Atmospheric Environment (v.42, #19)

Five day 3D back trajectories have been calculated for air parcels arriving at different pressure levels at Uccle (Belgium, 50 ∘ 48 ′ N , 4 ∘ 21 ′ E , 100 m asl) for the time period 1969–2001 on days where an ozone sounding took place. The trajectory model used is the APTRA model, available at the European Centre for Medium-Range Weather Forecasts (ECMWF). A nonhierarchical clustering method has been applied on the obtained 3D back trajectories in function of the season for the planetary boundary layer (PBL) and the lower free troposphere (LFT) to identify natural clusters of air masses. It was possible to derive distinctive clusters of air masses for every season.In the spring season, a reduction in ozone concentrations in the PBL within slow moving air masses from the west, combined with an increase in the frequency of occurrence, seems to be compensated by a positive trend in ozone concentrations at Uccle within the other source regions, mainly within the cluster representing slow moving air masses over the continent.More inflow from North America has been detected during the winter season, resulting in higher ozone concentrations in the PBL.
Keywords: Tropospheric ozone; PBL; 3D back trajectories; Cluster; Trends;

The effect of a water-soluble organics on efflorescence relative humidity (ERH) of ammonium sulfate or sodium chloride particles is theoretically investigated on the basis of a previously developed model for ERH of single-component particles [Gao et al., 2006. Efflorescence relative humidity for ammonium sulfate particles Journal of Physical Chemistry A 110, 7602–7608]. The central assumption made is that one species nucleates much faster than the other, and the critical nuclei formation of the former controls the rate of efflorescence. The water-soluble organics (WSOs) appeared to suppress the ERH of salt particles; the decrease in ERH can be more than 30% RH when the mole fraction of WSO is larger than 0.5. The developed model satisfactorily makes quantitative prediction only for the ERH of mixed particles containing WSO with low-surface active nature (glycerol, levoglucosan, and malonic acid). For mixed particles having more surface-active WSO (glutaric and maleic acid), the inaccurate prediction is attributable to the negligence of interactions between solutes and the estimation of interfacial tension between nuclei and the mixed solution.
Keywords: Homogeneous nucleation; Efflorescence relative humidity; Water-soluble organics;

Evaluation of a direct personal coarse particulate matter monitor by Martin W. Case; Ron Williams; Karin Yeatts; Fu-Lin Chen; James Scott; Erik Svendsen; Robert B. Devlin (4446-4452).
One aspect of the North Carolina Adult Asthma and Environment study (NCAAES) was to evaluate personal exposures to coarse particulate matter (PM10−2.5) and their associated variability. As part of this, we examined the ability of a community-based monitor to act as a surrogate for an individual's true exposure to this size fraction in linked health effect studies. To assess personal exposures to various particulate matter (PM) size fractions, a personal PM monitor was evaluated. This monitor featured a multi-stage cascade impactor that allowed for the simultaneous collection of PM10−2.5 and PM2.5 size fractions. The monitor was evaluated for collocated bias and comparability with a dichotomous (dichot) sampler (device for dividing aerosol PM population into two size fractions during sampling) at an outdoor monitoring site. Results of this evaluation indicated that the prototype was capable of agreement within ±20% of that provided by the reference methodology as well as 20% daily precision for PM10−2.5 mass measurements.
Keywords: Coarse particulate matter; PM10−2.5; PM2.5;

Modeling the effect of iodide distribution on ozone deposition to seawater surface by In-Bo Oh; Daewon W. Byun; Hyun-Cheol Kim; Soontae Kim; Bob Cameron (4453-4466).
Spatial changes in the dry deposition of ozone to the sea surface associated with ozone uptake by the dissolved iodide ions were analyzed in the northwestern Gulf of Mexico using the Community Multiscale Air Quality Model (CMAQ). The dry deposition module in CMAQ was modified using a formula developed by Chang et al. [2004. Ozone deposition to the sea surface: chemical enhancement and wind speed dependence. Atmospheric Environment 38, 1053–1059], which accounts for chemical enhancement by iodide reacting with ozone in seawater. In addition, an attempt was made to incorporate iodide concentrations from the satellite-derived estimates of near-surface chlorophyll a concentrations into the CMAQ gridded fields. One-month CMAQ simulations conducted with the modified module including iodide reaction showed a significant increase in the dry deposition velocity of ozone onto the sea surface, especially Texas and Louisiana Coast corresponding to the area with high iodide concentrations. On average, about 70% enhancement of ozone dry deposition velocity over the seawater was attributed to the iodide effect alone and the rest is mostly due to the effects of wind. The enhanced deposition velocity by iodide effect led to the marked increase in dry deposition amounts mostly near the coast, resulting in some changes in ambient ozone concentration. Interestingly, a small decrease in deposition amounts was found just inland from the shoreline, indicating that the iodide interaction can also affect ozone concentration in the inland coastal area. An in-depth analysis of a 2-day simulation showed the iodide effects on changes in the spatiotemporal distributions of the ozone deposition and concentration, which are highly dependent on coastal winds.
Keywords: Dry deposition; Ozone; Iodide ions; CMAQ; Chlorophyll a; Seawater;

Analysis of three separate urban data sets has identified significant weekend reductions of PM10, PM2.5 and PM2.5–10 mass concentrations compared to weekday values. Significant weekday–weekend differences were also found for elemental carbon in the fine size fraction, and calcium in the coarse size fraction. There was no significant weekday–weekend difference in the case of sea salt or compounds of nitrate or sulphate. Given the paucity of day of the week-specific activity data for sources other than road traffic, it has been assumed that non-traffic sources of particles are uniform throughout the week, allowing estimation of the traffic contribution to PM concentrations. While this approach may neglect a weekday–weekend difference in particulate matter from construction sources, the effect of such sources is believed to be small. Two methods (by calculation and regression) of deriving the non-vehicle contribution to the urban increment above the regional background were compared. Both resulted in values of 2.1–2.7 μg m−3 (with an estimated error of around 2 μg m−3) for the non-vehicle urban increment in PM10 measured by TEOM (gravimetric equivalent) at some urban background sites in London. The annual average traffic contribution to the urban increment is estimated as 1.6–4.4 μg m−3 for background sites in London, except Bloomsbury where the estimated traffic contribution is higher and that for non-traffic sources is lower. Use of the same method at the rural Harwell site leads to an estimate of 1.8 μg m−3 for the traffic contribution.
Keywords: PM10; PM2.5; Particulate matter; Urban increment; Road traffic;

Validation of OMI tropospheric NO2 observations during INTEX-B and application to constrain NO x emissions over the eastern United States and Mexico by K.F. Boersma; D.J. Jacob; E.J. Bucsela; A.E. Perring; R. Dirksen; R.J. van der A; R.M. Yantosca; R.J. Park; M.O. Wenig; T.H. Bertram; R.C. Cohen (4480-4497).
We compare tropospheric NO2 column measurements from the Ozone Monitoring Instrument (OMI) aboard the EOS Aura satellite with coincident in situ aircraft measurements on vertical spirals over the southern United States, Mexico, and the Gulf of Mexico during the INTEX-B campaign in March 2006. Good correlation with no significant bias ( r 2 = 0.67 , slope = 0.99 ± 0.17 , n = 12 ) is found for the ensemble of comparisons when the aircraft could spiral sufficiently low to sample most of the NO2 column. Urban spirals where large extrapolations were needed below the aircraft floor (1000 ft) showed poorer agreement. We use the OMI observations together with a global chemical transport model (GEOS-Chem) to estimate emissions of nitrogen oxides over the eastern United States and Mexico in March 2006. Comparison to EPA's National Emissions Inventory 1999 (NEI99) calls for a decrease in power plant emissions and an increase in on-road vehicle emissions relative to that inventory. The rise in vehicular emissions is offsetting the reduction in power plant and industry emissions. These findings are consistent with independent assessments. Our OMI-derived emission estimates for Mexico are higher by a factor of 2.0 ± 0.5 than bottom-up emissions, similar to a comparison between the recently released Mexican NEI99 inventory and the bottom-up showing that the Mexican NEI99 inventory is 1.6–1.8 × higher.
Keywords: INTEX-B; Validation; OMI; Tropospheric NO2; NO x emissions;

Emissions from light duty gasoline vehicles operating on low blend ethanol gasoline and E85 by Lisa A. Graham; Sheri L. Belisle; Cara-Lynn Baas (4498-4516).
The results of two recent vehicle emission studies are described in this paper, along with a statistical analysis of the changes in tailpipe emissions due to the use of ethanol that includes the results from these two studies in combination with results from other literature reports. The first study evaluates the effect of two low blend ethanol gasolines (E10, E20) on tailpipe and evaporative emissions from three multi-port fuel injection vehicles and one gasoline direct injection vehicle at two different test temperatures. The second study evaluates the differences in tailpipe emissions and fuel consumptions of paired flexible fuel and conventional gasoline vehicles operating on California RFG Phase 2 and/or E85 fuels at 20 °C. The vehicles were tested over the four-phase FTP or UDDS and US06 driving cycles. Tailpipe emissions were characterized for criteria pollutants (CO, NO X , NMHC, NMOG), greenhouse gases (CO2, CH4, N2O), and a suite of unregulated emissions including important air toxics (benzene, 1,3-butadiene, formaldehyde, acetaldehyde, acrolein), and ozone reactivity. In the low blend ethanol study, evaporative emissions were quantified and characterized for NMHC. While contradicting, results can be seen among the various literature reports and with these two new studies, the statistical analyses of the aggregated data offers much clearer pictures of the changes in tailpipe emissions that may be expected using either low blend ethanol gasoline (E10) or E85. The results of the statistical analysis suggest that the use of E10 results in statistically significant decreases in CO emissions (−16%); statistically significant increases in emissions of NMHC (9%), NMOG (14%), acetaldehyde (108%), 1,3-butadiene (16%), and benzene (15%); and no statistically significant changes in NO X , CO2, CH4, N2O or formaldehyde emissions. The statistical analysis suggests that the use of E85 results in statistically significant decreases in emissions of NO X (−45%), NMHC (−48%), 1,3-butadiene (−77%), and benzene (−76%); statistically significant increases in emissions of formaldehyde (73%) and acetaldehyde (2540%), and no statistically significant change in CO, CO2, and NMOG emissions.
Keywords: Ethanol–gasoline blends; Mobile source air toxics; Greenhouse gas emissions; Evaporative emissions;

Evaluation of a modelling system for predicting the concentrations of PM2.5 in an urban area by M. Kauhaniemi; A. Karppinen; J. Härkönen; A. Kousa; B. Alaviippola; T. Koskentalo; P. Aarnio; T. Elolähde; J. Kukkonen (4517-4529).
We present a modelling system that contains a treatment of the emissions and atmospheric dispersion of fine particulate matter (PM2.5) on an urban scale, combined with a statistical model for estimating the contribution of long-range transported aerosols. The model of PM2.5 emissions includes exhaust emissions, cold starts and driving, as well as, non-exhaust emissions originated from urban vehicular traffic. The influence of primary vehicular emissions from the road and street network was evaluated using a roadside emission and dispersion model, CAR-FMI, in combination with a meteorological pre-processing model, MPP-FMI. We have computed hourly sequential time series of the PM2.5 concentrations in 2002 in a numerical grid in the Helsinki Metropolitan Area. The predicted results were compared against measured data at two locations in central Helsinki: urban roadside station of Vallila and urban background station of Kallio. The predicted daily average PM2.5 concentrations agreed well with the measured values; e.g., the index of agreement values were 0.83 and 0.86 at Vallila and Kallio, respectively, and the absolute values of fractional bias ⩽0.13. As expected, the scatter of data points is substantially wider for the hourly concentration values; e.g., the index of agreement values were 0.69 and 0.74. We also computed the spatial concentration distributions of PM2.5. The predicted contribution from long-range transport to the street level PM2.5 varied spatially from 40% in the most trafficked areas to nearly 100% in the outskirts of the area. The emissions originated from cold starts and driving were responsible for <4% of the annual average concentrations at the roadside and urban stations. The model can potentially be used as a practical tool of assessment of urban PM2.5 contributions in various European regions.
Keywords: Urban pollution; Model; Evaluation; PM2.5; CAR-FMI;

Plant-specific correlations to predict the total VOC emissions from wastewater treatment plants by Ali K. Oskouie; David T. Lordi; Thomas C. Granato; Louis Kollias (4530-4539).
Simple linear correlations between the lumped parameter of raw wastewater flow rate, mixed liquor suspended solids (MLSS), and concentration of three volatile organic compounds (VOCs), chloroform, dichloromethane and toluene in the liquid and gas phases, Q × MLSS ( C in / ER ) , and T, wastewater temperature, were found for three large wastewater treatment plants operated by the Metropolitan Water Reclamation District of Greater Chicago (MWRDGC) using their monthly data for year 2000. These linear relationships were verified for these three dominant VOCs using the data from years 1987 to 1992, 1998, and 1999 for the three MWRDGC plants. The results of this theoretical study showed that linear functions could reasonably fit to the actual data, and the specific VOC compounds’ emission rate could be predicted upon having information on ambient temperature, MLSS, and VOC concentration in the liquid phase at the influent to the specific plant without having to use the Bay Area Sewage Toxics Emission (BASTE) fate model as a future emission estimator once the baseline correlation was determined.
Keywords: Emission; VOC; Wastewater; Modeling;

Isoprene emission from the major native Quercus spp. in Japan by Akira Tani; Yuijun Kawawata (4540-4550).
Broad-leaved Quercus trees are the major species in the temperate zone of Japan and other countries in Asia. In the present study, attempts were made to identify isoprene emitters among various Quercus tree species native to Japan, and the emission characteristics of each species were investigated.By using a branch-enclosure method, four deciduous trees taxonomically positioned in the section Prinus, Quercus serrata, Q. mongolica var. crispula, Q. aliena, and Q. dentate, were identified as isoprene emitters. Two other deciduous trees in the section Cerris, Q. acutissima, and Q. variabilis, emitted neither isoprene nor monoterpene. The evergreen tree species Q. acuta, Q. glauca, Q. salicina, Q. myrsinaefolia, and Q. sessilifolia included in the section Cyclobalanopsis were also identified as non-emitters.Cuvette measurements revealed that the temperature and light dependence of isoprene emissions from the four plant species were similar to that previously reported for many other plant species. However, the initial slope of the isoprene emission against photosynthetic photon flux (PPF) was higher than the slope proposed by the G93 algorithm. Online monitoring of isoprene emission was occasionally conducted, and the results revealed a difference in the response time against PPF between PPF increase and decrease measurements even at the same PPF and temperature. The ratio of carbon emitted as isoprene to carbon fixed by photosynthesis was calculated as 3–15% at 35 °C. The emission rates standardized to 30 °C and 1000 μmol m−2  s−1 PPF of the four emitter Quercus spp. were 18–30 nmol m−2  s−1.
Keywords: Quercus; Isoprene; BVOC inventory; Leaf temperature; PPF; Asia; PTR-MS;

Simulating present-day and future air quality as climate changes: Model evaluation by John P. Dawson; Pavan N. Racherla; Barry H. Lynn; Peter J. Adams; Spyros N. Pandis (4551-4566).
The global-regional climate-air pollution modeling system (GRE-CAPS) has been developed, coupling an existing general circulation model/chemical transport model (GCM/CTM), a regional meteorological model, and a regional chemical transport model. This system is intended to enable studies of the effects of changes in climate, intercontinental transport, and emissions on regional and urban air quality. The GRE-CAPS system consists of the GISS II′ GCM/CTM, the MM5 regional meteorological model, and the PMCAMx regional CTM. The modeling system is evaluated for the present day, with comparisons between model-predicted, measured ozone, and speciated PM2.5 concentrations. The ability of the model to predict present-day concentrations of ozone and PM2.5 is compared to that of PMCAMx when used for retrospective modeling. Comparisons between model-predicted temperatures and precipitation are also made. The model was used to simulate five present-day Januaries and six present-day Julys. The biases and errors in GRE-CAPS-predicted ozone concentrations were similar to those of PMCAMx when used for standard retrospective modeling. The fractional biases in mean daily peak ozone concentration and mean daily maximum 8-h average ozone concentration are both <10%. The model-predicted distribution of peak hourly and daily maximum 8-h average values agreed rather well with the measured distribution. There is less agreement between the model and measurements in the number of hours with ozone mixing ratios >70 or 80 ppb, though this is also the case with standard PMCAMx modeling. The predictions of PM2.5 concentrations by GRE-CAPS were also of similar quality to those of PMCAMx driven by historical meteorology. The fractional biases in the predictions of total PM2.5, sulfate, ammonium, and nitrate were all <25% in both January and July. The model agrees well with organic PM2.5 measurements from the IMPROVE network, though there is less agreement with measurements from the STN network. The GRE-CAPS system is shown to reproduce ozone and PM2.5 concentrations for the present day rather well, with model performance similar to that of PMCAMx for standard retrospective episode modeling with historical meteorology. GRE-CAPS will be used in future studies to examine the effects of changes in climate, global emissions, and intercontinental transport on regional air quality.
Keywords: Climate change; Ozone; Particulate matter; Model evaluation;

A model inter-comparison study focussing on episodes with elevated PM10 concentrations by R. Stern; P. Builtjes; M. Schaap; R. Timmermans; R. Vautard; A. Hodzic; M. Memmesheimer; H. Feldmann; E. Renner; R. Wolke; A. Kerschbaumer (4567-4588).
Five three-dimensional chemical transport models of different complexity were applied to Central Europe to assess the ability of models to reproduce PM10 concentrations under highly polluted conditions. The participating models were the French CHIMERE model, the Dutch LOTOS-EUROS model, as well as the REM-CALGRID, the EURAD and the LM–MUSCAT models from Germany. In the selected 80-day period, observed PM10 daily mean concentrations reached values well above 50 μg m−3 on many days in large parts of Northern Germany. This model evaluation shows that there is an increasing underestimation of primary and secondary species with increasing observed PM10. The high PM levels were observed under stagnant weather conditions, which are difficult to simulate with either prognostic or diagnostic, interpolation-based meteorological models. Thus, it is quite likely that uncertainties in PM emissions and incomplete process sub-modules each separately account for only a portion of the underestimation of high PM. Uncertainties in key boundary layer parameters, which can differ by a factor of two or more between the models, represent an additional source of error—both as direct sources of error through the transporting meteorological fields and indirect sources of error through the physico-chemical modules which rely on key boundary layer parameters.
Keywords: Air quality; Chemical transport models; Particulate matter; Model inter-comparison; Model evaluation; PM10 air pollution episodes;

Modelling the decay of concentrations of nitrogenous compounds with distance from roads by Theresa Faus-Kessler; Manfred Kirchner; Gert Jakobi (4589-4600).
Passive sampler concentration measurements of nitrogen dioxide (NO2) and ammonia (NH3) were performed in the framework of a transect study to investigate the impact of vehicle emissions on ecosystems dissected by highways. The concentrations of both gases decrease markedly with distance from highway to regional background pollution values.Modelling the functional form of the decay is of interest for reducing the amount of measurements, for exposure assessment, and for predicting background concentrations. Three modelling approaches are compared: the exponential decay function, the shifted power-law function, and the linear-logarithmic function. The models were fitted to four compound- and year-specific data sets from one transect, applying mixed-effects models for repeated-measurement designs. The goodness-of-fit did not differ consistently between the model classes. Combined data from four transects with different characteristics were analysed with the exponential decay model, allowing for transect-specific random coefficients.From the empirical point of view, none of the three model classes is consistently superior to the others. But for prediction beyond the observed distance range it is essential to consider a model with meaningful parameters. The final choice of a model depends on the amount of data and on the characteristics to be represented by the model.
Keywords: Statistical modelling; Mixed-effects models; Nitrogen dioxide; Ammonia; Emissions; Traffic;

In this paper, we investigate the atmospheric application of Monin's equations for the probability density functions (pdf) for the vertical position of particles diffusing in a turbulent flow with a finite diffusion speed as opposed to the infinite speed inherent in the parabolic diffusion equation and the Gaussian distributions of plumes. Monin's equations are modified for the case of particle dispersion in a convective boundary layer where the vertical distribution is asymmetrical. We also provide an analytical solution of the pdf of vertical dispersion applicable to this case of asymmetrical vertical distribution by making some suitable assumptions on the nature of turbulence.Vertical concentration profiles for particles emitted from stacks of various heights inside a convective boundary layer are compared with laboratory measurements. The agreement between predicted and observed concentration profiles is shown to be good.
Keywords: Plume dispersion; Probability density functions; Maximum ground level concentration; Convective boundary layer; Tall stacks;

Filter packs have been used to collect sulphur and oxygen from air for isotope analysis from many areas of the world. Here we discuss their use to determine the sulphur isotope systematics of SO2 and the sulphur and oxygen systematics of sulphate particles from volcanic vents. Our field data suggest that fractionation of sulphur isotopes occurs during the collection of SO2 from concentrated volcanic gas plumes on alkali-impregnated filter papers. The collection of volcanogenic HCl on the same filters may play a role in this fractionation. Comparison with previous studies, which sampled areas of cleaner atmosphere, suggests that isotopic fractionation only becomes significant where elevated filter loadings occur (e.g., when sampling gas streams with SO2 concentrations greater than ∼1 μmol m−3), although this requires further investigation. Previous studies also suggest that for volcanic sulphate particle samples collected at the same time, oxygen isotopes are fractionated while sulphur isotopes are not. Minimising the filter loading reduces these effects, but there is a trade-off with the amount of SO2 or SO 4 2 - required for isotopic measurements. Despite the convenience of the filter pack technique these fractionation effects limit the use of filter packs for determining δ 34S for SO2 in volcanic gases and δ 18O and δ 17O for the sulphate in volcanic particles, and they will certainly not be useful for determining small variations in the source isotopic signature of the sulphur in the SO2 or the oxygen in the SO 4 2 - being measured. This highlights the importance of collecting SO2 quantitatively for isotopic analysis. These effects may also have implications if using similar methods to collect SO2 in other environments, especially where concentrations are high.
Keywords: Sulphur emissions; Measurement techniques; Isotope fractionation;

Temporal variations in particulate exposure to wood smoke in a residential school environment by Simon Kingham; Michael Durand; Justin Harrison; Jo Cavanagh; Michael Epton (4619-4631).
Much research has examined associations between particulate pollution and health. The majority of this research has focused on outdoor air. Yet it is known that people spend most of their time indoors. This research has examined concentrations of PM10, PM2.5 and PM1 inside and outside of a boarding school in Christchurch, New Zealand. Christchurch is a city with a known wintertime particulate pollution problem as a result of burning wood for domestic heating. Data were collected over the winter of 2004 (May–September) using TEOM and GRIMM dust analysers. Results show that there is a close relationship between the fine fraction (PM2.5 and PM1) of indoor and outdoor particles. However, the activities of the building occupants resulted in the resuspension of coarse particulate fractions resulting in weaker indoor–outdoor relationships for PM10.
Keywords: Indoor air pollution; PM10; PM2.5; PM1; Boarding school; Wintertime; Wood smoke;

This article explains the new emission inventory for navigation in Denmark, covering national sea transport, fisheries and international sea transport. For national sea transport, the new Danish inventory distinguishes between regional ferries, local ferries and other national sea transport. Detailed traffic and technical data lie behind the fleet activity-based fuel consumption and emission calculations for regional ferries. For local ferries and other national sea transport, the new inventory is partly fleet activity based; fuel consumption estimates are calculated for single years, and full fuel consumption coverage is established in a time series by means of appropriate assumptions. For fisheries and international sea transport, the new inventory remains fuel based, using fuel sales data from the Danish Energy Authority (DEA).The new Danish inventory uses specific fuel consumption (sfc) and NO x emission factors as a function of engine type and production year. These factors, which are used directly for regional ferries and, for the remaining navigation categories, are derived by means of appropriate assumptions, serve as a major inventory improvement, necessary for making proper emission trend assessments.International sea transport is the most important fuel consumption and emission source for navigation, and the contributions are large even compared with the overall Danish totals. If the contributions from international sea transport were included in the Danish all-sector totals, the extra contributions in 2005 from fuel consumption (and CO2), NO x and SO2 would be 5%, 34% and 167%, respectively. The 1990–2005 changes in fuel consumption as well as NO x and SO2 emissions for national sea transport (−45, −45, −81), fisheries (−18, 6, −18) and international sea transport (−14, 1, −14) reflect changes in fleet activity/fuel consumption and emission factors. The 2006–2020 emission forecasts demonstrate a need for stricter fuel quality and NO x emission standards for navigation, in order to gain emission improvements in line with those achieved for other mobile sources.The new fuel consumption estimates for national sea transport are regarded as much more accurate than the DEA fuel sales data used previously, and the recommendation for DEA is to replace their current fuel sales figures by the new estimates calculated in this project. Such updated fuel consumption time series for national sea transport will lead, in turn, to changes in the energy statistics for fisheries (gas oil) and industry (heavy fuel oil), so the national energy balance can remain unchanged. For international transport, fuel sales data as such are regarded as highly accurate for Denmark, since they are compiled from audited information from the Danish oil suppliers, and the inventory approach follows good practice for the United Nations Framework Convention of Climate Changes (UNFCCC) and United Nations Economic Commission for Europe (UNECE) convention, when fleet activity data are missing. However, in order to make inventory upgrades and to support Danish policymakers in bunker emissions allocation, fleet activity-based estimates calculated in a further project would be useful.
Keywords: Sea transport; Heavy fuel oil; Gas oil; NO x ; SO2;

A simple model for assessing ammonia emission from ammoniacal fertilisers as affected by pH and injection into soil by T. Nyord; K.M. Schelde; H.T. Søgaard; L.S. Jensen; S.G. Sommer (4656-4664).
Ammonia (NH3) volatilisation following the application of ammoniacal fertilisers and liquid manure to agricultural land is a significant source of atmospheric NH3, which not only poses a risk to the environment, but may also result in a loss of plant available nitrogen (N). This study examined the potential for reducing NH3 emission through acidifying an ammoniacal solution and by injecting the solution. The combination of the two technologies was studied and a model for predicting the most optimal treatment was developed. In the laboratory, ammonium (NH4 +) hydroxide (aqueous NH3) was dissolved in water (pH 11) and injected into a loamy sand soil. The NH3 emission was measured with a dynamic chamber technology. Injecting the solution to 10 mm below the soil surface reduced NH3 emission by 10% compared to surface application, and injection to 30 mm reduced emission by 20% compared to surface application. Acidifying the ammoniacal solution by adding sulphuric acid and reducing pH to 10 reduced the emission by 60% at a 10 mm injection depth and 90% at 30 mm compared with non-acidified and surface-spread ammoniacal solution. The results show that there is an important interaction of pH and injection depth and that there is a need for models predicting a combined effect. This type of model could contribute to reduce cost and energy (traction force) by providing the optimal combination of acidifying and injection depth that gives a specific reduction in NH3 emission, which in this study was reducing pH to 10 and inject the fertiliser to 30 mm below surface. This study showed that relatively simple models can predict the NH3 emission from injected ammoniacal fertilisers, but that there is still a need for developing algorithms that predict the effect of pH, including the pH buffering capacity of the fertiliser and the soil.
Keywords: Ammonia; Emission; Injection; Aqueous ammonia; Model;

Greenhouse gas emissions from heavy-duty vehicles by Lisa A. Graham; Greg Rideout; Deborah Rosenblatt; Jill Hendren (4665-4681).
This paper summarizes greenhouse gas (GHG) emissions measurements obtained during several recent studies conducted by Environment Canada, Emissions Research and Measurement Division (ERMD). A variety of heavy-duty vehicles and engines operating on a range of different fuels including diesel, biodiesel, compressed natural gas (CNG), hythane (20% hydrogen, 80% CNG), and liquefied natural gas (LNG), and with different advanced aftertreatment technologies were studied by chassis dynamometer testing, engine dynamometer testing or on-road testing. Distance-based emission rates of CO2, CH4, and N2O are reported. Fuel consumption calculated by carbon balance from measured emissions is also reported. The measurement results show, for heavy-duty diesel vehicles without aftertreatment, that while CO2 emissions dominate, CH4 emissions account for between 0% and 0.11% and N2O emissions account for between 0.16% and 0.27% of the CO2-equivalent GHG emissions. Both of the aftertreatment technologies (diesel oxidation catalyst and active regeneration diesel particle filter) studied increased N2O emissions compared to engine out emissions while CH4 emissions remain essentially unchanged. No effect on tailpipe GHG emissions was found with the use of up to 20% biodiesel when the engine was equipped with an oxidation catalyst. Biodiesel use did show some reductions in tailpipe GHG emissions as compared to ULSD without aftertreatment and with the use of a diesel particle filter. Natural gas and hythane also offer decreased GHG emissions (10–20%) at the tailpipe when compared with diesel. Emission factors (g L−1 fuel) for CH4 and N2O are suggested for heavy-duty vehicles fueled with diesel-based fuels and natural gas. These emission factors are substantially lower than those recommended for use by IPCC methodologies for developing national inventories.
Keywords: Nitrous oxide; Methane; Greenhouse gases; Diesel engine emissions; Alternative fuels;

A circumpolar perspective of atmospheric organochlorine pesticides (OCPs): Results from six Arctic monitoring stations in 2000–2003 by Yushan Su; Hayley Hung; Pierrette Blanchard; Gregory W. Patton; Roland Kallenborn; Alexei Konoplev; Phil Fellin; Henrik Li; Charles Geen; Gary Stern; Bruno Rosenberg; Leonard A. Barrie (4682-4698).
Air concentrations of organochlorine pesticides (OCPs) were measured on a weekly basis in 2000–2003 at six Arctic stations, which include Alert, Kinngait, and Little Fox Lake in Canada; Point Barrow in the USA; Valkarkai in Russia; and Zeppelin in Norway. These stations cover a large region in the Arctic, providing a comprehensive perspective on OCPs in the circumpolar atmosphere. Currently used pesticide endosulfan I had similar concentrations across the stations in November–May, whereas large spatial divergence was found in June–October. This implies the extensive usage of endosulfan during summertime followed by long-range transport to the Arctic. The median air concentration of endosulfan I was 3.2 pg m−3 (n=245). Seasonally and spatially uniform concentrations of legacy chlordane-related compounds indicated that the influence of primary emissions on Arctic air has become less important than volatilization emissions. Median air concentrations (pg m−3) of trans-chlordane, cis-chlordane, trans-nonachlor, oxychlordane, and heptachlor exo-epoxide were 0.20 (n=413), 0.58 (n=413), 0.44 (n=413), 0.30 (n=245), and 0.54 (n=244), respectively. Although extensive usage was banned in the 1970s, large spatial variations reflected that DDT-related compounds were not well mixed in Arctic air. Concentrations of DDT-related compounds were low in general, and median concentrations of p,p′-DDT, o,p′-DDT, p,p′-DDE, o,p′-DDE, and ∑4DDT were 0.10, 0.18, 0.37, 0.10, and 0.79 pg m−3 (n=418), respectively. Air concentrations of pentachloroanisole and dieldrin showed strong seasonal/spatial variations with median values of 3.8 and 0.48 pg m−3 (n=245). Uniform concentrations were observed for octachlorostyrene with a median of 0.32 pg m−3 (n=245). Arctic air concentrations of other measured OCPs, such as endrin, heptachlor, methoxychlor, mirex, photomirex, tetrachloroveratrole, trichloroveratrol, and trifluralin, were generally low and mostly below method detection limits.
Keywords: Organochlorine pesticides; Circumpolar atmosphere; Seasonal; Spatial;

Ambient roadside concentrations of nitrogen dioxide (NO2) have stabilized in recent years while concentrations of nitrogen oxides (NO x ) decline. Oxidation catalytic converters of modern vehicles facilitating the formation of NO2 in the exhaust line, especially in diesel cars equipped with original equipment manufacturer (OEM) particle filters, are assumed to be responsible. NO2 is toxic and increased proportions of NO2 in total NO x in the atmosphere cause higher ambient ozone concentrations. These observations lead to a need for reliable emission factors for NO and NO2 for road vehicles, while only NO x is recorded in standard emission measurements. In this regard, it was recently shown that NO2 needs to be detected by an adequate online measuring method.The present work provides novel insight into these topics gained from an experimental campaign carried out with modern gasoline and diesel vehicles of certification categories Euro 3 and Euro 4. Reliable emission factors for NO and NO2 are presented for different driving situations, such as real-world driving, cold start and statutory tests, together with corresponding particle emission data. Highest emissions of NO x are recorded for diesel cars equipped with OEM particle filters with mass ratios of NO2 within NO x of up to 70%. The NO x emissions exceed the statutory emission limit and real-world emissions are even more pronounced, especially in urban driving conditions. Their particle emissions are greatly reduced, but the contribution of NO2 to soot oxidation is thought to be minor.
Keywords: NO2; Emission; Vehicle; Particle filter; Real-world;

Weekday/weekend difference of ozone and its precursors in urban areas of Japan, focusing on nitrogen oxides and hydrocarbons by Yasuhiro Sadanaga; Satoshi Shibata; Minoru Hamana; Norimichi Takenaka; Hiroshi Bandow (4708-4723).
This paper analyzes the weekday–weekend differences of ozone, NO x (=NO and NO2) and non-methane hydrocarbons (NMHCs) in Tokyo and Osaka, Japan, from 2001 to 2004, in order to investigate the ozone weekend effect (OWE). Data were measured at 24 and 23 general air monitoring stations in Tokyo and Osaka, respectively. We focused on NO x and NMHCs to investigate the causes of OWE. Specifically, we examined weekday/weekend differences in the titration of O3 by NO and the photochemical ozone production. Weekend ozone concentrations were confirmed to be greater than those of weekdays during most periods in both Tokyo and Osaka, although precursor concentrations were higher on weekdays. Weekday ozone concentrations in Tokyo (other than during 2003) and Osaka decreased due to the reaction of O3 with NO, resulting in higher ozone but lower O x (the sum of O3 and NO2) concentrations on weekends than on weekends. In 2003 in Tokyo, however, the effect of the photochemical ozone production on weekends was larger than on weekdays, as determined by the comparison of ozone concentration increase versus NMHCs/NO x ratio and O x between weekdays and the weekend. The weekend NMHCs/NO x ratio would be in the boundary area between volatile organic compound (VOC)- and NO x -limited regime, so it is considered that the difference between 2003 and the other periods in Tokyo might be due to a change in precursor limitation.
Keywords: Ozone weekend effect; Nitrogen oxides; Non-methane hydrocarbons; Photochemical ozone production;

Atmosphere/water partition of halocyclohexanes from vapour pressure and solubility data by Sabine Sarraute; Ilham Mokbel; Margarida F. Costa Gomes; Vladimir Majer; Jacques Jose (4724-4734).
Original values of the atmosphere/water partition coefficients of chlorocyclohexane and bromocyclohexane are reported at temperatures between 0 and 40 °C. These values could be obtained from the Henry's law constants calculated from aqueous solubility and vapour pressure data for the two solutes. Both properties were measured in this work and are reported in the temperature ranges 1 to 40 °C and −10 to 100 °C, respectively. Chlorocyclohexane is more volatile and more soluble in water than bromocyclohexane. At 25 °C, chlorocyclohexane has a vapour pressure of 1077.7 kPa and a mole fraction aqueous solubility of 3.22×10−5. Bromocyclohexane has a vapour pressure of 409.5 Pa and a mole fraction solubility of 0.781×10−5 at the same temperature. These values lead to atmosphere/water partition coefficients of 24.4 and 38.2 for chlorocyclohexane and bromocyclohexane, respectively. A simple group contribution scheme is presented that makes use of the present values and of literature data to allow the prediction of Henry's law constants, with reasonable accuracy, of halogenated-substituted organic compounds at 25 °C.
Keywords: Chlorocyclohexane; Bromocyclohexane; Aqueous solubility; Vapour pressure; Henry's law constant; Atmosphere/water partition coefficient;

Ionic constituents and source analysis of PM2.5 in three Korean cities by Young-Ji Han; Tae-Sik Kim; Hekap Kim (4735-4746).
Ambient PM2.5 samples were taken at 24-h intervals in three Korean cities from September 2002 to February 2004, and their ionic constituents were analyzed. The mean PM2.5 mass concentrations were 42.9, 42.8, and 40.8 μg m−3 in Seoul, Chuncheon, and Ulsan, respectively. In Ulsan, the concentrations in the two winters (2002–2003 and 2003–2004) were statistically different each other because in 2002–2003 the airborne trajectories passed through metropolitan and industrialized areas, whereas in 2003–2004 they did not. Ionic constituents amounted to about 39, 35, and 60% of the PM2.5 masses measured in Seoul, Chuncheon, and Ulsan, respectively. Sulfate was the largest constituent in both Chuncheon and Ulsan, while nitrate was in Seoul. Potential source contribution function (PSCF) was applied in order to identify both the local and regional sources affecting enhanced PM2.5 concentrations in Korea. The southern industrialized area in Korea, including the cities Pohang and Ulsan, was identified as the local sources, and industrial facilities located in eastern China and southern Japan were determined to be the regional sources.
Keywords: PM2.5; Korea; Ionic constituent; Trajectory; PSCF; Source;

Nitrogen isotopic signatures are very useful for identifying sources of atmospheric NO x or NO3 . Although soil is a major source of atmospheric nitric oxide (NO), yet nitrogen isotopic composition of soil-released NO has not been directly measured. Since a large portion of soil NO emission is induced by fertilizer application in food production, in the present study we determined N isotopic signatures of NO from cropland soils fertilized with urea and ammonium bicarbonate (ABC). NO was oxidized to NO2 and then converted to nitrite for nitrogen isotope analysis; tests with NO standard gas revealed no significant nitrogen isotopic fractioning during the trapping and processing procedures. While the applied urea and ABC had δ 15N values of +1.3‰ and +7.2‰, respectively, soil-released NO had δ 15N values increasing from −48.9‰ (day 2) to −28.0‰ (day 13) after urea fertilization and from −48.6‰ (day 2) to −19.9‰ (day 13) after ABC fertilization. This much 15N depleted isotopic composition of soil-released NO makes it possible to distinguish soil emission from fuel combustion for the contribution of atmospheric NO x or NO3 . Nitrogen isotopic compositions of soil substrate NH4 + and NO3 were also determined, and the instantaneous nitrogen isotopic enrichment factor of NO relative to those of substrate NH4 + and NO3 indicated both nitrification and denitrification occurred for NO production, although only NH4 +-based fertilizers were applied.
Keywords: Nitrogen isotope; Nitric oxide; Soil emission; Fertilization;

This study investigates the direct radiative effects of aerosols on the evolution of atmospheric boundary layer (ABL) over a tropical site, Anand, for 4 days, representative of each season, using land surface processes experiment (LASPEX) data sets used in a one-dimensional ABL and radiative-transfer models. Simulations with the ABL model incorporating fixed aerosol loading with three different levels of absorption and its perturbation with aerosol-free conditions were analyzed. The reduction in net available flux (NAF) increases with increase in aerosol absorption, resulting in maximum reduction for strongly absorbing type. In dry seasons, soil being dry, NAF is partitioned almost equally by latent (LE) and sensible (H) heat fluxes. In wet season, since soil moisture is abundant, LE dominates about 75% in compensating the reduction in NAF. The larger the absorption, the lesser the gradient between the surface and 2-m air temperature and hence more stable the surface layer. The reduction in vertical temperature gradient ranges from 1.74 (dry season) to 0.6 K (wet season). This stabilization of the surface layer reduces sensible heat flux and surface evaporation. Aerosol absorption decreases the turbulent heating but simultaneously increases the solar heating, and in turn increases the air temperature. This affects the inversion layer and hence the ABL height. Reduction in NAF at the surface decreases the ABL height, and the average decrease during the daytime is 167, 204 and 247 m for SSA=1.0, 0.9 and 0.8, respectively, during dry seasons. It is also found that absorbing aerosols delay the growth and promote early collapse of the ABL in all seasons.
Keywords: Aerosols; Radiation budget; Climate change; Land surface feedback;

Source identification of PCDD/Fs and PCBs in pine (Cedrus deodara) needles: A case study in Dalian, China by Fulin Tian; Jingwen Chen; Xianliang Qiao; Xiyun Cai; Ping Yang; Zhen Wang; Degao Wang (4769-4777).
Factor analysis model with nonnegative constraints (FA-NNC) and positive matrix factorization (PMF) were successful in source identification of polychlorinated dibenzo-p-dioxins/dibenzofurans (PCDD/Fs) and polychlorinated biphenyls (PCBs) in pine (Cedrus deodara) needle samples collected from Dalian, China. The source profiles and source contributions derived from the two receptor models were comparable. The results suggested that the main sources of PCDD/Fs were various combustion processes (58–74%), pentachlorophenol contamination (15–17%), secondary aluminum smelters (9–12%), and traffic emissions (2–13%). As for PCBs, two sources were identified as PCB3 and PCB5, two typical Chinese technical PCB products. The overall source contributions of PCB3 are 72–80% and PCB5 20–28%, which is qualitatively consistent with the proportions of technical PCB products produced in China. This can be the first attempt to semi-quantitatively apportion PCDD/Fs and PCBs in vegetation samples using different receptor models.
Keywords: PCDD/Fs; PCBs; Pine needles; FA-NNC; PMF;

This paper investigates regional sources and transport routes of Asian dust observed in Korea over the past 40 years, that is from 1965 to 2004. These long-term changes were studied in relation to climatic changes and causes. About 87% of dust events in Korea occur in the spring and have been increasing steadily since the 1980s. These trends can be attributed to regional changes in dust sources to windward and the resultant transport pathways of dust storms. This study establishes that dust events have greatly increased during the 3 years from 2000 to 2002. It may be the result of not only an eastward shift in the regional source of dust but also changes in upper-level synoptic transport patterns. Intensified atmospheric circulation and an associated increase in wind speed as well as changes in snow cover, surface wetness and potential evaporation rates throughout Inner Mongolia and Manchuria are likely to be the main causes of the steadily increasing number of dusty days in Korea.
Keywords: Asian dust; Long-range transport; Trajectory; Cluster analysis; Climate change;

Dust transport from northeastern China inferred from carbon isotopes of atmospheric dust carbonate by Bing Chen; Hiroyuki Kitagawa; Dongmei Jie; Ke Hu; Jaesoo Lim (4790-4796).
We made carbon and oxygen isotope analyses on the carbonates in atmospheric dust samples (hereafter, atmospheric dust carbonates) over the saline land of Songnen Plain (SSL) and at Changchun, 50 km eastward from the east margin of SSL, as well as in the surface soil samples in SSL. The atmospheric dust carbonates from SSL and Changchun had similar carbon isotopic composition as the soil carbonates from SSL, while showing a distinct difference with the atmospheric dust carbonates in the northwestern Chinese deserts. The atmospheric dust carbonates for two of the three heavy dust storms at Changchun had a similar carbon isotopic composition as those in SSL. The dust emission from SSL makes a significant contribution to the dust storms in the downwind area. Carbon isotopic composition of the atmospheric dust carbonates should be a useful indicator for inferring the dust source. We have also noted a depleting trend of 13C of atmospheric dust carbonates from west to east over northern China. The incorporating process of dust generated in areas under the pathway of the Asian dust transport might be investigated from the carbon isotopic composition in atmospheric dust carbonates.
Keywords: Soil carbonate; Carbon and oxygen isotopes; Asian dust; Dust generation; Northeastern China; Songnen Plain;

Methybutenol (MBO or 2-methyl-3-butene-2-ol) is a five-carbon alcohol produced and emitted in large amounts by many species of pine native to Western North America. Upon entering the atmosphere, MBO may engage in a series of chemical reactions which may ultimately lead to the production of tropospheric ozone which is a damaging pollutant. While the physical factors controlling MBO emission are well understood, the ecological factors controlling MBO emission have yet to be addressed. This study examines the response of MBO emission from Pinus ponderosa to herbivory simulated by needle clipping. Following defoliation early in the season, MBO emission from some plants tripled but similar increase did not occur later in the season. Anecdotal evidence suggests that the variable response of MBO emission to defoliation may have been due to the action of insect herbivores early in the season, or may have been due to phenological changes in the plants over the course of the season.
Keywords: 2-Methyl-3-butene-2-ol; Conifer; Herbivory; Isoprene; Leaf damage; VOC;