Atmospheric Environment (v.39, #12)

A new analytical approach to simulate the pollutant dispersion in the PBL by S. Wortmann; M.T. Vilhena; D.M. Moreira; D. Buske (2171-2178).
In this work, we present a new analytical approach for the solution of the advection–diffusion equation to simulate the pollutant dispersion in the planetary boundary layer. In this method the advection–diffusion equation after transformation by a generalized integral transform is solved by the Laplace transform technique with analytical inversion and is seen to be non-Gaussian. No approximation is made in this so that an exact solution is obtained except for the round-off error. The present model has been evaluated in moderately unstable conditions using the Copenhagen experiment. The performance of the model is discussed qualitatively as well as quantitatively. The proposed model has performed very well with the data from the diffusion experiment considered.
Keywords: GITT; Laplace transform; Atmospheric dispersion; Analytical solution; Advection–diffusion equation; Planetary boundary layer;

The respective rates of SO2, NO x , and NH3 anthropogenic emissions in the former Czechoslovakia (the Czech Republic and Slovakia (CS)) were <10, <5, and 33 mmol m−2  yr−1 in 1850, increased slowly until 1950 and rapidly in the 1950–1980 period, and peaked at ∼380, ∼180 and ∼80 mmol m−2 yr−1 in the 1980s. The emissions declined markedly after the political and economical changes in 1989 due to (1) restructuring of industry and farming in the early 1990s (∼35% decrease in energy production and 50–60% decrease in cattle numbers and fertilization rate of farmland), (2) sulfur emission controls, (3) changes in fuel supply, and (4) optimization of combustion regimes at stationary sources of NO x . The CS emission rates of SO2, NO x , and NH3 were 87%, 51%, and ∼44% lower, respectively, in 2000 than in 1985. Emissions of SO2 declined linearly throughout the 1990s (to 47 mmol m−2  yr−1 in 2000), while NO x and NH3 emissions declined rapidly during 1989–1994 and then slowly to ∼85 and ∼44 mmol m−2  yr−1, respectively, in 2000. Similar declines in SO2 and NO x emissions occurred in the entire central European region, while NH3 emission decreased less over a wider region due predominantly to more stable emission rates of NH3 in Germany. Emission rates of S and N compounds correlated tightly (P<0.001) with their deposition in the CS region.
Keywords: Atmospheric pollution; SO2; NO x ; NH3; Deposition; Acidification; Central Europe;

A large number of anthropogenic organic chemicals are emitted into the troposphere. Reactions with the hydroxyl radical are a dominant removal pathway for most organic compounds, but experimentally determined gas-phase reaction rate constants are only available for about 750 compounds. The lack of experimental data increases the importance of applying quantitative structure–activity relationships (QSAR) to evaluate and predict reactivities. It is generally acknowledged that these empirical relationships are valid only within the same domain for which they were developed. However, model validation is sometimes neglected and the application domain is not always well defined. The purpose of this paper is to outline how validation and domain definition can facilitate the modeling and prediction of the hydroxyl radical reaction rates for a large database. A substantial number of theoretical descriptors (867) were generated from 2D molecular structures for compounds present in the Syracuse Research Corporation's PhysProp Database. A QSAR model was developed for the hydroxyl radical reaction rate constant using a projection-based regression technique, partial least squares regression (PLSR). The PLSR model was subsequently validated with an external test set. The main factors of variation could be attributed to two reaction pathways, hydrogen atom abstraction and addition to double bonds or aromatic systems. A set of 17 293 compounds, drawn from the PhysProp Database, was projected onto the PLSR model and 74% were inside the applicability domain. The predicted hydroxyl reaction rates for 25% of these compounds were slow or negligible, with atmospheric half-lives in the range from days to years. Finally, the list of persistent organic compounds was matched against the OECD list of high production volume chemicals (HPVC). Together with the experimental data, nearly three hundred compounds were identified as both persistent and in high volume production.
Keywords: Molecular descriptors; Multivariate calibration; OH radical; Quantitative structure–activity relationship; Reaction rate constant;

Dust-loaded tree leaves from Kathmandu have been analyzed for magnetic susceptibility ( χ ) and heavy metal (HM) contents. For 221 samples of leaves of cypress (mainly Cupressus corneyana), silky oak (Grevillea robusta) and bottlebrush (Callistemon lanceolatus), χ has a range of (0.01–54)×10−8  m3  kg−1 with a median of about 10.0×10−8  m3  kg−1. Trees situated close to the busy road intersections, near the main bus station and sectors of roads with steep slope yield elevated susceptibility.Chemical analysis of 20 samples of varying susceptibility by atomic absorption spectrometry yields the following maximum HM contents: Fe (1.3 wt%), Mn (281.9 ppm), Zn (195.2 ppm), Cu (41.5 ppm), Pb (38.4 ppm), Ni (8.1 ppm), Cr (6.4 ppm), Co (4.1 ppm) and Cd (1.2 ppm). The logarithmic susceptibility on dry mass basis ( χ d ) shows significant linear relationship with HM contents: Pearson's correlation coefficient r > 0.8 with Zn, Fe, Cr; r > 0.7 with Mn, Cu; r > 0.6 with Pb, Ni. Magnetic phases are of soft (magnetite/maghemite) and hard (hematite) coercivities. Microscopy of magnetic extracts reveals spherules (mostly of 2–20 μm diameter) originated from vehicle exhausts through the combustion process as well as crystalline grains of lithogenic origin.The dust accumulation in leaves took place mainly after monsoon (beginning of October 2001) till the sampling period (first half of February 2002). Despite the dependence of susceptibility and HM contents on a variety of spatial and temporal factors (amount of particulate matter (PM), efficiency of deposition/removal of PM by wind, precipitation, birds etc.), a significant correlation of susceptibility to HM implies that the former serves as an effective proxy of metallic pollution. Hence, susceptibility-based bio-monitoring technique is recommended as an economic and rapid tool for assessment of environmental pollution in urban areas like Kathmandu.
Keywords: Magnetic bio-monitoring; Dust loadings; Urban pollution; Environmental magnetism; Magnetic spherules;

A new method to link PM10 concentrations from automatic monitors to the manual gravimetric reference method according to EN12341 by Robert Gehrig; Christoph Hueglin; Beat Schwarzenbach; Thomas Seitz; Brigitte Buchmann (2213-2223).
Automatic on-line monitors for particulate matter with an aerodynamic diameter up to 10 μm (PM10) (TEOM, beta attenuation) are widely used in air pollution monitoring networks. However, the data cannot always be considered equivalent to the manual gravimetric reference method, which is required in Europe as well as in US for compliance measurements. In this paper, a new method is described to obtain reference equivalent PM10 data series from automatic beta-attenuation monitors based on a limited number of gravimetric PM10 data. The correction procedure was tested with long-term data series from 5 Swiss sites with different exposure characters (urban street canyon, motorway, suburban, rural) and was shown to produce PM10 data, which fulfilled all requirements of EN12341, except at a background site with very low PM10 concentrations. At all sites, including the background site, the correction produced excellent agreement of the corrected monitor data for annual means and a satisfactory match of the number of days exceeding the short time limit value of 50 μg m−3 compared to reference equivalent PM10 data.
Keywords: Particulate matter; Beta attenuation monitor; Gravimetry; Adjustment factor; Continuous pm monitor;

A Long Path DOAS system (GIST LP-DOAS) developed by GIST has been used to simultaneously measure atmospheric monoaromatic hydrocarbons (MAHC) and other trace compounds. The validity of GIST LP-DOAS in measuring atmospheric MAHC was tested over 740 m beam paths at an urban site in Seoul, Korea, during two field campaigns held in February 2003. In order to remove the effects of interfering compounds (such as oxygen, ozone, and sulfur dioxide), two oxygen optical density spectra at two path lengths and the reference spectra of sulfur dioxide and ozone were incorporated in the fitting procedure for the determination of MAHC. The mean concentrations of MAHC measured with LP-DOAS system during the measurement period were 0.77 (benzene), 3.68 (toluene), 0.41 (p-xylene), and 0.54 ppbv (m-xylene), respectively. The results of our LP-DOAS measurements were compared with those obtained by a collocated on-line Gas Chromatography (on-line GC) system. The concept of a percent difference (PD) and linear regression methods were employed to explain the bias structure between LP-DOAS and on-line GC. The results of this comparative analysis indicated that both systems exhibited strong compatibility with relatively good correlation. According to our correlation analysis between PD values and meteorological parameters, the compatibility between the two systems increased under the conditions of improved visibility and meteorological homogeneity (wind speed >1.3 ms−1). Based on our study, it is concluded that the LP-DOAS system can be used to provide reliable information on both mixing ratios and temporal distribution characteristics of MAHC in urban air.
Keywords: DOAS; On-line GC; Aromatic hydrocarbons; Urban air pollution;

In an effort to provide detailed information concerning the analysis of reduced S compounds, we carefully examined the response properties of four different compounds (H2S, CH3SH, DMS, and DMDS) using the GC/PFPD system. Such properties were assessed mainly in terms of both absolute detectability in mass (or concentration) and relative calibration patterns across different S gases. The results of our analysis, when inspected in terms of calibration data over a wide concentration range, indicated that the patterns could be affected greatly by the absolute content of S analyzed with notable differences among different S compounds. The causes of such differences appeared to be associated with different processes (or mechanisms) such as either some type of (adsorptive) loss within the system (H2S) or moderate variabilities in linearity (DMS and DMDS). Relative response factors (RRF) of these S gases, when computed by their calibration slope values through normalization of the least variable results (CH3SH), were found to increase in the order of H2S, CH3SH, DMS, and DMDS. The DL values of all S gases for our analytical system were typically estimated in a few pg or a few ppb range (e.g., at 500 μl sample volume) with considerable differences in their linearity responses.
Keywords: Reduced sulfur; Hydrogen sulfide; Atmosphere; Gas chromatography; PFPD;

The denuder/filter-pack sampling system has been used to simultaneously measure the daily concentrations of inorganic compounds of fine and coarse aerosol and related gases in Fukue Island, Japan, in three springs (March–April of 2000–2002). Gaseous nitric acid concentrations are low, and gas-to-total (gas+aerosol) fractions of nitrate are also low. The gas-to-total fraction of ammonium and the production of non-sea-salt (nss)-sulfate on coarse aerosol increase with dust loading. Total nitrate concentration correlates with both total ammonium concentration and total aerosol nss-sulfate concentration, although these species are differently partitioned among the gas and fine- and coarse-aerosol phases. In some dust events, there is a time lag between an increase in nss-sulfate concentration and an increase in dust loading. Trajectory analysis shows that one of the dust events with a time lag is composed of nss-sulfate from the east affected by volcanic plumes and dust from the northwest passing over the loess areas in the Asian continent.
Keywords: Gas–aerosol partitioning; Fine aerosol; Dust aerosol; Denuder; East Asia;

Inorganic nitrogen storage in alpine snow pack in the Central Alps (Switzerland) by Erika Hiltbrunner; Margit Schwikowski; Christian Körner (2249-2259).
In the alpine regions, more than half of the year's precipitation is conserved as snow. We investigated inorganic ion storage in snow pack at 2500 m (a.s.l.) in the Central Alps, Switzerland. Chemical composition of snow was dominated by nitrogenous and sulphate ions. Ion pools showed high local and inter-annual variability (2002, 2003), but differences in ion pools were not simply due to varying snow depth. The highest soluble nitrogen (N) pools were found in March (1.1–1.7 kg N ha−1). Later, in spring (April and May), N pools in snow were significantly lower (0.5–0.8 kg N ha−1). Ion storage in snow was compared with N fluxes in rain, which ranged between 2.0 kg and 3.3 kg N ha−1  summer−1. Both forms of wet precipitation yielded a total wet N input into alpine grasslands of maximal 5.0 kg N ha−1  a−1.Atmospheric N deposition data for alpine ecosystems in the European Alps are rare and the monitored data here deviate by a factor of 2 from modelled N deposition. Nitrogen deposition in the alpine zone of the Central Alps is much smaller than previously assumed, but N pools stored in snow correspond to, at the most, 34% of N released by N mineralisation in alpine soils. Net N mineralisation accounts for only a fraction of the annual N uptake of alpine plant; thus, the additional N source by melting snow contributes substantially to alpine plants N uptake, particularly during periods when N demands are highest.
Keywords: Alpine grassland; Ammonium; Central Alps; High elevation; Nitrate; N deposition;

Estimating time series of aerosol particle number concentrations in the five HEAPSS cities on the basis of measured air pollution and meteorological variables by Pentti Paatero; Pasi Aalto; Sally Picciotto; Tom Bellander; Gemma Castaño; Giorgio Cattani; Josef Cyrys; Markku Kulmala; Timo Lanki; Fredrik Nyberg; Juha Pekkanen; Annette Peters; Jordi Sunyer; Francesco Forastiere (2261-2273).
Background: Ultrafine particles in urban air represent a potentially important health risk, and are not well characterized by mass concentrations like PM10 or PM2.5. The aerosol particle number concentration (PNC) is dominated by ultrafine particles, but urban PNC measurement campaigns have only recently started in many cities and missing data impedes much research. Hence, reliable estimation techniques are needed. Past estimations of ambient concentrations of particulate matter have focused on mass concentrations. This project developed city-specific models for estimating PNC using available data on other air pollutants and meteorological variables during a period when PNC was measured, and applied them retrospectively to predict daily PNC levels during the Health Effects of Air Pollution on Susceptible Subpopulations (HEAPSS) study period in order to enable epidemiological analyses. Methods: Monitoring of PNC began in April 2001 using condensation particle counters (3022A, TSI) in Augsburg, Barcelona, Helsinki, Rome, and Stockholm. Concurrent measurements of air pollutants and weather were used, as well as selected interactions between the two, to fit a regularized linear model (also called ridge regression). This technique is robust with respect to inclusion of irrelevant explanatory variables and can be modified to be highly tolerant of missing data, two highly beneficial features when there are many explanatory variables. Results: The most important predictor variables were the nitrogen oxides. The models appear to fit PNC data relatively well, with R 2 of 0.77, 0.80, 0.58, 0.84, 0.81 respectively for the five cities. Split-halves analysis (modelling on half of the data with validation on the other half) indicates that the modelling process was fairly reliable. Conclusion: A statistical model can be applied to existing data on traffic-related air pollutants and weather variables in order to predict PNC levels. The retrospective prediction of PNC levels appears to be sufficiently reliable for use in epidemiological research.
Keywords: Particulate matter; Retrospective assessment; Ultrafine particles; Regularized linear model;

Formaldehyde and acetaldehyde exchange during leaf development of the Amazonian deciduous tree species Hymenaea courbaril by S. Rottenberger; U. Kuhn; A. Wolf; G. Schebeske; S.T. Oliva; T.M. Tavares; J. Kesselmeier (2275-2279).
The effect of leaf age on the formaldehyde (HCHO) and acetaldehyde (CH3CHO) exchange pattern of the deciduous Amazonian tree species Hymenaea courbaril was investigated under field conditions. Branch enclosure measurements on senescent, young, and mature leaves showed that leaf development had a pronounced impact on the aldehyde exchange behavior with respect to both the direction and the magnitude of the exchange. The emission activity of senescent leaves was associated with a negative CO2 balance, even during daytime, indicative of a catabolic metabolism and decomposition processes leading to an increased aldehyde production within the leaf. The low exchange rates observed in young leaves were attributed to low stomatal conductance, while in mature leaves stomatal conductance and metabolic activities allowed efficient uptake. Within each leaf class the diurnal variations in the exchange of both aldehyde compounds were found to be mainly dependent on the respective ambient air concentrations. High ambient air concentrations resulted in decreased emission rates of senescent leaves and in enhanced uptake in young and mature leaves. CH3CHO compensation points decreased from 1.8 to 1.1 ppb with leaf maturation. We provide evidence that leaf-age-dependent variations in the stomatal conductance can account for the major share of differences in the CH3CHO deposition velocity. The results indicate that leaf surfaces of young and mature leaves may represent an effective additional non-stomatal sink for atmospheric aldehydes.
Keywords: Phenology; Carbonyls; Emission; Deposition; Deciduous tropical trees; Amazonia;

A comparison of the UCD/CIT air quality model and the CMB source–receptor model for primary airborne particulate matter by Tony Held; Qi Ying; Michael J. Kleeman; James J. Schauer; Matthew P. Fraser (2281-2297).
Source contributions to primary airborne particulate matter calculated using the source-oriented UCD/CIT air quality model and the receptor-oriented chemical mass balance (CMB) model are compared for two air quality episodes in different parts of California. The first episode occurred in the San Joaquin Valley on 4–6 January 1996, with peak 24 h average PM2.5 concentrations exceeding 100 μg m−3. This episode was characterized by low photochemical activity and high particulate nitrate concentrations, with localized regions of high particulate carbon concentrations around urban centers. The second episode occurred in the South Coast Air Basin on 7–9 September 1993, with peak 4 h average PM2.5 concentrations reaching 86 μg m−3. This episode was characterized by high photochemical activity and high secondary organic aerosol concentrations. The results from the two independent source apportionment calculations show strong agreement for source contributions to primary PM2.5 total organic mass at 7 receptor sites across the two studies, with a correlation slope of 0.84 and a correlation coefficient ( R 2 ) of 0.70. Agreement for source contributions to primary PM2.5 total mass was similarly strong, with a correlation slope of 0.83 and a correlation coefficient ( R 2 ) of 0.55. Wood smoke was identified as the dominant source of primary PM2.5 at urban locations in the SJV by both source apportionment techniques. Transportation sources including paved road dust, gasoline engines, and diesel engines, were identified as the dominant source of primary PM2.5 at all locations in the SoCAB by both models. The amount of secondary particulate matter (organic and inorganic) was in good agreement with the measured values minus the primary material identified by the CMB calculation.The UCD/CIT air quality model is able to predict source contributions to airborne particulate matter at all locations and times throughout the study domain. The regional plots of source contributions to primary PM2.5 mass concentrations generated by the UCD/CIT air quality model suggest that high concentrations (25 μg m−3) of primary PM2.5 mass released from the combustion of fuel with high sulfur content exist in areas adjacent to the Los Angeles International Airport and the port of Los Angeles. Emissions profiles for these sources should be developed so that they can be included in future CMB calculations.
Keywords: Airborne particles; Source apportionment; Source-oriented external mixture model; CMB;

Personal exposures to VOC in the upper end of the distribution—relationships to indoor, outdoor and workplace concentrations by Rufus D. Edwards; Christian Schweizer; Matti Jantunen; Hak Kan Lai; Lucy Bayer-Oglesby; Klea Katsouyanni; Mark Nieuwenhuijsen; Kristiina Saarela; Radim Sram; Nino Künzli (2299-2307).
Evaluation of relationships between median residential indoor, indoor workplace and population exposures may obscure potential strategies for exposure reduction. Evaluation of participants with personal exposures above median levels in the EXPOLIS study in Athens, Helsinki, Oxford and Prague illustrated that these participants frequently showed a different relationship to indoor and workplace levels than that shown by the population median. Thus, prioritization of environments for control measures based on median exposures may exclude important areas where effectively focused control measures are possible, and may therefore have little impact on the highest and most harmful exposures. Further, personal exposures at the upper end of the distribution may exceed the US EPA inhalation reference concentration (Rfc), illustrated here using hexane, naphthalene and benzene. For example upper 90th percentile personal exposures to benzene in Athens and Prague were 64 and 27 μg m−3 with peak exposures of 217 and 38 μg m−3, respectively for non-ETS exposed participants relative to an Rfc of 30 μg m−3. Strategies to reduce exposures to individual compounds, therefore, may benefit from focus on the high end of the distribution to identify activities and behaviors that result in elevated exposures. Control strategies targeting activities that lead to exposures in the upper end of the distribution would reduce the variability associated with population median values by bringing the upper end of the exposure distribution closer to median values. Thus, compliance with health-based standards would be more protective of the higher exposed fraction of the population, in whom health effects would be more expected.
Keywords: Volatile organic compounds; Indoor sources; Exposures; Microenvironment concentrations; Hexane; Benzene; Naphthalene;

Atmospheric concentrations and deposition of organochlorine pesticides in the US Mid-Atlantic region by Rosalinda Gioia; John H. Offenberg; Cari L. Gigliotti; Lisa A. Totten; Songyan Du; Steven J. Eisenreich (2309-2322).
Organochlorine pesticides (OCPs) were measured in the atmosphere over the period January 2000–May 2001 at six locations as part of New Jersey Atmospheric Deposition Network (NJADN). Gas phase, particle phase and precipitation concentrations of 22 OCP species, including chlordanes, DDTs, HCHs, endosulfan I and II, aldrin and diedrin, were measured. OCPs are found predominantly in the gas phase in all seasons, representing over 95% of the total air concentrations. Most of the pesticides measured display highest concentrations at urban sites (Camden and New Brunswick), although in many cases the differences in geometric mean concentrations are not statistically significant. The relationship of gas-phase partial pressure with temperature was examined using the Clausius–Clapeyron equation; significant temperature dependencies were found for all OCPs, except aldrin. Atmospheric depositional fluxes (gas absorption into water+dry particle deposition+wet deposition) to the New York–New Jersey Harbor Estuary of selected OCPs were estimated at NJADN sites. Atmospheric concentrations of dieldrin, aldrin and the HCHs are similar to those measured by the Integrated Atmospheric Deposition Network (IADN) in the Great Lake Region. In contrast, concentrations of DDTs, chlordanes and heptachlor are higher in the Mid-Atlantic compared to the Great Lakes, suggesting that the New York–New Jersey Harbor Estuary receives higher fluxes of these chemicals than the Great Lakes.
Keywords: Organochlorine pesticides; Atmospheric deposition; Volatilization; Clausius–Clapeyron equation; Enthalpy of the environment;

This study is an analysis of the impacts on urban air quality of restricting the operation of passenger vehicles during the 24th Asian Games (AG). Passenger vehicles in Busan were not allowed to operate on the alternative days during the AG period. This restricted operation of passenger vehicles was enforced to improve an urban air quality in Busan during the AG period. The average usage rate of passenger vehicles under an alternate (or restricted) operation was 95.4% and thus the average traffic flow rate (vehicle operation speed) increased approximately 28.1% as compared to normal periods. We analyzed the ambient concentrations of criteria air pollutants measured at 13 air-monitoring stations in Busan (Pusan), Korea, for the three periods of “before (13–28 September 2002)”, “during (29 September–14 October 2002)” and “after (15–30 October 2002)” the AG. The 1-h, 24-h and 16-day averages or median concentrations of each classified term were compared to those of other terms. The median concentrations, based on 24-h average data of each day, of PM10, CO, NO2, and SO2 in the ambient during the alternate operation period of 16 days substantially increased as compared to the terms before or after. However, the median concentration of O3 during the AG period was slightly less than that of the term before. The ambient O3 concentrations during daytime (12:00–19:00) under alternate operation substantially increased as compared to the terms before or after. However, the ambient O3 concentrations during nighttime (22:00–07:00) under alternate operation decreased when compared to the terms before or after. For the alternate operation period of passenger vehicles, the average concentrations of PM10, NO2, SO2, and daytime O3 measured at the air-monitoring stations near the stadiums were much higher than those of the other areas excluding the stadium areas. However, average CO concentrations at the other areas were higher than those nearby the stadiums during the alternate operation period.
Keywords: Asian Game; Vehicle emission; Alternate operation; Air pollution; Monitoring;