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Atmospheric Environment (v.41, #38)
Oxygenated volatile organic compounds (OVOCs) at an urban background site in Zürich (Europe): Seasonal variation and source allocation by Geir Legreid; Loov Jacob Balzani Lööv; Johannes Staehelin; Christoph Hueglin; Matthias Hill; Brigitte Buchmann; Andre S.H. Prevot; Stefan Reimann (pp. 8409-8423).
Twenty-one oxygenated volatile organic compounds (OVOCs) were measured in four seasonal campaigns at an urban background site in Zürich (Switzerland) with a newly developed double adsorbent sampling unit coupled to a gas chromatograph–mass spectrometer (GC–MS). In addition, selected non-methane hydrocarbons (NMHCs) were measured, as well as formaldehyde in the summer and winter campaign. The most abundant compound measured in all seasons was ethanol, with peak values of more than 60ppb. Its seasonal variation with a lower mean value in summer compared to that in winter implied mostly anthropogenic sources. In contrast, compounds with additional biogenic sources, or compounds known to be produced in the troposphere by oxidation processes, had seasonal maxima in summer (e.g. methanol, acetone, formaldehyde, methacrolein and 2-butenone (methyl vinyl ketone, MVK)).For the OVOCs it was estimated that local sources contributed 40% and 49% to the mixing ratios of the measured compounds in summer and in winter, respectively. Combustion was estimated to contribute 75% to these local sources independent of the season. About 50% of both the OVOC and NMHC levels in Zürich could be explained by the regional background, which included regional biogenic and anthropogenic sources in addition to secondary production. Industrial sources were identified for acetone, butanone (methyl ethyl ketone, MEK), n-propanol, iso-propanol, n-butanol, ethyl acetate and butyl acetate.
Keywords: OVOCs; Ozone precursors; Combustion; Source-ratio-tracer method; Urban emissions
Decline in the concentrations of chlorofluorocarbons (CFC-11, CFC-12 and CFC-113) in an urban area of Beijing, China by Dajun Qin (pp. 8424-8430).
During this study 352 whole air samples were collected in an urban area of Beijing between January 2005 and March 2007. The temporal variation of the concentrations of chlorofluorocarbons (CFCs: CFC-11, CFC-12, and CFC-113) in air in the Beijing urban atmosphere is presented and discussed. The weighted mean monthly values of these concentrations have been compared with the data from the north hemisphere. It has been concluded that, in the observed period of time, the mean enhancement of CFCs was relatively small, with increase of 10–15%, with respect to the global background. Change rate in concentrations of CFCs is −1.39, −1.04, and −0.16pptv/month for CFC-11, CFC-12, and CFC-113, respectively. The tendency of the CFC concentration of the three compounds toward background values is observed to fall and indicates that limitation of emission of CFCs is taking effect, under the Montreal Protocol.
Keywords: Urban air; CFCs; Ozone depletion gases; Beijing
Salinity of marine aerosols in a Brazilian coastal area—Influence of wind regime by G.R. Meira; C. Andrade; C. Alonso; I.J. Padaratz; J.C. Borba Jr (pp. 8431-8441).
This paper presents salinity data of marine aerosols in a Brazilian coastal area at sites closer to the shore and discusses the influence of wind regime. Results show that measurements of marine salt deposition are strongly influenced by wind speeds above the critical value of 3.0ms−1. Although there is no agreement in literature yet as to how much this threshold is, the level of 3.0ms−1 is similar to the one found in a study carried out in Spain. An exponential variation of salt concentration with wind speed is presented in previous published papers. However, in the studied case, another relationship is proposed, which is based on chloride deposition on the wet candle device and wind speeds higher than 3.0ms−1 weighted by the accumulated time in which these wind speeds are observed, what seems to be particularly useful when wind speed ranges around the critical value.
Keywords: Chloride deposition; Marine aerosol; Wet candle; Wind regime; Wind speed
A novel air pollution index based on the relative risk of daily mortality associated with short-term exposure to common air pollutants by E.K. Eugene K. Cairncross; Juanette John; Mark Zunckel (pp. 8442-8454).
Communication of the complex relationship between air pollutant exposure and ill health is essential to an air pollution information system. We propose a novel air pollution index (API) system based on the relative risk of the well-established increased daily mortality associated with short-term exposure to common air pollutants: particulate matter (PM10, PM2.5), sulphur dioxide, ozone, nitrogen dioxide and carbon monoxide.To construct our index system, the total incremental daily mortality risk of exposure to these pollutants was associated with an index value ranging from 0 to 10. The index scale is linear with respect to incremental risk. The index is open ended, although, for convenience, an index of 10 is assigned for exposures yielding indices ⩾10.To illustrate the application of this API system, a set of published relative risk factors are used to calculate sub-index values for each pollutant, in the range of air pollutant concentrations commonly experienced in urban areas. To account for the reality of ubiquitous simultaneous exposure to a mixture of the common air pollutants, the final API is the sum of the normalised values of the individual indices for PM10, PM2.5, sulphur dioxide, ozone, nitrogen dioxide and carbon monoxide. This establishes a self-consistent index system where a given index value corresponds to the same daily mortality risk associated with the combined exposure to the common air pollutants. To facilitate health-risk communication, index values are colour coded and associated with broad health-risk descriptors. The utility of the proposed API is illustrated by applying it to monitored ambient concentration data for the City of Cape Town, South Africa.
Keywords: Air pollution/quality index; Health-risk communication; DAPPS; Multiple pollutant exposure; South Africa
Quantifying the effect of urban tree planting on concentrations and depositions of PM10 in two UK conurbations by A.G. McDonald; W.J. Bealey; D. Fowler; U. Dragosits; U. Skiba; R.I. Smith; R.G. Donovan; H.E. Brett; C.N. Hewitt; E. Nemitz (pp. 8455-8467).
Trees are efficient scavengers of particulate matter and are characterised by higher rates of dry deposition than other land types. To estimate the potential of urban tree planting for the mitigation of urban PM10 concentrations, an atmospheric transport model was used to simulate the transport and deposition of PM10 across two UK conurbations (the West Midlands and Glasgow). Tree planting was simulated by modifying the land cover database, using GIS techniques and field surveys to estimate reasonable planting potentials. The model predicts that increasing total tree cover in West Midlands from 3.7% to 16.5% reduces average primary PM10 concentrations by 10% from 2.3 to 2.1μgm−3 removing 110ton per year of primary PM10 from the atmosphere. Increasing tree cover of the West Midlands to a theoretical maximum of 54% by planting all available green space would reduce the average PM10 concentration by 26%, removing 200ton of primary PM10 per year. Similarly, for Glasgow, increasing tree cover from 3.6% to 8% reduces primary PM10 concentrations by 2%, removing 4ton of primary PM10 per year. Increasing tree cover to 21% would reduce primary PM10 air concentrations by 7%, removing 13ton of primary PM10 per year.
Keywords: Urban trees; PM; 10; Deposition velocity; Dry deposition
Rate constants for the atmospheric reactions of alkoxy radicals: An updated estimation method by Roger Atkinson (pp. 8468-8485).
Alkoxy radicals are key intermediates in the atmospheric degradations of volatile organic compounds, and can typically undergo reaction with O2, unimolecular decomposition or unimolecular isomerization. Previous structure–reactivity relationships for the estimation of rate constants for these processes for alkoxy radicals [Atkinson, R., 1997. Atmospheric reactions of alkoxy and β-hydroxyalkoxy radicals. International Journal of Chemical Kinetics, 29, 99–111; Aschmann, S.M., Atkinson, R., 1999. Products of the gas-phase reactions of the OH radical with n-butyl methyl ether and 2-isopropoxyethanol: reactions of ROC(O)< radicals. International Journal of Chemical Kinetics, 31, 501–513] have been updated to incorporate recent kinetic data from absolute and relative rate studies. Temperature-dependent rate expressions are derived allowing rate constants for all three of these alkoxy radical reaction pathways to be calculated at atmospherically relevant temperatures.
Keywords: Alkoxy radical; Decomposition reaction; Reaction with O; 2; Isomerization reaction; Volatile organic compounds; Atmospheric chemistry
Scenarios of global anthropogenic emissions of air pollutants and methane until 2030 by Janusz Cofala; Markus Amann; Zbigniew Klimont; Kaarle Kupiainen; Höglund-Isaksson Lena Höglund-Isaksson (pp. 8486-8499).
We have used a global version of the Regional Air Pollution Information and Simulation (RAINS) model to estimate anthropogenic emissions of the air pollution precursors sulphur dioxide (SO2), nitrogen oxides (NO x), carbon monoxide (CO), primary carbonaceous particles of black carbon (BC), organic carbon (OC) and methane (CH4). We developed two scenarios to constrain the possible range of future emissions. As a baseline, we investigated the future emission levels that would result from the implementation of the already adopted emission control legislation in each country, based on the current national expectations of economic development. Alternatively, we explored the lowest emission levels that could be achieved with the most advanced emission control technologies that are on the market today. This paper describes data sources and our assumptions on activity data, emission factors and the penetration of pollution control measures. We estimate that, with current expectations on future economic development and with the present air quality legislation, global anthropogenic emissions of SO2 and NO x would slightly decrease between 2000 and 2030. For carbonaceous particles and CO, reductions between 20% and 35% are computed, while for CH4 an increase of about 50% is calculated. Full application of currently available emission control technologies, however, could achieve substantially lower emissions levels, with decreases up to 30% for CH4, 40% for CO and BC, and nearly 80% for SO2.
Keywords: Air pollution; Climate change; Anthropogenic emissions; Global analysis
Regional effects and efficiency of flue gas desulphurization in the Carpathian Basin by Tamas Benko; Claas Teichmann; Peter Mizsey; Daniela Jacob (pp. 8500-8510).
Although sulphur emissions (mainly as SO2) have been continuously decreasing over the last 20 years in most western industrialized countries, localized SO2 problems still exist in conjunction with strong local emission, meteorological, and topographical factors. In this study, the effect of supplementary installed flue gas desulphurization (FGD) units at high-capacity power plants on regional air pollution in the Carpathian Basin is investigated. The dispersion and accumulation of the SO2 air pollutant are studied with the regional three-dimensional on-line atmosphere-chemistry model REMOTE. The changes in the SO2 air pollution are investigated by parallel simulations in a case study, where the single modified parameter is the SO2 emission rate. The results show that FGD units significantly reduce the horizontal and the vertical dispersion of the emitted SO2, and its transboundary transport, too. Beside the SO2 removal efficiency, the dispersion and accumulation also depend on the seasonal weather conditions. During winter, the dispersion and accumulation are higher than in other seasons. Due to this phenomenon, higher SO2 removal efficiency is needed to guarantee similar air quality features like in the other seasons.
Keywords: Regional modelling; Flue gas desulphurization; Atmospheric SO; 2; chemistry; Carpathian Basin
Springtime depletion of tropospheric ozone, gaseous elemental mercury and non-methane hydrocarbons in the European Arctic, and its relation to atmospheric transport by Kristina Eneroth; Holmen Kim Holmén; Torunn Berg; Norbert Schmidbauer; Sverre Solberg (pp. 8511-8526).
Using a trajectory climatology for the period 1992–2001 we have examined how seasonal changes in transport cause changes in the concentrations of tropospheric ozone (O3), gaseous elemental mercury (GEM) and non-methane hydrocarbons (NMHCs) observed at the Mt. Zeppelin station, Ny-Ålesund (78.9°N, 11.9°E). During April–June O3 depletion events were frequently observed in connection with air transport across the Arctic Basin. The O3 loss was most pronounced in air masses advected close to the surface. This result supports the idea that the O3 depletion reactions take place in the lowermost part of the atmosphere in the central Arctic Basin. A strong positive correlation between springtime O3 depletion events and the oxidation of GEM to divalent mercury was found. During air mass advection from Siberia, the Barents Sea and the Norwegian Sea the strongest correlation was observed during April–May, whereas air masses originating from the Canadian Arctic and the central Arctic areas showed the highest O3–GEM correlation in May–June. We suggest that this 1-month lag could either be due to the position of the marginal ice zone or temperature differences between the northwestern and northeastern air masses. In connection with springtime O3 depletion events low concentrations of some NMHCs, especially ethane and ethyne, were observed, indicating that both bromine (ethyne oxidant) and chlorine radicals (ethane oxidant) are present in the Arctic atmosphere during spring. In winter, negative correlations between O3 and NMHCs were found in connection with air transport from Europe and Siberia, which we interpret as O3 destruction taking place in industrially contaminated plumes.
Keywords: Arctic; Tropospheric ozone depletion; Mercury; Non-methane hydrocarbons; Trajectories
Dioxins, furans and polycyclic aromatic hydrocarbons emissions from a hospital and cemetery waste incinerator by Giuseppe Mininni; Andrea Sbrilli; Camilla Maria Braguglia; Ettore Guerriero; Dario Marani; Mauro Rotatori (pp. 8527-8536).
An experimental campaign was carried out on a hospital and cemetery waste incineration plant in order to assess the emissions of polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs) and polycyclic aromatic hydrocarbons (PAHs). Raw gases were sampled in the afterburning chamber, using a specifically designed device, after the heat recovery section and at the stack. Samples of slags from the combustion chamber and fly ashes from the bag filter were also collected and analyzed. PCDD/Fs and PAHs concentrations in exhaust gas after the heat exchanger (200–350°C) decreased in comparison with the values detected in the afterburning chamber. Pollutant mass balance regarding the heat exchanger did not confirm literature findings about the de novo synthesis of PCDD/Fs in the heat exchange process. In spite of a consistent reduction of PCDD/Fs in the flue gas treatment system (from 77% up to 98%), the limit of 0.1ngITEQNm−3 at the stack was not accomplished. PCDD/Fs emission factors for air spanned from 2.3 up to 44μgITEQt−1 of burned waste, whereas those through solid residues (mainly fly ashes) were in the range 41–3700μgITEQt−1. Tests run with cemetery wastes generally showed lower PCDD/F emission factors than those with hospital wastes. PAH total emission factors (91–414μgkg−1 of burned waste) were in the range of values reported for incineration of municipal and industrial wastes. In spite of the observed release from the scrubber, carcinogenic PAHs concentrations at the stack (0.018–0.5μgNm−3) were below the Italian limit of 10μgNm−3.
Keywords: Cemetery wastes; Hospital wastes; PCDD/F; PAH; Emission factors; Incineration
Distinguishing the sources of Asian dust based on electron spin resonance signal intensity and crystallinity of quartz by Youbin Sun; Ryuji Tada; Jun Chen; Huizhong Chen; Shin Toyoda; Atsushi Tani; Yuko Isozaki; Kana Nagashima; Hitoshi Hasegawa; Junfeng Ji (pp. 8537-8548).
We report a newly developed provenance-tracing method by using a combination of electron spin resonance (ESR) signal intensity of the E1′ center in quartz and crystallinity index (CI) of quartz, which reflect the formation age and crystallization conditions of quartz in their source rocks, respectively. ESR signal intensity and CI were determined for quartz in fine silt plus clay fraction (<16μm) of 38 surface samples from nine Gobi and sandy deserts in north China and south Mongolia. Variations in ESR signal intensity and CI are minor within each desert, suggesting that fine-grained quartz in each desert is nearly homogeneous. Differences in ESR signal intensity and CI among the nine Gobi and sandy deserts are significant and, therefore, a combination of these two parameters can be used to effectively differentiate the nine Gobi and sandy deserts in East Asia. Spatial differences in these two parameters suggest that fine silt to clay-sized quartz in these deserts is heterogeneous and derived mainly from the nearby high-altitude mountains in East Asia.
Keywords: ESR signal intensity; Crystallinity index; Quartz; Dust sources; Asian deserts
Extended effects of air pollution on cardiopulmonary mortality in Vienna by Manfred Neuberger; Daniel Rabczenko; Hanns Moshammer (pp. 8549-8556).
Current standards for fine particulates and nitrogen dioxide are under revision. Patients with cardiovascular disease have been identified as the largest group which need to be protected from effects of urban air pollution.We sought to estimate associations between indicators of urban air pollution and daily mortality using time series of daily TSP, PM10, PM2.5, NO2, SO2, O3 and nontrauma deaths in Vienna (Austria) 2000–2004. We used polynomial distributed lag analysis adjusted for seasonality, daily temperature, relative humidity, atmospheric pressure and incidence of influenza as registered by sentinels.All three particulate measures and NO2 were associated with mortality from all causes and from ischemic heart disease and COPD at all ages and in the elderly. The magnitude of the effect was largest for PM2.5 and NO2. Best predictor of mortality increase lagged 0–7 days was PM2.5 (for ischemic heart disease and COPD) and NO2 (for other heart disease and all causes). Total mortality increase, lagged 0–14 days, per 10μgm−3 was 2.6% for PM2.5 and 2.9% for NO2, mainly due to cardiopulmonary and cerebrovascular causes.Acute and subacute lethal effects of urban air pollution are predicted by PM2.5 and NO2 increase even at relatively low levels of these pollutants. This is consistent with results on hospital admissions and the lack of a threshold. While harvesting (reduction of mortality after short increase due to premature deaths of most sensitive persons) seems to be of minor importance, deaths accumulate during 14 days after an increase of air pollutants. The limit values for PM2.5 and NO2 proposed for 2010 in the European Union are unable to prevent serious health effects.
Keywords: Abbreviations; PM; particulate matter (number denotes aerodynamic diameter in micrometer; 50% cut-off); TSP; total suspended particulates; NO; 2; nitrogen dioxide; SO; 2; sulfur dioxide; O; 3; ozone; COPD; chronic obstructive pulmonary diseaseAir pollution; Particulate matter; Nitrogen dioxide; Mortality; Time series; Cardiopulmonary mortality
Current and future emissions of selected heavy metals to the atmosphere from anthropogenic sources in Europe by Elisabeth G. Pacyna; Jozef M. Pacyna; Janina Fudala; Ewa Strzelecka-Jastrzab; Stanislaw Hlawiczka; Damian Panasiuk; Steffen Nitter; Thomas Pregger; Heiko Pfeiffer; Rainer Friedrich (pp. 8557-8566).
Current atmospheric emissions of As, Cd, Cr, Ni, and Pb (reference year 2000) from major anthropogenic sources in Europe are presented in this paper. Combustion of fuels in stationary sources was the main emission source for As, Cd, Cr, and Ni (more than a half of the total anthropogenic emissions), while combustion of gasoline was the main source of for lead. There is a continuous reduction of heavy metal emissions in Europe during the last 40 years. Better knowledge of heavy metal sources, emissions, pathways, and fate in the environment, and progress in developing efficient emission control equipment has resulted in more efficient regulatory efforts to curb heavy metal emissions from anthropogenic sources very substantially. There is a potential for further reduction of these emissions until the year 2010 up to about 40% for As, Cd, Cr, and Ni and about 57% for Pb, as estimated within various emission scenarios presented in the paper.
Keywords: Heavy metals; Atmospheric emission; Anthropogenic sources; Emission trends; Emission scenarios
Seasonal patterns of heavy metal deposition to the snow on Lambert Glacier basin, East Antarctica by Soon Do Hur; Xiao Cunde; Sungmin Hong; Carlo Barbante; Paolo Gabrielli; Khanghyun Lee; Claude F. Boutron; Yan Ming (pp. 8567-8578).
Al, V, Mn, Fe, Cu, As, Cd, Ba, Pb, Bi and U were determined in a continuous series of 46 snow samples from a 2.3-m snow pit, covering the time period from austral spring 1998 to summer 2002, at a site on the east side of the Lambert Glacier basin in East Antarctica. Concentrations are very low for all metals and differ by orders of magnitude from one metal to another, with the mean concentrations ranging from 0.028pgg−1 for Bi to 165pgg−1 for Al. It is estimated that anthropogenic contributions are dominant for Cu, Pb and probably As, in the snow in our study area while the natural contributions from rock and soil dust, sea-salt spray and volcanic emissions account for most of the measured concentrations of the other metals. Our snow profiles show pronounced seasonal variations for Mn, As, Ba, Pb and Bi throughout the year, but a very different situation is observed between different metals. These observations suggest that heavy metals determined in our samples are controlled by different transport and deposition mechanisms related to physical and chemical alterations in the properties and sources of aerosol.
Keywords: Heavy metals; Snow; Antarctica; Lambert Glacier basin; Seasonal variation
Synoptic-scale transport of ozone into Southern Ontario by Galvez Oscar Gálvez (pp. 8579-8595).
This study focuses on synoptic-scale transport of ozone as it affects Southern Ontario. This process has been analyzed for the summer in 2001, as an example period of a frequent event that usually occurs during summer in this region. The work was carried out using the mesoscale modeling system generation 5 (MM5)/sparse matrix operator kernel emission modeling system (SMOKE)/community multiscale air quality (CMAQ) regional air quality modeling system, together with observational data from monitoring stations located throughout the modeling domain. Other different analyses have been carried out to supply more information apart from that obtained by the modeling system. A back-trajectory cluster methodology was used to evaluate the magnitude of the effects studied and an analysis of wind direction and cloud cover revealed a significant correlation with ozone concentration ( R2=0.5–0.6). Synoptic sea-surface level pressure (SLP) patterns were also analyzed to examine other meteorological aspects. The contribution of natural background ozone to the total amount within the region was compared with that from synoptic-scale transport. The influence of emission of pollutants from selected areas on ozone concentrations in Southern Ontario was also analyzed. As relevant results of these analyses, the model predicts that background ozone is the largest contribution to the ground-level ozone concentration during days in which low values were recorded. However, when smog episodes occurred, the model predicts that around 60% of the ozone formed by anthropogenic emissions of pollutants is due to releases from nearby US states.
Keywords: Ozone transport; Transboundary; Modeling; Back trajectory; Synoptic scale
Source identification of atmospheric PCBs in Philadelphia/Camden using positive matrix factorization followed by the potential source contribution function by Songyan Du; Lisa A. Rodenburg (pp. 8596-8608).
The concentrations of gas-phase polychlorinated biphenyls (PCBs) in the atmosphere of the Camden, NJ, USA are elevated by as much as 20 times over regional background. These high PCB levels are a concern because they lead to atmospheric deposition loadings of PCBs to the tidal Delaware River that exceed the entire total maximum daily load (TMDL). Two models were applied to the atmospheric PCB concentration data from Camden in an attempt to identify the PCB source types and regions. Positive matrix factorization (PMF) was used to identify the source types. Four factors were identified which are thought to represent sources such as volatilized Aroclors and particle-phase PCBs. The potential source contribution function (PSCF) model was then used to identify the geographic source regions by examining the origination points for air parcels that result in high PCB concentrations at the Camden receptor site. The PSCF model for ΣPCBs indicates PCB source regions throughout the Philadelphia–Camden metro area, including portions of both Pennsylvania and New Jersey. The PSCF plots for the resolved PMF factors suggest that factors 1–4 show fewer distinct source regions, indicating that their sources are diffuse and/or lie very close to the receptor site. The PSCF plots for factors 2 and 3 reveal very different source regions. Factor 2 primarily arises from the city of Philadelphia, whereas factor 3 originates in southern New Jersey and south of Philadelphia. This study demonstrates the utility of the combined PMF/PSCF approach in identifying atmospheric PCB source types and regions.
Keywords: Aroclor; Source apportionment; Urban; Delaware River
Size distribution of particles emitted from grass fires in the Northern Territory, Australia by Arinto Y.P. Wardoyo; Lidia Morawska; Zoran D. Ristovski; Milan Jamriska; Steve Carr; Graham Johnson (pp. 8609-8619).
This study investigated particle size distributions from the burning of several grass species, under controlled laboratory conditions, and also in the field, conducted during the dry season in the Northern Territory, Australia. The laboratory study simulated conditions such as burning phases and burning rate, and particle diameter differed depending on the burning conditions. Under fast burning conditions, smaller particles were produced with a diameter in the range of 30–60nm, while larger particles, with a diameter between 60 and 210nm, were produced during slow burning. The airborne field measurements of biomass particles found that under the boundary layer most of the early dry season (EDS) particles came from fresh smokes with a count median diameter (CMD) of 83±13nm, and most of the late dry season (LDS) particles came from aged smokes with a CMD of 127±6nm. Vertical profiles of CMD showed that smaller particles were found higher within the atmosphere. These measurements provide insight into the scientific understanding of the properties of biomass burning particles in the Northern Territory, Australia.
Keywords: Biomass burning; Particle size distribution; Northern Territory of Australia; Airborne measurement; Vertical profile
Characteristics and diurnal variations of NMHCs at urban, suburban, and rural sites in the Pearl River Delta and a remote site in South China by J.H. Tang; L.Y. Chan; C.Y. Chan; Y.S. Li; C.C. Chang; S.C. Liu; D. Wu; Y.D. Li (pp. 8620-8632).
The Pearl River Delta (PRD) is one of the most industrialized and urbanized regions in China. With rapid growth of the economy, it is suffering from deteriorating air quality. Non-methane hydrocarbons (NMHCs) were investigated at urban and suburban sites in Guangzhou (GZ), a rural site in PRD and a clean remote site in South China, in April 2005. Additional roadside samples in GZ and Qingxi (QX, a small industrial town in PRD), ambient air samples at the rooftop of a printing factory in QX and exhaust samples from liquefied petroleum gas (LPG)—fueled taxis in GZ were collected to help identify the source signatures of NMHCs. A large fraction of propane (47%) was found in exhaust samples from LPG-fueled taxis in GZ and extremely high levels of toluene (2.0–3.1ppmv) were found at the rooftop of the printing factory in QX. Vehicular and industrial emissions were the main sources of NMHCs. The effect of vehicular emission on the ambient air varied among the three PRD sites. The impact of industrial emissions was widespread and they contributed greatly to the high levels of aromatic hydrocarbons, especially toluene, at the three PRD sites investigated. Leakage from vehicles fueled by LPG contributed mainly to the high levels of propane and n-butane at the urban GZ site. Ethane and ethyne from long-range transport and isoprene from local biogenic emission were the main contributors to the total hydrocarbons at the remote site. Diurnal variations of NMHCs showed that the contribution from vehicular emissions varied with traffic conditions and were more influenced by fresh emissions at the urban site and by aged air at the suburban and rural sites. Isoprene from biogenic emission contributed largely to the ozone formation potential (OFP) at the remote site. Ethene, toluene and m/ p-xylene were the main contributors to the OFP at the three PRD sites.
Keywords: Non-methane hydrocarbons; Source signature; LPG; PRD; South China
Daily variation in the properties of urban ultrafine aerosol—Part I: Physical characterization and volatility by Katharine F. Moore; Zhi Ning; Leonidas Ntziachristos; James J. Schauer; Constantinos Sioutas (pp. 8633-8646).
A summer air quality monitoring campaign focusing on the evolution of ultrafine (<180nm in diameter) particle concentrations was conducted at an urban site in Los Angeles during June–July 2006. Previous observations suggest that ultrafine aerosol at this site are generally representative of the Los Angeles urban environment. Continuous and intermittent gas and aerosol measurements were made over 4 weeks with consistent daily meteorological conditions. Monthly averages of the data suggest the strong influence of commute traffic emissions on morning observations of ultrafine particle concentrations. By contrast, in the afternoon our measurements provide evidence of secondary photochemical reactions becoming the predominant formation mechanism of ultrafine aerosols. The ultrafine number concentration peak occurs in the early afternoon, before the maximum ozone concentration is observed. The source of this offset is unknown and requires further investigation. It is possible that the chemical mechanisms responsible for secondary organic aerosol formation evolve as atmospheric conditions change and/or secondary semi-volatile components of the aerosol re-volatilize due to the elevated peak temperatures observed (ca. 30–35°C) combined with the increased atmospheric dilution during that time. Measurements of the volatility of the ultrafine aerosol are consistent with this interpretation as overall volatility increases in the afternoon and there is less evidence of external mixing. Composition data presented in the companion paper support these conclusions [Ning et al., 2007. Daily variation in chemical characteristics of urban ultrafine aerosols and inference of their sources. Environmental Science and Technology, in press].
Keywords: Ultrafine aerosol; Aerosol volatility; Motor vehicle emissions; Secondary organic aerosol
The effect of temperature on the gas–particle partitioning of reactive mercury in atmospheric aerosols by Andrew P. Rutter; James J. Schauer (pp. 8647-8657).
Measurements of gas–particle-partitioning coefficients for reactive mercury in dry urban and laboratory aerosol were found to strongly depend on ambient temperature. Samples of atmospheric and laboratory aerosols (defined as both the gas and particle phases) were collected using filter and absorbent methods and analyzed for reactive mercury using thermal desorption combined with cold vapor atomic fluorescence spectroscopy. Synthetic ambient aerosols were generated in the laboratory from ammonium sulfate and adipic acid mixed with mercuric chloride in a purpose-built aerosol reactor. The aerosol reactor was operated in a temperature-controlled laboratory. Linear relationships between the logarithm of inverse gas–particle partitioning and inverse temperature were observed and parameterized for use in the atmospheric modeling of reactive mercury. Reactive mercury was observed to partition from the particle to the gas phase as ambient temperature increased. Good agreement between measurements made using urban and laboratory aerosols was seen after gas–particle-partitioning coefficients were normalized for surface area instead of mass. Thermodynamic analyses of the urban and laboratory gas–particle-partitioning measurements revealed that the strength of interaction between reactive mercury and particle surfaces was suggestive of chemisorption. Gas–particle-partitioning coefficients made with the Tekran ambient mercury analyzer (AMA) also showed a dependence on temperature. However, the Tekran AMA partitioning coefficients did not agree well with partitioning coefficients measured using the filter-based methods. The disagreement is consistent with the 50°C operational temperature of the Tekran AMA.
Keywords: Partitioning; Reactive mercury; Temperature; Aerosols; Urban
Large PAHs detected in fine particulate matter emitted from light-duty gasoline vehicles by Sarah G. Riddle; Chris A. Jakober; Michael A. Robert; Thomas M. Cahill; M. Judith Charles; Michael J. Kleeman (pp. 8658-8668).
Emission factors of large PAHs with 6–8 aromatic rings with molecular weights (MW) of 300–374 were measured from 16 light-duty gasoline-powered vehicles (LDGV) and one heavy-duty diesel-powered vehicle (HDDV) operated under realistic driving conditions. LDGVs emitted PAH isomers of MW 302, 326, 350, and 374, while the HDDV did not emit these compounds. This suggests that large PAHs may be useful tracers for the source apportionment of gasoline-powered motor vehicle exhaust in the atmosphere. Emission rates of MW 302, 326, and 350 isomers from LDGVs equipped with three-way catalysts (TWCs) ranged from 2 to 10 (μgL−1 fuel burned), while emissions from LDGVs classified as low emission vehicles (LEVs) were almost a factor of 10 lower. MW 374 PAH isomers were not quantified due to the lack of a quantification-grade standard. The reduced emissions associated with the LEVs are likely attributable to improved vapor recovery during the “cold-start” phase of the Federal Test Procedure (FTP) driving cycle before the catalyst reaches operating temperature. Approximately 2 (μgg−1 PM) of MW 326 and 350 PAH isomer groups were found in the National Institute of Standards and Technology standard reference material (SRM)#1649 (Urban Dust). The pattern of the MW 302, 326, and 350 isomers detected in SRM#1649 qualitatively matched the ratio of these compounds detected in the exhaust of TWC LDGVs suggesting that each gram of Urban Dust SRM contained 5–10mg of PM originally emitted from gasoline-powered motor vehicles.Large PAHs made up 24% of the total LEV PAH emissions and 39% of the TWC PAH emissions released from gasoline-powered motor vehicles. Recent studies have shown certain large PAH isomers have greater toxicity than benzo[ a]pyrene. Even though the specific toxicity measurements on PAHs with MW >302 have yet to be performed, the detection of significant amounts of MW 326 and 350 PAHs in motor vehicle exhaust in the current study suggests that these compounds may pose a significant public health risk.
Keywords: Gasoline vehicle; Diesel vehicle; Source apportionment; Toxicity
PAHs associated with the leaves of Quercus ilex L.: Extraction, GC–MS analysis, distribution and sources by Santino Orecchio (pp. 8669-8680).
In this study, the leaves of Quercus ilex L. were selected as possible bioaccumulators of polycyclic aromatic hydrocarbons (PAHs). Quercus is an evergreen plant that occurs widely in both urban and rural areas. Several sites (urban roadside, urban, urban park, suburban and rural) in and around Palermo city were investigated.The purpose of this research was to optimize analytical method for quercus leaves, investigate the degree of contamination in the urban area of Palermo by comparing PAH concentration in leaves of quercus from the several sites, establish distribution patterns and relate them to possible sources of PAHs. To this aim, the 16 recommended as priority pollutants by the Environmental Protection Agency (EPA) and perylene were analyzed. PAHs were positively correlated to atmospheric particulate gravimetrically determined on filters aspiring a known volume of air in the various stations.The analyses have been performed by gas chromatography coupled to mass spectrometry (GC–MS) in selected ion monitoring (SIM) mode. The total PAH content in the samples ranged from 92 to 1454μgkg−1 d.w. The higher amounts of PAHs detected in leaves of quercus from the urban area of Palermo compared with the control site are diagnostic of air contamination, in particular in the zones with heavy traffic. The determination of PAHs in the leaves of quercus allows us, with very simple and fast procedures, to assess the quality of the air over a longer period, since PAHs are accumulated over the whole lifetime of the leaves, irrespective of atmospheric conditions at the moment of sampling.
Keywords: Quercus; PAHs; Biomonitoring; GC–MS; Leaves
A laboratory study of the effect of NO2 on the atmospheric corrosion of zinc by Castano J.G. Castaño; D. de la Fuente; M. Morcillo (pp. 8681-8696).
Studies on the effect of NO x on zinc corrosion are scarce and their results are variable and at times seemingly contradictory. This paper reports laboratory tests involving the dry deposition on zinc surfaces of 800μgm−3 NO2, alone and in combination with 800μgm−3 SO2, at temperatures of 35 and 25°C and relative humidities of 90% and 70%. From the gravimetric results obtained and from the characterisation of the corrosion products by optical microscopy, scanning electron microscopy (SEM/EDX), grazing incidence X-ray diffraction (GIXD) and X-ray photoelectron spectroscopy (XPS), it has been verified that the corrosive action of NO2 alone is negligible compared with SO2. However, an accelerating effect has been observed when NO2 acts in conjunction with SO2 at 25°C and 90% RH. At 35°C and 90% RH, the accelerating effect is smaller, and at low relative humidities (70%), the synergistic effect is only slight, which suggests it may be favoured by the presence of moisture. In those cases where an accelerating effect has been observed, a greater proportion of sulphate ions has been found in the corrosion products, and nitrogen compounds have not been detected, indicating that NO2 participates indirectly as a catalyst of the oxidation of SO2 to sulphate.
Keywords: NO; 2; SO; 2; Atmospheric corrosion; Zinc
A revised estimate of copper emissions from road transport in UNECE-Europe and its impact on predicted copper concentrations by H.A.C. Denier van der Gon; J.H.J. Hulskotte; A.J.H. Visschedijk; M. Schaap (pp. 8697-8710).
Comparisons of measured and model-predicted atmospheric copper concentrations show a severe underestimation of the observed concentrations by the models. This underestimation may be (partly) due to underestimated emissions of copper to air. Since the phase out of asbestos brake lining material, the composition of brake lining material has changed and may contain up to ∼15% copper. This makes brake wear from vehicles potentially an important source of atmospheric (particulate) copper concentrations. In this paper, we reassess the copper emissions due to exhaust emissions and brake wear from road transport. Overall, our reassessments result in an estimate of total copper emission to air in UNECE-Europe of 4.0–5.5ktonnesyr−1, which is substantially higher than the previous estimate of 2.8ktonnesyr−1. Copper concentrations over Europe are calculated with the LOTOS-EUROS model using the revised emission data as model input. The results show that the revised emission estimates are a major step towards gap closure of predicted versus observed copper concentrations in ambient air. Brake wear emissions may be responsible for 50–75% of the total copper emissions to air for most of Western Europe. The hypothesis that road transport is an important source of copper emissions is tested and confirmed by (1) reviewing available literature data of chemically speciated PM data from road tunnel studies and (2) the gradient observed in copper concentrations from ambient PM monitoring going from rural sites to street stations. The literature review and observational data suggest that the majority of the emitted PM10 brake wear particles is in the PM2.5–10 size range. The results of this study indicate that modification of brake lining composition is an important mitigation option to reduce copper exposure of the population in Western Europe.
Keywords: Particulate emissions; Brake wear; Copper; Road transport; Copper concentration; Exhaust emissions
Ft. McHenry tunnel study: Source profiles and mercury emissions from diesel and gasoline powered vehicles by Matthew S. Landis; Charles W. Lewis; Robert K. Stevens; Gerald J. Keeler; J. Timothy Dvonch; Raphael T. Tremblay (pp. 8711-8724).
During the fall of 1998, the US Environmental Protection Agency and the Florida Department of Environmental Protection sponsored a 7-day study at the Ft. McHenry tunnel in Baltimore, MD with the objective of obtaining PM2.5 vehicle source profiles for use in atmospheric mercury source apportionment studies. PM2.5 emission profiles from gasoline and diesel powered vehicles were developed from analysis of trace elements, polycyclic aromatic hydrocarbons (PAH), and condensed aliphatic hydrocarbons. PM2.5 samples were collected using commercially available sampling systems and were extracted and analyzed using conventional well-established methods. Both inorganic and organic profiles were sufficiently unique to mathematically discriminate the contributions from each source type using a chemical mass balance source apportionment approach. However, only the organic source profiles provided unique PAH tracers (e.g., fluoranthene, pyrene, and chrysene) for diesel combustion that could be used to identify source contributions generated using multivariate statistical receptor modeling approaches. In addition, the study found significant emission of gaseous elemental mercury (Hg0), divalent reactive gaseous mercury (RGM), and particulate mercury (Hg(p)) from gasoline but not from diesel powered motor vehicles. Fuel analysis supported the tunnel measurement results showing that total mercury content in all grades of gasoline (284±108ngL−1) was substantially higher than total mercury content in diesel fuel (62±37ngL−1) collected contemporaneously at local Baltimore retailers.
Keywords: Particulate matter; Mercury speciation; Receptor modeling
Multi-year measurements of polybrominated diphenyl ethers (PBDEs) in the Arctic atmosphere by Yushan Su; Hayley Hung; Ed Sverko; Phil Fellin; Henrik Li (pp. 8725-8735).
Weekly high-volume air samples have been collected in the Canadian High Arctic (Alert, Nunavut) since 1992. Fifteen polybrominated diphenyl ethers (PBDEs) are quantified in 104 samples over the time period of 2002–2004. To our knowledge, this study reports the first continuous multi-year measurements of PBDEs in Arctic air. Average air concentrations (in pgm−3) were 7.7 (0.40–47) and 1.6 (0.091–9.8) for 14 PBDEs (excluding BDE-209) and BDE-209, respectively, over the entire sampling period. BDE-28/33, 47, 99, 100, 153, 154, and 209 accounted for 90% (72–97%, n=104) of the 15 PBDEs. Occurrence of BDE-47, 99, and 209 suggests that PBDEs in Alert air were likely associated with the usage of “penta-BDE” and “deca-BDE” technical mixtures worldwide. Natural logarithm of concentrations for less brominated PBDEs correlated significantly with ambient temperatures in the summertime, suggesting importance of volatilization emissions in a local and/or regional scale. On the other hand, episodically elevated concentrations of the less brominated PBDEs in the wintertime and lack of seasonality for the non-volatile BDE-209 indicate potential inputs of particle-bound PBDEs through long-range transport (LRT), especially during the Arctic haze season. Inter-annual trend data further show that concentrations of the eight PBDEs increased inter-annually in 2002–2004 with doubling times of 2–6 years, which were similar to growth rates found in Arctic biotic samples. The results of this study and previous measurements suggest that potential sources of PBDEs in Arctic air include both volatilization emissions and LRT inputs.
Keywords: Polybrominated diphenyl ethers; Atmosphere; Arctic; Volatilization; Long-range transport
Biogenic VOC emissions from fresh leaf mulch and wood chips of Grevillea robusta (Australian Silky Oak) by Rosemary Fedele; Ian E. Galbally; Nichola Porter; Ian A. Weeks (pp. 8736-8746).
The emissions of VOC from freshly cut and shredded Grevillea robusta (Australian Silky Oak) leaves and wood have been measured. The VOC emissions from fresh leaf mulch and wood chips lasted typically for 30 and 20h respectively, and consisted primarily of ethanol, ( E)-2-hexenal, ( Z)-3-hexen-1-ol and acetaldehyde. The integrated emissions of the VOCs were 0.38±0.04gkg−1 from leaf mulch, and 0.022±0.003gkg−1 from wood chips. These emissions represent a source of VOCs in urban and rural air that has previously been unquantified and is currently unaccounted for. These VOCs from leaf mulch and wood chips will contribute to both urban photochemistry and secondary organic aerosol formation. Any CH4 emissions from leaf mulch and wood chips were <1×10−11ggdry mass−1s−1.
Keywords: Volatile organic compounds; Emissions; Methane; Grevillea robusta; Leaf mulch; Wood chips
Using CALINE dispersion to assess vehicular PM2.5 emissions by Elizabeth Ann Yura; Thomas Kear; Debbie Niemeier (pp. 8747-8757).
This paper explores the range of CALINE4's PM2.5 modeling capabilities by comparing previously collected PM2.5 data with CALINE4 predicted values. Two sampling sites, a suburban site located at an intersection in Sacramento, CA, and an urban site located in London, were used. Predicted concentrations are graphed against observed concentrations and evaluated against the criterion that 75% of the points fall within the factor-of-two prediction envelope. For the suburban site, data estimated by CALINE4 produced results that fell within the acceptable factor-of-two percentage envelope. A reverse dispersion test was also conducted for the suburban site using observed and calculated emission factors, and although it showed correlations between the observed values and CALINE4 predicted values, it could not conclusively prove that the model is accurate at predicting PM2.5 concentrations. Although the results suggest that CALINE4 PM2.5 predictions may be reasonably close to observed values, the number of observations used to verify the model was small and consequently, findings from the suburban site should be considered exploratory. For the urban site, a much larger data set was evaluated; however, the CALINE4 results for this site did not fall 75% within the factor-of-two envelope. Several factors, including street canyon effects, likely contributed to an inaccuracy of the emission factors used in CALINE4, and therefore, to the overall CALINE4 predictions. In summary, CALINE4 does not appear to perform well in densely populated areas and differences in topography may be a decisive factor in determining when CALINE4 may be applicable to modeling PM2.5. For critical transportation projects requiring PM2.5 analysis, use of CALINE4 may not be optimal because of its inability to produce reasonable estimates for highly trafficked areas. Additional data sets for CALINE4 analysis, particularly in urban environments, are required to fully understand CALINE4's PM2.5 modeling capabilities.
Keywords: CALINE; CALINE4; PM; 2.5; modeling
β-Ionone reactions with ozone and OH radical: Rate constants and gas-phase products by Crystal D. Forester; Jason E. Ham; J. Raymond Wells (pp. 8758-8771).
The bimolecular rate constants, kOH+ β-ionone (118±30)×10−12cm3molecule−1s−1 andkO3+β‐ionone, (0.19±0.05)×10−16cm3molecule−1s−1, were measured using the relative rate technique for the reaction of the hydroxyl radical (OH) and ozone (O3) with 4-(2,6,6-trimethyl-1-cyclohexen-1-yl)-3-buten-2-one ( β-ionone) at 297±3K and 1atm total pressure. To more clearly define part of β-ionone's indoor environment degradation mechanism, the products of the β-ionone+OH and β-ionone+O3 reactions were also investigated. The identified β-ionone+OH reaction products were: glyoxal (ethanedial, HC(=O)C(=O)H), and methylglyoxal (2-oxopropanal, CH3C(=O)C(=O)H) and the identified β-ionone+O3 reaction product was 2-oxopropanal. The derivatizing agents O-(2,3,4,5,6-pentafluorobenzyl)hydroxylamine (PFBHA) and N, O-bis(trimethylsilyl)trifluoroacetamide (BSTFA) were used to propose 2,6,6-trimethylcyclohex-1-ene-1-carbaldehyde as the other major β-ionone+OH and β-ionone+O3 reaction product. The elucidation of this other reaction product was facilitated by mass spectrometry of the derivatized reaction products coupled with plausible β-ionone+OH and β-ionone+O3 reaction mechanisms based on previously published volatile organic compound+OH and volatile organic compound+O3 gas-phase reaction mechanisms. The additional gas-phase products observed from the β-ionone+OH reaction are proposed to be the result of cyclization through a radical intermediate.
Keywords: β; -Ionone; 4-(2,6,6-Trimethyl-1-cyclohexen-1-yl)-3-buten-2-one; β; -Irisone; Reaction products; Kinetics; Oxygenated organic compounds; Annelation
The use of air quality forecasts to assess impacts of air pollution on crops: Methodology and case study by Daniel Tong; Rohit Mathur; Kenneth Schere; Daiwen Kang; Shaocai Yu (pp. 8772-8784).
It has been reported that ambient ozone (O3), either alone or in concurrence with acid rain precursors, accounts for up to 90% of US crop losses resulting from exposure to all major air pollutants. Crop damage due to O3 exposure is of particular concern as ambient O3 concentrations remain high in many major food-producing regions. Assessing O3 damage to crops is challenging due to the difficulties in determining the reduction in crop yield that results from exposure to surface O3, for which monitors are limited and mostly deployed in non-rural areas. This work explores the potential benefits of using operational air quality forecast (AQF) data to estimate rural O3 exposure. Using the results from the first nationwide AQF as a case study, we demonstrate how the O3 data provided by AQF can be combined with concurrent crop information to assess O3 damages to soybeans in the United States. We estimate that exposure to ambient O3 reduces the US soybean production by 10% in 2005.
Keywords: Crop loss; Ozone damage; Exposure; Air quality model; Cost benefit analysis
Characterization, identification of road dust PAHs in central Shanghai areas, China by M. Liu; S.B. Cheng; D.N. Ou; L.J. Hou; L. Gao; L.L. Wang; Y.S. Xie; Y. Yang; S.Y. Xu (pp. 8785-8795).
Road dust samples were collected from central Shanghai in winter (January) and summer (August), respectively. Sixteen polycyclic aromatic hydrocarbons (PAHs) in the United States Environmental Protection Agency (USEPA) priority-controlled list were determined by GC/MS. Total PAH (t-PAH) concentrations in winter samples ranged from 9176 to 32,573ngg−1 with a mean value of 20,648ngg−1, while they varied from 6875 to 27,766ngg−1 in summer with an average of 14,098ngg−1. Spatial variation showed that city park (CP) samples had the lowest t-PAH concentration, while industrial area (ID) and traffic area (TR) and commercial area (CO) were the most polluted, in both seasons. PAH homologues concentrations were getting higher with the more rings and higher molecular weight (HMW) in all areas. The study of effective factors showed that grain size was only a minor factor influencing the accumulation of PAHs, whereas total organic carbon (TOC) was found to be closely correlated with t-PAH concentration. Prevailing winds could directly affect on the spatial distribution of PAHs. Chemical source apportionment studies took the form of principal component analysis (PCA), followed by compositional analysis. It was demonstrated that road dust PAHs in central Shanghai mainly came from the mixing of traffic and coal combustion. The contribution percentages of pyrogenic and petrogenic sources were respectively 71.0% and 11.4% in winter, while they were, 64.9% and 14.1% in summer, respectively. Road dust PAHs in Shanghai city mostly came from local sources.
Keywords: PAHs; Source identification; Urban road dust; Shanghai; China
Primary product distribution from the Cl-atom initiated atmospheric degradation of furan: Environmental implications by Florentina Villanueva; Ian Barnes; Esperanza Monedero; Sagrario Salgado; Gomez Mª Victoria Gómez; Pilar Martin (pp. 8796-8810).
Furan is an aromatic hydrocarbon present in both urban and rural atmospheres, which is emitted mainly by biomass burning and the combustion of fossil fuel. Reaction of furan and Cl atoms may be important in areas where chlorine atom concentrations are potentially high such as marine and coastal regions or continental atmospheres where industrial activity emits molecular chlorine or photo-labile Cl-containing compounds. To assess the importance of this reaction and to investigate whether any unique chlorine-containing product is formed the products of the reaction of Cl atoms with furan have been determined under atmospheric conditions. For the study two different sampling/detection methods have been used: (1) Solid-Phase MicroExtraction, with subsequent analysis by thermal desorption, and gas chromatography with mass spectrometry or flame ionization detection (SPME/GC-MS/FID), and 2-“in situ” with long path fourier transform infrared spectroscopy (FTIR). The yields of primary reaction products in the absence of NO were: 5-chloro-2(5H)-furanone (64.5±10.7)%, E-butenedial (11±3)%, 5-hydroxy-2(5H)-furanone (⩽2.4%) and Z-butenedial (1.6±0.5)%. Other products generated by secondary reactions were 2(3H)-furanone (2.8±1.9)%, HCl (21.1±3%) and CO. Maleic anhydride was detected with a yield of about 2%, however, this yield may be a combination of both primary and secondary reactions. All errors are ±2 σ. The observed products confirm that addition of Cl atoms to the double bond of furan is the dominant reaction pathway.
Keywords: Furan; Chlorine atoms; Mechanism; Chlorofuranone; Reaction products; Quantitative determination
Oxygen and carbon isotopic signatures reveal a long-term effect of free-air ozone enrichment on leaf conductance in semi-natural grassland by Jaggi M. Jäggi; J. Fuhrer (pp. 8811-8817).
The effect of ozone on leaf gas diffusion was investigated by analyzing the stable oxygen isotopic signatures (δ18O) in leaves of Holcus lanatus L., Plantago lanceolata L., Ranunculus friesianus (Jord.), and Trifolium pratense L. grown in temperate, semi-natural grassland. Dried material from plants exposed to ambient or elevated ozone levels in a long-term free-air experiment was sampled in 2002 and 2003. A general increase in δ18O in elevated ozone indicated increased limitation to gas diffusion, which was strongest during the driest and warmest period in 2003. In three out of four species, the increase in δ18O paralleled an increase in δ13C measured earlier in the same samples, meaning that the dominant effect of ozone was on gas diffusion and not on CO2 fixation. Only in R. friesianus, ozone affected both processes simultaneously. It is concluded that elevated ozone not only affects productivity, but also the water status of important component species of grassland communities.
Keywords: Stable isotopes; δ; 18; O; δ; 13; C; Ozone; Grassland
Trade-offs between moving and stationary particle collectors for detecting a bio-agent plume by P.N. Phillip N. Price; A.J. Ashok J. Gadgil; M.D. Michael D. Sohn (pp. 8818-8824).
Outdoor air in several U.S. cities is now being continuously monitored for biological warfare agents. In the current implementation, all monitoring devices, which we refer to as “collectors,” are stationary. This paper discusses the trade-offs between stationary and moving collectors. A moving collector is more likely than a stationary collector to sample a clandestine release, but will experience a lower time-integrated concentration than an ideally placed stationary collector. Quantitative results are determined for some idealized cases, and suggest that moving collectors may offer substantial advantages over stationary collectors.
Keywords: Sampling strategies; Plume detection
Effect of natural compounds on reducing formaldehyde emission from plywood by Shigehisa Uchiyama; Erica Matsushima; Nahoko Kitao; Hiroshi Tokunaga; Masanori Ando; Yasufumi Otsubo (pp. 8825-8830).
The effects of natural compounds on reducing formaldehyde emission from plywood were investigated. Urea, catechin and vanillin were examined as the natural formaldehyde reducers. The microemission cell, with an internal volume of 35ml, the maximum exposed test surface area of 177cm2 and an air purge flow rate of 50mlmin−1, was used to measure specific emission rate (SER). In the case of no reducer treatment, formaldehyde emission from plywood was fast and SERs were 4.4mgm−2h−1 at 30°C and 15mgm−2h−1 at 60°C. When this plywood was treated with the natural compounds, the SERs of formaldehyde were decreased at all temperatures. In the case of urea treatment, the SERs of formaldehyde decreased to 0.30mgm−2h−1 at 30°C and 0.65mgm−2h−1 at 60°C. When the urea treatment was applied to the inside of kitchen cabinet (made from plywood; 270cm wide, 60cm deep, 250cm high), the concentration of formaldehyde was reduced substantially from 1600 to 130μgm−3. The reducing effect of formaldehyde continued during the observation period (6 months), with a mean concentration of 100μgm−3. Reducers in the plywood would react with released formaldehyde. Application of natural compounds such as urea, catechin and vanillin could provide a simple and effective approach for suppressing formaldehyde emission from plywood.
Keywords: Formaldehyde; Emission control; Urea; Indoor air; Natural compounds