Atmospheric Environment (v.45, #20)

A new sampling method using a mobile sampling system was developed to sample resuspended road dust on a paved road. To calculate the net mass concentration of resuspended road dust in the dust sample collected behind the front tire of the mobile sampling system, a background subtraction method was employed. The ratio of the PM2.5 concentration to the PM10 concentration in resuspended road dust ranged from 0.25 to 0.40, depending upon the sampling sites, which appears to be a function of traffic characteristics, land use, and so forth. The results of chemical analysis of PM samples demonstrated that specific source profiles for resuspended road dust exist according to sampling sites as well as particle size range. It is likely that, particularly in the case of Al, Ca, Fe, and OC, there exists a relatively small or approximately equal magnitude of dependence of sampling sites on the mass percentage of elements in the sampled PM compared with that of the particle size range. In view of the dependence of the Zn mass percentage and Cu/Sb on the average hourly traffic, it is clear that as traffic volume increases, tire wear and brake wear increase, and, accordingly, the amount of tire wear dust and brake wear dust deposited on paved roads increases. It turned out that OC and EC values do not change appreciably with the average hourly traffic. Nonetheless, it was noted that the OC values of PM coarse are two or three times larger than those of PM fine, showing a clear dependence of OC on the particle size range. In the case of EC, however, no clear dependence of EC on the particle size range was found.► A new sampling method was developed to sample resuspended dust on the paved road. ► The ratio of PM2.5 to PM10 in resuspended road dust ranged from 0.25 to 0.40. ► Specific source profiles exist according to sites as well as particle size range. ► The dependence of Zn mass percent and Cu/Sb on the hourly traffic was found. ► The OC values of PM coarse are two or three times larger than those of PM fine.
Keywords: Resuspended road dust; Mobile sampling method; PM10; PM2.5; Source profile; Incheon; Korea;

Air flow and pollutant dispersion characteristics in an urban street canyon are studied under the real-time boundary conditions. A new scheme for realizing real-time boundary conditions in simulations is proposed, to keep the upper boundary wind conditions consistent with the measured time series of wind data. The air flow structure and its evolution under real-time boundary wind conditions are simulated by using this new scheme. The induced effect of time series of ambient wind conditions on the flow structures inside and above the street canyon is investigated. The flow shows an obvious intermittent feature in the street canyon and the flapping of the shear layer forms near the roof layer under real-time wind conditions, resulting in the expansion or compression of the air mass in the canyon. The simulations of pollutant dispersion show that the pollutants inside and above the street canyon are transported by different dispersion mechanisms, relying on the time series of air flow structures. Large scale air movements in the processes of the air mass expansion or compression in the canyon exhibit obvious effects on pollutant dispersion. The simulations of pollutant dispersion also show that the transport of pollutants from the canyon to the upper air flow is dominated by the shear layer turbulence near the roof level and the expansion or compression of the air mass in street canyon under real-time boundary wind conditions. Especially, the expansion of the air mass, which features the large scale air movement of the air mass, makes more contribution to the pollutant dispersion in this study. Comparisons of simulated results under different boundary wind conditions indicate that real-time boundary wind conditions produces better condition for pollutant dispersion than the artificially-designed steady boundary wind conditions.► Boundary wind condition consistent with measured time series of wind data. ► A new scheme for realizing real-time boundary conditions is proposed. ► Intermittent flow feature and flapping of the shear layer are shown clearly. ► Pollutant dispersion mechanisms are studied under the real-time boundary condition. ► Large scale movements are found enhancing the pollutant dispersion in this work.
Keywords: Street canyon; Boundary condition; Air flow; Pollutant dispersion; Large eddy simulation;

The variations of total ozone column over Europe at the multiyear time scale have earlier been characterised by the changes in the phase of North Atlantic Oscillation. Spatial patterns over Europe in total ozone column response to weather pattern changes associated with the North Atlantic Oscillation are investigated here using the cross-wavelet transform. The average cross-wavelet powers and local relative phases are calculated. It is shown that near a centre of action associated with the NAO the changes of total ozone column are maximal and become apparent immediately after the changes in the weather pattern.► It can be registered positive correlations between daily NAO index and Arosa TOC. ► The cross-wavelet transform is useful to conclude a coherency between time series. ► Local time lags of TOC variability depend on the distance to NAO’s centre of action. ► Signs of pressure anomaly in the centre of action determine cross-wavelet power.
Keywords: North Atlantic Oscillation; Weather pattern; Total ozone column; Wavelet transform;

In this work, the dynamic range of gas chromatography (GC) combined with a thermal desorber (TD) was investigated through a series of calibration experiments. To this end, standard gases of reduced sulfur compounds (RSC: H2S, CH3SH, DMS, CS2 and DMDS) covering a relatively wide concentration range (2–100 nmol mol−1 (or ppb)) were analyzed by regulating sample loading range from 40 to 1200 mL (3.3–4900 pmol). It shows that the upper limits of GC–TD quantification are far higher than those of GC alone, although the cold trap unit in a TD suffers from breakthrough after a dose of RSC (e.g., 500 (DMDS) to 1600 pmol (H2S)). Its quantification uncertainties tend to grow systematically with decreases in standard concentrations and sample loading volume, especially with H2S. According to this study, the use of TD generally reduces the absolute detectability of GC by about one order of magnitude. Such reduction caused by TD application can be compensated efficiently with similar magnitude through the magnification of sample supply. Moreover, the TD system allows to increase sample volume (up to 3 orders of magnitude or above), it can ultimately help extend the practical range of RSC qualification in a fairly reliable manner.► The dynamic range of GC–TD is investigated for gaseous reduced sulfur compounds. ► The method is tested by using their standard gases with a highly diverse range. ► The results allow to discriminate the TD-based detection property of each RSC. ► The use of TD can alter their quantification range relative to direct injection.
Keywords: Gas chromatography; Reduced sulfur compounds; Hydrogen sulfide; Bag sampling; Thermal desorber;

Simultaneous observation of seasonal variations of beryllium-7 and typical POPs in near-surface atmospheric aerosols in Guangzhou, China by Jing Pan; Yong-Liang Yang; Gan Zhang; Jing-Lei Shi; Xiao-Hua Zhu; Yong Li; Han-Qing Yu (3371-3380).
Near-surface atmospheric aerosol samples were collected at the sampling frequency of 2–3 d per week for one year from August 2006 to August 2007 at a low latitude station in Tianhe District, Guangzhou, Guangdong Province of southern China. The samples were analyzed for cosmogenic nuclide 7Be and persistent organic pollutants, i.e. organochlorine pesticides (OCPs), polychlorinated biphenyls (PCBs), and polybrominated diphenyl ethers (PBDEs). The annual average 7Be concentration was 2.59 mBq m−3, with the maximum occurred in May (8.45 mBq m−3) and minimum in late August and early September (0.07 mBq m−3). Winter and spring were the seasons in which the 7Be concentrations were high while summer and autumn were the lower 7Be seasons. Spring peaks in 7Be in the near-surface atmospheric aerosols may have associated with the “spring leak maximum” episode. The annual average ∑OCPs concentration was 345.6 pg m−3, ∑33PCBs 317.6 pg m−3, and ∑31PBDEs 609.0 pg m−3. The variation trends in the time-series of 7Be, OCPs, PCBs, and PBDEs in near-surface atmospheric aerosol showed both common features and differences. Significant correlations (R 2 = 0.957 and 0.811. respectively, p = 0.01) were observed between the monthly average 7Be concentrations and those of ∑PCBs and ∑PBDEs in summer, autumn, and early winter. The difference between the seasonal variation features of OCPs and PCBs (and PBDEs) could be attributed to the different source functions and physical–chemical properties which could control the behaviors of these compounds in air–aerosol partitions as well as atmospheric transport.► Simultaneous observation of seasonal variations of 7Be and typical POPs in aerosols. ► Correlation was observed between 7Be and typical POPs in aerosol in monsoon season. ► Application of 7Be as a tracer for long-range transport of POPs was attempted.
Keywords: Beryllium-7; Aerosol; Persistent organic pollutants; Guangzhou; East Asia monsoon;

Assessment of reduced sulfur compounds in ambient air as malodor components in an urban area by Janice Susaya; Ki-Hyun Kim; Nhu-Thuc Phan; Jo-Chun Kim (3381-3390).
Long-term monitoring of reduced sulfur compounds (RSCs: hydrogen sulfide (H2S), methanethiol (CH3SH), dimethyl sulfide (DMS), and dimethyl disulfide (DMDS)) in ambient air was made using an on-line GC system at an odor monitoring station in the city of Ansan, South Korea (August 2005–December 2007). The results were examined to assess the status of RSC pollution, its relative contribution to malodor, and the controlling factors of its occurrence. H2S (mean of 0.27 ppb) was eminent in terms of both magnitude and occurrence frequency, while others were not with mean values of 0.11 (DMDS), 0.10 (DMS), and 0.07 ppb (CH3SH). Unlike others, the temporal trends of H2S were best represented by the combined effects of its source processes and meteorological conditions. The results of correlation analysis indicate strong correlations between RSCs and water-related parameters (e.g., rainfall, dew point, and relative humidity). The role of RSCs as malodor component appears to be pronounced during nighttime, especially in summer. If the relative contribution of RSCs to malodor is assessed by means of the sum of odor intensity (SOI), its impact is relatively low, with an SOI value of 1.22 (weak odor strength). Consequently, a more deliberate approach may be needed to effectively assess odor occurrence patterns in ambient air.► Concentration levels of reduced sulfur compounds (RSC) in ambient air are monitored. ► The target RSCs were selected to include H2S, CH3SH, DMS, and DMDS. ► The environmental behavior of RSCs were examined in relation to environmental parameters. ► The results will help establish an environmental management scheme for the key odorants.
Keywords: Reduced sulfur compounds; Ambient; Odorant monitoring; H2S; CH3SH; DMS; DMDS;

Background concentrations and source apportionment of polycyclic aromatic hydrocarbons in south-eastern Finland by Mika Vestenius; Sirkka Leppänen; Pia Anttila; Katriina Kyllönen; Juha Hatakka; Heidi Hellén; Antti-Pekka Hyvärinen; Hannele Hakola (3391-3399).
Polycyclic aromatic hydrocarbons (PAH compounds) were measured in the PM10 fraction [from ambient air] at Virolahti, Finland. The sampling site is located in a rural area in the south-eastern corner of Finland, near the Russian border. Altogether, 51 daily and 85 weekly filter samples were collected in 2007–2008. The yearly average concentration of benzo(a)pyrene at Virolahti in 2007 was 0.21 ng m−3, which is well below the annual target value of 1 ng m−3 set by the European Union. The positive matrix factorization (PMF) method was applied in source apportionment for daily PAH data combined with other pollutant data. A three-factor solution of the PMF analysis with 28 components was chosen. These three factors were identified as long-range transported secondary particles (F1), combustion (F2) and a sea-salt factor (F3). The conditional probability function (CPF) was used to combine wind direction sectors with the PMF factors. In cases F1 and F2, pollutants mainly originated from the south-east, whereas pollutants in F3 came from the south-western sector.PAHs entered into the combustion factor 2 together with SO2, NOx, black carbon and potassium. This suggests that the PAHs at Virolahti originated from traffic and industrial pollution, as well as biomass burning. Elevated concentrations occurred throughout the winter period and most frequently originated from the south-eastern sector between 90°–135°. This sector includes, among other transboundary areas, the metropolis of St. Petersburg at a distance of 160 km.► PAHs in PM10 were collected at Virolahti, Finland. ► Benzo(a)pyrene was relatively high compared to other European background sites. ► PMF method was applied for daily PAH data combined with other pollutant data. ► Major source area of PAHs was in the eastern sector.
Keywords: PAH; PM10; Air quality; Background areas; Positive matrix factorization;

Atmospheric nitrogen (N) deposition has been widely considered as an important N input into agroecosystems, but its measurement involves considerable uncertainties with various methods. In this study, a field sampler with distilled water as a surrogate surface was developed and trialed for the collection of dry and wet N deposition. The direct measuring results were compared with the value calculated by the N mass balance method (crop N uptake from plots receiving no N fertilizers of the long-term fertilization experiment in the monitoring station). The results indicated that exposure durations of 3–5 days and water volumes of 2000–2800 ml were tested to be suitable to collect dry N deposition, while water volumes of less than 1000 ml and sampling conducted immediately after rain event were found to be appropriate for wet N collection under the present experimental conditions. The monitoring work was conducted from June 2008 to May 2009, and annual N deposition totaled up to 40.32 kg N ha−1, of which dry deposition accounted for 62.45%. NH4–N was the dominant species in N deposition and contributed 62.68% and 66.00% to wet and dry deposition, respectively. Organic N (O-N) was found to make greater contributions than NO3–N in both dry and wet depositions. Total N deposition was parallel to the results estimated by the method of mass N balance from the long-term experiment, as 45.6 kg N ha−1. These results provide helpful knowledge to elucidate the N deposition scenario of a typical agroecosystem and can be of great importance for the calculation of fertilizer recommendations in the Huang-Huai-Hai Plain.► Water surface method was applicable in the collection of N deposition. ► Integrated wet and dry N collection reduced measuring uncertainties. ► Detailed information was presented for deposited N species. ► Sampling measurements were comparable to the estimated results.
Keywords: Atmospheric nitrogen (N) deposition; Water surface sampler; Agroecosystem; Huang-Huai-Hai Plain;

Emissions from soy biodiesel blends: A single particle perspective by Dabrina D. Dutcher; Joakim Pagels; Anil Bika; Luke Franklin; Mark Stolzenburg; Samantha Thompson; Juan Medrano; Nicholas Brown; Deborah S. Gross; David Kittelson; Peter H. McMurry (3406-3413).
Biodiesel has recently reemerged as a common fuel. However, emissions from biodiesel combustion have been studied in much less detail than those from traditional petroleum-based diesel. In this experiment, emissions from the combustion of different fuel blends (B00, B02, B20, B99, where the number after B indicates the percentage, by volume, of biodiesel in the fuel) in a VW TDi engine were analyzed by aerosol time-of-flight mass spectrometers (ATOFMS) for single-particle composition and vacuum aerodynamic size. The ATOFMS results show that the PAH molecular weight distribution is not significantly affected by the fuel composition, and that sulfates are reduced by increased biodiesel content. Octanedioic acid (a carbonyl species) is increased with increased biodiesel concentration. Clustering results from the single-particle spectra show that the particles fall in five main types by chemical composition. The aerodynamic size distribution of these individual clusters was also determined. These results also show that methods used to identify diesel particle emissions for source apportionment are not applicable when significant concentrations of biodiesel are used in fuels.► Particles from the combustion of biodiesel in a diesel engine were examined. ► More biodiesel results in a higher percentage of organic carbon dominated particles. ► More biodiesel results in a lower percentage of calcium dominated particles.
Keywords: Biodiesel; Aerosol; ATOFMS;

An urban solar flux island: Measurements from London by C.L. Ryder; R. Toumi (3414-3423).
Solar irradiance measurements from a new high density urban network in London are presented. Annual averages demonstrate that central London receives 30 ± 10 W m−2 less solar irradiance than outer London at midday, equivalent to 9 ± 3% less than the London average. Particulate matter and AERONET measurements combined with radiative transfer modelling suggest that the direct aerosol radiative effect could explain 33–40% of the inner London deficit and a further 27–50% could be explained by increased cloud optical depth due to the aerosol indirect effect. These results have implications for solar power generation and urban energy balance models.A new technique using ‘Langley flux gradients’ to infer aerosol column concentrations over clear periods of 3 h has been developed and applied to three case studies. Comparisons with particulate matter measurements across London have been performed and demonstrate that the solar irradiance measurement network is able to detect aerosol distribution across London and transport of a pollution plume out of London.► New measurements of solar irradiance from a high density urban network in London. ► Central London receives 9 ± 3% less irradiance than the rest of London. ► Inner London deficit plausibly explained by the aerosol direct and indirect effects. ► New technique to infer relative aerosol column concentrations has been developed. ► Solar irradiance network is able to detect aerosol distribution across London.
Keywords: Aerosol; London; Urban; Air pollution; Radiation; Network;

An assessment of Aviation’s contribution to current and future fine particulate matter in the United States by Matthew Woody; Bok Haeng Baek; Zachariah Adelman; Mohammed Omary; Yun Fat Lam; J. Jason West; Saravanan Arunachalam (3424-3433).
The impacts of aviation emissions on current and future year fine particulate matter (PM2.5) were investigated using the Community Multiscale Air Quality model, accounting for aviation emissions from 99 airports and below 3 km during landing and takeoff (LTO) cycles. Results indicated that current year aviation emissions increased annual average PM2.5 concentrations by 3.2 ng m−3 (0.05%) in the continental U.S. while projected 2025 aviation emissions increased annual average PM2.5 by 11.2 ng m−3 (0.20%). Ammonium nitrate aerosol was the largest contributor to the increase in PM2.5 concentrations, particularly in the future year. Using an indicator of inorganic PM2.5 change, we attributed ammonium nitrate aerosol contributions in both years to excess free ammonia (8% higher NH3 and 35% lower NOx emissions from non-aviation sources in 2025 than 2005), and higher aircraft emissions of NOx (which when converted to HNO3 forms ammonium nitrate aerosol) than SO2 (a precursor of ammonium sulfate aerosol). Our findings highlight the critical role that non-aviation emissions play in assessing the air quality impacts of aviation emissions in a future year scenario.► Aircraft LTO emissions in U.S. contribute 3.2 ng/m3 or 0.05% of annual PM2.5 in 2005. ► This contribution increases four fold to 0.20% for a future year scenario in 2025. ► Nitrate aerosol was the largest contributor to the changes in PM2.5. ► Non-aviation emissions combined with aircraft NOx impact future year concentrations. ► Free Ammonia explains the role of non-aviation sources in forming ammonium nitrate.
Keywords: Aviation emissions; PM2.5; CMAQ; NextGen; Inorganic PM2.5 change; Free ammonia;

Deterministic models have become essential tools to forecast and map concentration fields of atmospheric pollutants like ozone. Those models are regularly updated and improved by incorporating recent theoretical developments and using more precise input data. Unavoidable differences with in situ measurements still remain, which need to be better understood. This study investigates those discrepancies in a geostatistical framework by comparing the temporal variability of ozone hourly surface concentrations simulated by a chemistry-transport model, CHIMERE, and measured across France. More than 200 rural and urban background monitoring sites are considered. The relationship between modelled and observed data is complex. Ozone concentrations evolve according to various time scales. CHIMERE correctly accounts for those different scales of variability but is usually unable to reproduce the exact magnitude of each temporal component. Such difficulty cannot be entirely attributed to the difference in spatial support between grid cell averages and punctual observations. As a result of this exploratory analysis, the common multivariate geostatistical model, known as the linear model of coregionalization, is used to describe the temporal variability of ozone hourly concentrations and the relationship between simulated and observed values at each observation point. The fitted parameters of the model can then be interpreted. Their distribution in space provides objective criteria to delimitate the areas where the chemistry-transport model is more or less reliable.► Outputs of a chemistry-transport model (CTM) are compared to ozone measurements. ► Their temporal variability is analysed using a geostatistical approach. ► The linear model of coregionalization (LMC) makes a relevant framework for this analysis. ► The relationship between observations and CTM is quantified per variability scale. ► The parameters of the LMC can be interpreted in terms of CTM performance.
Keywords: Ozone; Chemistry-transport model; Monitoring data; Temporal variability; Cross-variogram; Linear model of coregionalization;

Mixing state of biomass burning particles by single particle aerosol mass spectrometer in the urban area of PRD, China by Xinhui Bi; Guohua Zhang; Lei Li; Xinming Wang; Mei Li; Guoying Sheng; Jiamo Fu; Zhen Zhou (3447-3453).
Single particle aerosol mass spectrometer (SPAMS) was used to characterize the single particle size and chemical composition of submicron aerosols in the urban area of the Pearl River Delta region, China, for the period April 30 through May 22, 2010. A total of 696,465 particles were sized and chemically analyzed with both positive and negative ion spectra, in which 141,338 biomass burning particles were identified representing a significant source of submicron particles ∼20.3% by number. The results have revealed that biomass burning particles have experienced extensive atmospheric processing, finding that as much as 90.5% of the particles have internally mixed with secondary inorganic species. Biomass burning particles were clustered into six distinct particle groups, comprising of K–Ca-rich, K–Na-rich, K–organic carbon (K–OC), K–elemental carbon (K–EC), K–the mixture of OC and EC (K–OCEC) and K–Secondary. K–OC was the largest contributor with a fraction of 22.9%, followed by K–Secondary type (21.4%) and K–OCEC (19.0%). K–Na-rich type was observed in 11.9% of the particles and 90% internally mixed with EC. The fraction of nitrate in biomass burning particles was 10% higher than in the non-biomass burning particles. The sodium and potassium in biomass burning particles could exhibit high affinity for nitrate gases during neutralization reactions, facilitating the particulate nitrate formation. Meanwhile, the particulate sulfate in particles in the droplet-mode size was also enhanced. The results added appreciably to the knowledge of aerosol characteristics in the PRD region atmosphere and could be applied to the climate models.► Biomass burning particles accounted for ∼20.3% by unscaled SPAMS number in PRD. ► 90.5% of the biomass burning particles internally mixed with sulfate and nitrate. ► K–OC was the largest contributor, followed by K–Secondary and K–OCEC mixture. ► Sulfate was preferentially mixed with the organics-containing particles. ► Biomass burning maybe facilitate the formation of particulate nitrate.
Keywords: Biomass burning; Mixing state; Single particle; Nitrate; Sulfate; SPAMS; ATOFMS; Aerosol; PRD;

The rapid growth of energy consumption in conjunction with economic development during past decades in East Asia, especially China, caused severe air pollution problems at local and regional scales. Understanding of the meteorological conditions for air pollution is essential to the understanding of the formation mechanism of air pollutants and the development of effective emission control strategies to reduce air pollution. In this paper, the Fifth Generation National Center for Atmospheric Research (NCAR)/Pennsylvania State University (PSU) Mesoscale Model (MM5) modeling system is applied to simulate meteorological fields during selected six 1-month periods in 2007/2008 over a triple-nested modeling domain covering East Asia, the eastern China, and Shandong Province at horizontal grid resolutions of 36-, 12-, and 4-km, respectively. MM5 generally reproduces well the observations in the eastern China but performs worse in the western China and northeastern China. Largest biases occur in 2-m temperatures (T2) and wind speed and wind direction at 10-m in haze months (i.e., winter) and daily mean precipitation (Precip) in non-haze months (i.e., summer), due to limitations of the model in simulating snow cover and convective precipitation. Meteorological predictions agree more closely with observations at urban sites than those at the coastal and mountain sites where the model performance deteriorates because of complex terrains, influences of urban heat island effect and land/sea breezes, and higher elevations. Model results at 12-km in Shandong Province show an overall better performance than those at 4- or 36-km while the results at 4-km show worst performance due to inaccurate land use and the model’s incapability in simulating meteorological processes at a fine scale.► MM5 reproduces observations in eastern China but performs worse in other regions. ► T2 & precip. has largest biases, due to inaccurate snow cover & convective precip. ► Predictions agree better with observations at urban sites than other sites. ► Results at 4-km are not the best due to inaccurate land use and model limitations.
Keywords: MM5; Meteorological model evaluation; Sensitivity to horizontal grid resolution; China;

Ambient PM10 concentrations from wood combustion – Emission modeling and dispersion calculation for the city area of Augsburg, Germany by Christian Brandt; Robert Kunde; Bernhard Dobmeier; Jürgen Schnelle-Kreis; Jürgen Orasche; Gerhard Schmoeckel; Jürgen Diemer; Ralf Zimmermann; Matthias Gaderer (3466-3474).
Ambient PM10 concentration monitoring as well as dispersion calculations were conducted to determine the influence of emissions from domestic heating on ambient PM10 concentrations in Augsburg, Germany. Based on the Augsburg emission inventory for domestic heating an average emission factor for particulate emissions from the combustion of different solid fuels (wood logs, pellets, briquettes) in different types of stoves under various combustion conditions was found to be 120 mg MJ−1 related to energy input. Hence an emission model as well as a wind field model were created for dispersion calculation of the emitted PM from wood combustion within Augsburg. The results of the dispersion calculation concurred with the ambient PM10 monitoring data measured during the heating period 2007/2008. One result found that in residential areas with a high density of stoves the observed maximum concentration value of 9 μg m−3 from wood combustion was up to 50% higher than in the city center. Ambient monitoring as well as dispersion calculation have shown a significant influence of wood combustion on ambient PM10 concentrations in Augsburg. Based on these results the impact of wood combustion in a city can be estimated.► Influence of wood combustion on ambient PM10 shown by monitoring and calculation. ► Results of dispersion calculation concurred with ambient PM10 monitoring data. ► PM10 max. concentration in residential areas up to 50% higher than in city center. ► The impact of wood combustion in a city can be estimated based on these results.
Keywords: Wood combustion; Emissions; Ambient PM10; Modeling; Dispersion calculation; Meteorology;

Decreasing trends in total gaseous mercury observations in baseline air at Mace Head, Ireland from 1996 to 2009 by R. Ebinghaus; S.G. Jennings; H.H. Kock; R.G. Derwent; A.J. Manning; T.G. Spain (3475-3480).
In this study, the concentrations of total gaseous mercury in baseline air masses arriving at Mace Head, Ireland after having traversed the thousands of kilometres uninterrupted fetch of the North Atlantic Ocean, have been used for the assessment of possible trends in the atmospheric mercury background concentration over a 14-year period (i.e., 1996–2009), a statistically significant negative (downwards) trend of −0.028 ± 0.01 ng m−3 yr−1, representing a trend of 1.6–2.0% per year, has been detected in the total gaseous mercury levels in these baseline air masses. These findings are set in the context of the available literature studies of atmospheric Hg trends.► Our data set is the longest existing time series for Hg in temperate background air. ► More than 40 000 concentration measurements could be attributed to NH background air. ► We find a downward trend of 1.6–2.0%/yr over the 14 years measurement period. ► This decline is large in comparison to that seen in other trace gases. ► This decline contradicts current global emission inventories for mercury.
Keywords: Total gaseous mercury; Long term trends; Mace Head; Hg;

Statistical relationships between ground-level daily maximum 8-h ozone (O3) concentrations and multiple meteorological parameters were developed for data drawn from ambient measurements and values that were simulated with the U.S. Environmental Protection Agency’s (EPA) Community Multiscale Air Quality (CMAQ) model. This study used concurrent and co-located data from both sources during the O3 season (May 1–September 30) for a four-year period (2002–2005). Regression models were developed for 74 areas across the Eastern U.S. The most important meteorological parameters used in the model were found to be daily maximum temperature and the daily average relative humidity (RH). Average morning and afternoon wind speed as well as factors for the day of the week and years were also included in the statistical models. R 2 values above 60% were obtained for the majority of the locations in the analysis for both the ambient and CMAQ statistical models. Analysis of the covariate-specific effects revealed a tendency for the CMAQ model to underestimate how O3 increases with temperature. These results suggest that air quality forecasts that incorporate the CMAQ model may be underestimating the climate penalty on future O3 concentrations from warmer temperatures.► Relationships between ozone and meteorology are assessed. ► These relationships are separately derived for CMAQ and measurement data. ► CMAQ underestimates the increases in ozone that result from increasing temperature. ► This finding may have implications for coupled climate – air quality models.
Keywords: Ozone; CMAQ; Statistical models;

Interlaboratory comparison exercise for the determination of As, Cd, Ni and Pb in PM10 in Europe by M. Gerboles; D. Buzica; R.J.C. Brown; R.E. Yardley; A. Hanus-Illnar; M. Salfinger; B. Vallant; E. Adriaenssens; N. Claeys; E. Roekens; K. Sega; J. Jurasović; S. Rychlik; E. Rabinak; G. Tanet; R. Passarella; V. Pedroni; V. Karlsson; L. Alleman; U. Pfeffer; D. Gladtke; A. Olschewski; B. O’Leary; M. O’Dwyer; D. Pockeviciute; J. Biel-Ćwikowska; J. Turšič (3488-3499).
This paper presents the results of an intercomparison exercise for the determination of arsenic (As), cadmium (Cd), nickel (Ni) and lead (Pb) in PM10, which are regulated by the European Directives for ambient air quality. Thirteen laboratories participated, generally using the European reference methods of measurement which consist of a microwave digestion followed by analysis with either ICP-MS or GFAAS. Each participant was asked to analyse five test samples: a liquid Certified Reference Material (CRM), two sub-samples of a NIST dust CRM (one already-digested and one to be digested by the participants) and two loaded filters (one already-digested and one to be digested by the participants).Participants were able to meet the Data Quality Objectives (DQOs) of the European Directives (expanded uncertainties of 25% for Pb and 40% for As, Cd and Ni) for 93% of all test samples, except for the loaded filter that were digested by the participants. In fact, only 76% of DQOs were met for this test sample, the closest to a routine sample analysis in the laboratory. The difficulties in analysing this test sample came mainly from digestion and contamination processes. Satisfactory results were also obtained using other digestion techniques (Soxhlet extraction and high pressure methods) and analytical methods (ICP-OES for Cd, Ni and Pb, EDXRF for Pb and Ni and Voltammetry for As, Ni, and Pb).Participants claimed uncertainties of about 10% for Pb and between 15 and 20% for As, Cd and Ni. These uncertainties were confirmed for 77% of results. The reproducibility of the methods of measurement was between 41 and 54% while repeatability remained between 5 and 12% except for the analysis of As on filters which was up to 20%. The majority of participant results showed higher between-day variability (14 ± 11%) than within-day variability (6.0 ± 5.3%).► Participants mainly analysed heavy metalbyICPMS/GFAAS after micro-wave digestion. ► 76% of participants had uncertainty <25% for Pb and 40% for As, Cd and Ni in PM10. ► Sample digestion and contamination processes were the major difficulties. ► Suitable digestion with Soxhlet and high pressure and partly analysis by ICP-OES, EDXRF and Voltammetry. ► Reproducibility: 41–54%, repeatability: 5–12% except for As (20%).
Keywords: Heavy metals; PM10; Particulate matter speciation; Air quality legislation; Uncertainty of measurement;

Published particle number emission factors for aircraft operations remain very sparse and so far such emissions have not been included in the International Civil Aviation Organization (ICAO) databases. This work addresses this gap in knowledge by utilizing recent progress in the quantification of aircraft particle emissions. Annual emissions of particle number (PN), particle mass (PM2.5) and NOx throughout the aircraft landing and takeoff (LTO) cycles and ground running procedures (GRP) are presented for aircraft using Brisbane Airport BNE (domestic and international). The aircraft are grouped according to an airframe based classification system. The resulting data are then used to develop an emissions inventory for large aircraft thrust engine operations on the ground, during LTO cycles and GRP, at the Airport.Annual PN, PM2.5 and NOx emissions from large aircraft operations during LTO cycles and GRP at BNE were 1.98 × 1024 yr−1, 1.35 × 104 kg yr−1 and 8.13 × 105 kg yr−1, respectively. Results showed that LTO cycles contribute more than 97% of these annual emissions at BNE in comparison to GRP related emissions. Analysis of the LTO cycle contribution to the daily emissions showed that the contribution of the climbout mode is considerably higher than for other individual LTO operational modes. Emissions during aircraft departures were significantly higher than those during arrival operations, due to the higher aircraft engine emission rates during takeoff and climbout.► This work presents particle emission factors from aircraft during takeoff, landing and ground running procedures. ► The landing and take-off cycles contributed more than 97% of the annual emissions at the airport, with the contribution of the climbout mode is considerably higher than for other individual operational modes. ► Emissions during aircraft departures were significantly higher than those during arrival operations, due to the higher aircraft engine emission rates during takeoff and climbout.
Keywords: Aircraft engine emissions; Airport emissions inventory; Particle and gaseous emissions Airborne particles;

Recently, the cosmic-ray-driven electron-induced reaction mechanism (CRE) was introduced to explain polar ozone depletion and surface temperature change. It was proposed that the dissociation of chlorofluorocarbons (CFCs) on ice surfaces of polar stratospheric clouds plays the dominant role in forming the ozone hole. Efforts have been made to predict polar ozone loss in future years. It was further proposed that CFCs and cosmic-ray-driven ozone depletion may control global surface temperatures. These assertions challenge the fundamental understanding of Antarctic stratospheric ozone loss and global warming. Here we show that these arguments based on the CRE mechanism are inconclusive. First, correlations of satellite data of CFC-12, N2O and CH4 from ACE-FTS show no evidence of significant loss of CFC-12 as predicted by the CRE mechanism. Second, conclusions drawn about a possible CRE impact on the atmosphere, based on correlations of different observed atmospheric parameters, do not have a physical basis. Finally, predictions on the future development of the atmosphere based on these correlations are not reliable for either the ozone hole or global surface temperatures.
Keywords: Ozone; Ozone depletion; Global warming; Cosmic rays; Dissociative electron attachment;