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Atmospheric Environment (v.40, #20)

Editorial board (pp. i).

Atmospheric corrosion effects of HNO₃—Influence of concentration and air velocity on laboratory-exposed copper by Farid Samie; Johan Tidblad; Vladimir Kucera; Christofer Leygraf (pp. 3631-3639).

A recently developed experimental set-up has been used to explore the atmospheric corrosion effects of nitric acid (HNO₃) on copper, in particular the influence of concentration and air velocity. Characterization and quantification of the corrosion products on exposed samples were performed with Fourier transform infrared (FT-IR) microspectrocscopy, ion chromatography, X-ray diffraction (XRD), micro-balance and microscopy. At low air velocity (0.03cms⁻¹) HNO₃ deposition and weight gain of copper increased linearly with concentration up to 400μgm⁻³ or 156ppb. The influence of air velocity on corrosion of copper was tested within the range of 0.03–35.4cms⁻¹. Although the air velocity in this study was significantly lower than typical outdoor wind values, a high HNO₃ concentration of the air velocity of 35.4cms⁻¹ resulted in a relatively high deposition velocity ( V_d) of 0.9cms⁻¹ on the metal surface and 1.2cms⁻¹ on an ideal absorbent, which would imply a limiting deposition velocity on the copper surface ( V_d,surf) of 3.6cms⁻¹. Results obtained in this study emphasize the importance for future research on the corrosion effects of HNO₃ on materials as very little has so far been done in this field.

Keywords: Nitric acid; Deposition rate; Mass transport; Materials degradation; Gerhardtite

Intercomparison of the DOAS and LOPAP techniques for the detection of nitrous acid (HONO) by J. Kleffmann; Lorzer J.C. Lörzer; P. Wiesen; C. Kern; S. Trick; R. Volkamer; M. Rodenas; K. Wirtz (pp. 3640-3652).

Recent studies have demonstrated that nitrous acid (HONO) is a source of hydroxyl radicals (OH) in the boundary layer not only early in the morning but also throughout the day. Despite its importance, all known instruments to detect HONO in the atmosphere suffer either from the great experimental effort necessary or from the possibility of significant interferences. In addition, only a few instruments are sensitive enough to detect low HONO concentrations during daytime. Accordingly, validated and sensitive measurements of nitrous acid are of paramount importance to describe the oxidation capacity of the atmosphere. Up to now, in intercomparisons of these chemical detectors with the well accepted DOAS technique significantly higher concentrations have been detected during the day with the chemical detectors, the discrepancy being attributed to interferences.In the present study, a recently developed HONO instrument (LOPAP) was validated against the DOAS technique, both in the field and in a large smog chamber under various conditions. Since sampling artefacts were minimised and interferences were measured and corrected for by the LOPAP instrument excellent agreement was obtained between these techniques during daytime as well as night-time. It is demonstrated that chemical instruments, which do not measure and do not correct interferences may significantly overestimate daytime concentrations of HONO caused by unknown interferences, which are particularly important during daytime, when HONO concentrations are low. For the DOAS technique, the possibility of HONO impurities in the NO₂ reference spectra used for the spectral analysis needs to be treated actively in the evaluation process, to avoid a potential negative interference at low HONO/NO₂ ratios. A simple procedure is presented that eliminates this possible error source in DOAS measurements of HONO in the atmosphere.

Keywords: Nitrous acid (HONO); Atmospheric chemistry; Oxidation capacity; Interferences; Field measurements

High-resolution spatial patterns of long-term mean concentrations of air pollutants in Haifa Bay area by Yuval; David M. Broday (pp. 3653-3664).

High-resolution maps of the mean concentrations ofSO2, NO,NO2,O3, andPM10 in the period 2002–2004 were produced using half-hourly data from the local air quality monitoring network in Haifa Bay area, Israel. The network consists of 20 monitoring stations within an area of206km2, which encompasses a major industrial and power generation centre in the midst of a population of about 500000. The pollutants’ spatial features agree well with their known sources and the expected dispersion by the prevailing meteorology. The ranking of their spatial variations agree with published observations on larger spatial scales. The high-resolution maps capture in a small spatial scale theNOx andO3 cycle relationships expected by theory, and previously observed by analyses of monitoring time series. High correlation was found between the spatial patterns of thePM10,NOx andO3, whereas the correlation between the spatial features of thePM10 andSO2 is low. This suggests that the traffic, a major source ofNOx, rather than industry, the major source ofSO2, is the main contributor to the anthropogenicPM10 in the study area. This inference is corroborated by the low sulphur to nitrogen ratio throughout the region, which is typical of traffic-dominated pollution. A general conclusion drawn from this study is that high-resolution monitoring and mapping can significantly contribute to air quality management programmes in terms of both pollution abatement and exposure and risk assessment.

Keywords: Air pollution management; Haifa Bay area; Mapping

Iron-catalyzed photochemical transformation of benzoic acid in atmospheric liquids: Product identification and reaction mechanisms by Yiwei Deng; Kai Zhang; Hao Chen; Taixing Wu; Metthew Krzyaniak; Amina Wellons; Dawn Bolla; Kenneth Douglas; Yuegang Zuo (pp. 3665-3676).

This study investigated iron-catalyzed photochemical oxidation of benzoic acid (BA), one of the major photodegradation products of petroleum hydrocarbons, under sunlight or monochromatic light irradiation in a wavelength range of 254–419nm. The photochemical degradation of BA in the absence of iron (III) occurred at irradiation wavelengths below 300nm. The photochemical transformation of BA in the presence Fe(III) was observed at both 254, 350, 419nm and under solar irradiation. The half-life for the photodegradation of BA (100μM) was 160±20min in the presence of 20μM Fe(III) at pH 3.20 on sunny August days at noon time. The degradation rate increased with increasing concentration of Fe(III). The reaction products were separated and identified using capillary electrophoresis (CE), gas chromatography/mass spectrometry (GC/MS) and UV-Visible spectrophotometry. The major reaction products were 2-hydroxybenzoic, 3-hydroxybenzoic and 4-hydroxybenzoic acids. Hydrogen peroxide (H₂O₂^{) and Fe(II) species were also formed during the photochemical reactions. The proposed reaction mechanisms include the photoexcitation of Fe(III) hydroxide complexes to form Fe(II) ions and hydroxyl radicals (OH}) that attack ortho, meta and para positions of BA to form corresponding monohydroxybenzoic acids and H₂O₂. The monohydroxybenzoic acids formed further react with hydroxyl and surperoxide radicals (HO₂⁻/O₂⁻) to yield dihydroxybenzoic acids in atmospheric water droplets.

Keywords: Benzoic acid; Photochemical degradation; Hydroxybenzoic acid; Fe(III)/Fe(II) redox cycling; Capillary electrophoresis; GC–MS; Atmosphere; Aquatic chemistry; Sunlight

The spatial distribution of pollutant transport to and from indoor surfaces by Glenn C. Morrison; Ping Zhao; Lenin Kasthuri (pp. 3677-3685).

Spatial distributions in surface flux and concentrations complicate the assessment of indoor mass-transfer coefficients and can bias the resulting estimates of indoor exposure. To better understand these phenomena, we quantify the spatial distribution of ozone flux and mass-transfer coefficients for indoor surfaces in several field locations using NaNO₂ coated filters. The 12-h average transport-limited deposition velocity for ozone,v¯t,ozone, corrected for the diameter of the filters, ranged from 1.2mh⁻¹ on a wall to 18.7mh⁻¹ near an operating recirculation supply vent in an apartment. For 10 filters distributed evenly around walls of a laboratory, large multi-person office, apartment with recirculation on (excluding a near-supply vent sample) and apartment with recirculation off, the averagev¯t,ozone were respectively, 3.3±1.1, 3.5±1.3, 2.8±0.8 and 2.3±0.8mh⁻¹. We observed (1) a tighter distribution of flux for filters placed near one-another than for filters separated by greater than one meter, (2) higher fluxes near sources of air movement such as supply vents and computers, and (3) consistent results in a single location over 5 days. Measurements obtained with devices such as coated filters can be corrected for size by using a range of device sizes during an experiment. We find the mass-transfer coefficient in a room-sized laboratory chamber to be proportional to the device diameter raised to the power of −0.45.

Keywords: Mass-transfer; Pollutant transport; Pollutant deposition; Indoor air; Spatial measurement; Deposition velocity

Quantification of pollutants emitted from very large wildland fires in Southern California, USA by Nicholas E. Clinton; Peng Gong; Klaus Scott (pp. 3686-3695).

This study investigates the efficacy of the first order fire effects model (FOFEM) implemented in a geographic information system for wildland fire emissions estimation. The objective of the study was to quantify the source and composition of smoke and emissions from wildland fires that burned 235,267ha in Southern California, USA, in October 2003. From inputs of vegetation, fuel model data, weather condition data, and fire perimeters, the model produces estimates of ten pollutant species (10 and 2.5μm particulates, carbon dioxide, carbon monoxide, methane, non-methane hydrocarbons, ammonia, nitrous oxide, oxides of nitrogen, sulfur dioxide) from ten fuel categories (duff, litter, woody debris in three size classes, herbs, shrubs, tree regeneration, live branch-wood and live foliage). From the Southern California fires, the model estimated over 5 million metric tons (megagrams) of total pollutant emissions over several days. These emissions include over 457,000tons of carbon monoxide, over 6 million tons (approximately 6Tg) of carbon dioxide, and over 46,000tons of particulates. Fuels that contributed the most mass to the fire emissions were predominantly shrubs and duff.

Keywords: GIS; Pollution; FOFEM; Smoke; Air quality; Modeling; Carbon cycle; Fire; Emissions; Carbon dioxide; Particulates

Long-term observation of real-world road traffic emission factors on a motorway in Switzerland by Christoph Hueglin; Brigitte Buchmann; Rudolf O. Weber (pp. 3696-3709).

Long-term air quality measurements from a roadside monitoring site of the Swiss national air pollution-monitoring network (NABEL) are analysed for average real-world road traffic emission factors (EFs) by evaluation of concentration differences under upwind and downwind conditions. Time series of relative EFs for NO _x, NO, NO₂, CO, SO₂, number of fine particles, and elemental carbon (EC) are estimated for the total vehicle fleet and converted into absolute EFs by scaling them with emission factors from an emission model [HBEFA, 2004. Handbuch für Emissionsfaktoren des Strassenverkehrs (handbook of emission factors for road traffic). Umweltbundesamt Berlin, Bundesamt für Umwelt, Wald und Landschaft Bern, Infras AG, Bern (published on CD-ROM, see alsowww.hbefa.net] for a specific reference year. For NO _x, NO, NO₂, CO, and SO₂ the EFs of the total vehicle fleet decreased during the time period from 1992 to 2004 by 44%, 51%, 5%, 71%, and 55%, respectively. The much smaller negative trend of NO₂ compared to NO _x indicates that the NO₂/NO _x road traffic emissions ratio increased during this period (from 14% in 1992 to 23% in 2004). It is shown that this trend is caused by increasing primary NO₂ road traffic emissions rather than by increasing secondary NO₂ formation via reaction of NO with O₃.Data for total particle number concentrations and EC are only available since the year 2004. For 2004, the estimated average emission of total particles with diameter larger than 7nm is 7.9×10¹⁴km⁻¹veh⁻¹, for EC an average emission factor of 21mgkm⁻¹veh⁻¹ is obtained.

Keywords: Road traffic emissions; NO; _x; Secondary NO; ₂; Elemental carbon; Particle number concentration

Chemical and biological characteristics of dew and rain water in an urban coastal area (Bordeaux, France) by D. Beysens; C. Ohayon; M. Muselli; O. Clus (pp. 3710-3723).

We report on a 1-year investigation (15 January 2002–14 January 2003) in Bordeaux, France, comparing the quality of dew water with respect to rain water. The following physico-chemical and bacteriological properties of dew and rain water were measured: pH, electric conductivity, cations (Na⁺, K⁺, Ca²⁺, Mg⁺⁺, Zn⁺⁺, Cu⁺⁺), anions (Cl⁻, SO₄²⁻, NO₃⁻, NO₂⁻), hardness (TH, calcical, magnesial, permanent), complete alkalimetric title, dry residue and number of colony-forming unities (CFU) at 22 and 36°C. The CO₃²⁻, HCO₃⁻, HPO₄²⁻ concentrations were found negligible. The ionic concentrations are in general lower in dew than in rain with NO₂⁻ as a noticeable exception. The mean rain pH (5.4) is lower than dew pH (6.3). The major ions are from the nearby Atlantic Ocean (within 50km). Average ion concentrations are found below the World Health Organization (WHO) limit requirements for potable water; dew composition is close to low mineralized commercial spring waters for the analyzed ions. The biological analyses are concerned with CFU at 22 and 36°C. Dew is seen to exceed on various occasions the WHO limits.

Keywords: Atmospheric deposition; Dew chemistry; Dew biology; Water quality

Estimation of the seasonal variation of particulate nitrate and sensitivity to the emission changes in the greater Seoul area by Sihye Lee; Young Sung Ghim; Yong Pyo Kim; Jin Young Kim (pp. 3724-3736).

Seasonal variation of fine particulate nitrate and sensitivity of fine particle mass concentration to the emission changes of VOCs and NO _x were estimated in the greater Seoul area. SBOX, a photochemical box model was used to obtain the total nitric acid (HNO₃^T) concentration, and SCAPE2, a gas/particle equilibrium model was used to determine the partitioning of nitric acid/nitrate and particulate water content. Most HNO₃^T existed as nitrate except in summer (∼60%) since there was enough ammonia to form particulate ammonium nitrate. In summer, high temperature was favorable to gaseous nitric acid. Also, because of average relative humidity (RH) higher than the deliquescence points of most salts, water content in summer was higher than those in other seasons by a factor of two. For all seasons, fine particle mass concentration (the sum of ion concentrations and water content) increased until considerable amount of NO _x emissions was reduced. This phenomenon is a typical example of the so-called ‘NO _x disbenefits’ that has been discussed in relation to the abatement of ozone pollution.

Keywords: Inorganic ions; Ammonia availability; Volatilization; Relative humidity; NO; _x; disbenefits

Evaluation of the GEM-AQ air quality model during the Québec smoke event of 2002: Analysis of extensive and intensive optical disparities by N.T. O’Neill; M. Campanelli; A. Lupu; S. Thulasiraman; J.S. Reid; M. Aubé; L. Neary; J.W. Kaminski; J.C. McConnell (pp. 3737-3749).

The root-mean-square (rms) differences between the Canadian air quality model GEM-AQ and measurements for intensive and extensive optical variables (aerosol optical depth or AOD and Ångström exponent orα) were investigated using data from the July 2002 Québec smoke event. In order to quantify regional differences between model and measurements we employed a three component analysis of rms differences. The behaviour of the two absolute amplitude rms components of AOD (difference of the means and the difference of the standard deviations) enabled us to infer emission properties which would otherwise have been masked by the larger ‘anti-correlation’ component. We found the inferred emission fluxes to be significantly higher than the original geostationary, satellite-derived FLAMBÉ (fire locating and modelling of burning emissions) emissions flux estimates employed as inputs to the simulations. The model captured the regional decrease of the intensiveα exponent (increase of particle size with trajectory time), while the agreement with the extensive AOD parameter was marginal but clearly dependent on the nature of the spatio-temporal statistical tools employed to characterize model performance. In establishing theα versus trajectory time trend, the modelled AOD data was filtered in the same way as the measured data (very large AODs are eliminated). This processing of modelled results was deemed necessary in order to render theα results comparable with the measurements; in the latter case it was difficult, if not impossible, to discriminate between measuredα trends due to instrumental artifacts (non-linearities at low signal strength) versus trends due to coagulative effects.

Keywords: Forest fire; Aerosol optical depth; Ångström exponent

Correlation of hydrogen, ammonia and nitrogen monoxide (nitric oxide) emissions of gasoline-fueled Euro-3 passenger cars at transient driving by Norbert V. Heeb; Christian J. Saxer; Anna-Maria Forss; Bruhlmann Stefan Brühlmann (pp. 3750-3763).

Ammonia (NH₃) emissions from gasoline-fueled vehicles have become an important source of pollution affecting urban air chemistry. NH₃ influences the acidity of atmospheric depositions and it is involved in secondary aerosol formation. NH₃ has to be considered as a secondary pollutant of the three-way-catalyst (TWC), since it is formed de novo during the DeNOx process. The extent of traffic-related hydrogen (H₂) emissions and its impact on atmospheric redox chemistry is not well understood but is of increasing importance when we develop towards a hydrogen-based society. Herein we report on tail-pipe H₂, NH₃, and NO emissions of gasoline-fueled Euro-3 passenger cars at transient driving from 0 to 150kmh⁻¹. The effects of velocity, acceleration, deceleration, and cold start were deduced from time-resolved EI- and CI-MS data. On a molar basis, H₂ emissions were always higher than those of NH₃ and NO by about an order of magnitude. H₂ and NH₃ emissions are correlated to some degree, as soon as catalyst light-off occurred. NH₃ emissions exceeded those of NO for most vehicle conditions. Mean NH₃/NO mixing ratios around two were observed with the exception of the cold start, where NO was present in large excess. Catalyst light-off is indicated by a fast transition from a NO- to a NH₃-rich exhaust gas. All emissions clearly depend on speed and acceleration. Mean velocity-dependent emission factors varied by about one order of magnitude from 17 to 720, 8 to 170, and 7 to 80mgkm⁻¹ for H₂, NH₃, and NO, respectively, with emission minima for all three pollutants when driving 70–90kmh⁻¹. We conclude that the investigated Euro-3 vehicles are mainly operated under slightly reducing conditions, where NH₃ and H₂ emissions dominate over those of NO. Under these conditions, all vehicles fulfill the valid emission limit for NO _x.

Keywords: Vehicle emissions; Catalytic reduction of nitrogen oxides; Secondary pollutant; Time-resolved exhaust gas analysis; Chemical ionization mass spectrometry (CI-MS); Electron impact mass spectrometry (EI-MS).

OH reaction rate constants and UV absorption cross-sections of unsaturated esters by M.A. Teruel; S.I. Lane; A. Mellouki; G. Solignac; G. Le Bras (pp. 3764-3772).

Absolute rate coefficients have been determined for the gas-phase reactions of hydroxyl radicals with methyl acrylate ( k₁), methyl methacrylate ( k₂) and ethyl acrylate ( k₃). Experiments were performed using two different techniques, the relative rate method and the pulsed laser photolysis-laser induced fluorescence technique. The kinetic data obtained were used to derive the following Arrhenius expressions in the temperature range 253–374K (in units of cm³molecule⁻¹s⁻¹):k1=(2.0±0.8)×10-12exp[(553±51)/T],k2=(2.5±0.8)×10-12exp[(821±55)/T],k3=(2.3±0.8)×10-12exp[(580±65)/T]. At 298K, the reaction rate constants obtained by the two methods were in good agreement. In addition, the UV absorption spectra for the three unsaturated esters have been determined at (298±2)K and the absorption cross-sections in the wavelength region 215–298nm were reported. The results are presented, discussed and used to estimate the atmospheric lifetimes for the studied esters.

Keywords: Unsaturated esters; Hydroxyl radicals; Rate coefficients; UV spectra; Tropospheric chemistry

Use of GIS and ancillary variables to predict volatile organic compound and nitrogen dioxide levels at unmonitored locations by Luther Smith; Shaibal Mukerjee; Melissa Gonzales; Casson Stallings; Lucas Neas; Gary Norris; H. Ozkaynak Halûk Özkaynak (pp. 3773-3787).

In late 1999, passive air sampling of nitrogen dioxide (NO₂) and volatile organic compounds was conducted at 22 school locations and two intensive sites in El Paso, Texas. Our goal was to predict concentrations of NO₂ and benzene, toluene, ethylbenzene, o-xylene, and m, p-xylene at a total of 55 schools. The predictive equations were developed by regressing the passive monitor measurements at the 22 monitored schools on land-use variables derived from a geographic information system (GIS). These GIS-based ancillary variables included distance to the nearest border crossing, elevation, population density, distance to roads with specified traffic volumes, traffic intensity around the schools, and distance to the nearest petroleum facility. The reliability of the predictive equations was assessed at the two intensive monitoring sites. For all pollutants, the most useful predictive ancillary variables were elevation, population density, distance to a border crossing, and distance to a petroleum facility. For estimating NO₂, traffic intensity was also important.

Keywords: Air pollution; GIS; Spatial analysis; Generalized additive models (GAM); Traffic

Source apportionment and analysis on ambient and personal exposure samples with a combined receptor model and an adaptive blank estimation strategy by Weixiang Zhao; Philip K. Hopke; Gary Norris; Ron Williams; Pentti Paatero (pp. 3788-3801).

The objective of this study is to characterize the airborne particle sources that are common to four different environments (personal, residential indoor, residential outdoor and ambient) and to study the relationships between PM_2.5 exposure and emission sources. Twenty-four hour integrated filter samples were collected on 7 days in each of 4 seasons from June 2000 to May 2001 for 38 individuals in four different type of environments in Raleigh and Chapel Hill, NC. An expanded receptor model (since different environments were analyzed simultaneously, it was also called combined model) was established for this study. The organic carbon (OC) and the first component of OC (OC1) measurements were not blank corrected in this study, so an adaptive blank estimation process was integrated into the combined receptor model and the best OC and OC1 blank values were estimated while the source profiles were being extracted. Four external sources (motor vehicle emission, soil, secondary sulfate, and secondary nitrate) and four internal sources (environmental tobacco smoking and its mixture, personal care/activity, Cu-factor mixed with indoor soil, and cooking) were resolved. The contributions of each source to the different environments were estimated. The contribution of external sources to the composition of personal and indoor samples, and various infiltration factors were also discussed. This study also provided a novel method for blank value estimation.

Keywords: Combined receptor model; Source apportionment; Exposure analysis; Blank estimation

Source areas and chemical composition of fine particulate matter in the Pearl River Delta region of China by G.S.W. Hagler; M.H. Bergin; L.G. Salmon; J.Z. Yu; E.C.H. Wan; M. Zheng; L.M. Zeng; C.S. Kiang; Y.H. Zhang; A.K.H. Lau; J.J. Schauer (pp. 3802-3815).

Fine particulate matter (PM_2.5) was measured for 4 months during 2002–2003 at seven sites located in the rapidly developing Pearl River Delta region of China, an area encompassing the major cities of Hong Kong, Shenzhen and Guangzhou. The 4-month average fine particulate matter concentration ranged from 37 to 71μgm⁻³ in Guangdong province and from 29 to 34μgm⁻³ in Hong Kong. Main constituents of fine particulate mass were organic compounds (24–35% by mass) and sulfate (21–32%). With sampling sites strategically located to monitor the regional air shed patterns and urban areas, specific source-related fine particulate species (sulfate, organic mass, elemental carbon, potassium and lead) and daily surface winds were analyzed to estimate influential source locations. The impact of transport was investigated by categorizing 13 (of 20 total) sampling days by prevailing wind direction (southerly, northerly or low wind-speed mixed flow). The vicinity of Guangzhou is determined to be a major source area influencing regional concentrations of PM_2.5, with levels observed to increase by 18–34μgm⁻³ (accounting for 46–56% of resulting particulate levels) at sites immediately downwind of Guangzhou. The area near Guangzhou is also observed to heavily impact downwind concentrations of lead. Potassium levels, related to biomass burning, appear to be controlled by sources in the northern part of the Pearl River Delta, near rural Conghua and urban Guangzhou. Guangzhou appears to contribute 5–6μgm⁻³ of sulfate to downwind locations. Guangzhou also stands out as a significant regional source of organic mass (OM), adding 8.5–14.5μgm⁻³ to downwind concentrations. Elemental carbon is observed to be strongly influenced by local sources, with highest levels found in urban regions. In addition, it appears that sources outside of the Pearl River Delta contribute a significant fraction of overall fine particulate matter in Hong Kong and Guangdong province. This is evident in the relatively high PM_2.5 concentrations observed at the background sites of 18μgm⁻³ (Tap Mun, southerly flow conditions) and 27μgm⁻³ (Conghua, northerly flow conditions).

Keywords: Pearl River Delta region; PM; _2.5; Chemical composition; Source regions; Transport

Prediction of air pollution concentration using an in situ real time mixing height model by Sunita Nath; R.S. Rashmi S Patil (pp. 3816-3822).

Mixing height (MH), which represents the dispersion depth of the atmospheric boundary layer, is a crucial input parameter in air pollution models. However, there is enormous uncertainty in its estimation since it is not a directly measurable variable. Generally, MH is estimated from the twice daily radiosonde measurements from the nearest meteorological station, especially in developing countries. But, these extrapolated values cause severe errors in prediction since MH is site and time dependent. In this paper, a simple in situ mixing height growth (IMG) model, which can estimate onsite real time values of MH from readily available surface measurements of wind and temperature, is applied to some commonly used air pollution prediction models.Box models (BM) are often used for large-scale predictions, but assume a constant lid height, though their accuracy is highly dependant upon its variation. IMG was applied to a photochemical box model, since ozone formation is strongly dependent upon insolation and is controlled by real time values of MH. The ozone concentrations predicted by IMG–BM showed a 13% improvement as compared to those estimated from the usual extrapolated radiosonde values. Further, gaussian diffusion model (GDM) is recommended in India and many other countries for regulatory use. Application of IMG to GDM for industries showed that the IMG model considerably improves the prediction accuracy and can be used in a cost effective manner.

Keywords: Mixing height; Pollutant dispersion; Box model; Ozone prediction; Gaussian diffusion model

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Atmospheric Environment (v.40, #20)