Atmospheric Environment (v.40, #4)

Comparison of model-simulated tropospheric NO2 over China with GOME-satellite data by Jianzhong Ma; Andreas Richter; John P. Burrows; Hendrik Nüß; John A. van Aardenne (593-604).
Tropospheric NO2 column densities over China simulated with a regional model using different emission inventory input are compared with Global Ozone Monitoring Experiment (GOME) satellite data. These emission inventories include (i) emission estimates for the year 1995 from the Emission Database for Global Atmospheric Research (EDGAR), (ii) regional emission inventory used in the Transport and Chemical Evolution over the Pacific (TRACE-P) program with emission estimates for the year 2000 and (iii) national emission inventory used in the Chinese Ozone Research Programme (CORP) with emission estimates for the year 1995. Model simulations were performed for a summertime period and the results under clear-sky conditions were selected for comparison with GOME data of the years 1996 and 2000. The model generally reproduces high tropospheric NO2 column densities in polluted areas of China that have been observed by GOME. However, the model simulations do not agree with the GOME measurements in a quantitative sense for some regions. Region-to-region comparisons show that with all the emission inventories the model underestimates the tropospheric NO2 column density in remote and rural areas of China. It is found that TRACE-P underestimates the tropospheric NO2 column density in all the regions with respect to the GOME measurements (by more than 50%). CORP and EDGAR appear to behave well for the model simulations in the North of China (within 15% deviations), but poorer for the model simulations in other regions (within 30–80% deviations). Linear regressions were performed with the NO2 column densities available from GOME, Y, and the model, X, of each grid cell in selected regions. For all the region of China, comparison statistics are Y = 0.3 6 1 × X + 0.9 3 5 with r 2 = 0.3 6 0 and bias=−41% for EDGAR, Y = 1.1 2 4 × X + 0.9 2 0 with r 2 = 0.4 7 2 and bias=−67% for TRACE-P, and Y = 0.4 3 1 × X + 0.8 3 5 with r 2 = 0.5 0 9 and bias=−31% for CORP.
Keywords: Tropospheric NO2; Emission inventory; Regional model; Satellite data; Gome; China;

Cloud condensation nuclei activation of limited solubility organic aerosol by Kara E. Huff Hartz; Joshua E. Tischuk; Man Nin Chan; Chak K. Chan; Neil M. Donahue; Spyros N. Pandis (605-617).
The cloud condensation nuclei (CCN) activation of 19 organic species with water solubilities (C sat) ranging from 10−4 to 102  g solute 100 g−1 H2O was measured. The organic particles were generated by nebulization of an aqueous or an alcohol solution. Use of alcohols as solvents enables the measurement of low solubility, non-volatile organic CCN activity and reduces the likelihood of residual water in the aerosol. The activation diameter of organic species with very low solubility in water (C sat<0.3 g 100 g−1 H2O) is in agreement with Köhler theory using the bulk solubility (limited solubility case) of the organic in water. Many species, including 2-acetylbenzoic acid, aspartic acid, azelaic acid, glutamic acid, homophthalic acid, phthalic acid, cis-pinonic acid, and salicylic acid are highly CCN active in spite of their low solubility (0.3 g 100 g−1 H2O<C sat<1 g 100 g−1 H2O), and activate almost as if completely water soluble. The CCN activity of most species is reduced, if the particles are produced using non-aqueous solvents. The existence of the particles in a metastable state at low RH can explain the observed enhancement in CCN activity beyond the levels suggested by their solubility.
Keywords: Organic aerosol; Cloud droplet activation; Köhler theory; Hygroscopicity; Surface tension;

Greenhouse gas emissions from stored liquid swine manure in a cold climate by Kyu-Hyun Park; Andrew G. Thompson; Michèle Marinier; Karen Clark; Claudia Wagner-Riddle (618-627).
Current global warming has been linked to increases in greenhouse gas (GHG) concentrations. Animal manure is an important source of anthropogenic GHG, mostly of methane (CH4) and nitrous oxide (N2O). Country-specific emission estimates of these GHG can be obtained using IPCC 2000 guidelines, or suggested improvement, such as the USEPA approach for CH4 emissions, which is based on monthly air temperature ( T air ). These approaches have not been validated against measured CH4 and N2O fluxes for liquid swine manure storage in cold climates due to the scarcity of year-round studies. A four-tower micrometeorological mass balance method was used at three swine farms (Arkell, Guelph, and Jarvis) in Ontario, Canada (annual T air <10 °C), from July 2000 to May 2002. Methane and N2O concentrations were measured using two tunable diode laser trace gas analyzers, and manure temperature ( T man ), redox potential ( E h ) and composition were also measured. Dry matter content and E h between sites and seasons varied from 0.6% to 3%, and −232 and −333 mV, respectively. Annual T air was 8.4 °C, and T man was on average 4 °C warmer. Mean N2O fluxes were not significantly different from zero, except for Jarvis with mean fluxes of 337.6 ng m−2  s−1 in summer and 101.8 ng m−2  s−1 in fall. Mean yearly N2O emission was estimated as 3.6 g head−1  yr−1, and was lower than the IPCC-based emission factor (EF) of 17 g head−1  yr−1. Our data suggests that N2O emissions from non-aerated liquid swine manure storage could be ignored in GHG inventories. Mean monthly CH4 fluxes obtained from half-hourly data varied between 4.6×10−3 and 1.05 mg m−2  s−1 (number of measurements per month=25–562). Measured CH4 emissions from May to October were mostly larger, and from January to April were lower than values predicted using the USEPA approach. Use of T man improved monthly CH4 emission prediction using the USEPA approach compared to T air with a lower limit of 7.5 °C ( r 2 = 0.64 vs. 0.355). The methane conversion factor derived from measured fluxes was 0.23, comparable to the USEPA derived values of 0.22–0.25, but much lower than the IPCC recommended value for cold climates (0.39).
Keywords: Methane; Nitrous oxide; Micrometeorological mass balance method; Manure temperature; IPCC methodology; Liquid swine manure;

Estimation of dispersion coefficient in the troposphere from satellite images of volcanic plumes: Application to Mt. Etna, Italy by A. Tiesi; M.G. Villani; M. D’Isidoro; A.J. Prata; A. Maurizi; F. Tampieri (628-638).
The lateral dispersion of volcanic plumes in the troposphere is investigated using satellite images. Two plume images have been selected from the Mount Etna eruption that occurred in October/November 2002.To reproduce the satellite images two modelling approaches are presented. The first one uses deterministic trajectories released from a line source extending over a range of altitudes chosen from direct observations. The second uses stochastic trajectories from an area source located at a fixed height, where the source size and the effective diffusion coefficient are determined by data analysis. The meteorological model BOLAM (Bologna Limited Area Model) supplies the atmospheric dynamics. Both approaches reproduce the main features of the observed plumes, with differences in the cross section distribution of the density.
Keywords: Transport; Turbulent dispersion; Lagrangian stochastic model; Volcanic eruptions;

Agricultural burning smoke in eastern Washington—part I: Atmospheric characterization by Jorge Jimenez; Chang-Fu Wu; Candis Claiborn; Tim Gould; Christopher D. Simpson; Tim Larson; L.-J. Sally Liu (639-650).
Agricultural burning has been subject to intense debate in Eastern Washington. Rural communities are concerned about health impacts related to smoke exposure from field burning. However, the short-duration excursions of smoke often do not violate air quality standards at locations where air quality monitors are situated. The purpose of this study was to characterize the air quality in Pullman, WA during the fall 2002 prescribed field burning season, as part of a larger study conducted to examine community exposure to agricultural burning smoke and the related short-term health effects. Data collected included continuous PM2.5, PM10, CO2, nitrogen oxides, and 12-h integrated PM2.5, OC, EC, and levoglucosan (a biomass burning marker). Four episodes were defined when three consecutive 30-min PM2.5 averages exceeded 40 μg m−3. Two source-receptor models; the chemical mass balance model (CMB) and positive matrix factorization (PMF) were used to estimate smoke intrusion from regional agricultural burning. During this study, the average PM2.5, OC, and EC were similar during the daytime and nighttime, while LG was twice as high during the night. The CMB results showed major contributions of PM2.5 from soil (38%), vegetative burning (35%), and sulfate aerosol (20%), and much less from vehicles (2%) and cooking (1%). The 3-source profiles generated by PMF were consistent with those selected for CMB modeling. The PM2.5 estimates from these two models were highly correlated for individual sources. The LG, NO x , CO2, OC, and apportioned PM2.5 from vegetative burning and soil were higher during the episodes than during non-episode days, while EC and PM2.5 from secondary sulfate, vehicles, and cooking sources were similar throughout the study. We characterized the episodes of agricultural field burning with elevated LG, OC, and biomass burning contribution to PM2.5.
Keywords: Biomass burning; Smoke impact in rural communities; Source apportionment; Exposure assessment; Receptor model;

Microanalysis of ambient particles from Lexington, KY, by electron microscopy by Yuanzhi Chen; Naresh Shah; Frank E. Huggins; Gerald P. Huffman (651-663).
Analytical transmission electron microscopy has been used for in-depth characterization of the individual submicron (physical size<1 μm) particulate matter (PM) from the urban atmosphere of Lexington, Kentucky, USA. Carbonaceous particles and sulfur-bearing particles dominate the PM samples on a particle count basis. Soot aggregates are the major form of carbonaceous particles. Organic-type and biogenic carbonaceous particles are also observed and exhibit quite different morphologies and microstructures compared with combustion-generated soot and char particles. Ammonium sulfate is the dominant chemical type of sulfur-bearing particles. Other types of sulfur-bearing particles include crystalline sodium, potassium and calcium sulfates. Silicon-bearing particles consist mainly of silicon oxides and aluminosilicates. Iron and titanium oxide particles are the major metal oxides found in this study. Considerable amounts of iron oxide with other transition metal elements (e.g. Mn and Zn) have been observed, typically in the form of spinel nanocrystals. Minor amounts of other species (e.g. phosphates, lead compounds, and carbonates) have also been observed.The combined use of these analytical techniques is capable of revealing much new information on the microcharacteristics of individual submicron particles; such information should be relevant to toxicological, epidemiological, and source apportionment studies.
Keywords: Ambient; Airborne; PM; TEM; Characterization; Combustion; Carbonaceous;

Joint application of Doppler Lidar and differential absorption lidar to estimate the atomic mercury flux from a chlor-alkali plant by M. Bennett; H. Edner; R. Grönlund; M. Sjöholm; S. Svanberg; R. Ferrara (664-673).
We have combined differential absorption lidar (DIAL) measurements of mercury concentrations downwind of a chlor-alkali plant (Rosignano Solvay) with measurements of wind profiles made with a Doppler Lidar based on modern fibre-optic technology. Since the flux of pollutant is equal to the cross-wind integral of the product of concentration and wind speed, this should permit us to make a more precise estimate of the fugitive emission of mercury from the plant than could be obtained by using anemometer measurements of the wind. The flux was estimated to be 54 g Hg h−1 using an anemometer on the plant building; 49 g Hg h−1 using an anemometer on a nearby 10 m mast; and 48 g Hg h−1 using wind speed corrections estimated from the Doppler Lidar measurements. Because of difficulties with the range resolution of the Doppler Lidar, the precision of this estimate was not as good as it should have been, though the difference from the rooftop anemometer remains statistically significant. Corrections of this magnitude are irrelevant to the Rosignano plant, where the emission rate varies strongly with the meteorological conditions. Where a precise estimate of a steady flux is required, however, reliable measurements of the wind profile in the wake of the source are essential. Doppler Lidar provides a possible method for acquiring such measurements.
Keywords: DIAL; Fibre-optics; Optical coherence tomography; OCT; Fugitive emissions; EMECAP; Building-affected flow; Wind measurements;

A dispersion modelling system SILAM and its evaluation against ETEX data by M. Sofiev; P. Siljamo; I. Valkama; M. Ilvonen; J. Kukkonen (674-685).
This paper presents the SILAM dispersion modelling system that has been developed for solving various forward and inverse dispersion problems. The current operational version is based on a Lagrangian dispersion model that applies an iterative advection algorithm and a Monte Carlo random-walk diffusion representation. The system can utilize meteorological data from either the HIRLAM or ECMWF numerical weather prediction models. We present an evaluation of SILAM against the data of the European Tracer Experiment (ETEX). The model showed an overall time correlation coefficient of 0.6 (over 150 stations), with specific values for the two ETEX measurement arcs of 0.75 and 0.74, respectively. The number of well-reproduced observation sites are 55, 37, and 40—for a Figure of Merit in Time of >0.2, a correlation coefficient of >0.7, and mean observed and modelled values being within a factor of 2, respectively. We have also investigated the sensitivity of the model to the meteorological input data and model setup. The most important factors with regard to the model performance were (i) the selection of the meteorological input data set and (ii) the method used for the atmospheric boundary layer height estimation. The study allowed selection of the optimum setup for the operational model configuration. We also tried to find explanations for the successes and failures of the specific methodologies in order to facilitate broader conclusions on their applicability in emergency dispersion modelling.
Keywords: Dispersion modelling; Model validation; Emergency preparedness;

To assess the influence of biomass burning and regional pollution on CO levels in Northeast Asia, trajectory analysis and satellite observations from the Measurement of Pollution in the Troposphere (MOPITT) instrument were applied. As a case study, data for April 2000 were used. Ground measurement data at remote sites in Korea showed high CO levels and did not have typical seasonal variations due to regional pollution. Therefore, MOPITT data over the East/Japan Sea was recommended for identification of long-range transport of CO. The locations of biomass burning, distribution of MOPITT CO, and backward trajectories clearly indicated that Siberian fires and industrial activities in East China affected CO levels in Korea and Japan. CO levels over East China for the first two weeks were enhanced more than 35 ppb by biomass burning in Myanmar and Indo-China, and high CO levels over the East/Japan Sea for the last two weeks were affected by both anthropogenic emissions and biomass burning. The average difference in CO concentrations over the East/Japan Sea between fire days (217±18 ppb) and non-fire days (186±15 ppb) was 31 ppb (p<0.05). These results suggest again that regional pollution as well as biomass burning plays an important role for CO levels in Northeast Asia and that MOPITT is a promising tool for the comprehensive understanding of CO emissions and transport.
Keywords: Carbon monoxide; Forest fire; Biomass burning; MOPITT;

Three different size fractions of aerosols free fall (FF), suspended particulate matter (SPM) and particles less than 10 μm (PM10) as well as surface sediments were collected from four different locations situated along a dust transport path of nearly 600 km in NW India starting from Bikaner in the Thar to Garhmuktesar through Jhunjhunu and Delhi and were studied for their heavy-metal chemistry. NW India is characterized by hot arid to semiarid climate with prevailing S–SW winds causing dust storms in summer and low intensity N–NW winds during winter months. The aerosol load in the atmosphere increased to several orders of magnitude for all size ranges (FF=21 g m−2  day−1; SPM=10,702 μg m−3 and PM10=2907 μg m−3) during the summer dust storm period compared to national air quality standards as well as to the aerosol load in winter. Aerosol sources are dominantly crustal with a significant anthropogenic contribution during the winter. We also note multiplicity of sources for the heavy metals studied here. Sr, V and Cr are dominantly crustal. Ba and Pb are added largely by fossil fuel burning; Cu, Ni and Zn are contributed by various industries. Anthropogenically added heavy metals show maximum enrichment relative to the upper continental crustal component in finer fractions and especially in winter. We suggest that the aerosol loading in the atmosphere and its heavy-metal chemistry is strongly influenced by the climatic regime and the presence of desert and industrialization in this area.
Keywords: Atmospheric loading; Dust storms; Air pollution; Trace metals; Metal sources;

Cluster analysis is used to determine groups of 8-h ozone episodes occurring between 1996 and 2003 in the San Francisco, CA Bay Area that have similar spatial distributions for ozone composition. An ensemble of randomly initialized runs of a nonhierarchical clustering algorithm (k-means) is aggregated to form a single, hierarchical solution. A proper range for the number of clusters represented in the ensemble ensures a converging, reproducible labeling of the episode days. Four clusters are identified which correspond to different meteorological regimes favorable to ozone buildup. Two modes have anomalous wind patterns likely influenced by offshore low pressure systems and are not representative of summer weather systems in the Bay Area. The other two clusters capture stagnation of the boundary layer more typical of the Bay Area summer season. One dominant cluster indicates a persistent synoptic state producing some of the highest temperatures and lowest wind speeds during the years studied. The final cluster, often occurring on the last day of multi-day exceedance periods, represents an atmospheric transition state from stagnant to more ventilated conditions. The study region can be decomposed into several geographical subregions, each with a single mechanism capable of producing episodes under certain meteorological conditions. Two inland regions are affected by stagnation due to weak marine layer flow, a local valley by precursor transport driven by differential heating, and the region closest the ocean by reversal of the typical shoreward marine flow.
Keywords: Air quality; k-means ensemble; Aggregation; Geospatial patterns; Episode representativeness;

A bimolecular rate constant, k OH+citronellol, of (170±43)×10−12  cm3  molecule−1  s−1 was measured using the relative rate technique for the reaction of the hydroxyl radical (OH) with 3,7-dimethyl-6-octen-1-ol (citronellol) at (297±3) K and 1 atmosphere total pressure. Additionally, a bimolecular rate constant, k O 3 + citronellol , of (2.4±0.1)×10−16  cm3  molecule−1  s−1, was measured by monitoring the decrease in ozone (O3) concentration in an excess of citronellol. To more clearly define part of citronellol's indoor environment degradation mechanism, the products of the citronellol+OH and citronellol+O3 reactions were also investigated. The positively identified citronellol/OH and citronellol/O3 reaction products were: acetone, ethanedial (glyoxal, HC(=O)C(=O)H), and 2-oxopropanal (methylglyoxal, CH3C(=O)C(=O)H). The use of derivatizing agents O-(2,3,4,5,6-pentafluorobenzyl)hydroxylamine (PFBHA) and N,O-bis(trimethylsilyl) trifluoroacetamide (BSTFA) were used to propose 6-hydroxy-4-methylhexanal as the other major citronellol/OH and citronellol/O3 reaction product. The elucidation of this other reaction product was facilitated by mass spectrometry of the derivatized reaction products coupled with plausible citronellol/OH and citronellol/O3 reaction mechanisms based on previously published volatile organic compound/OH and volatile organic compound/O3 gas-phase reaction mechanisms.
Keywords: Citronellol; 3,7-dimethyl-6-octen-1-ol; Reaction products; Kinetics; Oxygenated organic compounds;

Source contributions to PM2.5 nitrate, sulfate and ammonium ion concentrations in California's San Joaquin Valley (SJV) (4–6 January 1996) and South Coast Air Basin (SoCAB) surrounding Los Angeles (23–25 September 1996) were predicted using a three-dimensional source-oriented Eulerian air quality model. The air quality model tracks the formation of PM2.5 nitrate, sulfate and ammonium ion from primary particles and precursor gases emitted from different sources though a mathematical simulation of emission, chemical reaction, gas-to-particle conversion, transport and deposition. The observed PM2.5 nitrate, sulfate and ammonium ion concentrations, and the mass distribution of nitrate, sulfate and ammonium ion as a function of particle size have been successfully reproduced by the model simulation. Approximately 45–57% of the PM2.5 nitrate and 34–40% of the PM2.5 ammonium ion in the SJV is formed from precursor gaseous species released from sources upwind of the valley. In the SoCAB, approximately 83% of the PM2.5 nitrate and 82% of the PM2.5 ammonium ion is formed from precursor gaseous species released from sources within the air basin. In the SJV, transportation related sources contribute approximately 24–30% of the PM2.5 nitrate (diesel engines ∼13.5–17.0%, catalyst equipped gasoline engines ∼10.2–12.8% and non-catalyst equipped gasoline engines ∼0.3–0.4%). In the SoCAB, transportation related sources directly contribute to approximately 67% of the PM2.5 nitrate (diesel engines 34.6%, non-catalyst equipped gasoline engine 4.7% and catalyst equipped gasoline engine 28.1%). PM2.5 ammonium ion concentrations in the SJV were dominated by area (including animal) NH3 sources (16.7–25.3%), soil (7.2–10.9%), fertilizer NH3 sources (11.4–17.3%) and point NH3 sources (14.3–21.7%). In the SoCAB, ammonium ion is mainly associated with animal sources (28.2%) and catalyst equipped gasoline engines (16.2%). In both regions, the majority of the relatively low PM2.5 sulfate (<5 μg m−3) is associated with upwind sources. Most of the locally generated sulfate is emitted from diesel engines and high-sulfur fuel combustion processes in both modeling domains. Emissions control programs should target the sources listed above to reduce PM2.5 concentrations.
Keywords: Source-oriented air quality model; Source apportionment; Secondary particulate matter; Los Angeles; San Joaquin valley;

Speciation of three trace elements (Zn, Pb, Cu) in air particulates of two Syrian cities (Tartous and Darya) with different climate conditions and industrial emissions has been studied. Air filters were collected during 2000–2001 and extracted chemically using different selective fluids in an attempt to identify the different forms of trace elements. Approximately 60% of lead in air particulates of both cities was found to be associated with organic materials produced by incomplete burning of vehicles fuels and residential heating; the remaining 40% of lead was as lead oxides and mineral acids soluble compounds. Zinc was found in oxides (28–65%) samples collected in Tartous city, indicating that the Tartous cement factory and phosphate loading cargoes are the main source of emissions. In the Darya filters, zinc associated with organic materials (28–49%) was related to the presence of plastic molding industries and corroding car tires. In addition, copper was also found to be in the form of oxides (19–46%) in both cities in the summer periods, while 13–25% and 35% are associated with organic materials and silicates, respectively. Differences in chemical forms of the studied trace elements in air particulates were found to be related to differences in air pollution sources and differences in human behaviour throughout the year. Therefore, chemical fractionation of trace elements in air particulates using sequential leaching can be used for identification of air pollutions sources in urban and industrial areas.
Keywords: Chemical forms; Trace elements; Air pollution; Tartous; Darya; Syria;

Improved k–ε two-equation turbulence model for canopy flow by Li Liang; Li Xiaofeng; Lin Borong; Zhu Yingxin (762-770).
A three-dimensional k–ε turbulence model was developed to examine air flow both through and above a small forest stand submerged in an otherwise undisturbed boundary-layer flow. The effects of the forest canopy were modeled conventially using a sink for momentum and a source for the generation of turbulence energy. In addition, a further sink was added to the k- and ε-budget equations to account for the additional loss of turbulence energy. The flow equations were solved using the PHOENICS fluid dynamic program by adding the necessary source/sink terms into the standard k–ε turbulence model. The thermal stratification is not included in the model simulation and wind tunnel experiment. Predictions from the model were compared against wind tunnel data, and good agreement was observed. Moreover, three different canopy shapes of the forest were introduced into the simulation. With the wind tunnel data as a reference, their results were compared and some useful conclusions were drawn. Finally, a design case study analyzed the effect of canopies on the wind environment of urban micro-climates. It showed that the developed tree canopy model is applicable in the design and evaluation stage.
Keywords: Tree canopy; Urban environments; Source/sink terms; Leaf area density (LAD); Computational fluid dynamics (CFD);

Seasonal and site-specific variation in vapour and aerosol phase PAHs over Flanders (Belgium) and their relation with anthropogenic activities by Khaiwal Ravindra; László Bencs; Eric Wauters; Johan de Hoog; Felix Deutsch; Edward Roekens; Nico Bleux; Patrick Berghmans; René Van Grieken (771-785).
The concentrations of 16 US-EPA criteria polycyclic aromatic hydrocarbons (PAHs) were monitored during various seasons at six different cities/locations in the northern part of Belgium. Pressurized liquid extraction (PLE) was used for the fast recovery of PAHs from quartz fibre filters (QFFs) and polyurethane foams (PUFs) in less than 30 min with minimum solvent consumption prior to their analysis with high-performance liquid chromatography. The concentrations of PAHs varied significantly at the studied sites and showed relation to different anthropogenic activities, such as vehicular emission (diesel/gasoline), incinerator, petroleum/oil burning, coke production, and wood/coal combustion. The annual average PAH concentration ranged from 17 (at a rural site) to 114 ng m−3 (near a petroleum harbour and industry). Most of the human carcinogenic PAHs were found to be associated with suspended particulate matter, which forms around ∼55% of the total PAH levels in aerosols. Relatively higher concentrations of PAHs were detected in aerosol samples during winter compared with other seasons, whereas no clear seasonal trend was observed for the vapour phase PAHs. This fraction is likely to be more local in origin; hence, it can be used as a site-specific characteristic. The site-specific concentrations of individual PAHs were also used in diagnostic ratio evaluations and in principal component analysis to find their relation with various anthropogenic activities. These results show that the vehicular emission is a major source of PAHs in Flanders, although other anthropogenic sources, as above, have also an impact on the total PAH levels.
Keywords: PAHs; Human carcinogen; Pressurized liquid extraction (PLE); Diagnostic ratio; Principal component analysis (PCA); Source markers;

Rate coefficients for reactions of nitrate radicals (NO3) with the anthropogenic emissions 2-methylpent-2-ene, (Z)-3-methylpent-2-ene, ethyl vinyl ether, and the stress-induced plant emission ethyl vinyl ketone (pent-1-en-3-one) were determined to be (9.3±1.1)×10−12, (9.3±3.2)×10−12, (1.7±1.3)×10−12 and (9.4±2.7)×10−17  cm3 molecule−1  s−1. We performed kinetic experiments at room temperature and atmospheric pressure using a relative-rate technique with GC–FID analysis. Experiments with ethyl vinyl ether required a modification of our established procedure that might introduce additional uncertainties, and the errors suggested reflect these difficulties. Rate coefficients are discussed in terms of electronic and steric influences. Atmospheric lifetimes with respect to important oxidants in the troposphere were calculated. NO3-initiated oxidation is found to be the strongly dominating degradation route for 2-methylpent-2-ene, (Z)-3-methylpent-2-ene and ethyl vinyl ether. Atmospheric concentrations of the alkenes and their relative contribution to the total NMHC emissions from trucks can be expected to increase if plans for the introduction of particle filters for diesel engines are implemented on a global scale. Thus more kinetic data are required to better evaluate the impact of these emissions.
Keywords: Alkene; Diesel; Particle filters; Troposphere; Nitrate;

Erratum to “The composition of aerosol particles in the middle troposphere over the western Pacific Ocean: Aircraft observations from Australia to Japan, January 1994” by Miwako Ikegami; Kikuo Okada; Yuji Zaizen; Yukitomo Tsutsumi; Yukio Makino; Jorgen B. Jensen; John L. Gras (793).