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Atmospheric Environment (v.44, #7)

Editorial board (pp. i).

A passive sampling method for radiocarbon analysis of atmospheric CO2 using molecular sieve by Mark H. Garnett; Iain P. Hartley (pp. 877-883).
Radiocarbon (14C) analysis of atmospheric CO2 can provide information on CO2 sources and is potentially valuable for validating inventories of fossil fuel-derived CO2 emissions to the atmosphere. We tested zeolite molecular sieve cartridges, in both field and laboratory experiments, for passively collecting atmospheric CO2. Cartridges were exposed to the free atmosphere in two configurations which controlled CO2 trapping rate, allowing collection of sufficient CO2 in between 1.5 and 10 months at current levels.14C results for passive samples were within measurement uncertainty of samples collected using a pump-based system, showing that the method collected samples with14C contents representative of the atmosphere. δ13C analysis confirmed that the cartridges collected representative CO2 samples, however, fractionation during passive trapping means that δ13C values need to be adjusted by an amount which we have quantified. Trapping rate was proportional to atmospheric CO2 concentration, and was not affected by exposure time unless this exceeded a threshold. Passive sampling using molecular sieve cartridges provides an easy and reliable method to collect atmospheric CO2 for14C analysis.

Keywords: Atmospheric CO; 2; Radiocarbon; Passive sampling; Molecular sieve


A comparative evaluation of passive and active samplers for measurements of gaseous semi-volatile organic compounds in the tropical atmosphere by Jun He; Rajasekhar Balasubramanian (pp. 884-891).
The polyurethane foam (PUF) disk-based passive air samplers (PAS), mounted inside two aluminium bowls to buffer the air flow to the disk and to shield it from precipitation and sunlight, were used for the collection of atmospheric SVOCs in Singapore during April 2008–June 2008. Data obtained from PAS measurements are compared to those from active high-volume air sampling (AAS). Single factor ANOVA tests show that there were no significant differences in chemical distribution profiles between actively and passively collected samples (PAHs, F = 3.38 × 10−8 < Fcritical = 4.17 with p > 0.05; OCPs, F = 2.71 × 10−8 < Fcritical = 4.75 with p > 0.05). The average air-side mass transfer coefficient (k A) for PAS, determined from the loss of depuration compounds such as 13C6 – HCB (1000 ng), 13C12 – 4,4′ DDT (1000 ng) and 13C12 – PCB 101 (1000 ng)spiked on the disks prior to deployment, was 0.12 ± 0.04 m s−1. These values are comparable to those reported previously in the literature. The average sampling rate was 3.78 ± 1.83 m3 d−1 for the 365 cm2 PUF disk. Throughout the entire sampling period (∼68 d), most of the PAHs and all OCPs exhibited a linear uptake trend on PAS, while naphthalene, acenaphthylene, acenaphthene and fluorene reached the curvilinear phase after the first ∼30 d exposure. Theoretically estimated times to equilibrium (t eq) ranged from around one month for Acy to hundreds of years for DB(ah)A. Sampling rates, based on the time integrated active sampling-derived concentrations and masses collected by PUF disks during the linear uptake phase, were determined for all target compounds with the average values of 2.50 m3 d−1 and 3.43 m3 d−1 for PAHs and OCPs, respectively. More variations were observed as compared to those from the depuration study. These variation were most likely due to the difference of physicochemical properties of individual species. Lastly, multiple linear regression models were developed to estimate the log-transformed gaseous concentration of an individual compound in air based on the mass collection rate of the gaseous SVOCs measured using the PAS and the molecular weight (MW) of the particular compound for both PAHs and OCPs, respectively.

Keywords: SVOCs; Passive sampling; PUF disk; Air-side mass transfer coefficient


Distant source contributions to PM10 profile evaluated by SOM based cluster analysis of air mass trajectory sets by Ferhat Karaca; Fatih Camci (pp. 892-899).
This paper evaluates the effects of long-range transport patterns of air masses to the regional PM profile in a megacity, Istanbul, Turkey. Five-day hourly backward trajectories were obtained by the HYSPLIT model for selected episodic events in 2008. Self Organizing Maps (SOM), a very powerful classification tool, was used to cluster these trajectories. In total, eight cluster groups were obtained. All of the clusters were evaluated with respect to inhalable particulate matter (PM10) concentrations observed in Istanbul for the arrival times of the trajectories. Istanbul is generally under the effect of trajectories in three clusters (1, 2 and 4) (52% of all pre-selected episodic events), which have higher mean concentration values than the mean value of all the samples. These clusters typically make significant PM contributions to Istanbul's air quality. PM loadings of the trajectories in these clusters were attributed to massive anthropogenic activity over all of Europe and southwestern air flow most likely carrying PM10 atmospheric particles originating from the Saharan Desert and other global dust generation regions located in the northern part of Africa.

Keywords: Long-range transport; Cluster analysis; Artificial neural networks (ANN); Air pollution; HYSPLIT model


The influence of sampling protocol on nonmethane hydrocarbon mixing ratios by Lambert A. Doezema; Chris Bigley; Gabriele Canzi; Kylee Chang; Andrew J. Hirning; Joyce Lee; Nick Von der Ahe (pp. 900-908).
The effect of sampling protocol on ambient air hydrocarbon mixing ratios was examined on eight sampling days in Los Angeles during 2007 and 2008. Four protocols, which were based on previously published multi-city urban hydrocarbon studies in the United States, were compared and differences were quantified. Whole air canister samples were collected and analyzed for nonmethane hydrocarbons (NMHCs). Differing sampling protocols resulted in large differences in mixing ratios, up to an order of magnitude, for certain NMHCs on the same sampling day. However, the magnitude of the variability between NMHC levels obtained by the four protocols was not consistent throughout the eight sampling days. It was found that sampling time, followed by sampling location, had the greatest influence on the magnitude of the mixing ratio. Ratios between hydrocarbons, often used in urban studies to gain information on emission sources, also varied depending on the protocol used. Comparison of absolute NMHC mixing ratios collected in urban environments using differing sampling protocols should be made with care.

Keywords: NMHCs; Urban air pollution; Ozone precursors; Sampling protocol; Los Angeles


Diesel passenger car PM emissions: From Euro 1 to Euro 4 with particle filter by Theodoros Tzamkiozis; Leonidas Ntziachristos; Zissis Samaras (pp. 909-916).
This paper examines the impact of the emission control and fuel technology development on the emissions of gaseous and, in particular, PM pollutants from diesel passenger cars. Three cars in five configurations in total were measured, and covered the range from Euro 1 to Euro 4 standards. The emission control ranged from no aftertreatment in the Euro 1 case, an oxidation catalyst in Euro 2, two oxidation catalysts and exhaust gas recirculation in Euro 3 and Euro 4, while a catalyzed diesel particle filter (DPF) fitted in the Euro 4 car led to a Euro 4 + DPF configuration. Both certification test and real-world driving cycles were employed. The results showed that CO and HC emissions were much lower than the emission standard over the hot-start real-world cycles. However, vehicle technologies from Euro 2 to Euro 4 exceeded the NOx and PM emission levels over at least one real-world cycle. The NOx emission level reached up to 3.6 times the certification level in case of the Euro 4 car. PM were up to 40% and 60% higher than certification level for the Euro 2 and Euro 3 cars, while the Euro 4 car emitted close or slightly below the certification level over the real-world driving cycles. PM mass reductions from Euro 1 to Euro 4 were associated with a relevant decrease in the total particle number, in particular over the certification test. This was not followed by a respective reduction in the solid particle number which remained rather constant between the four technologies at 0.86 × 1014 km−1 (coefficient of variation 9%). As a result, the ratio of solid vs. total particle number ranged from ∼50% in Euro 1–100% in Euro 4. A significant reduction of more than three orders of magnitude in solid particle number is achieved with the introduction of the DPF. However, the potential for nucleation mode formation at high speed from the DPF car is an issue that needs to be considered in the over all assessment of its environmental benefit. Finally, comparison of the mobility and aerodynamic diameters of airborne particles led to fractal dimensions dropping from 2.60 (Euro 1) to 2.51 (Euro 4), denoting a more loose structure with improving technology.

Keywords: Particle number; Exhaust emissions; DPF; Emission standard; Particle density


Applications of satellite remote sensing data for estimating biogenic emissions in southeastern Texas by M.S. Feldman; T. Howard; E. McDonald-Buller; G. Mullins; D.T. Allen; A. Hansel; A. Wisthaler (pp. 917-929).
The sensitivity of biogenic emission estimates and air quality model predictions to the characterization of land use/land cover (LULC) in southeastern Texas was examined using the Global Biosphere Emissions and Interactions System (GloBEIS) and the Comprehensive Air Quality Model with extensions (CAMx). A LULC database was recently developed for the region based on source imagery collected by the Landsat 7 Enhanced Thematic Mapper-Plus sensor between 1999 and 2003, and field data for land cover classification, species identification and quantification of biomass densities.  Biogenic emissions estimated from the new LULC data set showed good general agreement in their spatial distribution, but were approximately 40% lower than emissions from the LULC data set currently used by the State of Texas, primarily because of differences in the biomass estimates of key species such as Quercus. Predicted ozone mixing ratios using the biogenic emissions produced from the new LULC data set were as much as 26 ppb lower in some areas on some days, depending on meteorological conditions. Satellite data and image classification techniques provide useful tools for mapping and monitoring changes in LULC. However, field validation is necessary to link species and biomass densities to the classification system used for accurate biogenic emissions estimates, especially in areas such as riparian corridors that contain dense spatial coverage of key species.

Keywords: Biogenic Emissions; Isoprene; Remote sensing satellite data; Land cover; Regional air quality modeling; Ozone


An experimental study of the influence of biofuel origin on particle-associated PAH emissions by R. Ballesteros; J.J. Hernández; L.L. Lyons (pp. 930-938).
The chemical speciation of the 16 polycyclic aromatic hydrocarbons associated to the particulate matter of conventional diesel fuel, rapeseed methyl esters, waste cooking oil methyl esters, waste cooking oil ethyl esters and their conventional fuel blends has been carried out. The speciation of these individual compounds was made by a combination of thermal extraction, solid phase micro-extraction and GC/MS analysis. This PAH speciation method was applied to a real samples obtained from a diesel engine under two different operating modes, urban and extraurban modes. The purpose of this work was to study the relationship between the amount, type and carcinogenic potency of polycyclic aromatic hydrocarbons in engine emissions and the multi-component biodiesel fuel composition.

Keywords: Diesel particulate matter; PAHs; Regulated emissions; Carcinogenic; Biofuels; Speciation


Why ozonolysis may not increase the hydrophilicity of particles by T.M. McIntire; O.S. Ryder; P.L. Gassman; Z. Zhu; S. Ghosal; B.J. Finlayson-Pitts (pp. 939-944).
It is commonly assumed that atmospheric oxidation of hydrocarbon particles or hydrocarbon coatings on particles leads to polar products and increased water uptake, altering atmospheric visibility and increasing the likelihood they will act as cloud condensation nuclei (CCN). We show here through laboratory experiments that increased water uptake depends on the 3-dimensional structure of the particles. Laboratory studies of particles formed during ozonolysis of surface-bound alkenes, present as terminally unsaturated self-assembled monolayers (C8= SAM) on a silica substrate, were carried out at room temperature and 1 atm pressure. SAMs were exposed to ∼1013 O3 molecules cm−3 for 40 min and resultant particles were analyzed using single particle Fourier transform infrared micro-spectroscopy (micro-FTIR) and secondary ion mass spectroscopy (SIMS). Spectroscopy results show that –COOH and other polar groups are formed but are buried inside a hydrophobic shell, consistent with earlier observations () that water uptake does not increase after reaction of the terminal alkene with O3. These insights into the 3-D structure of particles formed on oxidation have important implications for the ability of secondary organic aerosols to act as CCN. In addition, the nature of the surface of the particles is expected to determine their uptake into biological systems such as the surface of the lungs.

Keywords: Ozonolysis; Organic oxidation; Water uptake; NanoSIMS; FTIR; Secondary organic aerosol; Self-assembled monolayer


Modeling the surface–atmosphere exchange of ammonia by R.J. Wichink Kruit; W.A.J. van Pul; F.J. Sauter; M. van den Broek; E. Nemitz; M.A. Sutton; M. Krol; A.A.M. Holtslag (pp. 945-957).
New parameterizations for surface–atmosphere exchange of ammonia are presented for application in atmospheric transport models and compared with parameterizations of the literature. The new parameterizations are based on a combination of the results of three years of ammonia flux measurements over a grassland canopy (dominated by Lolium perenne and Poa trivialis) near Wageningen, the Netherlands and existing parameterizations from literature. First, a model for the surface–atmosphere exchange of ammonia that includes the concentration at the external leaf surface is derived and validated. Second, a parameterization for the stomatal compensation point (expressed asΓ s, the ratio of [NH4+]/[H+] in the leaf apoplast) that accounts for the observed seasonal variation is derived from the measurements. The new, temperature-dependentΓ s describes the observed seasonal behavior very well. It is noted, however, that senescence of plants and field management practices will also influence the seasonal variation ofΓ s on a shorter timescale. Finally, a relation that linksΓ s to the atmospheric pollution level of the location through the ‘long-term’ NH3 concentration in the air is proposed.

Keywords: Ammonia; Dry deposition; Compensation point; Resistance analogue; Atmospheric transport model


Contribution of atmospheric emissions to the contamination of leaf vegetables by persistent organic pollutants (POPs): Application to Southeastern France by Solen Quéguiner; Luc Musson Genon; Yelva Roustan; Philippe Ciffroy (pp. 958-967).
A modeling approach has been developed to estimate the contribution of atmospheric emissions to the contamination of leaf vegetables by persistent organic pollutants (POPs). It combines an Eulerian chemical transport model for atmospheric processes (Polair3D/Polyphemus) with a fate and transport model for soil and vegetation (Ourson). These two models were specifically adapted for POPs. Results are presented for benzo(a)pyrene (BaP). As expected no accumulation of BaP in leaf vegetables appears during the growth period for each harvest over the 10 years simulated. For BaP and leaf vegetables, this contamination depends primarily on direct atmospheric deposition without chemical transfer from the soil to the plant. These modeling results are compared to available data.

Keywords: Persistent organic pollutant; Atmospheric pollution; Multi-media modeling; Leaf vegetable contamination; Benzo(a)pyrene


A lagrangian approach to analyse the tropospheric ozone climatology in the tropics: Climatology of stratosphere–troposphere exchange at Reunion Island by G. Clain; J.-L. Baray; R. Delmas; P. Keckhut; J.-P. Cammas (pp. 968-975).
Sixteen years of ozone measurements (1992–2006) at Reunion Island (21°S, 55.5°E) have been processed to detect stratospheric signatures on each single ozone profile.The characterisation method consists in the advection of the potential vorticity (PV) over two to ten days of backtrajectory with the lagrangian trajectory code LACYTRAJ. LACYTRAJ is a Trajectory-Reverse Domain Filling code using the ERA40 ECMWF database and allowing the reconstruction of high resolution advected PV profiles. Correlation between high values of ozone mixing ratio and high PV is interpreted as a stratospheric signature.A climatology of STE events at Reunion has been derived and reveals that STE events occur more frequently during spring (SON) and summer (DJF). The method is tested for a set of PV threshold values (i.e. 1 PVU, 1.5 PVU and 2 PVU) and for a set of duration of backtrajectories (i.e. 2 days, 5 days and 10 days). The number of detected STE is sensitive to PV threshold values and duration criterions. For instance, the number of stratospheric intrusions detected in October with a 1.5 PVU criterion ranges between 25% (2 days of backtrajectories) and 56% (10 days of backtrajectories). The vertical distributions of STE show intrusions covering the whole free troposphere (between 7 and 15 km) and mainly located in the upper troposphere.Finally, results show that an important number of stratospheric intrusions are detected during spring and in the upper troposphere what points at the contribution of the stratospheric source to the tropospheric ozone spring maximum which is strongly influenced by the biomass burning emissions from South Africa and Madagascar.

Keywords: Stratosphere–troposphere exchange; Reverse domain filling; Potential vorticity; Trajectory; Ozone


Roadside aerosol study using hygroscopic, organic and volatility TDMAs: Characterization and mixing state by Petri Tiitta; Pasi Miettinen; Petri Vaattovaara; Jorma Joutsensaari; Tuukka Petäjä; Annele Virtanen; Tomi Raatikainen; Pasi Aalto; Harri Portin; Sami Romakkaniemi; Harri Kokkola; Kari E.J. Lehtinen; Markku Kulmala; Ari Laaksonen (pp. 976-986).
Traffic-related aerosol particles are ubiquitous in the urban atmosphere. As they are produced at ground level, they can also cause adverse health effects to urban dwellers. However, knowledge of the formation, transformation and chemically resolved size distribution of urban ultrafine particles is incomplete. Thus, more of these measurements are needed for better assessment of ambient air quality and its potential health effects. The particle number concentration, aerosol black carbon (BC) concentration and size distribution of traffic-related aerosols were measured near two major roads in Kuopio, Finland, from 16 June to 5 July, 2004. Furthermore, the properties of roadside aerosol particles were examined with the Tandem Differential Mobility Analyzer technique (TDMA). A suite of TDMA instruments relying on water (hygroscopic TDMA) and ethanol (organic TDMA) condensation as well as heating (volatility TDMA) were deployed to study the composition of the nucleation and Aitken mode particles ( Dp = 10–50 nm) formed from vehicle exhaust. The results show that a simple three-component model was able to reproduce characteristic insoluble, organic and water-soluble volume fractions. Insoluble constituents were dominant in the Aitken mode particles, whereas organic compounds dominated the nucleation mode sizes. On average, only a small volume fraction was water-soluble, but a clear external mixing was observed particularly when enough time was allowed after the tail pipe emissions. The contribution of the insoluble material was seen to increase as a function of particle size, being typically less than 10% at 10 nm and between 20 and 50% at 50 nm, in contrast to the organic fraction, which decreased from about 80% at nucleation mode size range to 50–60% at 50 nm.

Keywords: Ultrafine particles; Vehicular emissions; Volatility; Hygroscopicity; Organic compounds


Temporal patterns in daily measurements of inorganic and organic speciated PM2.5 in Denver by Steven J. Dutton; Balaji Rajagopalan; Sverre Vedal; Michael P. Hannigan (pp. 987-998).
Airborne particulate matter less than 2.5 μm in aerodynamic diameter (PM2.5) has been linked to a wide range of adverse health effects and as a result is currently regulated by the U.S. Environmental Protection Agency. PM2.5 originates from a multitude of sources and has heterogeneous physical and chemical characteristics. These features complicate the link between PM2.5 emission sources, ambient concentrations and health effects. The goal of the Denver Aerosol Sources and Health (DASH) study is to investigate associations between sources and health using daily measurements of speciated PM2.5 in Denver.The datxa set being collected for the DASH study will be the longest daily speciated PM2.5 data set of its kind covering 5.5 years of daily inorganic and organic speciated measurements. As of 2008, 4.5 years of bulk measurements (mass, inorganic ions and total carbon) and 1.5 years of organic molecular marker measurements have been completed. Several techniques were used to reveal long-term and short-term temporal patterns in the bulk species and the organic molecular marker species. All species showed a strong annual periodicity, but their monthly and seasonal behavior varied substantially. Weekly periodicities appear in many compound classes with the most significant weekday/weekend effect observed for elemental carbon, cholestanes, hopanes, select polycyclic aromatic hydrocarbons (PAHs), heavy n-alkanoic acids and methoxyphenols. Many of the observed patterns can be explained by meteorology or anthropogenic activity patterns while others do not appear to have such obvious explanations. Similarities and differences in these findings compared to those reported from other cities are highlighted.

Keywords: Particulate matter; PM; 2.5; Chemical speciation; Organic molecular markers; Weekday/weekend


Use of an inverse dispersion technique for estimating ammonia emission from surface-applied slurry by Alberto Sanz; Thomas Misselbrook; Maria José Sanz; Antonio Vallejo (pp. 999-1002).
Ammonia (NH3) emission from land application of manure is typically measured using the integrated horizontal flux (IHF) micrometeorological method. However, there are some situations in which alternative techniques (such as an inverse dispersion modelling technique) might be preferable, for example when measuring from large or irregularly shaped source areas. In this study, an inverse dispersion technique using the backward Lagrangian stochastic (bLS) model, with 2 different experimental configurations, was compared with the Integrated Horizontal Flux method (i.e. IHF), which was used as reference technique. Pig slurry was surface-applied at 125 kg N ha−1 to bare soil on a large plot (80 × 125 m). Cumulative emissions were 19.3, 21.2 and 18.4 kg N ha−1 from the IHF and the bLS technique (experimental configurations I and II), respectively. Mean flux within each sampling period as estimated by the two techniques compared extremely well, with a slope not significantly different from 1 and r2 of 0.99. Although limited in extent, this dataset agree with a previous study in demonstrating the use of the bLS technique with longer period time-averaged concentration measurements.

Keywords: Ammonia emission; Micrometeorological technique; Backward Lagrangian stochastic method; Dispersion model; Central Spain
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