Atmospheric Environment (v.38, #23)

Measuring self-pollution in school buses using a tracer gas technique by Eduardo Behrentz; Dennis R Fitz; David V Pankratz; Lisa D Sabin; Steven D Colome; Scott A Fruin; Arthur M Winer (3735-3746).
A potentially important, but inadequately studied, source of children's exposure to pollutants during school bus commutes is the introduction of a bus's own exhaust into the passenger compartment. We developed and applied a method to determine the amount of a bus's own exhaust penetrating into the cabin in a study of six in-use school buses over a range of routes, roadway types, fuels, and emission control technologies. A tracer gas, SF6, was metered into the bus's exhaust system using a mass flow controller whose flow rate was logged by a data acquisition system and processed with the concurrent real-time pollutant measurement data. At the same time, the SF6 concentration inside the bus was measured using an AeroVironment CTA-1000 continuous analyzer connected to a series of solenoids that switched the sample inlet between the front and rear of the bus cabin. To account for a baseline drift of the CTA-1000, SF6-free air was also drawn through a line located outside at the front of the bus. Although this third sample line generally provided a reference zero value, it also showed that under certain wind conditions (i.e., wind from the rear) when the bus was stopped and was idling, significant amounts of the bus's own exhaust reached this location at the front of the bus. Self-pollution, the percentage of a bus's own exhaust that can be found inside its cabin, was a function of bus type and age, and a strong function of window position (i.e., open or closed). We estimated up to 0.3% of the air inside the cabin was from the bus's own exhaust in older buses, approximately 10 times the percentage observed for newer buses, and 25% of the black carbon concentration variance was explained by the buses’ self-pollution. Analysis of the tracer gas concentrations provided a powerful tool for identifying potentially high-exposure conditions.
Keywords: Children's exposure; Pollutant intrusion; Diesel exhaust; Aethalometer; SF6;

A temporally and spatially resolved ammonia emission inventory for dairy cows in the United States by Robert W Pinder; Ross Strader; Cliff I Davidson; Peter J Adams (3747-3756).
Previous inventories of ammonia emissions for the United States have not characterized the seasonal and geographic variations that are necessary for accurately predicting ambient concentrations of ammonium nitrate and ammonium sulfate aerosol. This research calculates the seasonal and geographic variation in ammonia emissions from dairy cows in the United States. Monthly, county-level emission factors are calculated with a process-based model of dairy farm emissions, the national distribution of farming practices, seasonal climate conditions, and animal populations. Annual, county-level emission factors are estimated to range between 13.1 and 55.5, with a national average of 23.9 kg NH3 cow−1 yr−1. The seasonal variation of the emission factor is estimated to be as high as a factor of seven in some counties. Emissions are predicted to be the highest in the spring and fall, because of high manure application rates during the spring planting and after the fall harvest. Summer emissions are higher than winter, resulting from the temperature dependence of housing and storage emissions. In the summer and winter, the majority of emissions are from animal housing. In the spring and fall, the majority of emissions are from field applied manure. The 5% and 95% confidence interval about the national annual average emission factor is between 18 and 36 kg NH3  cow−1  yr−1. Uncertainties in farming practices contribute most to the total uncertainty, yet uncertainty in the timing of manure application, the quantity of manure and nitrogen excreted by cows, and the physical processes of volatilization affecting applied manure are also significant.
Keywords: Ammonia; Emission inventory; Agriculture; PM2.5; Aerosol;

An exploration of aqueous oxalic acid production in the coastal marine atmosphere by Kathleen K Crahan; Dean Hegg; David S Covert; Haflidi Jonsson (3757-3764).
Oxalic acid is the most abundant dicarboxylic acid found in the troposphere, yet there is still no scientific consensus concerning its origins or formation process. Recent studies have suggested mechanisms for its formation in cloud water from gaseous precursors. Comparison of the characteristics of oxalic acid and nss sulfate, a chemical with a known in-cloud formation pathway, provides some support for an aqueous formation mechanism for oxalic acid. Analysis of the filters collected from the CIRPAS Twin Otter aircraft during CARMA I, a field campaign designed to study the marine stratocumulus off the coast of Monterey, CA, by a five stage Micro-Orifice Impactor (MOI) revealed a peak in the concentration distribution at a diameter of 0.26–0.44 μm, similar to the size distribution found for nss sulfate and corresponding to the droplet mode in the aerosol size distribution. An air-equivalent average of 2.03±0.47 μg m−3 (standard error) of sulfate was observed in the collected marine cloud water, in excess to below-cloud concentrations by 1.16 μg m−3 on average. This suggests in-cloud production similar in concentration to previous field campaigns in coastal marine atmospheres. Oxalate was observed in the clouds at air-equivalent concentrations of 0.21±0.04 μg m−3, in excess to below-cloud concentrations by 0.14 μg m−3 and suggesting an in-cloud production as well. The tentative identification in cloud water of one of the intermediate species in the aqueous oxalate production mechanism lends further support to an in-cloud oxalate source.
Keywords: Cloud chemistry; Aerosol; Mechanism; California; Dicarboxylic acid;

A 3-D Lagrangian particle dispersion model, including the photochemical reaction developed by Song et al. (Atmos. Environ. 37 (2003) 4607), has been applied to the data obtained from the Southern Oxidants Study field campaign to examine the effect of the intermixing process between the superposed Lagrangian particles on the spatial distribution of the non-reactive pollutant of SO2 and the photochemical compound of O3 with several different Lagrangian particle releasing time intervals. It is found that the intermixing process tends to disperse the centerline maximum concentration of the non-reactive gas toward the edges of the plume and to enhance the entrainment rate into the plume, thereby reducing the maximum concentration at the center of the plume and widening the width of the plume. The Lagrangian particle releasing time interval of up to 5 min does not significantly affect the non-reactive SO2 concentration across the plume within 49 km (T4 traverse) in the downwind direction from the source. However, a much shorter releasing time interval (an order of minute) is required to simulate the reactive pollutant of O3 concentration compared to the non-reactive SO2 concentration due to excessive entrainment of the background reactive pollutant into the plume center and the overweighed mass of each Lagrangian particle. This result suggests that the present model with the Lagrangian particle releasing time interval of one minute and with the intermixing process between the superposed Lagrangian particles can be used more practically to simulate concentration of both the non-reactive SO2 and the photochemical compound of O3.
Keywords: Intermixing process; Lagrangian particle releasing time interval; Non-reactive pollutant; Photochemical compound; Southern oxidants study;

Effects of sulphurous gases in two CO2 springs on total sulphur and thiols in acorns and oak seedlings by D Grill; M Müller; M Tausz; B Strnad; A Wonisch; A Raschi (3775-3780).
Quercus ilex and Quercus pubescens acorns were collected at two CO2 springs in Tuscany (Bossoleto and Viterbo, resp.). In addition to elevated CO2, these springs are a source of H2S and SO2. Acorns from a comparable field site distant from CO2 springs were used as controls. Acorns from CO2 springs contained significantly higher sulphur concentrations than controls (0.67 vs. 0.47 mg g−1 dw in Q. ilex cotyledons and 1.01 vs. 0.80 in Q. pubescens) and, in Q. ilex, also more glutathione (1634 vs. 1393 nmol g−1  dw). When acorns were germinated and seedlings grown under ambient air conditions in the Botanical Garden in Graz for one year, leaves of Q. pubescens grown from CO2 spring acorns showed significantly higher S-concentrations than leaves grown from control acorns (2.27 mg g−1 vs. 1.56 mg g−1  dw), and those of Q. ilex higher glutathione concentrations (929 vs. 462 nmol g−1  dw, CO2 spring vs. control acorns). One-year-old Q. ilex seedlings grown from CO2 spring acorns also showed elevated rates of chromosomal aberrations in root tips (a widely used test for environmental impacts), suggesting a permanent stress situation of the seedlings originating from the CO2 springs.
Keywords: Stress; Glutathione; Sulphur dioxide; Hydrogen sulphide; Cytogenetic;

High resolution temporal and spatial control of atmospheric pollutants is of crucial importance for environmental health monitoring. Passive sampling using natural vegetation biomonitoring allows acquisition of well-defined samples at affordable costs. We here present results from a study conducted in the conurbation of Cologne, Germany, based on airborne pollutants accumulated on pine needles. This integrated study includes (i) the microscopic analysis of pine needles and analysis of their magnetic properties, (ii) PAH, and (iii) selected trace elements (Fe, Cd, Pb, Ni, Cr, Cu). A major proportion of atmospheric pollutants is bound to particles, for which in part I of the study we present data on magnetic susceptibility, remanence measurements (IRM, ARM) and total Fe content. SEM-analysis indicates that particles accumulated on needles are mostly <2.5 μm in diameter and comprise pollen or spores, mineral dust and silica-glassy or metallic spheroids. The latter were identified as magnetite with minor pyrrhotite. These particles derive from combustion of coal in power plants or fuels in vehicular engines. A close correlation of magnetic properties (susceptibility, SIRM, ARM) and Fe content shows that non-destructive, time-efficient enviromagnetics of needles serves as an excellent proxy for biomonitoring of combustion pollutants. Their spatial distribution within the conurbation of Cologne was determined for 43 locations integrated in a GIS-database. The dominant sources of fine metallic particulates (PM2.5) are emissions from road traffic, including fuel combustion, corrosion and brake-wear and from railroad and tram traffic preferentially due to material wear. Parks, forests and agricultural areas show the lowest levels of pollution by magnetic particles, followed by residential areas. This implies that traffic emissions with short transportation distances (<1.0 km) are dominant in the Cologne conurbation, whereas the contribution from power plants is negligible.
Keywords: Atmospheric pollution; Environmental magnetics; Source assignment; Spatial distribution; GIS;

Emissions from fossil fuel combustion pose a serious thread to public health and impose the need for an improved monitoring of polycyclic aromatic hydrocarbons (PAH), a major class of persistent organic pollutants. For this purpose, utilization of evergreen conifers offers significant biomonitoring potential. In part I of this series we inspected the load of combustion derived magnetic particles in pine needles from 43 locations of the Cologne Conurbation, Germany; we here report the corresponding PAH concentrations and distribution patterns. Concentrations (dry weight) of summed 3–6-ring PAH range between 51 and 410 ng g−1 with a median of 123.8 ng g−1; thus being in agreement with other urban studies. Phenanthrene was the dominating PAH with median concentrations of 47 ng g−1 followed by fluoranthene and pyrene at 22 and 13 ng g−1, respectively. The major proportion of PAH was attributed to traffic sources, with minor contribution from power plant, domestic heating, industrial, and vegetation burn emissions. Significant differences between major and minor roads were not observed indicating a thorough mixing of PAH-loaded air masses in the Cologne Conurbation. Needles in inner city parks gave much higher PAH concentrations than those in suburban green areas. Although distribution patterns of PAH were variable a PAH source reconciliation based on isomer compositions is difficult, due to thorough mixing of air masses and associated loss of source specificity. Ambient air monitoring in urban areas based on persistent organic pollutant load of vegetation is a feasible and cost effective way of controlling environmental quality.
Keywords: PAH; Pine needle; Biomonitoring; Passive sampler; Cologne;

Assessment of urban air quality in Istanbul using fuzzy synthetic evaluation by Guleda Onkal-Engin; Ibrahim Demir; Halil Hiz (3809-3815).
Little attention was paid to growing air quality concerns until about a decade earlier in Istanbul. With a population of over 12 million people and some occurred episodes imposed threats to the local government, and continuous monitoring of the urban air quality was started about a decade ago. This is part of a national strategy program which includes urban air quality assessment. This paper addresses a methodology for urban air quality using fuzzy synthetic evaluation techniques. The European part of Istanbul was selected for this purpose. Air pollutants data such as sulphur dioxide (SO2), carbon monoxide (CO), nitrogen dioxide (NO2), ozone (O3), and total suspended particulate matter (PM) collected at five different air quality monitoring stations located in western part of Istanbul was used in this evaluation. The results obtained were compared to those applied to EPA air quality index. It was demonstrated that fuzzy synthetic evaluation techniques are quite appropriate techniques for air quality management. A case study was presented for this purpose.
Keywords: Fuzzy synthetic evaluation; Air quality index; Fuzzy similarity method; Simple fuzzy classification; Fuzzy comprehensive assessment;

Re-entrainment around a low-rise industrial building: 2D versus 3D wind tunnel study by Adrian W.K Law; Edmund C.C Choi; Rex E Britter (3817-3825).
We investigate the re-entrainment of pollutants around a low-rise industrial building under opposing cross winds through experimental means in a wind tunnel. Two scaled models of an industrial building for electrowinning metal extraction were tested. The first model was a two-dimensional simplified segment of the building with a scale ratio of 1:40, while the second was a 1:100 three-dimensional model of the full building. Particle image velocimetry was adopted to provide the planar velocity measurements that illustrated the flow distribution around the building. Flame ionization detection with propane tracer gas was used to measure the concentration distribution. The results of the 2D model show that the exhaust plume interacted with the opposing wind in two different stages, namely ground attachment and bent-over. The ground attachment stage occurred under low wind speeds, whereby the exhaust plume exhibited Coanda attachment with the ground surface before being lifted off by the cross wind and circulated to the leeward wake cavity. Upon further increase in the wind speed, the bent-over stage occurred with the exhaust plume being detached from the ground and deflected upward over the roof, before entrained by the wake. The re-entrainment ratio decreased with the increase in wind speed within the range of wind speeds tested, indicating that the range did not include the critical wind speed. Results from the 3D model painted a somewhat different picture and pointed to the significance of the end conditions. The maximum re-entrainment always occurred near the two ends of the building, where the pollutants mostly flowed around the ends rather than over the roof. The re-entrainment ratio was consistently higher at the two ends compared to the central sections. Finally, a building re-entrainment index, (K R), is proposed to characterize the re-entrainment performance of a specific building geometry.
Keywords: Re-entrainment; Industrial building; Exhaust plume; Intake; Wind tunnel modeling;

This paper describes a statistical analysis of a large number of NO x and CO emission data from natural gas-fired industrial combustion plants in The Netherlands. Many of these emission data are based on stack measurements. The implied emission factors observed for these combustion processes show a high variability, both between different installations and within one installation over time. This variability is well described by lognormal probability distribution functions with a width of 1–2 orders of magnitude.Due to the large number of plants included in the national inventory of The Netherlands, time trends in the national NO x emissions of a few percent per year can be detected despite this large variability. A significant trend for CO could not be observed. This suggests that the variability is not disturbing monitoring of emission trends at the national level.At the individual plant level, this variability however introduces a high uncertainty in a priori emission estimates. This could severely hamper emission reporting in the framework of a plant level emission trading scheme.
Keywords: Nitrogen oxides; Carbon monoxide; Uncertainty; Trend;

Terrestrial sources and sinks of halomethanes near Cape Grim, Tasmania by Michelle L Cox; Paul J Fraser; Georgina A Sturrock; Steven T Siems; Lawrence W Porter (3839-3852).
The terrestrial sources and sinks of halomethanes, at and nearby the Cape Grim Baseline Air Pollution Station, Tasmania (41°S, 145°E), have been investigated over 12 months (July 2000–June 2001) using a flux chamber technique. The sites studied are representative of the soils and vegetation within 20 km of Cape Grim and include soil/plant litter under melaleuca scrub and eucalypt forest canopies, native tussock grass/soil, improved pasture grass/soil and coastal wetland. On average, the soil, tussock and pasture sites were found to be sinks for methyl chloride (CH3Cl), whereas the coastal wetland site was a source for CH3Cl, methyl bromide (CH3Br) and methyl iodide (CH3I). The grassland sites (pasture and tussock) were a small source for CH3Br and the soil sites (melaleuca and eucalypt) a sink. All sites were significant sources of chloroform (CHCl3). The interspecies ratios for significantly correlated halomethane net fluxes at some terrestrial sites were compared with the ratios found for AGAGE Cape Grim in situ data characterising north and west coast Tasmania. Flux ratios for CH3Br/CH3I at the coastal wetland and pasture sites were found to be similar to ratios found for the Cape Grim in situ data. Common production mechanisms were indicated for CH3Br and CH3Cl which were significantly correlated at the coastal wetland, eucalypt and melaleuca sites and for CH3Br and CH3I at the pasture and coastal wetland sites. A seasonal variation in the net flux was observed at the coastal wetland site for CH3Cl and CH3Br.
Keywords: Chloroform; Dichloromethane; Methyl chloride; Methyl bromide; Methyl iodide; Flux chamber techniques; Annual cycles;

Isoprene and monoterpenes biogenic emissions in France: modeling and impact during a regional pollution episode by Fabien Solmon; Claire Sarrat; Dominique Serça; Pierre Tulet; Robert Rosset (3853-3865).
Biogenic emission of isoprene and monoterpenes are modeled in order to study their impact on regional atmospheric chemistry and pollution in France. First, an emission potential inventory is developed using a fine scale landuse database, forest composition statistics, biometric data and species emission factors. Considering the main emission patterns, the results show consistency with previously published European and global inventories. When downscaling to sub-region of France, this database is likely to provide refined sources distribution, an important issue for regional atmospheric chemistry studies. The temporal evolution of biogenic fluxes with meteorological conditions is calculated on line in the MesoNH–C meso-scale atmospheric chemistry model. Leaf-level algorithms are integrated at the ecosystem scale using sub-grid prognostic surface temperature and canopy shading effects. Finally, ecosystem to landscape integration is performed by aggregating biogenic fluxes at the model grid cell scale. Uncertainties associated with these estimations are discussed with respect to different spatial scales. In the second part of the paper, these developments are used to study biogenic emission impacts on regional ozone formation. We focus on a summer pollution event over Paris and northern France, documented during the ESQUIF experiment. The introduction of biogenic fluxes led to an increase in simulated surface ozone concentrations, reaching 18–30% in the Paris plume and about 20–30% in some rural areas. This impact was mainly due to large biogenic fluxes as well as to the chemical conditions prevailing in the anthropogenic plumes reaching biogenic sources. In this situation, some comparisons with air quality measurements pointed out an improvement of simulated ozone concentrations when accounting for biogenic fluxes, both in urban plumes and over rural areas.
Keywords: Isoprene; Monoterpenes; Emission inventories; Regional pollution; Atmospheric chemistry modeling;

An understanding of the likely pattern of dry deposition of small particles over a landscape is a key prerequisite to designing strategies for sampling ground contamination following routine or accidental releases to atmosphere. Wind tunnel and computational fluid dynamics studies of flow and particle deposition over landscape features have been carried out. The presence of elevated landscape features showed a strong effect on the pattern of deposition relative to a flat landscape case. A relatively small area of increased deposition occurred on the upwind face, with a larger area of decreased deposition in the wake. The slope of the landscapes affected the magnitude of the effect and the size of the affected region in the wake. The pattern of deposition for a three-dimensional landscape was complex. Good quantitative agreement was seen between the CFD predicted deposition and the wind tunnel results for the two-dimensional cases and reasonable qualitative agreement for the three-dimensional case, suggesting that CFD studies might be an appropriate tool to systematically explore the influence of complex topography on particle deposition.
Keywords: Aerosol; CFD; Complex terrain; Hills; Turbulence;

Monitoring of viable airborne SARS virus in ambient air by Igor E Agranovski; Alexander S Safatov; Oleg V Pyankov; Alexander N Sergeev; Alexander P Agafonov; Georgy M Ignatiev; Elena I Ryabchikova; Alexander I Borodulin; Artemii A Sergeev; Hans W Doerr; Holger F Rabenau; Victoria Agranovski (3879-3884).
Due to recent SARS related issues (Science 300 (5624) 1394; Nature 423 (2003) 240; Science 300 (5627) 1966), the development of reliable airborne virus monitoring procedures has become galvanized by an exceptional sense of urgency and is presently in a high demand (In: Cox, C.S., Wathers, C.M. (Eds.), Bioaerosols Handbook, Lewis Publishers, Boca Raton, FL, 1995, pp. 247–267). Based on engineering control method (Aerosol Science and Technology 31 (1999) 249; 35 (2001) 852), which was previously applied to the removal of particles from gas carriers, a new personal bioaerosol sampler has been developed. Contaminated air is bubbled through porous medium submerged into liquid and subsequently split into multitude of very small bubbles. The particulates are scavenged by these bubbles, and, thus, effectively removed. The current study explores its feasibility for monitoring of viable airborne SARS virus. It was found that the natural decay of such virus in the collection fluid was around 0.75 and 1.76 lg during 2 and 4 h of continuous operation, respectively. Theoretical microbial recovery rates of higher than 55 and 19% were calculated for 1 and 2 h of operation, respectively. Thus, the new sampling method of direct non-violent collection of viable airborne SARS virus into the appropriate liquid environment was found suitable for monitoring of such stress sensitive virus.
Keywords: SARS; Bioaerosol; Personal monitoring; Viable microorganisms; Collection efficiency;

Observation of boundary layer aerosols using a continuously operated, portable lidar system by Nofel Lagrosas; Yotsumi Yoshii; Hiroaki Kuze; Nobuo Takeuchi; Suekazu Naito; Akihiro Sone; Hirofumi Kan (3885-3892).
A compact, continuously operated lidar system has been developed and applied for unattended, continuous monitoring of troposphere. We demonstrate the effectiveness of the automatic procedure that routinely optimizes the lidar alignment in a definite interval. On the basis of the data taken from December 2002 to June 2003, oscillatory behavior of the aerosol layer height, vertical motion of the aerosol layer, and speed of raindrops are discussed. A good correlation is found between the lidar signal backscattered inside the boundary layer and the data of suspended particulate matter simultaneously measured at the ground level.
Keywords: Portable lidar; Automatic alignment; Buoyancy oscillation; Raindrop speed; SPM concentration;

Size-selective assessment of airborne particles in swine confinement building with the UVAPS by Victoria Agranovski; Zoran Ristovski; Patrick J Blackall; Lidia Morawska (3893-3901).
The ultraviolet aerodynamic particle sizer (UVAPS) is a novel aerosol counter for real-time monitoring of viable bioaerosols. The previous validation studies on the UVAPS were either laboratory based or were conducted outdoor with the artificially generated aerosols. In this study, the spectrometer was applied to investigate particulate pollution inside a swine confinement building (SCB). Real-time capabilities of the instrument were used to investigate the effect of on-farm-activities, such as an effluent flushing with recycled water, on aerosols load inside the SCB. In addition to the UVAPS, monitoring of viable bioaerosols (bacteria and fungi) was simultaneously conducted with the six-stage Andersen microbial impactor and the AGI-30 impingers. The UVAPS measurements showed that the concentrations of both viable (fluorescent) and total (fluorescent and non-fluorescent) particles inside the SCB were in order of 106–107  particles m−3. These concentrations were approximately seven times the outside concentrations for total particles and up to 12 times for viable particles. Approximately 95% of both total and viable particles were respirable (<7 μm) and approximately 60% of total and 50% of viable particles accounted for the fine particle fraction (<2.5 μm). The concentration of culturable bacteria and fungi ranged from 1.12×105 to 5.17×105  CFU m−3 and from 1.12×103 to 2.79×103  CFU m−3, respectively. Approximately 50–80% of airborne particles which carried culturable fungi were within the respirable size range. The concentration of viable particles measured with the UVAPS was at least one order of magnitude higher than the concentration of the culturable microorganisms measured with the AGI-30 impingers. Nevertheless, the trends in the concentration changes of viable bioaerosols measured with the UVAPS followed the trends in the concentration changes of the culturable airborne microorganisms quite adequately. Thus, it was concluded that the UVAPS is an appropriate method for investigating the dynamic of viable bioaerosols in the SCBs. The results obtained in this study assist in advancing an understanding of the UVAPS performance in the real-life agricultural settings. In addition, the data provide a new insight on the particles size distribution inside the SCB, depending on their nature.
Keywords: The UVAPS; Swine confinement buildings; Viable bioaerosols; Particle size; Bacteria; Fungi;