VOC emissions due to the existence of public transportation lowers peak ozone by 11-33% during the summer months. © 2008 Elsevier Ltd. All rights reserved

Excavations at the Viking Barrow Cemetery at Heath Wood, Ingleby, Derbyshire

The cemetery at Heath Wood, Ingleby, Derbyshire, is the only known Scandinavian cremation cemetery in the British Isles. It comprises fifty-nine barrows, of which about one-third have been excavated on previous occasions, although earlier excavators concluded that some were empty cenotaph mounds. From 1998 to 2000 three barrows were examined. Our investigations have suggested that each of the barrows contained a burial, although not all contain evidence of a pyre. A full report of the 1998-2000 excavations is provided, alongside a summary of the earlier finds. The relationship of Heath Wood to the neighbouring site at Repton is examined, in order to understand its significance for the Scandinavian settlement of the Danelaw. It is concluded that Heath Wood may have been a war cemetery of the Viking Great Army of AD 873-8

Biological Records Centre Annual Report 2005-2006

The period covered by this report is the first year of a new six-year partnership between CEH and JNCC. For this period, there is increased emphasis on targeted survey, on analysis and interpretation and on communications and outreach. These activities were always part of BRC’s work, but they have been given greater prominence as a result of rapid developments in information technology. Data are increasingly reaching BRC in electronic form, so that the effort of data entry and collation is reduced. The data, collected by many volunteers and then collated and analysed at BRC, document the changing status and distribution of plants and animals in Britain. Distribution maps are published in atlases and are available via the internet through the NBN Gateway. The effects of change or loss of habitats, the influence of climate change and the consequences of changing water quality are all examples of the environmental factors that affect our biodiversity and which BRC aims to document and understand. The results are vital for developing environmental policies, to support conservation, and for fundamental ecological research. BRC is funded jointly by JNCC and NERC through a partnership based on a Memorandum of Agreement (MoA). The partnership started in 1973 when the Nature Conservancy was divided to form the successor bodies Nature Conservancy Council (NCC) and Institute of Terrestrial Ecology (ITE). NCC was in turn divided further to form JNCC and three Country Agencies, while ITE was merged with other NERC units to form CEH. Through all these changes, the partnership has been maintained. A six-year memorandum of agreement ended on 31 January 2005 (Hill et al. 2005). The present report covers the first full year, 2005-6, of the new agreement for 2005-2010. Rapid progress in information technology continues to be highly beneficial for BRC, whose data are increasingly used by the UK country conservation agencies, environmental consultants, NGOs, research workers, policy makers and volunteers. It is gratifying to know that, through our ability to display data on the National Biodiversity Network (NBN) Gateway, some of our data suppliers now have immediate access to their own data in a convenient form. The year 2005-6 has been one of steady progress, with new datasets added to BRC, substantial additions to existing data, and improved communication with the NBN Gateway. The most high profile activity of the year has been the Harlequin Ladybird Survey, which has enabled us to observe the early stages of colonization by a mobile insect in greater detail than has been possible in any previous case

Trends in total column ozone measurements

It is important to ensure the best available data are used in any determination of possible trends in total ozone in order to have the most accurate estimates of any trends and the associated uncertainties. Accordingly, the existing total ozone records were examined in considerable detail. Once the best data set has been produced, the statistical analysis must examine the data for any effects that might indicate changes in the behavior of global total ozone. The changes at any individual measuring station could be local in nature, and herein, particular attention was paid to the seasonal and latitudinal variations of total ozone, because two dimensional photochemical models indicate that any changes in total ozone would be most pronounced at high latitudes during the winter months. The conclusions derived from this detailed examination of available total ozone can be split into two categories, one concerning the quality and the other the statistical analysis of the total ozone record

Trends in source gases

Source gases are defined as those gases that, by their breakdown, introduce into the stratosphere halogen, hydrogen, and nitrogen compounds that are important in stratospheric ozone destruction. Given here is an update of the existing concentration time series for chlorocarbons, nitrous oxide, and methane. Also reviewed is information on halogen containing species and the use of these data for establishing trends. Also reviewed is evidence on trends in trace gases that influence tropospheric chemistry and thus the tropospheric lifetimes of source gases, such as carbon dioxide, carbon monoxide, or nitrogen oxides. Much of the information is given in tabular form

Limitations of variable number of tandem repeat typing identified through whole genome sequencing of Mycobacterium avium subsp. paratuberculosis on a national and herd level

Background: Mycobacterium avium subsp. paratuberculosis (MAP), the causative bacterium of Johne’s disease in dairy cattle, is widespread in the Canadian dairy industry and has significant economic and animal welfare implications. An understanding of the population dynamics of MAP can be used to identify introduction events, improve control efforts and target transmission pathways, although this requires an adequate understanding of MAP diversity and distribution between herds and across the country. Whole genome sequencing (WGS) offers a detailed assessment of the SNP-level diversity and genetic relationship of isolates, whereas several molecular typing techniques used to investigate the molecular epidemiology of MAP, such as variable number of tandem repeat (VNTR) typing, target relatively unstable repetitive elements in the genome that may be too unpredictable to draw accurate conclusions. The objective of this study was to evaluate the diversity of bovine MAP isolates in Canadian dairy herds using WGS and then determine if VNTR typing can distinguish truly related and unrelated isolates.<p></p> Results: Phylogenetic analysis based on 3,039 SNPs identified through WGS of 124 MAP isolates identified eight genetically distinct subtypes in dairy herds from seven Canadian provinces, with the dominant type including over 80% of MAP isolates. VNTR typing of 527 MAP isolates identified 12 types, including “bison type” isolates, from seven different herds. At a national level, MAP isolates differed from each other by 1–2 to 239–240 SNPs, regardless of whether they belonged to the same or different VNTR types. A herd-level analysis of MAP isolates demonstrated that VNTR typing may both over-estimate and under-estimate the relatedness of MAP isolates found within a single herd.<p></p> Conclusions: The presence of multiple MAP subtypes in Canada suggests multiple introductions into the country including what has now become one dominant type, an important finding for Johne’s disease control. VNTR typing often failed to identify closely and distantly related isolates, limiting the applicability of using this typing scheme to study the molecular epidemiology of MAP at a national and herd-level.<p></p&gt

Quenched QCD with O(a) improvement: I. The spectrum of light hadrons

We present a comprehensive study of the masses of pseudoscalar and vector mesons, as well as octet and decuplet baryons computed in O(a) improved quenched lattice QCD. Results have been obtained using the non-perturbative definition of the improvement coefficient c_sw, and also its estimate in tadpole improved perturbation theory. We investigate effects of improvement on the incidence of exceptional configurations, mass splittings and the parameter J. By combining the results obtained using non-perturbative and tadpole improvement in a simultaneous continuum extrapolation we can compare our spectral data to experiment. We confirm earlier findings by the CP-PACS Collaboration that the quenched light hadron spectrum agrees with experiment at the 10% level.Comment: 36 pages, 7 postscript figures, REVTEX; typo in Table XVIII corrected; extended discussion of finite-size effects in sections III and VII; version to appear in Phys. Rev.