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Atmospheric Environment (v.41, #13)

Editorial board (pp. i).

A review of parameterizations for modelling dry deposition and scavenging of radionuclides by Bruno Sportisse (pp. 2683-2698).

This article aims at reviewing the state-of-the-science parameterizations for modelling dry deposition and scavenging of atmospheric tracers, with a focus on radionuclides. These parameterizations are key components of the numerical models that are used for environmental forecast. We present detailed models and parameterizations. Both are characterized by many uncertainties.

Keywords: Dispersion models; Dry deposition; Wet scavenging; Parameterizations

Seasonal variation of black carbon aerosols over a tropical urban city of Pune, India by P.D. Safai; S. Kewat; P.S. Praveen; P.S.P. Rao; G.A. Momin; K. Ali; P.C.S. Devara (pp. 2699-2709).

Black carbon (BC) aerosols were monitored continuously at Pune, a tropical urban location in southwest India, using aethalometer AE-42 model. Results of the data for the 1-year period (January to December 2005) have been discussed here. Seasonal and diurnal variations of BC in relation to changes in the regional meteorological conditions and local boundary layer characteristics have been studied along with the mass fraction of BC to the total suspended particulates (TSP) in different months. Also, using the Hysplit model, back-trajectories are studied to assess the sources for transported BC particles. The data collected during January to December 2005 indicated that annual average BC concentration (4.1μgm⁻³) at Pune was comparable to that reported for other urban locations in southern Indian region. During winter season, BC concentrations were maximum (about 80% more than annual mean), mainly due to prevailing meteorological conditions like low wind speeds and low ventilation coefficients; as well as due to the transport from northeast regions. Minimum BC concentrations were observed during monsoon season (about 68% less than annual mean), which could be attributed to the wash-out effects due to precipitation as well as due to southwesterly winds coming from marine areas. Diurnal variation of BC showed two peaks, one in morning and another in the evening, which are mostly related to the daily changes in the local boundary layer. However, the intensity of local traffic emissions could have some impact on the magnitude of these peaks. BC aerosols formed about 2.3% of the total aerosol mass fraction at Pune.

Keywords: Seasonal BC changes; Diurnal BC changes; BC mass fraction to TSP; Back-trajectory analysis

Long-range transport of polycyclic aromatic hydrocarbons from China to Japan by X.-Y. Xiao-Yang Yang; Yumi Okada; Ning Tang; Siori Matsunaga; Kenji Tamura; Jin-Ming Lin; Takayuki Kameda; Akira Toriba; Kazuichi Hayakawa (pp. 2710-2718).

Airborne particulate matter was collected at Wajima, on the Noto Peninsula, Ishikawa, Japan by a high-volume air sampler with a quartz filter every week from 17 September 2004 to 16 September 2005. Polycyclic aromatic hydrocarbons (PAHs) extracted from filters were analyzed by HPLC with fluorescence detection. The atmospheric concentrations of PAHs at Wajima were higher during the heating period of China (when coal is burned for heat) than during the no-heating period. A meteorological analysis indicated that the air samples collected in that heating period at Wajima were transported mainly from Northeast China over the Japan Sea. Principal component analysis of nine PAHs indicated a Chinese origin of the PAHs. These results strongly suggest that the high-level PAHs detected at Wajima were the result of long-range transport from China.

Keywords: PAHs; Airborne particulate matter; Long-range transport; Principal component analysis; China; Japan

Evaluation of dynamic subgrid-scale models in large-eddy simulations of neutral turbulent flow over a two-dimensional sinusoidal hill by Feng Wan; Porte-Agel Fernando Porté-Agel; Rob Stoll (pp. 2719-2728).

Large-eddy simulation (LES) is used to simulate neutral turbulent boundary-layer flow over a rough two-dimensional sinusoidal hill. Three different subgrid-scale (SGS) models are tested: (a) the standard Smagorinsky model with a wall-matching function, (b) the Lagrangian dynamic model, and (c) the recently developed scale-dependent Lagrangian dynamic model [Stoll, R., Porté-Agel, F., 2006. Dynamic subgrid-scale models for momentum and scalar fluxes in large-eddy simulation of neutrally stratified atmospheric boundary layers over heterogeneous terrain. Water Resources Research 42, W01409. doi:10.1029/2005WR003989]. The simulation results obtained with the different models are compared with turbulence statistics obtained from experiments conducted in the meteorological wind tunnel of the AES (Atmospheric Environment Service, Canada) [Gong, W., Taylor, P.A., Dörnbrack, A., 1996. Turbulent boundary-layer flow over fixed aerodynamically rough two-dimensional sinusoidal waves. Journal of Fluid Mechanics 312, 1–37]. We find that the scale-dependent dynamic model is able to account, without any tuning, for the local changes in the eddy-viscosity model coefficient. It can also capture the scale dependence of the coefficient associated with regions of the flow with strong mean shear and flow anisotropy. As a result, the scale-dependent dynamic model yields results that are more realistic than the ones obtained with the scale-invariant Lagrangian dynamic model.

Keywords: Large-eddy simulation; Subgrid-scale modeling; Two-dimensional sinusoidal hill

Size distribution of polycyclic aromatic hydrocarbon particulate emission factors from agricultural burning by Haleh Keshtkar; Lowell L. Ashbaugh (pp. 2729-2739).

Burning of agricultural waste residue is a common method of disposal when preparing land following crop harvest. This practice introduces volatile organic compounds, including polycyclic aromatic hydrocarbons (PAHs), into the atmosphere. This study examines the particle size distribution in the smoke emissions of two common agricultural waste residues (biofuels) in California, almond prunings and rice straw. The residues were burned in a combustion chamber designed specifically for this purpose, and the smoke emissions were collected on 10-stage MOUDI impactors for analysis of PAH and total particle mass. The results, in units of emission factors, show that combustion temperature is an important factor in determining the smoke particle PAH composition. Total PAH emissions from rice straw burns were 18.6mgkg⁻¹ of fuel, while the emissions from almond prunings were lower at 8.03mgkg⁻¹. The less volatile five- and six-ring PAH was predominately on smaller particles where it condensed in the early stages of combustion while the more volatile three- and four-ring PAH formed on larger particles as the smoke cooled.

Keywords: Polycyclic aromatic hydrocarbons; PAH; Particle size distribution; Agricultural smoke; Emission factors

Atmospheric dispersion in the presence of a three-dimensional cubical obstacle: Modelling of mean concentration and concentration fluctuations by I. Mavroidis; S. Andronopoulos; J.G. Bartzis; R.F. Griffiths (pp. 2740-2756).

This paper presents computational simulations of atmospheric dispersion experiments conducted around isolated obstacles in the field. The computational tool used for the simulations was the code ADREA-HF, which was especially developed for the simulation of the dispersion of positively or negatively buoyant gases in complicated geometries. The field experiments simulated involve a single cubic obstacle normal to the mean wind direction and two upwind sources of ammonia and propane, with the ammonia source located at different lateral positions [Mavroidis, I., Griffiths, R.F., Hall, D.J., 2003. Field and wind tunnel investigations of plume dispersion around single surface obstacles. Atmospheric Environment 37, 2903–2918]. Concentrations and concentration fluctuations for both gases were calculated by the model and compared with the experimental results. Certain modelling aspects were studied, such as the effect of using different turbulence closure schemes in the computations. Furthermore, specific characteristics of dispersion were investigated using the computational tool, such as the effect of the lateral displacement of a source on the concentration fluctuations intensity, the effects of natural variability and the sensitivity of concentrations to wind direction fluctuations. The results showed a good level of agreement between calculated and measured concentrations and concentration fluctuations when ensemble averaged data were available from the field experiments. Differences observed between measured and predicted concentrations and concentration fluctuations, in the case of laterally displaced sources, were mainly attributed to the specificities of the experimental cases, such as the interaction of a laterally displaced plume with an obstacle, and to the variability observed in the field. The effect of this variability is indicated by the difference between the predicted-to-observed ratios of ensemble-averaged centreline values for propane and the respective ratios from the single ammonia experiment with co-located gas sources, the latter being higher by upto 30% for concentrations and 70% for concentration fluctuations. Using the computational tool it was shown that, for a laterally displaced source, a change of 5° in the mean wind direction can lead up to a 100% variation in the measured concentrations.

Keywords: Atmospheric dispersion around obstacles; Variability of field experiments; Model evaluation; Concentration fluctuations; Turbulence closure; Laterally displaced source; Wind direction fluctuations

What environmental fate processes have the strongest influence on a completely persistent organic chemical's accumulation in the Arctic? by Torsten Meyer; Frank Wania (pp. 2757-2767).

Fate and transport models can be used to identify and classify chemicals that have the potential to undergo long-range transport and to accumulate in remote environments. For example, the Arctic contamination potential (ACP), calculated with the help of the zonally averaged global transport model Globo-POP, is a numerical indicator of an organic chemical's potential to be transported to polar latitudes and to accumulate in the Arctic ecosystem. It is important to evaluate how robust such model predictions are and in particular to appreciate to what extent they may depend on a specific choice of environmental model input parameters. Here, we employ a recently developed graphical method based on partitioning maps to comprehensively explore the sensitivity of ACP estimates to variations in environmental parameters. Specifically, the changes in the ACP of persistent organic contaminants to changes in each environmental input parameter are plotted as a function of the two-dimensional hypothetical “chemical space” defined by two of the three equilibrium partition coefficients between air, water and octanol. Based on the patterns obtained, this chemical space is then segmented into areas of similar parameter sensitivities and superimposed with areas of high default ACP and elevated environmental bioaccumulation potential within the Arctic. Sea ice cover, latitudinal temperature gradient, and macro-diffusive atmospheric transport coefficients, and to a lesser extent precipitation rate, display the largest influence on ACP-values for persistent organic contaminants, including those that may bioaccumulate within the polar marine ecosystems. These environmental characteristics are expected to be significantly impacted by global climate change processes, highlighting the need to explore more explicitly how climate change may affect the long-range transport and accumulation behavior of persistent organic pollutants.

Keywords: Persistent organic contaminants; Global fate model; Climate change; Sensitivity analysis; Temperature

An instrument for semi-continuous monitoring of the size-distribution of nitrate, ammonium, sulphate and chloride in aerosol by Harry ten Brink; René Otjes; Piet Jongejan; Sjaak Slanina (pp. 2768-2779).

An instrument was developed for semi-continuous measurement of the size-distribution of submicron nitrate, ammonium, sulphate and chloride. Novel in the instrumentation is the size-classification, which is realised with a pre-separator that consists of a set of four parallel impactors. The cut-off diameters of the impactors are at 0.18, 0.32, 0.56 and 1.0μm. Aerosols smaller than the associated cut-off size pass the respective impactor and arrive in the detector. The manifold with impactors contains two additional lines, one open line and one containing a filter that removes all aerosols. This latter line provides an on-line field-blank. The sample air-flow is automatically switched by wide-bore ball valves to one of the six sampling lines for a period of 20min; a measuring cycle thus takes 2h.Down-stream of the pre-separator the sampling and automated on-line analysis of the transmitted aerosol is accomplished with a “MARGA”. In this instrument steam condensation is used to grow the aerosol. The droplets formed are collected in a cyclone that drains to wet-chemical analysis systems. A wet-denuder between pre-separator and collector removes interfering gases, like nitric acid and ammonia. This enables artefact-free and thus representative semi-continuous measurement of the size-distribution of the semi-volatile (ammonium) nitrate.The novel MARGA-sizer was first used in a 1week field-test. After modifications it was then deployed in a monitoring campaign of 2months in the summer of 2002, at the top level of the meteo-tower of Cabauw in the centre of the Netherlands. The high location, 200m, was chosen to obtain data on ammonium nitrate that are minimally affected by surface emissions of ammonia. The data coverage over the period was over 60%; failure of the instrumentation was mainly associated with spells of extreme solar heating of the tower and associated high temperatures inside.The average concentration of nitrate was 2.6μgm⁻³, which was very similar to the value interpolated from data in the national network. The mass concentration of submicron nitrate was 2.0μgm⁻³, of which 46% was in particles smaller than 0.32μm. To put this in perspective: the concentration of submicron sulphate was similar to that of nitrate, while 53% was in particles smaller than 0.32μm. The ion balance showed that the compounds were present as the fully neutralised salts. Quite large diurnal variations were observed for nitrate, with a surprising maximum in the afternoon. The size-distribution of the semi-volatile nitrate was rather constant over a daily cycle.

Keywords: Nitrate; Ammonium; Sulphate; Light-scattering

Monoterpene and isoprene emissions from typical tree species in forests around Mexico City by P. Dominguez-Taylor; L.G. Ruiz-Suarez; I. Rosas-Perez; J.M. Hernández-Solis; R. Steinbrecher (pp. 2780-2790).

The isoprenoid emission of sacred fir ( Abies religiosa (Kunth) Schltdl. & Cham.), patula pine ( Pinus patula Schiede, Schltdl. & Cham.) and net-leaf oak ( Quercus rugosa Née) was investigated in Mexico City during the years 2002 and 2003. Chemical compound specific emission factors were obtained for different months of the year. Net-leaf oak is an isoprene emitter whereas the other tree species emit monoterpenes.α-Pinene and linalool are the main compounds emitted from sacred fir and patula pine, respectively. In general, the emission of monoterpenes is temperature dependent, whereasα-pinene emission of sacred fir is controlled by light and temperature like the isoprene emission of net-leaf oak. All isoprenoids show a strong seasonality which is plant species specific. Emission factors for the conifers were high in October and low in April (sacred fir:6.07μgCg-1dwh-1 in October and0.02μgCg-1dwh-1 in April; patula pine:4.22μgCg-1dwh-1 in October and1.13μgCg-1dwh-1 in June). Isoprene emission potential of net-leaf oak was very variable in the different seasons with low source strengths in July (rainy season:1.19μgCg-1dwh-1) and November (cold/dry season:18.50μgCg-1dwh-1) but high in May (warm/dry season:66.27μgCg-1dwh-1). The results indicate that present biogenic emission inventories of the Mexico City area have to be revised by using the new emission factors of native tree species including the seasonal impact.

Keywords: Biogenic emissions; Seasonal variation; Abies religiosa; Pinus patula; Quercus rugosa

Intercomparison of two different thermal-optical elemental carbons and optical black carbon during ABC-EAREX2005 by M.-S. Min-Suk Bae; C.-S. Chun-Sang Hong; Young J. Kim; J.-S. Jin-Seok Han; K.-J. Kwang-Ju Moon; Yutaka Kondo; Yuichi Komazaki; Yuzo Miyazaki (pp. 2791-2803).

A formal intercomparison of fine particle elemental (black) carbon is conducted involving three real-time semi-continuous measurement systems. Two-hourly interval time-resolved measurements of organic carbon (OC) and elemental carbon (EC) were performed at the Gosan site, Korea during Atmospheric Brown Clouds–East Asian Regional Experiment 2005 (ABC-EAREX2005) campaign. They were operated by the same semi-continuous field carbon instruments of Sunset Laboratory (thermal optical transmittance) in PM_2.5 particulate. However, their thermal protocols (four and two steps for OC and five and two steps for EC) were different. The co-located 1min black carbon (BC) concentrations were compared by an Aethalometer for an intercomparison study.As a result, the poor R² of OC between two different temperature protocols suggested that OC can be significantly more biased by the slight differences of maximum temperature (870 and 840°C) and a number of temperature steps (four steps and two steps) with their hold times. However, EC that is a smaller fraction of total carbon (TC) shows the good agreement between two different protocols, which are under a mixture of 2% O₂ and 98% He in six temperature steps and two temperature steps as max as 900 and 880°C with the slope of 1.05±0.15 ( R² of 0.98). The different slopes between EC and BC, which show the range of 1.23–1.61, demonstrate the variability of the attenuation coefficient of the BC particulate.

Keywords: Comparison; Organic carbon; NIOSH 5040; Thermal-optical analysis; OC; EC

Top-down estimate of mercury emissions in China using four-dimensional variational data assimilation by Li Pan; Tianfeng Chai; Gregory R. Carmichael; Youhua Tang; David Streets; Jung-Hun Woo; Hans R. Friedli; Lawrence F. Radke (pp. 2804-2819).

An inverse modeling method using the four-dimensional variational data assimilation approach is developed to provide a top-down estimate of mercury emission inventory in China. The mercury observations on board the C130 aircraft during the Asian Pacific Regional Aerosol Characterization Experiment (ACE-Asia) campaign in April 2001 are assimilated into a regional chemical transport model, STEM. Using a 340Mg of elemental mercury emitted in 1999, the assimilation results in an increase in Hg⁰ emissions for China to 1140Mg in 2001. This is an upper limit amount of the elemental mercury required in China. The average emission-scaling factor is ∼3.4 in China. The spatial changes in the mercury emissions after the assimilation are also evaluated. The largest changes are estimated on the China north-east coastal areas and the areas of north-center China. The influences of the observation and inventory uncertainties and the initial and boundary conditions on the emission estimates are discussed. Increasing the boundary conditions of Hg from 1.2 to 1.5ngm⁻³, results in a top-down estimate of Hg⁰ emissions for China of 718Mg, and leads the average scaling factor from 3.4 to 2.1.

Keywords: Mercury; Inventory evaluation; China; Data assimilation; 4D-Var

Single-particle analysis of atmospheric aerosols at Cape Gris-Nez, English Channel: Influence of steel works on iron apportionment by Choel Marie Choël; Karine Deboudt; Pascal Flament; Laure Aimoz; Meriaux Xavier Mériaux (pp. 2820-2830).

The chemical composition of atmospheric aerosols from an environment subjected to air masses of multiple origins was investigated at a northern French in-shore site away from any direct urban influence. During a continuous 1-year campaign, particles were sampled weekly onto polycarbonate membranes. Twelve 1-week samples of distinct air-mass origins, according to computed backward trajectories, were characterized by scanning electron microscopy combined with energy-dispersive X-ray spectrometry (SEM-EDX). Approximately, 1000 particles per sample were automatically analyzed. Semi-quantitative analysis was carried out by applying Castaing's first approximation to characteristic X-ray intensities of 16 elements ( Z>8). A total of 11,842 particles were classified into five clusters, based upon similarities in composition, using a hierarchical clustering analysis. These clusters include: Na-rich (70%), referred to as marine particles, Ca–S-rich (17%), Al–Si-rich (8%), Fe-rich (4%) and Si-rich (1%), assigned to continental—including both natural and anthropogenic—sources. In this area, which is frequently subjected to meteorological depressions, the total particle number concentration is significantly correlated ( r²=0.97) with the number concentration of marine particles regardless of the global origin of the air mass (i.e. oceanic and/or continental). In the case of air masses originating predominantly from the continent, marine particles presumably come from an external mixing due to the convergence of separate air masses before the sampling site.Due to their key role in marine primary production and in global climate by radiative forcing, Fe-bearing particles have been intensively studied for the past two decades. Fe-containing particles were interpreted here as iron (oxy(hydr))oxides (55%) and aluminosilicates (34%). A statistical reanalysis of all Fe-bearing particles (including particles with low Fe contents, not initially tabulated in the distribution statistics) clearly discloses their large abundance in air masses transported over steel works.

Keywords: Atmospheric aerosols; Iron species; Steel works; SEM-EDX; Single-particle analysis

Source identification analysis for the airborne bacteria and fungi using a biomarker approach by Alex K.Y. Lee; Arthur P.S. Lau; Jessica Y.W. Cheng; Ming Fang; Chak K. Chan (pp. 2831-2843).

Our recent studies have reported the feasibility of employing the 3-hydoxy fatty acids (3-OH FAs) and ergosterol as biomarkers to determine the loading of the airborne endotoxin from the Gram-negative bacteria and fungal biomass in atmospheric aerosols, respectively [Lee, A.K.Y., Chan, C.K., Fang, K., Lau, A.P.S., 2004. The 3-hydroxy fatty acids as biomarkers for quantification and characterization of endotoxins and Gram-negative bacteria in atmospheric aerosols in Hong Kong. Atmospheric Environment 38, 6807–6317; Lau, A.P.S., Lee, A.K.Y., Chan, C.K., Fang, K., 2006. Ergosterol as a biomarker for the quantification of the fungal biomass in atmospheric aerosols. Atmospheric Environment 40, 249–259]. These quantified biomarkers do not, however, provide information on their sources. In this study, the year-long dataset of the endotoxin and ergosterol measured in Hong Kong was integrated with the common water-soluble inorganic ions for source identification through the principal component analysis (PCA) and backward air mass trajectory analysis. In the coarse particles (PM_2.5–10), the bacterial endotoxin is loaded in the same factor group with Ca²⁺ and accounted for about 20% of the total variance of the PCA. This implies the crustal origin for the airborne bacterial assemblage. The fungal ergosterol in the coarse particles (PM_2.5–10) had by itself loaded in a factor group of 10.8% of the total variance in one of the sampling sites with large area of natural vegetative coverage. This suggests the single entity nature of the fungal spores and their independent emission to the ambient air upon maturation of their vegetative growth. In the fine particles (2.5), the endotoxin and ergosterol associated closely with K⁺ and accounted for 34–38% of the total variance in the two sites studied. The K⁺/Na⁺ ratio is indicative of the possible sources of K⁺, which in turn, provides information on the sources of the associated endotoxin and ergosterol. High K⁺/Na⁺ ratios (>2.0) in the fine particles of the continental air masses imply the microbial source from activities related to biomass burning and industries from the north. The low K⁺/Na⁺ ratios (1.2–1.4) in the fine particles of the mixed air masses suggest microbial sources from the local and regional indoor environment through kitchen emissions and the re-suspension of the road dust due to vehicular exhausts.

Keywords: Endotoxin; Ergosterol; Biomarkers; Source identification; Principal component analysis; Backward air mass trajectory

Feasibility of a simple laboratory approach for determining temperature influence on SPMD–air partition coefficients of selected compounds by Aurelija Cicenaite; James N. Huckins; David A. Alvarez; Walter L. Cranor; Robert W. Gale; Violeta Kauneliene; P.-A. Per-Anders Bergqvist (pp. 2844-2850).

Semipermeable membrane devices (SPMDs) are a widely used passive sampling methodology for both waterborne and airborne hydrophobic organic contaminants. The exchange kinetics and partition coefficients of an analyte in a SPMD are mediated by its physicochemical properties and certain environmental conditions. Controlled laboratory experiments are used for determining the SPMD–air ( K_sa's) partition coefficients and the exchange kinetics of organic vapors. This study focused on determining a simple approach for measuring equilibrium K_sa's for naphthalene (Naph), o-chlorophenol ( o-CPh) and p-dichlorobenzene ( p-DCB) over a wide range of temperatures. SPMDs were exposed to test chemical vapors in small, gas-tight chambers at four different temperatures (−16, −4, 22 and 40°C). The exposure times ranged from 6h to 28d depending on test temperature. K_sa's or non-equilibrium concentrations in SPMDs were determined for all compounds, temperatures and exposure periods with the exception of Naph, which could not be quantified in SPMDs until 4 weeks at the −16°C temperature. To perform this study the assumption of constant and saturated atmospheric concentrations in test chambers was made. It could influence the results, which suggest that flow through experimental system and performance reference compounds should be used for SPMD calibration.

Keywords: Temperature; SPMDs; Partition coefficients; Naphthalene; o; -chlorophenol; p; -dichlorobenzene

Characteristics of carbonyls: Concentrations and source strengths for indoor and outdoor residential microenvironments in China by B. Wang; S.C. Lee; K.F. Ho (pp. 2851-2861).

Indoor and outdoor carbonyl concentrations were measured simultaneously in 12 urban dwellings in Beijing, Shanghai, Guangzhou, and Xi’an, China in summer (from July to September in 2004) and winter (from December 2004 to February 2005). Formaldehyde was the most abundant indoor carbonyls species, while formaldehyde, acetaldehyde and acetone were found to be the most abundant outdoor carbonyls species. The average formaldehyde concentrations in summer indoor air varied widely between cities, ranging from a low of 19.3μgm⁻³ in Xi’an to a high of 92.8μgm⁻³ in Beijing. The results showed that the dwellings with tobacco smoke, incense burning or poor ventilation had significantly higher indoor concentrations of certain carbonyls. It was noticed that although one half of the dwellings in this study installed with low emission building materials or furniture, the carbonyls levels were still significantly high. It was also noted that in winter both the indoor and outdoor acetone concentrations in two dwellings in Guangzhou were significantly high, which were mainly caused by the usage of acetone as industrial solvent in many paint manufacturing and other industries located around Guangzhou and relatively longer lifetime of acetone for removal by photolysis and OH reaction than other carbonyls species. The indoor carbonyls levels in Chinese dwellings were higher than that in dwellings in the other countries. The levels of indoor and ambient carbonyls showed great seasonal differences. Six carbonyls species were carried out the estimation of indoor source strengths. Formaldehyde had the largest indoor source strength, with an average of 5.25mgh⁻¹ in summer and 1.98mgh⁻¹ in winter, respectively. However, propionaldehyde, crotonaldehyde and benzaldehyde had the weakest indoor sources.

Keywords: Formaldehyde; Carbonyls; Indoor air quality; Source strength; Residential environment; China

Laboratory measurement of the dry deposition of sulfur dioxide onto northern Chinese soil samples by Atsuyuki Sorimachi; Kazuhiko Sakamoto (pp. 2862-2869).

We investigated soil surface resistance R_c to dry deposition of sulfur dioxide (SO₂) onto different types of soils in laboratory experiments, using samples collected from the arid loess plateau and deserts of northern China. We evaluated the factors that affect R_c, which depends on the physical and chemical interaction between a trace constituent and the deposition surface. We observed that the values of R_c for SO₂ decreased with increase of soil weight and increased with SO₂ concentration, although surface coverage had little effect on R_c. The SO₂ uptake rate by all the northern Chinese soil samples seemed to be, on the whole, dependent on relative humidity (RH). In all of the northern Chinese soil samples, R_c was in the range 0.028–0.65smm⁻¹, and was exponentially related to the effective surface area of each soil sample, regardless of RH. Wet chemical analysis of sulfur deposited onto the soil samples showed that oxidation ratio of sulfur(IV) to sulfur(VI) was related to RH, which might be related to complex interactions among the amount of water on the soil sample, the pH, and the metallic ions in the liquid phase.

Keywords: China; Deposition velocity; Oxidation; Soil surface resistance; Sulfur dioxide

Appropriateness of selecting different averaging times for modelling chronic and acute exposure to environmental odours by G.H. Drew; R. Smith; V. Gerard; C. Burge; M. Lowe; R. Kinnersley; R. Sneath; P.J. Longhurst (pp. 2870-2880).

Odour emissions are episodic, characterised by periods of high emission rates, interspersed with periods of low emissions. It is frequently the short term, high concentration peaks that result in annoyance in the surrounding population. Dispersion modelling is accepted as a useful tool for odour impact assessment, and two approaches can be adopted. The first approach of modelling the hourly average concentration can underestimate total odour concentration peaks, resulting in annoyance and complaints. The second modelling approach involves the use of short averaging times. This study assesses the appropriateness of using different averaging times to model the dispersion of odour from a landfill site. We also examine perception of odour in the community in conjunction with the modelled odour dispersal, by using community monitors to record incidents of odour. The results show that with the shorter averaging times, the modelled pattern of dispersal reflects the pattern of observed odour incidents recorded in the community monitoring database, with the modelled odour dispersing further in a north easterly direction. Therefore, the current regulatory method of dispersion modelling, using hourly averaging times, is less successful at capturing peak concentrations, and does not capture the pattern of odour emission as indicated by the community monitoring database. The use of short averaging times is therefore of greater value in predicting the likely nuisance impact of an odour source and in framing appropriate regulatory controls.

Keywords: Odour; Annoyance; Dispersion modelling; Averaging times

Estimated tropospheric ozone levels on the southeast Spanish Mediterranean coast by S. Caballero; N. Galindo; C. Pastor; M. Varea; J. Crespo (pp. 2881-2886).

The objective of this study is to estimate the spatial variability of tropospheric ozone in an area using a simple model. The area in this case was applied in the western Mediterranean basin. The study period was from May to September in 2003 and 2004.A multiple linear regression between ozone concentrations, altitude and distance to the precursor sources in a fluvial basin can be used to estimate ozone values at other sites during the warmer seasons. The correlation coefficients obtained with 2-week ozone values measured at five points with a passive sampling technique were high enough to apply the model (0.77< r<0.99).To verify the model, ozone concentrations were measured with passive samplers and continuous analyzers at some selected sites, and the values were compared with the estimated concentration. The results of the validations were satisfactory, in 80% of the measurements the estimated levels differ from measured less than 20%, which is included in the bound error for the type of sampler used in this study.

Keywords: Tropospheric ozone; Spatial variability; Passive samplers; Multiple linear regression

PM_2.5–10, PM_2.5 and associated water-soluble inorganic species at a coastal urban site in the metropolitan region of Rio de Janeiro by Rauda L. Mariani; William Z. de Mello (pp. 2887-2892).

The concentrations of PM_2.5−10, PM_2.5 and associated water-soluble inorganic species (WSIS) were determined in a coastal site of the metropolitan region of Rio de Janeiro, Southeastern Brazil, from October 1998 to September 1999 ( n=50). Samples were dissolved in water and analyzed for major inorganic ions. The mean (± standard deviation; median) concentrations of PM_2.5−10 and PM_2.5 were, respectively, 26 (± 16; 21)μgm⁻³ and 17 (± 13; 14)μgm⁻³. Their mean concentrations were 1.7–1.8 times higher in dry season (May–October) than in rainy season (November–April). The WSIS comprised, respectively, 34% and 28% of the PM_2.5−10 and PM_2.5 masses. Chloride, Na⁺ and Mg²⁺ were the predominant ions in PM_2.5−10, indicating a significant influence of sea-salt aerosols. In PM_2.5, SO₄²⁻ (∼97% nss-SO₄²⁻) and NH₄⁺ were the most abundant ions and their equivalent concentration ratio (SO₄²⁻/NH₄⁺ ∼1.0) suggests that they were present as (NH₄)₂SO₄ particles. The mean concentration of (NH₄)₂SO₄ was 3.4μgm⁻³. The mean equivalent PM_2.5 NO₃⁻ concentration was eight times smaller than those of SO₄²⁻ and NH₄⁺. The PM_2.5 NO₃⁻ concentration in dry season was three times higher than in rainy season, probably due to reaction of NaCl (sea salt) with HNO₃ as a result of higher levels of NO _y during the dry season and/or reduced volatilization of NH₄NO₃ due to lower wintertime temperature. Chloride depletion was observed in both size ranges, although more pronouncely in PM_2.5.

Keywords: PM; _2.5; PM; _2.5−10; Aerosol chemistry; Ammonium sulfate; Chloride depletion; Niterói

Erratum to “Potential of the cryoplane technology to reduce aircraft climate impact: A state-of-the-art assessment” by Michael Ponater; Susanne Pechtl; Robert Sausen; Ulrich Schumann; Huttig Gerhard Hüttig (pp. 2893-2893).

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Atmospheric Environment (v.41, #13)