Atmospheric Environment (v.40, #37)
Editorial board (i).
First gaseous sulfuric acid measurements in automobile exhaust: Implications for volatile nanoparticle formation by F. Arnold; L. Pirjola; H. Aufmhoff; T. Schuck; T. Lähde; K. Hämeri (7097-7105).
Gaseous sulfuric acid (GSA) is thought to represent an important if not the most important nucleating gas present in modern diesel automobile exhaust. It triggers the formation of new aerosol particles, which grow by condensation and coagulation. Here we report on the first measurements of GSA in automobile exhaust. The experiment was made using a modern passenger diesel car equipped with an exhaust after-treatment system composed of an oxidation catalyst and a diesel-particle filter. The diesel fuel used had an ultra-low sulfur mass fraction of only 5×10−6. Measured GSA number concentrations reached up to 1×109 cm−3. Freshly nucleated particles with diameters larger than 3 nm were also measured. The concentrations reached up to 1×105 cm−3 and were positively correlated with GSA for GSA exceeding a threshold value in the range of 5×107–2×108 cm−3. This suggests that GSA was involved in the formation of new volatile particles.
Keywords: Sulfuric acid measurements; Diesel nanoparticles; Conversion factor; After-treatment system;
Simplified approach to measuring semivolatile inorganic particulate matter using a denuded cellulose filter without backup filters by Lothar Keck; Klaus Wittmaack (7106-7114).
The use of uncoated denuded cellulose (CE) fibre filters without backup filters was explored as a simple means of accurately sampling semivolatile inorganic particulate matter. CE filters are particularly well suited for the purpose in question because they quantitatively absorb the gaseous constituents evolving from volatilised ammonium nitrate and chloride. A CE filter was placed behind a pair of recently developed mini parallel-plate denuders to form a very compact “Denuded-CE-filter Sampler” (DCES). The concentrations of the three major inorganic ions (SO4 2−, NO3 −, and NH4 +) determined with the DCES were compared with results obtained with a collocated ChembComb sampling cartridge featuring two honeycomb denuders, a Teflon (Tf) particle filter, and two backup filters. The SO4 2− concentrations, measured with the two units to validate correspondence for non-volatile inorganic salts, were found to be in excellent agreement. The NO3 − concentrations also agreed very well, even for sampling campaigns during which up to 95% of the particulate nitrate had evaporated from the Tf filter of the ChembComb. This agreement provides evidence that the DCES concept is reliable. The NH4 + concentrations, on the other hand, repeatedly differed significantly. The differences are attributed to the evaporation of NH3 from particulate matter other than NH4NO3, presumably organic ammonia compounds or bioaerosols. This evaporating NH3 is presumably not retained by the CE filter. As to the gases, the concentrations determined with the two types of denuders agreed quite well for HNO3. In case of SO2, the results obtained with the ChembComb were lower by about 10% than with the DCES. Large differences in both directions were observed for the (apparent) NH3 concentrations, which furthermore, were quite high. Sampling close to vegetation might have been the cause of the observed discrepancies.
Keywords: Sampling artefacts; Particulate nitrate; Cellulose filter; Denuder; Ammonia;
Impact of wood combustion on particle levels in a residential area in Denmark by M. Glasius; M. Ketzel; P. Wåhlin; B. Jensen; J. Mønster; R. Berkowicz; F. Palmgren (7115-7124).
The influence of residential wood-combustion on local air quality was studied during two periods in 2002 and 2003/04 in a small rural town with widespread use of wood combustion for heating. During one 6-week winter period, particle levels (PM2.5) in the residential area were about 4 μg m−3 higher than at a nearby background site. This was comparable to the local traffic contribution observed at a busy street (about 70,000 vehicles per day) in the city of Copenhagen. The diurnal variation in the residential area showed increased particle levels (PM2.5) in the evening and night as expected from local heating sources. Particle size distributions showed highest volume concentrations of particles with diameters of 400–500 nm, and the diurnal variation of particle volume was similar to PM2.5. The particle measurements were supported by measurements of combustion gases in both the residential area and at a background site. Receptor modelling and source apportionment of the results confirmed that the most important sources to particles were long-range transport (both organic and inorganic compounds) and local heating (particularly organic compounds) in addition to regional traffic emissions. Local wood combustion sources affected especially the organic particle component.
Keywords: Wood-stove emissions; PM2.5; Organic carbon; COPREM;
Estimation of the emission factors of particle number and mass fractions from traffic at a site where mean vehicle speeds vary over short distances by Alan M. Jones; Roy M. Harrison (7125-7137).
Emission factors for particle number in three size ranges (11–30; 30–100 and >100 nm) as well as for PM2.5, PM2.5−10 and PM10 mass have been estimated separately for heavy and light-duty vehicles in a heavily trafficked street canyon in London where traffic speeds vary considerably over short distances. Emissions of NO x were estimated from published emission factors, and emissions of other pollutants estimated from their ratio to NO x in the roadside concentration after subtraction of the simultaneously measured urban background. The estimated emission factors are compared with other published data. Despite many differences in the design and implementation of the various studies, the results for particulate matter are broadly similar. Estimates of particle number emissions in this study for light-duty vehicles are very close to other published data, whilst those for heavy-duty vehicles are lower than in the more comparable studies. It is suggested that a contributory factor may be the introduction of diesel particle oxidation traps on some of the bus fleet in London. Estimates of emission factors for particle mass (PM2.5 and PM2.5−10) are within the range of other published data, and total mass emissions estimated from the ratio of concentration to NO x are tolerably close to those estimated using emission factors from the National Atmospheric Emissions Inventory (NAEI). However, the method leads to an estimate of carbon monoxide emissions 3–6 times larger than that derived using the NAEI factors.
Keywords: Particulate matter; Particle number; PM10; PM2.5; Street canyon; Emission factor;
Health effects of metropolitan traffic-related air pollutants on street vendors by P. Kongtip; W. Thongsuk; W. Yoosook; S. Chantanakul (7138-7145).
Traffic-related air pollutants are a commonly important source of air pollution. Research on the effects of multiple traffic-related air pollutants on street vendors is scarce. This study evaluated the health effect of traffic-related air pollutants in street vendors. It was designed as a panel study, covering 61 d of data collection, on the daily concentration of air pollutants and daily percentage of respiratory and other health symptoms reported. An adjusted odds ratio was used to estimate the risk of developing respiratory and other adverse health symptoms for street vendors exposed to multiple air pollutants, fine particulate (PM2.5), nitrogen dioxide (NO2), ozone (O3), carbon monoxide (CO) and total volatile organic chemicals (VOCs), after controlling for confounding factors. In the first model, significant associations were found with the adjusted odds ratios of 1.022 and 1.027 for eye irritation and dizziness for PM2.5 respectively. The adjusted odds ratio of total VOCs was 1.381 for phlegm, 4.840 for chest tightness and 1.429 for upper respiratory symptoms, and the adjusted odds ratio for CO was 1.748 for a sore throat and 1.880 for a cold and 1.655 for a cough. In the second model, the effect of PM2.5, total VOCs and CO gave a slightly lower effect with the symptoms. The results clearly show the health effects of traffic-related air pollutants on street vendors, and imply suggestions about how to reduce exposure of street vendors.
Keywords: Traffic-related air pollutants; Air pollution; Street vendors; Health effects;
A note on the temperature dependence of Henry's Law coefficients for methanol and ethanol by Peter Warneck (7146-7151).
Measurements reported in the literature of gas–liquid partition coefficients for methanol and ethanol dissolved in water are compiled and critically evaluated to establish the temperature dependence. The data are linearly correlated in the ln(K H[mol dm−3 atm−1]) versus reciprocal absolute temperature coordinate frame and, when treated by a linear regression analysis, yield: ln(K H)=−(12.46±0.25)+(5312.4±76.0)/T in the case of methanol (0–80 °C) and ln(K H)=−(15.87±0.82)+(6274.0±241.6)/T in the case of ethanol (0–60 °C). The measurements at 25 °C average to K H(298.15)=(2.16±0.14)×102 mol dm−3 atm−1 (n=8) and K H(298.15)=(1.94±0.13)×102 mol dm−3 atm−1 (n=8), respectively. Enthalpies of solution derived from the temperature dependence are 44.17±0.63 kJ mol−1 for methanol and 52.16±2.01 kJ mol−1 for ethanol.
Keywords: Methanol; Ethanol; Henry's Law coefficients; Gas phase-aqueous phase partition coefficients;
Relationships between aerosol and snow chemistry at King Col, Mt. Logan Massif, Yukon, Canada by Kaplan Yalcin; Cameron P. Wake; Jack E. Dibb; Sallie I. Whitlow (7152-7163).
Simultaneous samples of aerosol ( n = 48 ) and recent snow ( n = 193 ) chemistry were collected at King Col (4135 m) in the St. Elias Mountains, Yukon, between 17 May and 11 June 2001. Major ion concentrations in aerosol samples were low with the total ionic burden averaging 5.52 neq m−3 at standard temperature and pressure (STP). Interspecies aerosol relationships indicate the presence of (NH4)2SO4 aerosol at King Col. An aerosol Cl− deficiency relative to seawater suggests volatilization of HCl by reaction with unneutralized SO 4 2 - that is present in half of the samples. Backwards trajectories for select aerosol concentration peaks document the transport of Asian dust and anthropogenic emissions, the eruption plume from the 22 May eruption of Sheveluch, Kamchatka, and sea salt from the marine boundary layer over the Gulf of Alaska to King Col during the sampling period. Fresh snow chemistry generally mimics aerosol chemistry with similar relative abundances and interspecies relationships except for large enrichments in snow Cl− and NO 3 - relative to aerosol due to snow scavenging of gas-phase HCl and HNO3. Although relatively strong correlations between aerosol and snow concentrations were observed for species associated with accumulation mode aerosols, e.g. NH 4 + ( r = 0.56 ) and SO 4 2 - ( r = 0.43 ), only weak correlations were observed for dust and sea-salt species. These results are influenced by greater variability in concentrations between replicate snow samples for species associated with coarse mode dust and sea-salt particles and by snow scavenging of gas-phase HCl and HNO3.
Keywords: Aerosols; Air–snow transfer; Major ions; Mt. Logan; Yukon;
Intake fraction assessment of the air pollutant exposure implications of a shift toward distributed electricity generation by Garvin A. Heath; Patrick W. Granvold; Abigail S. Hoats; William W Nazaroff (7164-7177).
Small-scale, distributed electricity generation (DG) technologies have been promoted for their many benefits as compared to the traditional paradigm of large, centralized power plants. To evaluate the implications for human inhalation exposure resulting from a shift toward DG, we combined Gaussian plume modeling and a GIS-based inhalation exposure assessment of existing and hypothetical power-generation facilities in California. Twenty-five existing central stations (CSs) were analyzed and compared with hypothetical DG technologies deployed in the downtown areas of the 11 most populous cities in California. The intake fraction (iF) for primary pollutants was computed for populations living within 100 km of each source, using meteorological conditions typical of the long-term observational record and population, lifetime-average breathing rates. The iF (a dimensionless term representing the proportion of pollutant mass emitted by a source that is eventually inhaled) concisely expresses the source-to-intake relationship, is independent of the emissions characteristics of the plants assessed, and normalizes for the large scale differences between the two paradigms of electricity generation. The median iF for nonreactive primary pollutants emitted from the 25 CSs is 0.8 per million compared to 16 per million for the 11 DG units. The difference is partly attributable to the closer proximity of DG sources to densely populated areas as compared to typical CS facilities. In addition, the short stacks of DG sources emphasize near-source population exposure more than traditional CSs, and increase exposures during periods of low wind speed, low mixing height and stable atmospheric conditions. Strategies that could reduce the potential increase in air pollutant intake from DG include maximally utilizing waste heat in combined heat and power operations, increasing the release height of DG effluents and deploying DG technologies that do not emit air pollutants.
Keywords: Intake fraction; Gaussian plume model; Exposure assessment; Electricity generation; Distributed generation;
Reference values for indoor air pollutant concentrations in new, residential buildings in Finland by H Järnström; K Saarela; P Kalliokoski; A.-L. Pasanen (7178-7191).
Eight buildings, representing the present construction practice in Finland, were investigated to create numeric reference data for indoor air quality (IAQ) in new residential buildings. Low-emitting materials according to the “Finnish Classification of Building Materials” were used in all the buildings. The airborne volatile organic compounds (VOCs), formaldehyde, and ammonia concentrations as well as temperature, relative humidity, and the air exchange rate were determined in the newly finished buildings and after 6 and 12 months. Target values for the indoor air concentrations were not generally reached in newly finished buildings. The lowest concentration levels were measured in buildings with mechanical supply and exhaust air systems. Formaldehyde concentrations fulfilled best the target values. The TVOC concentration usually reached the S2/S3-class values within 6 months. However, the ammonia concentration remained above the S3 limit during the whole first year. The concentrations of ammonia and formaldehyde showed seasonal variations, i.e., higher concentrations were measured in summer. The concentrations of individual VOCs generally decreased most strongly during the first 6 months and the final mean concentration levels were generally less than 15 μg m−3. As the occupancy period got longer, the VOCs originating from the construction phase were increasingly replaced by new ones. Reference values based on means and on 95 percentiles are presented to facilitate interpretation of the results of measurements done to ensure that proper construction practices have been applied or to investigate IAQ problems.
Keywords: Indoor air; VOC; Formaldehyde; Ammonia; Reference values; New buildings;
Crossed optical and chemical evaluations of modern glass soiling in various European urban environments by Olivier Favez; Hélène Cachier; Anne Chabas; Patrick Ausset; Roger Lefevre (7192-7204).
As part of the MULTI-ASSESS and VIDRIO EC projects, the soiling of modern glass is characterised in various European urban atmospheres. Our original methodology relies on crossed chemical measurements of the deposit (evaluation of the ion, elemental and organic carbon contents, and subsequent “mass closure”) and exhaustive measurements of glass optical properties (light reflectance, transmittance and absorption). Samples were exposed sheltered from rain in Athens, Krakow, London, Montelibretti (Italy), Prague and Troyes (France), during increasing exposure durations, up to more than two years. Although a slowing down of the deposition rate is observed for some species at some sites, no obvious saturation phenomenon seems to occur for the particle deposition. The chemical composition of the deposit is shown to reflect the atmospheric environment of the exposure site. Some post-deposit evolutions, such as the disappearance of ammonium and possibly of particulate organic matter, are found to occur. For thin deposits, the glass optical properties (e.g. light absorption and diffuse transmittance) are found to evolve quasi-linearly with species concentrations (EC and ions, respectively). However, for conditions creating heavier deposits such as long time exposures in rather polluted environments, a saturation phenomenon is observed. Using a simple model, light absorption, which is primarily due to EC particles, is shown to reach the saturation level (S) for A≈16% and the concentration for which the semi-saturation level is reached (C1/2) is found to be about 15 μgC of EC/cm2. For diffuse transmittance, due to scattering species, these parameters are found to be about 30% and 65 μg of ions/cm2, respectively. These values may be considered as representative of the soiling in Europe.
Keywords: Glass soiling; Particle deposition; Chemical mass closure; VIDRIO; MULTI-ASSESS;
Traffic-related particulate air pollution exposure in urban areas by C. Borrego; O. Tchepel; A.M. Costa; H. Martins; J. Ferreira; A.I. Miranda (7205-7214).
In the last years, there has been an increase of scientific studies confirming that long- and short-term exposure to particulate matter (PM) pollution leads to adverse health effects.The development of a methodology for the determination of accumulated human exposure in urban areas is the main objective of the current work, combining information on concentrations at different microenvironments and population time–activity pattern data. A link between a mesoscale meteorological and dispersion model and a local scale air quality model was developed to define the boundary conditions for the local scale application. The time–activity pattern of the population was derived from statistical information for different sub-population groups and linked to digital city maps. Finally, the hourly PM10 concentrations for indoor and outdoor microenvironments were estimated for the Lisbon city centre, which was chosen as the case-study, based on the local scale air quality model application for a selected period.This methodology is a first approach to estimate population exposure, calculated as the total daily values above the thresholds recommended for long- and short-term health effects. Obtained results reveal that in Lisbon city centre a large number of persons are exposed to PM levels exceeding the legislated limit value.
Keywords: Atmospheric modelling; Mesoscale; Local scale; Particulate matter; Exposure;
Influence of sampling air flow rate in the decay correction applied to the determination of 7Be and short-lived radionuclides in aerosol samples by M.C. Jiménez-Ramos; G. Manjón; J.M. Abril (7215-7221).
An original decay correction procedure is proposed for the activity determination of short-lived radionuclides in airborne dust samples. To this end, the hypothesis of air flow rate attenuation during sampling is considered and tested. The other decay corrections: to the delay time, from the end of the sampling until the start of the counting; and to the counting time, were executed as standard. Differences from classic corrections, which consider a constant air flux rate in the sampling with a weekly sampling duration, are of the order of 1% for 7Be and approximately 10% for 131I.Moreover, the procedure can be applied to estimate the air volume sampled in the last 24 h before the end of the sampling. This volume can be used to calculate the activity concentration of a radionuclide (short-or long-lived radionuclide) if a major nuclear accident causes an instantaneous contamination immediately before the end of sampling.
Keywords: Radioactivity; Aerosol; Sampling; Decay correction;
Cost-effective means of reducing ammonia emissions from UK agriculture using the NARSES model by J. Webb; M. Ryan; S.G. Anthony; A. Brewer; J. Laws; M.F. Aller; T.H. Misselbrook (7222-7233).
To comply with International agreements to improve air quality, signatory states need to reduce emissions of ammonia (NH3). Since the majority of NH3 emissions come from agriculture, measures may need to be implemented by the farming industry. Member states of the EU will, by 2010, require large pig and poultry production units to reduce NH3 emissions to comply with the integrated pollution prevention and control directive (IPPC). The NARSES model uses a mass-flow method to estimate NH3 emission from UK agriculture and to identify the most cost-effective means of reducing NH3 emissions. Model runs were carried out to assess the likely impact of the IPPC Directive on UK NH3 emissions and the sensitivity of model output to input data on the costs and abatement efficiencies of proposed abatement measures. The impact of the IPPC Directive is likely to be small, offering a reduction of c. 8700 t, 3.5% of total UK agricultural NH3 emissions. Even large (30%) changes in our estimates of cost or changes of 10% in our estimates of abatement efficiency will make little difference to the ranking of abatement techniques according to cost-effectiveness. The most cost-effective reductions may be achieved by replacing urea fertilizer with ammonium nitrate, immediate incorporation of manures and slurries to tillage land by discs, storing all FYM and poultry manures before spreading to land and applying slurries to grassland by trailing shoe.
Keywords: Abatement; IPPC; Sensitivity analysis; Cost-curves;
Tracer dispersion simulation in low wind speed conditions with a new 2D Langevin equation system by D. Anfossi; S. Alessandrini; S. Trini Castelli; E. Ferrero; D. Oettl; G. Degrazia (7234-7245).
The simulation of atmospheric dispersion in low wind speed conditions (LW) is still recognised as a challenge for modellers. Recently, a new system of two coupled Langevin equations that explicitly accounts for meandering has been proposed. It is based on the study of turbulence and dispersion properties in LW. The new system was implemented in the Lagrangian stochastic particle models LAMBDA and GRAL. In this paper we present simulations with this new approach applying it to the tracer experiments carried out in LW by Idaho National Engineering Laboratory (INEL, USA) in 1974 and by the Graz University of Technology and CNR-Torino near Graz in 2003. To assess the improvement obtained with the present model with respect to previous models not taking into account the meandering effect, the simulations for the INEL experiments were also performed with the old version of LAMBDA. The results of the comparisons clearly indicate that the new approach improves the simulation results.
Keywords: Low wind speeds; Meandering; Dispersion; Tracer experiments; Langevin equation system;
Atmospheric flux of ammonia from sprinkler application of dairy waste by Brian Rumburg; George H. Mount; David Yonge; Brian Lamb; Hal Westberg; Jenny Filipy; Jay Bays; Ron Kincaid; Kristen Johnson (7246-7258).
Atmospheric ammonia ( NH 3 ) emissions are a growing environmental and human health concern in the U.S. This paper describes an experiment to measure NH 3 emissions from the sprinkler application of dairy slurry to a grass field. The slurry was from milking cows that are housed in a freestall barn that is scraped daily and the waste is stored in a series of anaerobic lagoons that are emptied annually. Atmospheric measurements of NH 3 were made using differential optical absorption spectroscopy (DOAS) and tracer ratio flux experiments were used to determine field fluxes after application. An area source tracer ratio method was used to determine NH 3 field fluxes, it involved releasing SF 6 as the tracer gas from the upwind edge of the applied slurry and measuring the tracer concentration downwind along with the DOAS NH 3 measurements. The flux is calculated from the ratio of the NH 3 and SF 6 concentrations and the SF 6 release rate and taking into account the differences in area and dispersion. An emissions model was also developed for NH 3 volatilization after application based upon tracer flux data and modeling of the concentration data. Of the total ammonical nitrogen entering from the sprinkler pump, 18% volatilized before reaching the ground. The initial flux during the tracer experiment was 47 μ g m - 2 s - 1 and this decreased to 17 μ g m - 2 s - 1 during the experiment. Ambient measurements showed an exponential decay with time. An empirical exponential equation was fit to the measurement data and it had a mean bias of - 0.10 ppbv and a normalized mean bias of - 0.050 % . A theoretical model had a mean bias of - 11 ppbv and a normalized mean bias of - 5.5 % . Overall sprinkler waste application emissions for the 175 milking cows was 5900 kg NH 3 yr - 1 or 34 kg NH 3 cow - 1 yr - 1 .
Keywords: Ammonia; Emission; Dairy; Tracer gas; Waste application;
Contribution of water soluble organic nitrogen to total nitrogen in marine aerosols over the East China Sea and western North Pacific by Tokuhiro Nakamura; Hiroshi Ogawa; Dileep Kumar Maripi; Mitsuo Uematsu (7259-7264).
This paper presents information on concentrations, size distributions, geographical distributions and sources of water soluble organic nitrogen (ONws) in aerosols over the East China Sea and western North Pacific to understand its impact on the atmospheric processes and the oceanic ecosystems in the autumn and spring in the East Asian region. Results revealed ONws contributions to the total nitrogen in aerosols to be ∼24% and ∼10% over the East China Sea in the autumn and the spring, respectively. The particulate ONws mainly existed in fine sized particles. Gas to particle conversion may be the major formation process for ONws. Occurrence of particulate ONws in both fine and coarse modes during the Kosa event suggests gaseous ON adsorption and/or adhesion to the coarse mode mineral. This behavior of ONws is unique whereas NH 4 + occurred dominantly in fine mode and NO 3 - in coarse mode.
Keywords: Organic nitrogen; Marine atmosphere; Nitrogen cycling; Atmospheric particulate matter;
Erratum to “A new analytical approach to simulate the pollutant dispersion in the PBL”[Atmos. Environ. 39 (2005) 2171–2178] by S. Wortmann; M.T. Vilhena; D.M. Moreira; D. Buske (7265).