Atmospheric Environment (v.38, #13)

Evolution of nanoparticle size and mixing state near the point of emission by Mark Z. Jacobson; John H. Seinfeld (1839-1850).
This study examines the evolution of the size distribution and mixing state of soot and background particles near a point and line source of emission. This evolution occurs invariably at a spatial scale smaller than that of the grid scale of urban through global atmospheric models, and the evolved distribution is that which is properly the source distribution “emitted” into such models. A recent set of field data showed that, within minutes of emission, the soot particle size distribution evolved substantially, and it was hypothesized that Brownian coagulation was the main cause of the evolution. Here, it is found that Brownian coagulation, alone, may be insufficient to account for the observed rapid evolution of the size distribution. Enhancement of Brownian coagulation due to van der Waals forces offset by viscous forces and fractal geometry may account for a greater share of the evolution. These coagulation processes are represented together with aerosol emissions, nucleation, condensation, dissolution, hydration, and chemistry among 10 aerosol classes in a high-resolution three-dimensional numerical simulation. Dilution is found to be more important than coagulation at reducing the total number concentration of particles near the source of emission, but the relative importance of dilution versus coagulation varies with concentration. It is also found that heterocoagulation of emitted soot with background particles produces new mixtures in increasing concentration with increasing distance from the emission source. However, self-coagulation of emitted soot reduces particle number concentration by an order of magnitude more than does heterocoagulation of emitted soot with background particles in the first few minutes after emission. Heterocoagulation increases in relative importance as emitted particles age.
Keywords: Nanoparticles; Coagulation; Dilution; Three-dimensional modeling; Fractals;

This paper presents the air pollutant emission inventory of primary pollutants for Izmir, which is a highly industrialized area situated in the western part of Turkey. A proper emission inventory is very important for planning pollution control programs, particularly in coastal sites like Izmir, where environmental quality is of growing concern owing to their typical meteorological conditions. The sources were broadly classified as point, line and area sources in a systematic way. The data on activity levels of industries, fuel consumption in vehicles and domestic activities along with the respective emission factors were used for estimating the emissions for the year 2000. The results showed that industry is the most polluting sector for sulfur dioxide (SO2) in the study area contributing about 88% of total emissions. On the other hand, domestic heating is the most polluting sector contributing about 56% of total PM emissions while traffic has the highest portion for NO X emissions. Especially, emissions from industries located outside the metropolitan city center are much higher in amount. Industries located around the Izmir metropolitan center contribute to the industrial SO2 emissions by 93%, PM emissions by 59% and NO X emissions by 80% of the total.
Keywords: Emission; Emission inventory; Pollutant source; Air quality; Izmir;

Water uptake by particles containing humic materials and mixtures of humic materials with ammonium sulfate by Sarah D. Brooks; Paul J. DeMott; Sonia M. Kreidenweis (1859-1868).
Recent field studies show that a large fraction of the previously uncategorized organic compounds in atmospheric aerosols are polycarboxylic acids resembling the humic materials (HMs) in soil. The presence of these compounds may alter the water uptake and deliquescence characteristics of particles. We have measured the water uptake by pure HM and by mixed HM/ammonium sulfate particles as a function of relative humidity (RH). We find that the water uptake behavior varies with the type, source, and isolation method of the HM. Two of the three pure humic acids (HAs) and the fulvic acid (FA) studied here exhibited very little water uptake up to ∼90% RH, while the fourth material, HA from the Fluka chemical company, deliquesced at 70% RH and showed continuous water uptake to ∼90% RH. For comparison, water uptake by polyacrylic acids of two chain lengths and by phthalic acid were also measured. These species also took up small amounts of water over the range of RHs studied. Particle size and chain length had very little effect on water uptake. The mixed organic/ammonium sulfate particles took up a reduced amount of water relative to pure ammonium sulfate, with the exception of the Fluka HA. We modeled the water uptake of mixed particles assuming that ammonium sulfate and HM took up water independently, and results are consistent with the measured water uptake by mixed particles.
Keywords: Humic acid; Fulvic acid; Organic; Aerosol; Hygroscopicity;

A drought-based predictor of recent haze events in western Indonesia by Robert D. Field; Yonghe Wang; Orbita Roswintiarti; Guswanto (1869-1878).
Indonesia's fire and haze problem is reviewed, and a model quantifying the relationship between drought and haze from biomass burning in western Indonesia is presented. Visibility observations from weather stations in Sumatra and Kalimantan were used as a haze indicator. The Drought Code component of the Canadian Forest Fire Weather Index System was used as a drought indicator. Using meteorological data from 1994 to 1998, we obtained regional haze and drought signals for western Indonesia. Nonlinear regression analysis was performed between the two signals to obtain a model of haze potential based on the Drought Code. Using the curvature properties of the nonlinear model, we estimated that severe haze is likely above a threshold Drought Code of 388.2. Using this threshold value, we propose four levels of drought that can be used operationally as an early warning tool in managing Indonesia's serious haze problem.
Keywords: Air quality; Forest fires; Peat; El Niño; Bootstrap;

Biogenic sources contribute a large portion of emissions of volatile organic compounds (VOCs), a precursor to tropospheric ozone (O3). These emissions are difficult to control and are affected by land-use and climate. A sensitivity analysis was performed using an emissions scenario with a 100% increase in biogenic emissions and another scenario with an additional 100% increase in motor vehicle emissions. Meteorological and air pollution models were used to generate hourly ozone estimates for a case study high ozone episode. Resulting concentration estimates correspond to the total effect of changes from emissions, incorporating the interaction between anthropogenic and biogenic emissions.Biogenic VOCs had a greater impact than a comparable percent increase in motor vehicle emissions of ozone precursors, in this case study. The 100% increase in biogenic VOC emissions raised ozone levels, with an estimated maximum 1-h concentration 30% higher than that of the baseline scenario. The additional emissions of ozone precursors from motor vehicles raised the maximum 1-h concentration 40% over that of the baseline. The largest increases in ozone concentrations occurred near peak values. Urban areas had larger increases in ozone levels than rural regions. Both adjusted emissions scenarios resulted in ozone concentrations lower than that of the baseline for some estimates. These reductions occurred near low ozone levels however and were generally small.This research demonstrates the importance of biogenic VOC emissions in ozone formation for this region and of biogenic emissions inventories. Results also imply that climate change-induced increases in biogenic VOC emissions could significantly impact ozone concentrations.
Keywords: Biogenic emissions; Ozone; Volatile organic compounds; Air pollution; Modeling;

Intercontinental transport and the origins of the ozone observed at surface sites in Europe by R.G. Derwent; D.S. Stevenson; W.J. Collins; C.E. Johnson (1891-1901).
A global three-dimensional Lagrangian chemistry-transport model is used to describe the formation, transport and destruction of tropospheric ozone using 1990s global emissions and 1998 meteorological archives. Using a labelling technique, the geographical origins of the ozone formed within the troposphere have been revealed, showing whether the ozone found at the surface in Europe has had its origins above the continents of North America, Europe or Asia or elsewhere in the world. In this way, contributions to the ozone found at 21 surface monitoring sites across Europe can be attributed to production over North America and Asia, demonstrating that intercontinental ozone transport is an efficient process. Sensitivity tests to the global man-made sources of NO x and carbon monoxide indicate that global ozone precursor emission controls may contribute towards reaching regional air quality policy goals for ozone in Europe.
Keywords: Intercontinental transport; Ozone; Seasonal cycles; Emission controls;

The direct-acting mutagenicity of soluble organic fraction (SOF) of airborne particles, and the concentration of five gaseous air pollutants and two nitroarenes, 1-nitropyrene (1-NP) and 2-nitrofluoranthene (2-NF) were determined to clarify their diurnal variation pattern by collecting airborne particles every 3 or 4 h in a slightly polluted residential area at southern Osaka, Japan. The direct-acting mutagenicity of SOF toward Salmonella typhimurium YG1024 strain, i.e. mutagenicity in the absence of microsomal activation, was high early in the morning and late in the evening, while it was low both in the daytime and in the nighttime. The diurnal variation pattern of the mutagenicity was similar to those of the concentration of NO, CO, and 1-NP, which were primarily emitted from combustion processes such as diesel-powered vehicles. On the other hand, a significant correlation was observed between diurnal variations of the concentration of 2-NF and hydroxyl radical in October. The concentration of 2-NF in airborne particles collected in July was comparable to that in October. Based on the specific mutagenic activity of 1-NP and 2-NF, their contribution to the total direct-acting mutagenicity of SOF toward YG1024 strain were estimated to be small as 0.03–0.06% and 0.2–1.1%, respectively. However, some of atmospherically formed nitroarenes would contribute to the direct-acting mutagenicity of the air in the daytime, when atmospheric formation of nitroarenes initiated by the reactions with radical species is expected to occur even since the mutagenicity originated from primarily emitted mutagens should be suppressed by photo-decomposition of the mutagens.
Keywords: Salmonella typhimurium YG1024 strain; 1-nitropyrene; 2-nitrofluoranthene; Hydroxyl radical; Primary emission;

This paper is an evaluation of the gas phase collection efficiency of a commercially available annular denuder sampler used to collect gas and particle phase semivolatile organic compounds. Laboratory and field experiments were carried out to determine the gas phase collection efficiency using naphthalene as reference compound. Laboratory tests were performed to study the influence of environmental conditions (temperature, relative humidity and gas phase concentration) and sampling conditions (sampling flow rate, and sampling duration) on the collection efficiency. During laboratory experiments, the collection efficiency of the gas phase was measured using a dynamic gas generator. It was above 90% for a range of experimental conditions covering: temperature from 9°C to 39°C, relative humidity from 30% to 90%, sampling duration up to 14 h, flow rate of 1 and 2 m3  h−1 and quantity of gaseous naphthalene considerably higher than the one usually collected during atmospheric sampling.Additionally, field experiments were carried out to test the matrix effect on the denuder performances. During these field experiments, and because the gaseous and particle atmospheric phases were trapped and analysed separately, it was possible to calculate the collection efficiency of the most volatile polycyclic aromatic hydrocarbons (PAHs). It was 100% assuming a relative standard deviation of 10% on this calculation. This set of results shows that the denuder-based sampling method is suitable for the sampling of the most volatile PAHs.
Keywords: Annular denuder; Gaseous PAH; Air sampling;

Evaluation of an annular denuder for atmospheric PAH partitioning studies—2: evaluation of mass and number particle losses by Brice Temime-Roussel; Anne Monod; Catherine Massiani; Henri Wortham (1925-1932).
Transmission efficiency of particles through an eight-channel annular denuder coated with XAD-4 was experimentally determined for particles ranging between 0.04 and 8.24 μm. Two sampling flow rates were tested, 17 and 34 l min−1. The results show that the mean transmission efficiencies in number are, respectively, 96% and 95% for a sampling flow rate of 17 and 34 l min−1 (particle size ranging between 0.04 and 8.24 μm), while in mass it is, respectively, 84 (±14)% and 81 (±21)% for a sampling flow rate of 17 and 34 l min−1. A comparison between these experimental results and theoretical transmission calculations shows that XAD-4 coating has no significant effect on the transmission efficiency.
Keywords: Annular denuder; Particulate PAH; Calibration;

Dry deposition velocity of particles has been parameterized in the global multi-scale Chemistry and Transport Model MOCAGE as a function of particle size and density, surface properties, and micro-meteorological conditions near the surface. Hourly deposition velocities have been simulated over the year 2000 using the analyses and forecasts of the French operational numerical weather prediction model ARPEGE. Results were compared with measurements available in the literature. Predictions of our model are generally satisfactory, showing the largest uncertainty in the 0.1–1  μm particle size interval over highly rough surfaces. According to the one-year global average, deposition velocity over continents is about an order of magnitude higher than over oceans, for all particle sizes. Seasonal variations are nearly undetectable, while diurnal variations over land exist with a maximum around 12–15  h local solar time. Spatially, mid-latitudes regions usually have higher deposition velocities than tropical and polar ones, particularly over continents.
Keywords: Particle dry deposition velocity; Chemistry and transport model; Aerosol module; Particle size;

PM2.5 and NO2 assessment in 21 European study centres of ECRHS II: annual means and seasonal differences by Marianne E. Hazenkamp-von Arx; Thomas Götschi; Ursula Ackermann-Liebrich; Roberto Bono; Peter Burney; Josef Cyrys; Deborah Jarvis; Linnea Lillienberg; Christina Luczynska; Jose A. Maldonado; Angeles Jaén; Roberto de Marco; Yahong Mi; Lars Modig; Lucy Bayer-Oglesby; Felix Payo; Argo Soon; Jordi Sunyer; Simona Villani; Joost Weyler; Nino Künzli (1943-1953).
The follow-up of cohorts of adults from more than 20 European centres of the former ECRHS I (1989–1992) investigates long-term effects of exposure to ambient air pollution on respiratory health, in particular asthma and change of pulmonary function. Since PM2.5 is not routinely monitored in Europe, we measured PM2.5 concentrations in 21 participating centres to estimate ‘background’ exposure in these cities. Winter (November–February), summer (May–August) and annual mean (all months) values of PM2.5 were determined from measuring periods between June 2000 and November 2001. Sampling was conducted for 7 days per month for a year. Annual and winter mean concentrations of PM2.5 vary substantially being lowest in Iceland and highest in centres in Northern Italy. Annual mean concentrations ranged from 3.7 to 44.9 μg m−3, winter mean concentrations from 4.8 to 69.2 μg m−3, and summer mean concentrations from 3.3 to 23.1 μg m−3. Seasonal variability occurred but did not follow the same pattern across all centres. Therefore, ranking of centres varied from summer to winter. Simultaneously, NO2 concentrations were measured using passive sampling tubes. Annual mean NO2 concentrations range from 4.9 to 72.1 μg m−3 with similar seasonal variations across centres and constant ranking of centres between seasons. The correlation between annual NO2 and PM2.5 concentrations is fair (Spearman correlation coefficient r s=0.75), but when considered as monthly means the correlation is far less consistent and varies substantially between centres.The range of PM2.5 mass concentrations obtained in ECRHS II is larger than in other current cohort studies on long-term effects of air pollution. This substantial variation in PM2.5 exposure will improve statistical power in future multi-level health analyses and to some degree may compensate for the lack of information on within-city variability. Seasonal means may be used to indicate potential differences in the toxicity across the year. Across ECRHS cities annual NO2 might serve as a surrogate for PM2.5, especially for past exposure assessment, when PM2.5 is not available.
Keywords: Exposure assessment; Air quality; Air pollution; Particle; Epidemiology; Traffic;

Two back trajectory-based statistical models, simplified quantitative transport bias analysis and residence-time weighted concentrations (RTWC) have been compared for their capabilities of identifying likely locations of source emissions contributing to observed particle concentrations at Potsdam and Stockton, New York. Quantitative transport bias analysis (QTBA) attempts to take into account the distribution of concentrations around the directions of the back trajectories. In full QTBA approach, deposition processes (wet and dry) are also considered. Simplified QTBA omits the consideration of deposition. It is best used with multiple site data. Similarly the RTWC approach uses concentrations measured at different sites along with the back trajectories to distribute the concentration contributions across the spatial domain of the trajectories. In this study, these models are used in combination with the source contribution values obtained by the previous positive matrix factorization analysis of particle composition data from Potsdam and Stockton. The six common sources for the two sites, sulfate, soil, zinc smelter, nitrate, wood smoke and copper smelter were analyzed. The results of the two methods are consistent and locate large and clearly defined sources well. RTWC approach can find more minor sources but may also give unrealistic estimations of the source locations.
Keywords: Ambient aerosol; Receptor model; Back trajectory; Simplified quantitative transport bias analysis; Residence-time weighted concentrations;

Indian methane and nitrous oxide emissions and mitigation flexibility by Amit Garg; P.R. Shukla; Manmohan Kapshe; Deepa Menon (1965-1977).
Methane (CH4) and nitrous oxide (N2O) contributed 27% and 7%, respectively, to India's CO2 equivalent greenhouse gas (GHG) emissions in 2000, the remaining being the carbon dioxide (CO2) emissions. Presently, agriculture and livestock related emissions contribute above 65% of Indian CH4 emissions and above 90% of N2O emissions. Since these activities are widely dispersed, with a considerable portion being sub-sustenance activities, emission mitigation requires considerable efforts. We use geographical information system (GIS) interfaced Asia-Pacific Integrated Model (AIM/Enduse), which employs technology share projections, for estimating future CH4 and N2O emissions. The future emissions and mitigation flexibility are analyzed for a reference scenario and two mitigation scenarios (medium and strong). Future CH4 emissions in 2030 are projected to reach 24.4 Tg (reference scenario), 21.3 Tg (medium mitigation scenario) and 17.6 Tg (strong mitigation scenario). Future CH4 emission scenarios indicate rising shares of municipal solid waste (MSW) and coal bed methane, where mitigation technologies have good penetration potential. Improved cattle feed and digesters, and better rice paddy cultivation practices that are adopted for higher yields and improved irrigation coverage also offer CH4 mitigation as ancillary benefits. Future N2O emissions in 2030 are projected to reach 0.81 Tg (reference scenario), 0.69 Tg (medium mitigation scenario) and 0.6 Tg (strong mitigation scenario). Better utilization of nitrogen fertilizer and increased use of organic fertilizers, partly produced from MSW, offer interesting mitigation opportunities for N2O emissions. Some of these technology initiatives are already visible in India at different stages of development and appropriate policy thrust may strengthen them in future.
Keywords: Future emissions; Mitigation technologies; Methane; Nitrous oxide;

Seasonal variation of palladium, elemental carbon and aerosol mass concentrations in airborne particulate matter by Andreas Limbeck; Josef Rendl; G. Heimburger; A. Kranabetter; Hans Puxbaum (1979-1987).
Palladium, elemental carbon (EC) and mass concentrations in the aerosol fraction below 10 μm aerodynamic diameter (PM10) were investigated in a 1 year time series in Klagenfurt and Salzburg, two urban sites in Austria. For PM10 mass and EC concentrations no remarkable differences were observed between the two sites whereas for palladium distinctly different concentration levels were determined. The monthly averaged palladium concentration in Salzburg varied between 7.1 and 31.2 pg m−3. In Klagenfurt the palladium concentration ranged from 2.9 to 5.0 pg m−3. The higher traffic density and the different driving conditions in Salzburg were assessed to be responsible for the enhanced palladium concentrations. At both sampling sites the seasonal variation of PM10 and EC was similar showing decreased concentrations in the warm period of the year and increased concentrations in the cold season. Generally the seasonal pattern of an individual aerosol constituent depends on meteorological variations and changes in the source emission and transformation rates of the investigated species. With the use of palladium as an atmospheric dilution tracer it was possible to eliminate seasonal meteorological variations and to determine changes in source emission or atmospheric transformation rates of PM10 mass and elemental carbon concentrations. Approximately 20% of the enhanced PM10 mass and EC concentrations in the cold season could be attributed to reduced atmospheric dilution. The remaining variation (+22–50%) reflects changes in other processes such as source emission or atmospheric transformation rates of the examined aerosol constituents.
Keywords: Urban aerosol; PM10; Palladium; Seasonal pattern; Atmospheric tracer;

Elemental concentrations in tropospheric and lower stratospheric air in a Northeastern region of Poland by Janusz Braziewicz; Ludwika Kownacka; Urszula Majewska; Andrzej Korman (1989-1996).
Element concentrations of K, Ca, Ti, Cr, Fe, Ni, Cu, Zn, Se, Br, Sr and Pb as well as the activity of natural radionuclides 210 Pb and 226 Ra in air were measured. The aerosol samples were collected during tropospheric and stratospheric aircraft flights over the Northeastern region of Poland, which is mostly an agricultural and wooded area. The air volumes were filtered using Petrianov filters at 1, 3, 6, 9, 12 and 15  km above the ground level by special equipment attached to a jet plane. Aircraft flights were provided from September 1997 to August 1998 in 5 separate sampling runs. The long sampling distances served as a good representation of mean aerosol composition and distribution. Concentrations of the same elements were also measured using stationary equipment near the ground level at the outskirts of Warsaw. The vertical profiles of element concentration were obtained and the elemental compositions for the tropospheric and stratospheric aerosols were compared with those from the near-ground level. Contribution of K, Ca, Ti and Fe, which are the main components of soil, in total mass of all detected ones was estimated. Relative concentrations of all measured elements, which show any differences in the composition of the aerosol were calculated. The results obtained confirm the fact that the stratospheric reservoir is observed in the bottom stratosphere. The XRF method based on molybdenum X-ray tube was used as an analytical tool in the determination of aerosols trace elements. The altitude distributions of radioactivity of 226 Ra and 210 Pb were determined using radiochemical methods.
Keywords: Air aerosols; Air radioactivity; XRF method; Vertical distribution;

Characteristics of C2–C15 hydrocarbons in the air of urban Kaohsiung, Taiwan by C.H. Lai; K.S. Chen; Y.T. Ho; M.S. Chou (1997-2011).
The concentrations of 71 hydrocarbons (HC) from C2 to C15 were measured simultaneously at two sites in Kaohsiung city in the morning (07–10), the afternoon (13–16), and the evening (18–21) on 14 days in spring 2003. A total of 84 3-h integrated air samples were collected using multibed stainless-steel thermal adsorption tubes and then analyzed using a GC/FID or a GC/ECD. The most abundant species of Kaohsiung's air is toluene (43.36–54.49 μg m−3), followed by i-pentane, 1,2,4-trimethylbenzene, benzene, n-butane, propane and acetylene, in the range 10.36–17.11 μg m−3. The concentrations of 14 halocarbons are in the range 0.25–4.57 μg m−3. Alkanes (around 44.8%) represent the largest proportion of the total HC, followed by aromatics (35.1%), alkenes (15.5%) and halocarbons (5.4%). The afternoon HC concentrations are much lower than those in the morning and at night, due to relatively intense photochemical reaction and favorable dispersion conditions from noon to afternoon. Notable increases in daily HC concentrations are consistent with high temperature, and low HC concentrations on Sunday coincide with low traffic volume. Photochemical activity is investigated, and HC concentrations are found to decline as the NO2/NO x ratio increases. Correlation analyses imply that vehicle exhaust is the dominant source of atmospheric hydrocarbons in Kaohsiung.
Keywords: Hydrocarbons; Aromatics; Halocarbons; Urban air quality; Vehicle exhaust;

Occurrence of 4-Nonylphenol in rain and snow by Elke Fries; Wilhelm Püttmann (2013-2016).
The present technical note reports on the endocrine disruptor 4-nonylphenol (4-NP) in rain and snow. In July 2001, November 2001 and January 2002, rain and snow sampling was conducted at different urban, suburban and rural areas in Germany and Belgium. The mean concentration of 4-NP in rain water and roof run off was 0.253 μg dm−3 (n=8) with a higher mean concentration in suburban areas at 0.534 μg dm−3 and considerable lower mean concentrations in rural and urban areas at 0.099 and 0.062 μg dm−3, respectively. The mean concentration of 4-NP at 0.099 μg dm−3 (n=3) was significantly lower in summer rain than in winter rain at 0.346 μg dm−3. In snow samples, 4-NP was detected with a mean value of 0.242 μg dm−3 (n=8). A higher mean value of 4-NP in snow at 0.478 μg dm−3 (n=4) was found at urban sites whereas in snow from suburban areas the mean concentration of 4-NP at 0.030 μg dm−3 (n=2) was much lower. 4-NP was never detected above its determination limit in snow samples from rural areas.
Keywords: 4-Nonylphenol; Alkylphenol polyethoxylates; Endocrine disruptors; Non-ionic surfactants; Rain; Snow; Solid-phase extraction; GC/MS;