3541. Year-long measurements of C1-C3 halocarbons at an urban site and their relationship with meteorological parametersM Anwar K Khan, M Iqbal Mead, Iain R. White, Ben Golledge, Graham Nickless, Alan Knights, Damien Martin, Alison C Rivett, Brian G R Greally, Dudley E Shallcross, 2009, original scientific article Abstract: The mixing ratios of 11 C1–C3 halocarbons have been measured using a GC–twin‐linked ECD system over the period from October 2004 to December 2005 at an urban site in Bristol, UK. Time series and seasonal variations of the halocarbons were analysed over the period to determine biogenic and anthropogenic sources and sinks. Correlations between the target halocarbons were also observed, suggesting common sources within the area. Wind rose plots for all halocarbons have been used to assist in the determination of halocarbons sources. Halocarbon concentrations are highest at low‐wind speeds and decrease as wind speed increases, a few species (CCl4 and CH3Cl most notably) rise at very high‐wind speeds suggesting release from the Bristol Channel.
Keywords: adsorption–desorption system, anthropogenic halocarbons, biogenic halocarbons, electron capture detector, gas chromatography, methyl bromide
Published in RUNG: 18.07.2019; Views: 3034; Downloads: 0
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3542. Short-range urban dispersion experiments using fixed and moving sourcesDudley E. Shallcross, Damien Martin, Catheryn S Price, Graham Nickless, Iain R. White, Fredrik Petterson, Rex E Britter, Marina K Neophytou, James Tate, Alison S Tomlin, Stephen E Belcher, Janet F Barlow, Alan Robins, 2009, original scientific article Abstract: Four perfluorocarbon tracer dispersion experiments were carried out in central London, United Kingdom in 2004. These experiments were supplementary to the dispersion of air pollution and penetration into the local environment (DAPPLE) campaign and consisted of ground level releases, roof level releases and mobile releases; the latter are believed to be the first such experiments to be undertaken. A detailed description of the experiments including release, sampling, analysis and wind observations is given. The characteristics of dispersion from the fixed and mobile sources are discussed and contrasted, in particular, the decay in concentration levels away from the source location and the additional variability that results from the non-uniformity of vehicle speed.
Keywords: dapple, perfluorocarbon, tracer, mobile source
Published in RUNG: 18.07.2019; Views: 2977; Downloads: 0
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3543. Stable carbon isotope analysis of selected halocarbons at parts per trillion concentration in an urban locationM Iqbal Mead, M Anwar H Khan, Ian D Bull, Iain R. White, Graham Nickless, Dudley E Shallcross, 2008, original scientific article Abstract: ∂13C values of a suite of halocarbons have been determined in an urban background site in Bristol, UK. A novel mobile preconcentration system, based on the use of multi-adsorbent sample tubes, has been developed for trapping relatively large-volume air samples in potentially remote areas. An Adsorption Desorption System-Gas Chromatography-Electron Capture Detector was used to measure the mixing ratios of the selected halocarbon species, while a Gas ChromatographyCombustionIsotope Ratio Mass Spectrometer was used to determine ∂13C values. For the species with strong local sources, the variation of isotope ratios has been observed over the experimental period. Some of the results reported in the present study differ from previously reported values and reasons for this are discussed. The reporting of different ∂13C values for selected halocarbons from different areas in the present study suggests that ∂13C values may be used to determine the relative magnitudes of anthropogenic and biogenic sources.
Keywords: Adsorption Desorption System (ADS), Automated Thermal Desorber (ATD), Electron Capture Detector (ECD), Gas Chromatography (GC), Isotope Ratio Mass Spectrometry (IRMS)
Published in RUNG: 18.07.2019; Views: 3195; Downloads: 0
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3545. Methyl halide emission estimates from domestic biomass burning in AfricaM Iqbal Mead, M Anwar H Khan, Iain R. White, Graham Nicless, Dudley E Shallcross, 2008, original scientific article Abstract: Inventories of methyl halide emissions from domestic burning of biomass in Africa, from 1950 to the present day and projected to 2030, have been constructed. By combining emission factors from Andreae and Merlet [2001. Emission of trace gases and aerosols from biomass burning. Global Biogeochemical Cycles 15, 955-966], the biomass burning estimates from Yevich and Logan [2003. An assessment of biofuel use and burning of agricultural waste in the developing world. Global Biogeochemical Cycles 17(4), 1095, doi:10.1029/2002GB001952] and the population data from the UN population division, the emission of methyl halides from domestic biomass usage in Africa has been estimated. Data from this study suggest that methyl halide emissions from domestic biomass burning have increased by a factor of 4-5 from 1950 to 2005 and based on the expected population growth could double over the next 25 years. This estimated change has a non-negligible impact on the atmospheric budgets of methyl halides.
Keywords: Africa, Biofuel, Domestic biomass burning, Emission factor, Methyl halide
Published in RUNG: 17.07.2019; Views: 3306; Downloads: 0
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3546. A study of pollutant concentration variability in an urban street under low wind speedsDamien Martin, Catheryn S Price, Iain R. White, Graham Nickless, Adrian Dobre, Dudley E Shallcross, 2008, original scientific article Abstract: The short time‐scale variability in pollutant concentrations in an urban street under very low wind speed conditions and short source–receptor distance has been investigated using the inert tracer sulfur hexafluoride (SF6) as a continuous point‐source (release times ≥ 5 min), and fast detection using separation by gas chromatography coupled with a μ‐electron capture detector (ECD). The results are complex but can be broadly interpreted in terms of horizontal wind speed and direction coherence. Comparisons with a simple dispersion model suggest that observed time‐averaged maximum concentrations approach predicted values, whilst instantaneous maximum concentrations vary greatly and would therefore be difficult to predict.
Keywords: dispersion, tracer, intermittency
Published in RUNG: 17.07.2019; Views: 3131; Downloads: 128
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3547. An estimation of the global emission of methyl bromide from rapeseed (Brassica napus) from 1961 to 20032008, original scientific article Abstract: Gan et al. [Gan, J., Yates, S.R., Ohr, H.D., Sims, J.J., 1998. Production of methyl bromide by terrestrial higher plants. Geophysical Research Letters 25 (19), 3595–3598] have reported that plants of the family Brassicaceae take up bromide from soils and subsequently release methyl bromide (CH3Br) to the atmosphere deriving a significant emission from this source of about 7 Gg(109 g) yr−1. In this study, we determine a yearly global emission rate for CH3Br from one such species, rapeseed, from 1961 to 2003 using data on crop harvest index and growth rate in conjunction with global production data. This study suggests that CH3Br emissions from rapeseed have increased 10-fold from 1961 to 2003 and by a factor of 3–4 since 1980. It also suggests that the geographical distribution of emissions has also changed substantially in the last 40 yr. The annual emission of CH3Br from mustard and cabbage is also estimated; whilst relative levels emitted from these species are less significant, as these crops are continually exploited for new applications CH3Br emissions are set to increase.
Keywords: CH3Br, Rapeseed, Brassica, Ozone, Biosphere
Published in RUNG: 17.07.2019; Views: 2975; Downloads: 0
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3550. Experimental determination of black and brown carbon heating rate from mid-latitudes to the Arctic ocean, and related energy gradientLuca Ferrero, Luca Cataldi, Griša Močnik, Asta Gregorič, Piotr Markuszewski, Przemek Makuch, Paulina Pakszys, Tomek Petelski, E. Bolzacchini, Tymon Zielinski, 2019, published scientific conference contribution abstract Keywords: black carbon, heating rate, Arctic
Published in RUNG: 17.07.2019; Views: 3600; Downloads: 0
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