Atmospheric Environment (v.39, #27)

Trend of atmospheric aerosols over the north western Himalayan region, India by Khwairakpam Gajananda; Jagdish C. Kuniyal; G.A. Momin; P.S.P. Rao; P.D. Safai; S. Tiwari; K. Ali (4817-4825).
Total suspended particulate (TSP), size-separated atmospheric aerosols and aitken nuclei (AN) were monitored at Mohal (Kullu) and Manali tourist complex, in the northwestern part of the Himalayas from 1996 and onwards. Long-term trend analysis for TSP indicated a significant increase since January 1996 to December 2003 at Mohal ( P < 0.05 ) and at Manali there is no increase in the TSP level ( P = 0.9 ). The results indicate that the eight years average concentration of TSP at Mohal is 78.4 μg m−3 and 66.9 μg m−3 at Manali. Seasonal average shows that the TSP is highest during summer (Mohal 90.3 μg m−3, P = 0.2 ; and Manali 74.1 μg m−3, P = 0.5 ) followed by winter season (Mohal 84.3 μg m−3, P < 0.05 ; and Manali 71.0 μg m−3, P = 0.7 ). The mass size distribution of aerosols showed bimodal distribution having one peak in fine mode (0.08–2.1 μm) and the other in coarse mode (3.3–10 μm) at both the locations. The highest value of fine size separated aerosol showed the maximum values at 0.43 μm mode. AN (0.001–0.1 μm) density shows fine particles of air pollutants more at low altitude as compared to high altitude. The diurnal variation of AN showed maximum values between 1100 and 1400 h. The daily average concentration of AN at Mohal, Manali and Kothi was found to be 3990, 3200 and 1350 N cm−3, respectively. The increasing trend of TSP, high value of size separated aerosols in the fine mode and the peaking of fine particles during noontime are the indication of rising air pollution due to anthropogenic activities in this region.
Keywords: Total suspended particulate; Size-separated aerosols; Aitken nuclei; Air pollution; Kullu;

PM2.5 aerosols were collected from an urban and a coastal site in southern Taiwan in January (winter) and April (spring) of 2002. Under controlled relative humidity (RH) of 35±1%, NH 4 + , SO 4 2 – and NO 3 – were found to be the dominant water-soluble ionic species in both winter and spring. At the urban site, these ionic species accounted for an average 44.6% of PM2.5 mass in winter and 36.0% in spring, while at the coastal site they accounted for 44.7% of PM2.5 mass in winter and 38% in spring, thus demonstrating that secondary aerosols contributed a larger portion of the PM2.5 mass in winter at both sites. In winter, NH 4 + constituted a lower percentage of the PM2.5 mass than SO 4 2 – and NO 3 – at both sites, whereas in spring NH 4 + were the most dominant chemical species. At constant temperature (25±1 °C) and RH (60±1%), the water mass as a percentage of PM2.5 mass was higher in the coastal area than in the urban area. This was true both in winter (coastal 28.9% versus urban 22.4% in the daytime and coastal 33.0% versus urban 27.4% at night) and spring (32.7% versus 28.4% in the daytime and 35.7% versus 32.7% at night). Nighttime aerosols always had higher water content than their daytime equivalents. The water content as measured at 60±1% RH was noticeably higher than and different from values calculated using the water descending model.
Keywords: PM2.5 aerosol; Water mass; GC-TCD; Karl Fischer; Seasonal variations;

Lagrangian stochastic (LS) models of dispersion in the convective boundary layer (CBL) are modified here to include the effects of particle fall velocity. This is accomplished by subtracting the fall velocity in the calculation of the vertical displacement, by reducing the decorrelation time-scale, and by making a new modification to the deterministic acceleration term in the vertical velocity increment equation. This new modification has an impact on downwind concentrations predicted by LS models of heavy particle transport in the CBL.
Keywords: Atmospheric dispersion modeling; Inhomogeneous turbulence; Skewed probability distribution function; Particle fall velocity; Langevin equation;

The impact of changing nitrogen oxide emissions on wet and dry nitrogen deposition in the northeastern USA by Thomas J. Butler; Gene E. Likens; Francoise M. Vermeylen; Barbara J.B. Stunder (4851-4862).
This study is an attempt to quantify the relation between changes in NO x emissions and nitric acid (HNO3) in the northeastern USA. From this relation, and previous work relating NO x emission changes and wet NO3 deposition, we can estimate how changing NO x emissions may impact total (wet+dry) measured nitrogen (N) deposition.Electric utility emissions account for 1 4 , and vehicle emissions account for over 1 2 of the total NO x emissions in the eastern USA. Canadian NO x emissions from the seven easternmost provinces (Manitoba and east) represent less than 10% (1.2 teragrams (Tg) NO x ) of the NO x emissions compared with those from the eastern USA. Emissions from eastern Canada are dominated by vehicle NO x emissions, which account for 2 3 of the total NO x emissions from eastern Canada.Data from the EPA National Emissions Inventory show, for the period 1991–2001, that nitrogen oxide (NO x ) emissions in the eastern USA have declined by 17% to from 16.1 to 13.1 Tg. Large declines in vehicle emissions in 2001 may be questionable. If 2001 data are excluded the decline in total NO x is only 7%. A recent assessment of EPA's emissions estimates suggest that vehicle NO x emissions may be underestimated, and total NO x emissions reductions may be less than what is reported by the EPA.The CASTNet (Clean Air Status and Trends Network) measurements of N dry deposition include HNO3, particulate NO3 and NH4 +. The dominant N dry deposition product measured is HNO3, which represents 80% of measured N dry deposition for the sites used in this study. Amounts of NH3, NO2, organic nitrate and PAN dry deposition are not measured by CASTNet. The NH3 and NO2 deposition are probably significant, and may be major N dry deposition components in some areas.Random coefficient models with total NO x emissions as the independent variable, and HNO3 concentrations as the dependent variable, show that reducing total NO x emissions by 50% should reduce HNO3 concentrations by 36%. The average efficiency (the ratio of % change in HNO3 to % change in NO x emissions) is 72%. Random coefficient models with non-vehicle NO x emissions as the independent variable, and HNO3 concentrations as the dependent variable, show a 50% decline in non-vehicle NO x emissions (which is a 23% decline in total NO x emissions) should reduce HNO3 by 17–20%. The average efficiency in this case is 81%. Because non-vehicle NO x emissions data are more reliable than vehicle NO x emissions, non-vehicle NO x models are likely more accurate than the total NO x models.Combining the results of this study with previous work, which examined the relation between NO x emissions and wet NO3 concentrations, show that reducing total NO x emissions by 50% should reduce total NO3 deposition by 37% (wet+dry combined efficiency is 74%), and total N deposition (as measured by CASTNet sites in the northeastern USA) by 25%. A decline in total NO x emissions of 23%, from a 50% reduction in non-vehicle NO x emissions should, on average, reduce total NO3 deposition by 20% (wet+dry combined efficiency is 87%), and total N deposition, as measured by CASTNet sites, by 15%.
Keywords: CASTNet; Nitrogen oxide; Atmospheric deposition; Emission reductions; Nitric acid; Total nitrogen deposition;

Estimating gas emissions from a farm with an inverse-dispersion technique by Thomas K. Flesch; John D. Wilson; Lowry A. Harper; Brian P. Crenna (4863-4874).
We use an inverse–dispersion technique to diagnose gas emissions (ammonia) from a swine farm. A backward Lagrangian stochastic (bLS) model gives the emission-concentration relationship, so that downwind gas concentration establishes emissions. The bLS model takes as input the average wind velocity and direction, surface roughness, and atmospheric stability. Despite ignoring wind complexity and assuming a simplified source configuration in the model calculations, we argue that with concentration and wind measured sufficiently far from the farm the errors can be relatively small. An important part of our analysis was identifying periods likely to give erroneous results. The resulting emission calculations (6.5 and 16 g animal−1 day−1 in March and July, respectively) are plausible in the light of comparative figures.
Keywords: Lagrangian stochastic models; Inverse–dispersion; Trace gas; Ammonia emissions; Monin–Obukhov similarity theory; Dispersion models;

A portable dynamic air sampler (PDAS) using a porous polymer solid-phase microextraction (SPME) fibre has been validated for the determination of biogenic enantiomeric and non-enantiomeric monoterpenes in air. These compounds were adsorbed in the field, and then thermally desorbed at 250 °C in a gas chromatograph injector port connected via a β -cyclodextrin capillary separating column to a mass spectrometer. The optimized method has been applied for investigating the emissions of enantiomeric monoterpenes from Pseudotsuga menziesii (Douglas-fir), Rosmarinus officinalis (Rosemary) and Lavandula lanata (Lavender) which were selected as representative of coniferous trees and aromatic plants, respectively. The enantiomers of α -pinene, sabinene, camphene, δ -3-carene, β -pinene, limonene, β -phellandrene, 4-carene and camphor were successfully determined in the emissions from the three plants. While Douglas-fir showed a strong predominance toward (−)-enantiomers, Rosemary and Lavender demonstrated a large variation in enantiomeric distribution of monoterpenes. The simplicity, rapidity and sensitivity of dynamic sampling with porous polymer coated SPME fibres coupled to chiral capillary gas chromatography/mass spectrometry (GC/MS) makes this method potentially useful for in-field investigations of atmosphere–biosphere interactions and studies of optically explicit atmospheric chemistry.
Keywords: Monoterpenes; Enantiomers; Atmosphere–biosphere interactions; PDAS/SPME; CW/DVB; PDMS/DVB; β -cyclodextrin capillary chromatography; GC/MS; Biogenic emission; Pseudotsuga menziesii (Douglas-fir); Rosmarinus officinalis; Lavandula lanata;

Effect of ventilation strategies on particle decay rates indoors: An experimental and modelling study by Jérôme Bouilly; Karim Limam; Claudine Béghein; Francis Allard (4885-4892).
A cubic experimental chamber of 2.5 m×2.5 m×2.5 m was designed to study the impact of ventilation strategies on the indoor particle concentration. Particles of 0.3–15 μm aerodynamic diameter were used. The combined effects of the ventilation rate (0.5 and 1.0 ach) and the inlet and outlet locations (six different strategies) were tested. Results show that the ventilation acts differently according to the particle size. For small particles (particle diameter lower than 5 μm in diameter), deposition is increased by a factor 2 when the airflow was changed from the Top–Top to the Bottom–Top inlet/outlet configuration. Increasing the ventilation rate from 0.5 to 1.0 h−1 does not modify deposition for the Top–Top configuration but decreases it by 2.8 for the Bottom–Top. The effect of the inlet and outlet locations is less notable for coarse particles. This experimental study reveals that the ventilation strategy has to be well adapted to the particle size in order to improve its effectiveness. We show that the locations of the inlet and the outlet can be a very important parameter and have to be taken into account to predict particle indoor air quality. In addition, a numerical model of particle dispersion was developed. The program calculates instantaneous distributions of air velocity, using the large eddy simulation (LES) method. Trajectories of particles are obtained by implementing a Lagrangian particle model into the LES program. We simulated the experimental conditions in the three-dimensional numerical model and results show that ventilation strategy influences particle deposition in the room. A comparison of numerical and experimental results is given for 5 and 10μm particles. Particle behaviour is well predicted and this model seems to be adapted to predict indoor particle air quality in buildings. More experimental results are needed for a better validation of the numerical model, essentially for small particles.
Keywords: Air quality; Particle matter; Large eddy simulation; Lagrangian model; Building physics;

Deposition to indoor surfaces influences human exposures and material damage from airborne particulate matter. Experiments were conducted to study the deposition of monodisperse particles in the diameter range 0.9–9 μm from turbulent flow onto smooth and rough vertical chamber surfaces. Fluorescent particles were injected continuously into a stirred 1.8-m3 aluminum chamber for a period of several hours. Deposition was measured on smooth glass plates and sandpaper with four different roughness scales that had been mounted on two opposing vertical sidewalls. Deposition velocities were determined as the ratio of deposited particle flux density to airborne particle concentrations. Contrary to expectations, particle deposition onto smooth and rough vertical surfaces was observed to increase with diameter for most conditions, especially for the larger particle sizes. Deposition velocity increased only moderately with increasing surface roughness.
Keywords: Aerosol; PM10; Pollutant dynamics; Indoor air quality; Soiling;

HCB, PCB, PCDD and PCDF emissions from ships by D.A. Cooper (4901-4912).
Since current estimates of hexachlorobenzene (HCB), polychlorinated biphenyls (PCB), dioxins (PCDD) and furans (PCDF) from ships are based on a relatively limited and old data set, an update of these emission factors has been outlined as a target towards improved Swedish emission inventories. Consequently, a comprehensive study was undertaken focusing on these emissions from three different ships during December 2003 to March 2004. Analyses were performed on 12 exhaust samples, three fuel oil samples and three lubricating oil samples from a representative selection of diesel engine models, fuel types and during different “real-world” operating conditions.The determined emissions corresponded reasonably well with previous measurements. The data suggest however that previous PCDD/PCDF emission factors are somewhat higher than those measured here. As expected the greatest emissions were observed during main engine start-up periods and for engines using heavier fuel oils. Total emissions for 2002, using revised emission factors, have been calculated based on Swedish sold marine fuels and also for geographical areas of national importance. In terms of their toxic equivalence (WHO-TEQ), the PCDD/PCDF emissions from ships using Swedish fuels are small (0.37–0.85 g TEQ) in comparison to recent estimates for the national total (ca. 45 g TEQ). Emissions from other land-based diesel engines (road vehicles, off-road machinery, military vehicles and locomotives) are estimated to contribute a further 0.18–0.42 g TEQ. Similarly, HCB and PCB emissions from these sources are small compared to 1995 national emission inventories.
Keywords: Marine emissions; Diesel engines; Real world; Dioxin; Polychlorinated biphenyls;

Chemical composition of fine aerosol measured by AMS at Fukue Island, Japan during APEX period by Akinori Takami; Takao Miyoshi; Akio Shimono; Shiro Hatakeyama (4913-4924).
The size distribution and chemical composition of ambient aerosols was analyzed using an Aerodyne aerosol mass spectrometer (AMS) at Fukue, Japan in the spring of 2003. The average concentration of ammonium, nitrate, sulfate, chloride and organics was 1.57, 0.56, 4.80, 0.07 and 5.03 μg m−3, respectively. The size distribution showed that the modes of ammonium, sulfate and organics were all about 400–700 nm throughout the entire observation period with the exception of a few cases, indicating that these species were internally mixed. The average equivalent ratio of ammonium to sulfate was 0.88, which means that the aerosol was slightly acidic. When air masses came from China and Korea with high aerosol concentration (25–27 March and 6–7 April), nitrate was found in fine particles with ammonium and sulfate. The average ratio of organics to sulfate was 1.05, indicating that the contribution of organics is not negligible in this region. Mass spectra showed that the largest signal in organic fragments was m / z = 44 , which shows that organic species are well-oxygenated.
Keywords: Aerodyne aerosol mass spectrometer; Fukue; Chemical composition; Sulfate; Organics;

Effects of a catalysed and an additized particle filter on the emissions of a diesel passenger car operating on low sulphur fuels by Leonidas Ntziachristos; Zissis Samaras; Efthimios Zervas; Pascal Dorlhène (4925-4936).
This paper presents the emission characteristics of a diesel passenger car operated on low sulphur fuels (8 and 38 ppm) when fitted with either a catalysed diesel particle filter (DPF) or a non-catalysed one combined with a fuel-borne catalyst. Measurements were conducted over the New European Driving Cycle and a higher speed driving cycle to monitor the off-cycle DPF emission behaviour. Regulated gaseous pollutants and particle mass, number and surface were recorded. Aerosol samples were collected with a dedicated sampling system, which provided identical dilution conditions, regardless of the vehicle configuration, and allowed a distinction between volatile and non-volatile particles. The results showed that DPFs have the potential of filtration efficiencies which may exceed 99.5% in all airborne particle properties measured, over the transient cycles. As a result, the cycle average particle number was reduced from 1014 to about 1011  particles km−1 when fitting any DPF and the particle mass was reduced from ∼40 mg km−1 to the detection limit of the current measurement procedure. The exact particle concentration depended on the filter material properties. However, the efficiency in reducing mass appears lower than the airborne number, which suggests a sampling artefact of the present particulate matter measurement procedure. A nucleation mode formed at high exhaust gas temperature with the use of the higher sulphur fuel in combination with the catalysed DPF, thus decreasing the apparent DPF filtration efficiency. This was removed when any of the contributing factors (high temperature, higher sulphur fuel, catalysed DPF) were not present, suggesting sulphate particle formation downstream of the filter. Finally, results show that the DPF soot loading has an insignificant effect on particle size distribution downstream of the filter, when operating within soot-loading limits that are typically encountered in normal on-road operation.
Keywords: Exhaust aerosol; Nucleation mode; Diesel aftertreatment; Filtration efficiency;

The chemical and physical properties of haze particles in the Dead Sea were measured using airborne and ground-based instruments. The results show a very distinct layering of the haze with two major layers, one below about 300 m ASL and the other at around −150 m ASL, which is around +250 m above the Dead Sea surface.The lower layer was found to contain a large fraction of sodium nitrate particles with sizes larger than 1 μm . The particles in this layer are likely transported at night from pollution sources to the south west of the Dead Sea. The upper layer contained large concentrations of fine sulfate particles that are transported from distance sources such as the Israeli Mediterranean coastal regions or even from sources as far away as Europe. The two haze layers appear to be separated in the morning hours, but as the day marches on and the temperature of the land surface on both sides of the lake increases, thermal convection sets in and the two layers become homogenized. A third layer around 1000 m ASL is also observed. This layer is the commonly observed marine boundary layer over Israel and is not affected by the circulation in and around the Dead Sea.In the afternoon the Mediterranean sea breeze reaches the Dead Sea valley and is diverted first into a weak easterly and then into stronger northerly winds, which clear the haze particles from the valley. The land breeze over the lake during the night brings new pollution particles from the Rotem Plato to the southeast of the Dead Sea and is responsible for the formation of the early morning lower haze layer.
Keywords: Haze; Haze formation; Dead Sea; Pollution particles; Fine particles;

Atmospheric speciation of mercury in two contrasting Southeastern US airsheds by Mark C. Gabriel; Derek G. Williamson; Steve Brooks; Steve Lindberg (4947-4958).
Simultaneous measurement of gaseous elemental, reactive gaseous, and fine particulate mercury took place in Tuscaloosa AL, (urban airshed) and Cove Mountain, TN (non-urban airshed) during the summers of 2002 and 2003. The objective of this research was to (1) summarize the temporal distribution of each mercury specie at each site and compare to other speciation data sets developed by other researchers and (2) provide insight into urban and non-urban mercury speciation effects using various statistical methods. Average specie concentrations were as follows: 4.05 ng m−3 (GEM), 13.6 pg m−3 (RGM), 16.4 pg m−3 (Hg-p) for Tuscaloosa; 3.20 ng m−3 (GEM), 13.6 pg m−3 (RGM), 9.73 pg m−3 (Hg-p) for Cove Mountain. As a result of urban airshed impacts, short periods of high concentration for all mercury species was common in Tuscaloosa. At Cove Mountain a consistent mid-day rise and evening drop for mercury species was found. This pattern was primarily the result of un-impacted physical boundary layer movement, although, other potential impacts were ambient photochemistry and air-surface exchange of mercury. Meteorological parameters that are known to heavily impact mercury speciation were similar for the study period for Tuscaloosa and Cove Mountain except for wind speed (m s−1), which was higher at Cove Mountain. For both sites statistically significant ( p < 0.0001 ), inverse relationships existed between wind speed and Hg0 concentration. A weaker windspeed-Hg0 correlation existed for Tuscaloosa. By analyzing Hg concentration—wind speed magnitude change at both sites it was found that wind speed at Cove Mountain had a greater influence on Hg0 concentration variability than Tuscaloosa by a factor of 3. Using various statistical tests, we concluded that the nature of Tuscaloosa's atmospheric mercury speciation was the result of typical urban airshed impacts. Cove Mountain showed atmospheric mercury speciation characteristics indicative of a non-urban area along with potential influence from steady regional input of mercury pollution from larger sources.
Keywords: Meteorology; Landuse; Gaseous elemental mercury; Reactive gaseous mercury; Fine particulate mercury;

Measurement of regional distribution of atmospheric NO2 and aerosol particles with flashlight long-path optical monitoring by Si Fuqi; Hiroaki Kuze; Yotsumi Yoshii; Masaya Nemoto; Nobuo Takeuchi; Toru Kimura; Toyofumi Umekawa; Taisaku Yoshida; Tadashi Hioki; Tsuyoshi Tsutsui; Masahiro Kawasaki (4959-4968).
We report on an air-pollution monitoring campaign in the urban Kyoto area conducted during December 2003 and January 2004. The method is based on the differential optical absorption spectroscopy (DOAS) using an aviation obstruction light (white flashlight). Three sets of DOAS spectrometers, each consisting of a telescope and a compact charge-coupled device (CCD) spectrometer, were operated to cover the southern part of the city area. Three sites were chosen in the urban Kyoto area, and the average concentrations of NO2 were measured with optical path lengths of 2.7, 4.1, and 7.1 km. The aerosol optical thickness was simultaneously measured for the path length of 2.7 km. It is found that the temporal variations of the retrieved amount of the pollution species agree with each other and they are also consistent with concurrent results of the ground sampling measurements.
Keywords: Flashlight DOAS; Urban atmosphere; Air pollution distribution; Aerosol extinction; Ground sampling;

Hygroscopic properties of an organic-laden aerosol by William C. Malm; Derek E. Day; Sonia M. Kreidenweis; Jeffrey L. Collett; Christian Carrico; Gavin McMeeking; Taehyoung Lee (4969-4982).
Observation and appreciation of scenic landscape features, airport runway visibility, and the earth's radiation balance are all dependent on the radiative properties of the atmosphere, which in turn are dependent on the scattering and absorption characteristics of ambient aerosols. Atmospheric scattering and, to a lesser degree, absorption characteristics are highly dependent on the amount of water vapor absorbed by aerosols under ambient relative humidity (RH) conditions. Water vapor absorptive properties of inorganic aerosols have been extensively measured and modeled; however, hygroscopic properties of organic aerosols are less understood, especially as they occur in the ambient atmosphere. Therefore, an aerosol characterization study was conceived and implemented at Yosemite National Park, which is highly impacted by carbonaceous aerosols. The overall objective of the study was to characterize the physical, chemical, and optical properties of a carbon-dominated aerosol, including the ratio of total organic matter weight to organic carbon, organic mass scattering efficiencies, and the hygroscopic characteristics of a carbon-laden ambient aerosol. The study was conducted during July, August, and the first week of September at Turtleback Dome on the south rim of the entrance to Yosemite Valley. The ratio of the scattering coefficient at some RH divided by the scattering coefficient at some minimum RH ( f ( RH ) = b scat ( RH ) / b scat ( RH min ) ) was measured over a wide range of RHs. f(85<RH<90) decreased from about 2.0 to <1.2 as the organic carbon mass (OMC/(NH4)2(SO4)) ratio increased from a low of 0.57 to 11.15, implying that the f(RH) associated with organics is small, possibly on the order of 1.1 or less. Furthermore, modeling f(RH) as a function of RH suggested that ambient organic mass aerosols may be weakly hygroscopic with an f(RH) at RH=85–90% of about 1.1.
Keywords: Hygroscopicity; Aerosol scattering; Organic optical properties; Mass scattering efficiency; Particle size distributions;

Wildfires in eastern Texas in August and September 2000: Emissions, aircraft measurements, and impact on photochemistry by Victoria Junquera; Matthew M. Russell; William Vizuete; Yosuke Kimura; David Allen (4983-4996).
The accuracy of wildfire air pollutant emission estimates was assessed by comparing observations of carbon monoxide (CO) and particulate matter (PM) concentrations in wildfire plumes to predictions of CO and PM concentrations, based on emission estimates and air quality models. The comparisons were done for observations made in southeast Texas in August and September of 2000. The fire emissions were estimated from acreage burned, fuel loading information, and fuel emission factor models. A total of 389 km2 (96,100 acres) burned in wildfires in the domain encompassing the Houston/Galveston-Beaumont/Port Arthur (HGBPA) area during August and September 2000. On the days of highest wildfire activity, the fires resulted in an estimated 3700 tons of CO emissions, 250 tons of volatile organic carbon (VOC) emissions, 340 tons of PM2.5, and 50 tons of NO x emissions; estimated CO and VOC emissions from the fires exceeded light duty gasoline vehicle emissions in the Houston area on those days. When the appropriate aircraft data were available, aloft measurements of CO in the fire plumes were compared to concentrations of CO predicted using the emission estimates. Concentrations estimated based on emission predictions and air quality models were within a factor of 2 of the observed values. The estimated emissions from fires were used, together with a gridded photochemical model, to characterize the extent of dispersion of the fire emissions and the photochemistry associated with the fire emissions. Although the dispersion and photochemical impacts varied from fire to fire, for wildfires less than 10,000 acres, the greatest enhancements of CO and ozone concentrations due to the fire emissions were generally confined to regions within 10–100 km of the fire. Within 10 km of these fires, CO concentrations can exceed 2 ppm and ozone concentrations can be enhanced by 60 ppb. The extent of photo-oxidant formation in the plumes was limited by NO x availability and isoprene emissions from forested areas downwind of the fires provided most of the hydrocarbon reactivity in the plumes.
Keywords: Wildfires; Wildfire inventory; Wildfire emissions; Emissions inventory; Emissions modeling; TexAQS; Photochemical modeling; CAMx; Plume rise;

Barry Smith by Helen ApSimon (4997-4998).