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Atmospheric Environment (v.45, #34)
Long-term trend of aerosol composition and direct radiative forcing due to aerosols over Gosan: TSP, PM10, and PM2.5 data between 1992 and 2008 by N.K. Kim; Y.P. Kim; C.-H. Kang (pp. 6107-6115).
In this study, size segregated measurement data between 1992 and 2008 at Gosan, Jeju, Korea were analyzed. Long-term trend of aerosol composition changes related to the emission change was analyzed and direct radiative forcing due to aerosols over Gosan was calculated. The concentration variations of ion components and carbonaceous aerosols matched well to the emission changes in Northeast Asia, and the concentration variations of the elements with natural origin were highly correlated to the frequency of dust storms in the region. The net aerosol forcing varied from −4.48 W m−2 to 0.53 W m−2 at Gosan and it was increasing. This was mainly because of continuous decrease of sulfate concentration and steady increase of EC concentration in the region. It was found that for the determination of the direct aerosol radiative forcing, relative humidity (RH) was most critical during summer season when it was high (over 75%), and EC was most critical during spring and fall.► Size segregated measurement data between 1992 and 2008 at Gosan were analyzed. ► Concentration variations of aerosols were well matched to the regional emissions. ► Concentrations of natural elements were highly correlated to dust storm frequency. ► The net aerosol forcing varied from −4.48 W m−2 to 0.53 W m−2 and it was increasing.
Keywords: Size segregated aerosols; Ions; Elements; Carbonaceous aerosols; Direct aerosol radiative forcing; Air pollutant emissions
Influence of water surface properties on the heterogeneous reaction between O3(g) and I(aq)− by Dorea I. Reeser; D.J. Donaldson (pp. 6116-6120).
The production of molecular iodine via the interfacial reaction between aqueous iodide and gas-phase ozone in the presence of octanol films was studied as a function of reactant and octanol concentrations using absorption spectroscopy. The total production of iodine displayed a Langmuir–Hinshelwood dependence on the concentrations of bulk aqueous iodide and gas-phase ozone, in agreement with earlier studies. The amount of iodine released into the gas phase relative to that remaining in solution depended on the concentrations of iodide and octanol. The amount of gas-phase I2 was smaller for higher iodide concentrations, while the amount remaining in solution increased. The total amount of I2 product increased somewhat on octanol-coated surfaces. However, the more striking result is that the release of I2 into the gas phase was diminished by ∼50%, and the amount retained in solution increased correspondingly in the presence of an octanol monolayer.Display Omitted► The O3(g)/I(aq)− reaction was studied as a function of I− and octanol monolayers. ► As I− increases I2 product remaining in solution increases via sequestration by I−. ► An organic coating influences the gas – solution partitioning of the I2 product. ► Laboratory studies of the O3/I− reaction may not relate to the “real” sea surface.
Keywords: Iodine; Iodide ozonation; Octanol films; Heterogeneous reactions; Air–aqueous interface
OC/EC ratio observations in Europe: Re-thinking the approach for apportionment between primary and secondary organic carbon by Casimiro Pio; Mário Cerqueira; Roy M. Harrison; Teresa Nunes; Fátima Mirante; Célia Alves; César Oliveira; Ana Sanchez de la Campa; Begoña Artíñano; Manuel Matos (pp. 6121-6132).
This study explores a large set of OC and EC measurements in PM10 and PM2.5 aerosol samples, undertaken with a long term constant analytical methodology, to evaluate the capability of the OC/EC minimum ratio to represent the ratio between the OC and EC aerosol components resulting from fossil fuel combustion (OCff/ECff). The data set covers a wide geographical area in Europe, but with a particular focus upon Portugal, Spain and the United Kingdom, and includes a great variety of sites: urban (background, kerbside and tunnel), industrial, rural and remote. The highest minimum ratios were found in samples from remote and rural sites. Urban background sites have shown spatially and temporally consistent minimum ratios, of around 1.0 for PM10 and 0.7 for PM2.5.The consistency of results has suggested that the method could be used as a tool to derive the ratio between OC and EC from fossil fuel combustion and consequently to differentiate OC from primary and secondary sources. To explore this capability, OC and EC measurements were performed in a busy roadway tunnel in central Lisbon. The OC/EC ratio, which reflected the composition of vehicle combustion emissions, was in the range of 0.3–0.4. Ratios of OC/EC in roadside increment air (roadside minus urban background) in Birmingham, UK also lie within the range 0.3–0.4. Additional measurements were performed under heavy traffic conditions at two double kerbside sites located in the centre of Lisbon and Madrid. The OC/EC minimum ratios observed at both sites were found to be between those of the tunnel and those of urban background air, suggesting that minimum values commonly obtained for this parameter in open urban atmospheres over-predict the direct emissions of OCff from road transport. Possible reasons for this discrepancy are explored.► OC/EC ratio is commonly used in the source apportionment of carbonaceous aerosol. ► European urban aerosol has a similar minimum OC/EC ratio. ► Ambient aerosol seems to be always contaminated with secondary OC. ► Tunnel OC/EC ratios are probably a better indicator of primary fossil fuel OC.
Keywords: Organic carbon; Elemental carbon; OC/EC ratio; Secondary organic carbon; Size distribution
The study on vertical variability of PM10 and the possible sources on a 220 m tower, in Tianjin, China by Yu-Fen Zhang; Hong Xu; Ying-Ze Tian; Guo-Liang Shi; Fang Zeng; Jian-Hui Wu; Xiao-Yong Zhang; Xiang Li; Tan Zhu; Yin-Chang Feng (pp. 6133-6140).
In this study, PM10 samples were collected at a meteorological tower in Tianjin, China. Four height levels (10 m, 40 m, 120 m and 220 m) were selected as the sampling sites. During the measurement campaign, the highest PM10 and species concentrations were obtained at 10 m, while lower concentrations were obtained at higher sampling sites. According to the vertical variability analysis of species concentrations and fractions (%), significant differences between different heights were found for certain species, such as Al, Si, Ca, OC and EC, while such differences forNO3− andSO42− were insignificant. In addition, the source contributions at each sampling site were calculated by a chemical mass balance (CMB) model. In all sampling sites, secondary sulfate accounted for the largest contributions (24.11–30.96%). The other estimated contributions were secondary nitrate (16.19–20.95%), crustal dust (10.74–11.37%), coal combustion (12.47–14.39%), vehicle exhaust (13.92–14.78%) and cement dust (4.60–9.89%). Finally, the conditional probability function (CPF) plots and potential source contribution function (PSCF) maps show that the ambient samples might be from local potential sources at lower sampling heights as well as regional potential sources at higher sampling heights during this measurement campaign.► PM10 samples were collected at 4 heights (10 m, 40 m, 120 m and 220 m). ► Secondary sulfate and nitrate were the important sources. ► PM10 samples were mainly contributed from local potential sources at lower height. ► PM10 samples were attributed more from regional potential sources at higher height.
Keywords: Vertical variability; Sources; Chemical mass balance; Conditional probability function; Potential source contribution function
Ultrafine particles, and PM2.5 generated from cooking in homes by Man-Pun Wan; Chi-Li Wu; Gin-Nam Sze To; Tsz-Chun Chan; Christopher Y.H. Chao (pp. 6141-6148).
Exposure to airborne particulate matters (PM) emitted during cooking can lead to adverse health effects. An understanding of the exposure to PM during cooking at home provides a foundation for the quantification of possible health risks. The concentrations of airborne particles covering the ultrafine (14.6–100 nm) and accumulation mode (100–661.2 nm) size ranges and PM2.5 (airborne particulate matters smaller than 2.5 μm in diameter) during and after cooking activities were measured in 12 naturally ventilated, non-smoking homes in Hong Kong, covering a total of 33 cooking episodes. The monitored homes all practiced Chinese-style cooking. Cooking elevated the average number concentrations of ultrafine particles (UFPs) and accumulation mode particles (AMPs) by 10 fold from the background level in the living room and by 20–40 fold in the kitchen. PM2.5 mass concentrations went up to the maximum average of about 160 μg m−3 in the kitchen and about 60 μg m−3 in the living room. Cooking emitted particles dispersed quickly from the kitchen to the living room indicating that the health impact is not limited to occupants in the kitchen. Particle number and mass concentrations remained elevated for 90 min in the kitchen and for 60 min in the living room after cooking. Particles in cooking emissions were mainly in the ultrafine size range in terms of the number count while AMPs contributed to at least 60% of the surface area concentrations in the kitchen and 73% in the living room. This suggests that AMPs could still be a major health concern since the particle surface area concentration is suggested to have a more direct relationship with inhalation toxicity than with number concentration. Particle number concentration (14.6–661.2 nm) in the living room was about 2.7 times that in the outdoor environment, suggesting that better ventilation could help reduce exposure.► Ultrafine particles and PM2.5 were measured in 12 homes in Hong Kong, covering a total of 33 cooking episodes. ► Cooking emitted particles can disperse quickly from the kitchen to the living room. ► Particles in cooking emissions were mainly in the ultrafine size range in terms of number. ► Accumulation mode particles are the major contributors for surface area concentration.
Keywords: Ultrafine particles; Fine particles; PM; 2.5; Site measurement; Surface area concentration; Hong Kong
Assimilation of observations of radiation level into an atmospheric transport model: A case study with the particle filter and the ETEX tracer dataset by Paul H. Hiemstra; Derek Karssenberg; Arjan van Dijk (pp. 6149-6157).
Atmospheric transport models and observations from monitoring networks are commonly used aids for forecasting spatial distribution of contamination in case of a radiological incident. In this study, we assessed the particle filter data-assimilation technique as a tool for ensemble forecasting the spread of radioactivity. We used measurements from the ETEX-1 tracer experiment and model results from the NPK-Puff atmospheric dispersion model. We showed that assimilation of observations improves the ensemble forecast compared to runs without data assimilation. The improvement is most prominent for nowcasting: the mean squared error was reduced by a factor of 7. For forecasting, the improvement of the mean squared error resulting from assimilation of observations was found to dissipate within a few hours. We ranked absolute model values and observations and calculated the mean squared error of the ranked values. This measure of the correctness of the pattern of high and low values showed an improvement for forecasting up to 48 h. We conclude that the particle filter is an effective tool in better modeling the spread of radioactivity following a release.► We used the particle filter to model the ETEX tracer dataset. ► The particle filter is successful in modeling the pattern of tracer concentration. ► The particle filter is less successful in modeling absolute concentration values. ► The particle filter is an effective tool for modeling the spread of radioactivity.
Keywords: Particle filter; Data assimilation; Atmospheric transport model; Ensemble forecasting; ETEX dataset; Nuclear release
Characterizing priority polycyclic aromatic hydrocarbons (PAH) in particulate matter from diesel and palm oil-based biodiesel B15 combustion by Nestor Y. Rojas; Harvey Andrés Milquez; Hugo Sarmiento (pp. 6158-6162).
A set of 16 priority polycyclic aromatic hydrocarbons (PAH) associated with particulate matter (PM), emitted by a diesel engine fueled with petroleum diesel and a 15%-vol. palm oil methyl ester blend with diesel (B15), were determined. PM was filtered from a sample of the exhaust gas with the engine running at a steady speed and under no load. PAH were extracted from the filters using the Soxhlet technique, with dichloromethane as solvent. The extracts were then analyzed by gas chromatography using a flame ionization detector (FID). No significant difference was found between PM mass collected when fueled with diesel and B15. Ten of the 16 PAH concentrations were not reduced by adding biodiesel: Benz(a)anthracene, benzo(a)pyrene, benzo(b)fluoranthene, chrysene, dibenz(a,h)anthracene, fluoranthene, fluorene, indeno(1,2,3-c,d)pyrene, naphthalene and phenanthrene. The acenaphthene, acenaphthylene and anthracene concentrations were 45%–80% higher when using diesel, whereas those for benzo(k)fluoranthene, benzo(g,h,i)perylene and pyrene were 30%–72% higher when using the B15 blend. Even though the 16 priority-PAH cumulative concentration increased when using the B15 blend, the total toxic equivalent (TEQ) concentration was not different for both fuels.► Particulate and 16 priority PAH emissions from diesel and biodiesel B15 combustion were measured. ► No difference in particulate matter mass emitted was found. ► The concentrations of 8 priority HAP were lower when using B15. ► No significant difference in the total toxicity equivalent concentration was found.
Keywords: Polycyclic aromatic hydrocarbons; Biodiesel; Particulate matter; Toxicity equivalent factor
Aerosol radiative forcing deduced from observations and models over an urban location and sensitivity to single scattering albedo by Rohit Srivastava; S. Ramachandran; T.A. Rajesh; Sumita Kedia (pp. 6163-6171).
Aerosol radiative forcing at the Earth’s surface is estimated by simultaneous measurements of broad-band global fluxes and aerosol optical depths (AODs) over an urban location in western India during 2008. AODs at 0.5 μm show large seasonal variability with higher values (0.52) during monsoon. Higher AOD during monsoon is mainly due to increase in relative humidity which overwhelms the effects of wet removal of aerosols and addition of sea salt. Forcing efficiency for monsoon season is found to be lower as compared to other seasons. Surface aerosol radiative forcing has the highest value of −44 Wm−2 during monsoon. The forcing values are similar for model independent and semi model dependent methods. Single scattering albedo (SSA) is higher in monsoon followed by pre-monsoon, winter and lowest in post-monsoon. SSA derived from ground-based measurements (aethalometer and nephelometer) is lower than columnar SSA estimated from Goddard Chemistry Aerosol Radiation and Transport (GOCART) model and derived from Ozone Monitoring Instrument (OMI). Lower radiative forcing at the surface is attributed to higher SSA during pre-monsoon. Model estimated surface forcing using ground-based SSA is about two times higher than observed forcing for different seasons except for monsoon. However, model estimated forcing using columnar SSA agrees well with observations except in monsoon. The differences during monsoon are probably caused by overestimation of SSA from GOCART and OMI. The study reveals that a small change in SSA can lead to significant change in aerosol forcing.► Aerosol forcing and seasonal variation obtained using the measured flux. ► Different methodologies applied to estimate forcing from measured flux. ► Increase in AOD due to RH increase overwhelms BC removal and addition of sea salt. ► Forcing using columnar SSA match well with observation in all seasons except monsoon.
Keywords: Observations; Model estimates; Aerosol radiative forcing; Single scattering albedo; Urban region
Investigation on the potential generation of ultrafine particles from the tire–road interface by Marcel Mathissen; Volker Scheer; Rainer Vogt; Thorsten Benter (pp. 6172-6179).
There has been some discussion in the literature on the generation of ultrafine particles from tire abrasion of studded and non-studded tires tested in the laboratory environment.In the present study, the potential generation of ultrafine particles from the tire road interface was investigated during real driving. An instrumented Sport Utility Vehicle equipped with summer tires was used to measure particle concentrations with high temporal resolution inside the wheel housing while driving on a regular asphalt road. Different driving conditions, i.e., straight driving, acceleration, braking, and cornering were applied. For normal driving conditions no enhanced particle number concentration in the size range 6–562 nm was found. Unusual maneuvers associated with significant tire slip resulted in measurable particle concentrations. The maximum of the size distribution was between 30 and 60 nm. An exponential increase of the particle concentration with velocity was measured directly at the disc brakes for full stop brakings. A tracer gas experiment was carried out to estimate the upper limit of the emission factor during normal straight driving.► New experimental setup to measure ultrafine particles from the tire road interface. ► Emission factor for steady straight driving estimated with a tracer gas experiment. ► Compared to exhaust emissions (DPF-car), the emission factor is of minor importance. ► Under normal driving conditions no enhanced particle generation was found. ► Under extreme driving conditions, ultrafine particles (30–80 nm) could be measured.
Keywords: Tire wear; Ultrafine particles; Size distribution; Emission factor; Brake wear
Emissions inventory of anthropogenic PM2.5 and PM10 in Delhi during Commonwealth Games 2010 by Saroj Kumar Sahu; Gufran Beig; Neha S. Parkhi (pp. 6180-6190).
As part of the System of Air quality Forecasting and Research (SAFAR) project developed for air quality forecasting during the Commonwealth Games (CWG) – 2010, a high resolution Emission Inventory (EI) of PM10 and PM2.5 has been developed for the metropolitan city Delhi for the year 2010. The comprehensive inventory involves detailed activity data and developed for a domain of 70km×65km with a 1.67km×1.67km resolution covering Delhi and surrounding region using Geographical Information System (GIS) technique. The major sectors considered are, transport, thermal power plants, industries, residential and commercial cooking along with windblown road dust which is found to play a major role for Delhi environment. It has been found that total emissions of PM10 and PM2.5 including wind blown dust over the study area are found to be 236Ggyr−1 and 94Ggyr−1 respectively. The contribution of windblown road dust is found to be as high as 131Ggyr−1 for PM10.► A high resolution inventory of PM10 and PM2.5 are developed for mega city Delhi. ► Inventories are used for air quality forecasting during Commonwealth Games 2010. ► Inventory incorporate the activity data generated during one year field campaign. ► Total emission of PM10 and PM2.5 is found to be 236Ggyr−1 and 94Ggyr−1 for year 2010. ► Surprisingly emission from paved and unpaved roads is as high as 131Ggyr−1 for PM10.
Keywords: Particulate matter; Emission inventory; Pollution; GIS
Characterization of biogenic volatile organic compounds (BVOCs) in cleaning reagents and air fresheners in Hong Kong by Yu Huang; Steven Sai Hang Ho; Kin Fai Ho; Shun Cheng Lee; Yuan Gao; Yan Cheng; C.S. Chan (pp. 6191-6196).
Biogenic volatile organic compounds (BVOCs) emitted from cleaning products and air fresheners indoors are prone to oxidation resulting in the formation of secondary pollutants that can pose health risks on residents. In this study, a solid phase microextraction (SPME) coupled with gas chromatography/mass spectrometry (SPME-GC/MS) method was applied for the determination of BVOCs compositions in three categories of cleaning products including floor cleaners (FC), kitchen cleaners (KC) and dishwashing detergents (DD), and also air fresheners (AF). The analysis results demonstrated that chemical composition and concentration of individual BVOC varied broadly with household products in the view of their different functions and scents as indicated on the labels. The concentration of total BVOCs for sample FC1 was the highest up to 4146.0 μg g−1, followed by FC2 of 264.6 μg g−1, FC4 of 249.3 μg g−1 and FC3 of 139.2 μg g−1.d-limonene was the most abundant detected BVOCs in KC samples with the chemical composition varying from 19.6 ± 1.0 to 1513.0 ± 37.1 μg g−1. For dishwashing detergents, onlyd-limonene was detected and quantified. The BVOCs compositions of air freshener samples are much more complicated. It was estimated that the consumption of floor cleaners contributed 51% of the total BVOCs amount indoors in Hong Kong, followed by air fresheners 42%, kitchen cleaners 5% and dishwashing detergents 2%.► BVOCs compositions in cleaning products and air fresheners were determined by SPME-GC/MS method. ► Concentration of individual BVOC varied broadly with different household products. ► The use of floor cleaners was estimated to contribute most to total indoor BVOCs. ► Secondary products formation potential varied in the order AF > FC > KC > DD in the presence of ozone.
Keywords: Biogenic volatile organic compounds (BVOCs); Cleaning products and air fresheners; Chemical compositions; Solid phase microextraction (SPME)
Chemical mechanism and kinetics study on the ocimene ozonolysis reaction in atmosphere by Xiaomin Sun; Jing Bai; Yuyang Zhao; Chenxi Zhang; Yudong Wang; Jingtian Hu (pp. 6197-6203).
The ocimene ozonolysis reaction is one of the most important processes for the formation of secondary organic aerosol (SOA). In this paper, molecular orbital theory has been performed for the reaction of ocimene with O3, and the detailed reaction mechanisms of active intermediates with H2O or NO are also presented. The geometry parameters and vibrational frequencies of the stationary points are calculated at the MPWB1K level with the 6-31G(d,p) basis set. Single-point energy calculations are carried out at the MPWB1K/6-311+G(3df,2p) level. On the basis of the quantum chemical information, the Rice–Ramsperger–Kassel–Marcus (RRKM) theory and the canonical variational transition state theory (CVT) with small-curvature tunneling effect (SCT) are used to calculate the rate constants over the temperature range of 200–800 K. The arrhenius formulas of rate constants with the temperature are fitted, which can provide helpful information for the model simulation study. The atmospheric lifetimes of the reaction species are estimated according to the rate constants.► The reaction of CC(CH3)2 has a large proportion among three double bonds. ► The H2O molecule acts as an activator in the OH group transport process. ► Most of the obtained products have high polarity and water-solubility.
Keywords: Ozonolysis reaction of ocimene; SOA formation mechanism; Chemical mechanism and kinetics study; Rate constant; Atmospheric lifetime
Pig feeding strategy coupled with effluent management – fresh or stored slurry, solid phase separation – on methane potential and methane conversion factors during storage by Guillaume Jarret; José Martinez; Jean-Yves Dourmad (pp. 6204-6209).
In the guideline for the determination of methane (CH4) emission from animal manure (IPCC) the amount of CH4 emitted is generally calculated according to an equation combining the amount of organic matter (OM) or volatile solids excreted, the ultimate CH4 potential ( B0) of excreta and a system-specific methane conversion factor (MCF, %) that reflects the portion of B0 that is really converted into CH4. The objective of the present study was to investigate the effect of the modification of dietary crude protein and fibre levels on B0 of pig slurry and on subsequent MCF according to different strategies of slurry management. Five experimental diets differing mainly in their crude protein and fibre content were compared. Two types of measurement of CH4 emission were performed. The first was the measurement of B0 of slurry using biomethanogene potential (BMP) test. The second consisted in a storage simulation, which was performed on different kinds of effluents: fresh slurry (FSl), stored slurry (SSl), and faeces mixed with water (FaW). The type of diet and the type of effluent affected ( P < 0.001) CH4 production after 30, 50 and 100 days. Moreover, the interaction between type of effluent and type of diet was significant for CH4 emission and for MCF. CH4 production was the highest for BMP, the average production of CH4 during storage from FaW, FSl and SSl samples representing 77%, 58% and 64% of the B0 value. The dynamic of CH4 production during BMP tests was rather similar for all dietary treatments whereas it differed for storage simulation studies with significant effects of dietary CP and fibre contents. The results from this study indicate that the type of diet has a significant but rather limited effect on B0 value of effluent. The effect of diet is much more marked on MCF, with lower values for high protein diets, and higher values for high fibre diets. MCF is also affected by manure management, the values measured on separated faeces from urine being much higher than for slurry.► The amount of organic matter and nitrogen excreted per pig is affect by the diet. ► Dynamic of effluent methane production differs according to diet composition. ► Dietary protein and fibre affect methane conversion factor (MCF). ► MCF is also affected by manure management with higher values for separated faeces.
Keywords: Diet; Effluent; Fibre; Protein; Methane; Pig
Trace elements and lead isotopic composition of PM10 in Lhasa, Tibet by Zhiyuan Cong; Shichang Kang; Chunling Luo; Qing Li; Jie Huang; Shaopeng Gao; Xiangdong Li (pp. 6210-6215).
This paper presents the first detailed investigation on airborne trace metals and their potential major sources at Lhasa, the largest city in Tibetan Plateau (TP). The whole year PM10 samples were collected during September 2007 and August 2008. The annual average concentration of PM10 in Lhasa was 51.8±42.5μgm−3, lower than those of major Asian cities. Distinct seasonal patterns were observed in PM10 concentration, with higher concentrations in winter, and lower in summer. The mean elemental concentrations were generally comparable with other urban areas, but significantly higher than those from a remote site in TP (i.e., Nam Co). Crustal elements, including Na, Mg, Al, K, Ca, Sc, Ti, V, Mn, Fe, As and Ba, had similar seasonal patterns in PM10, while other elements, such as Cr, Co, Ni, Cu, Zn, and Cd, had less distinct seasonal variations, suggesting more anthropogenic inputs of the latter group. The result of principle component analysis (PCA) on trace elements demonstrated that fugitive dusts, traffic emissions and waste incineration activities were probably the major sources of anthropogenic metals in the atmosphere at Lhasa. The Pb isotopic compositions revealed that the metal was mainly originated from nature background with a minor contribution from the cement factory. The data obtained in this study can be useful for making pollution control strategies in the city, and also valuable for trace element studies in other environmental medium, such as snow, ice core, and lake sediments in the TP region.►The annual PM10 loading in Lhasa was lower than major Asian cities. ►Elemental concentrations and Pb isotope in PM10 were analyzed by ICP-MS. ►Fugitive dusts, traffic emissions and waste incineration were major sources for metals. ► Pb was mainly originated from nature background with a minor contribution from the cement factory.
Keywords: Atmospheric aerosols; Trace elements; Pb isotope; Lhasa; Tibetan Plateau
Tracheobronchial and alveolar dose of submicrometer particles for different population age groups in Italy by G. Buonanno; G. Giovinco; L. Morawska; L. Stabile (pp. 6216-6224).
Exposure to ultrafine particles (diameter less than 100 nm) is an important topic in epidemiological and toxicological studies. This study used the average particle number size distribution data obtained from our measurement survey in major microenvironments, together with the people activity pattern data obtained from the Italian Human Activity Pattern Survey to estimate the tracheobronchial and alveolar dose of submicrometer particles for different population age groups in Italy. We developed a numerical methodology based on Monte Carlo method, in order to estimate the best combination from a probabilistic point of view. More than 106 different cases were analyzed according to a purpose built sub-routine and our results showed that the daily alveolar particle number and surface area deposited for all of the age groups considered was equal to 1.5 × 1011 particles and 2.5 × 1015 μm2, respectively, varying slightly for males and females living in Northern or Southern Italy. In terms of tracheobronchial deposition, the corresponding values for daily particle number and surface area for all age groups was equal to 6.5 × 1010 particles and 9.9 × 1014 μm2, respectively. Overall, the highest contributions were found to come from indoor cooking (female), working time (male) and transportation (i.e. traffic derived particles) (children).► We estimate particle number and surface area deposition for different age groups and lifestyles through an indirect approach. ► Particle number distribution range for each microenvironment was obtained from our measurement survey data. ► Deposition increases as a function age group, with the maximum value observed for 41–65 years old. ► Major contributions arise from indoor cooking and eating times (female), working time (male) and transportation (children).
Keywords: Tracheobronchial particle deposition; Alveolar particle deposition; Ultrafine particle exposure; Time activity pattern; Monte Carlo method
Satellite-based estimates of ground-level fine particulate matter during extreme events: A case study of the Moscow fires in 2010 by Aaron van Donkelaar; Randall V. Martin; Robert C. Levy; Arlindo M. da Silva; Michal Krzyzanowski; Natalia E. Chubarova; Eugenia Semutnikova; Aaron J. Cohen (pp. 6225-6232).
We estimate fine particulate matter (PM2.5) concentrations daily using MODIS satellite observations of aerosol optical depth (AOD) for a major biomass burning event around Moscow during summer 2010. Evaluation of MODIS AOD with the Moscow AERONET site supports a MODIS-AOD error estimate of ±(0.05+0.2×AOD) for this event. However, since the smoke was often thick (AOD>4.0) and spatially variable, the standard MODIS algorithm incorrectly identifies some aerosol as cloud. We test relaxed cloud screening criteria that increase MODIS coverage by 21% and find excellent agreement with coincident operational retrievals ( r2=0.994, slope=1.01) with no evidence of false aerosol detection. We relate the resultant MODIS AOD to PM2.5 using aerosol vertical profiles from the GEOS-Chem chemical transport model. Our estimates are in good agreement with PM2.5 values estimated from in-situ PM10 ( r2=0.85, slope=1.06), and we find that the relationship between AOD and PM2.5 is insensitive to uncertainties in biomass burning emissions. The satellite-derived and in-situ values both indicate that peak daily mean concentrations of approximately 600μgm−3 occurred on August 7, 2010 in the Moscow region of the Russian Federation. We estimate that exposure to air pollution from the Moscow wildfires may have caused hundreds of excess deaths.► Satellite-derived estimates of PM2.5 are effective during Moscow fires in summer 2011. ► Relaxed MODIS AOD cloud screening improves coverage/agreement during major fire event. ► Relaxed MODIS cloud screening shows good agreement with operational product. ► Peak daily PM2.5 of 600μgm−3 in the Moscow region on August 7th, 2011. ► The 2011 Moscow wildfires likely caused hundreds of excess deaths.
Keywords: MODIS; PM; 2.5; Moscow wildfires; Aerosol optical depth
Comparison of laser-induced fluorescence and chemiluminescence measurements of NO2 at an urban site by Hiroyuki Suzuki; Yuka Miyao; Tomoki Nakayama; Julie K. Pearce; Yutaka Matsumi; Kenshi Takahashi; Kazuyuki Kita; Kenichi Tonokura (pp. 6233-6240).
In situ measurements of nitrogen dioxide (NO2) concentrations were conducted at an urban site in Tokyo (35°71′N, 139°76′E), Japan during the summers of 2007–2009. A chemiluminescence instrument equipped with a molybdenum oxide converter (Mo-CL) and a laser-induced fluorescence (LIF) instrument were used simultaneously for determining the ambient NO2 concentrations. A tight linear correlation between the NO2 concentrations determined by the LIF and Mo-CL techniques was evident except for high ozone concentration periods over 50 ppbv. During the high ozone episodes, correlation plots of the NO2 concentrations between Mo-CL and LIF techniques indicated an overestimation of Mo-CL NO2. To examine in detail the systematic differences between two techniques, a thermal dissociation laser-induced fluorescence (TD-LIF) instrument was employed in the summer of 2009 to measure total peroxy nitrates (ΣPNs) and total reactive nitrogen (NO z). We found that the ΣPNs concentrations correlated well with the discrepancies in NO2 concentrations determined by the Mo-CL and LIF techniques. This result suggests that peroxy nitrate species significantly contribute to the observed interference in the Mo-CL measurements under high O3 concentrations in our observation at the urban site in Tokyo.► In situ measurements of nitrogen dioxide were conducted at an urban site. ► A chemiluminescence and a laser-induced fluorescence instruments were used. ► During high ozone episodes, the chemiluminescence method overestimated NO2. ► A thermal dissociation laser-induced fluorescence instrument was also employed. ► Peroxy nitrate species contribute to interferences in chemiluminescence measurements.
Keywords: Nitrogen oxides; Chemiluminescence; Thermal dissociation laser-induced fluorescence; Reactive nitrogen; Tokyo
Application of WRF/Chem-MADRID for real-time air quality forecasting over the Southeastern United States by Ming-Tung Chuang; Yang Zhang; Daiwen Kang (pp. 6241-6250).
A Real-Time Air Quality Forecast (RT-AQF) system that is based on a three-dimensional air quality model provides a powerful tool to forecast air quality and advise the public with proper preventive actions. In this work, a new RT-AQF system is developed based on the online-coupled Weather Research and Forecasting model with Chemistry (WRF/Chem) with the Model of Aerosol Dynamics, Reaction, Ionization, and Dissolution (MADRID) (referred to as WRF/Chem-MADRID) and deployed in the southeastern U.S. during May–September, 2009. Max 1-h and 8-h average ozone (O3) and 24-h average fine particulate matter (PM2.5) are evaluated against surface observations from the AIRNow database in terms of spatial distribution, temporal variation, and domain-wide and region-specific discrete and categorical performance statistics. WRF/Chem-MADRID demonstrates good forecasting skill that is consistent with current RT-AQF models. The overpredictions of O3 and underprediction of PM2.5 are likely due to uncertainties in emissions such as those of biogenic volatile organic compounds (BVOCs) and ammonia, inaccuracies in simulated meteorological variables such as 2-m temperature, 10-m wind speed, and precipitation, and uncertainties in the boundary conditions. Sensitivity simulations show that the use of the online BVOC emissions can improve PM2.5 forecast in areas with high BVOC emissions and adjusting lateral boundaries can improve domain-wide O3 and PM2.5 predictions. Several limitations and uncertainties are identified to further improve the model’s forecasting skill.► A New RT-AQF Model based on online-coupled WRF/Chem with an advanced aerosol module. ► A good forecasting skill for O3 and PM2.5 that is consistent with other RT-AQF models. ► The use of the online BVOC emissions can potentially improve PM2.5 forecast. ► The model is sensitive to boundary conditions.
Keywords: O; 3; PM; 2.5; WRF/Chem-MADRID; Online-coupled model; Discrete evaluation; Categorical evaluation
A study on the extent of neutralization of sulphate aerosol through laboratory and field experiments using an ATOFMS and a GPIC by Xiaohong Yao; Peter J.G. Rehbein; Colin J. Lee; Greg J. Evans; Joel Corbin; Cheol-Heon Jeong (pp. 6251-6256).
Extent of neutralization (EoN) of atmospheric aerosol is an important parameter in understanding related nucleation mechanisms, acid-catalyzed reactions and gas–aerosol partitioning. Ion m/ z −195(HSO4H2SO4−) detected by the Aerosol Time-of-Flight Mass Spectrometer (ATOFMS) has been used as an indicator of incompletely-neutralized sulphate aerosol, but there are no laboratory data to support this assumption. In this study, experiments using artificially generated sulphuric acid nucleated aerosol and metal sulphate aerosol across a range of EoN found that the peak area ratio and hit ratio of ion m/ z −195(HSO4H2SO4−) to ion m/ z −97(HSO4−) detected by the ATOFMS increased with decreasing EoN. Area ratio and hit ratio are sensitive to EoN at the low and high value zones, respectively. In ambient air measured by the ATOFMS and a Gas Particle Ion Chromatograph (GPIC) in Toronto, Canada, ion m/ z −195 was always detected in ammonium sulphate aerosol, and its hit number and peak area varied widely, regardless of EoN indicated by the equivalent ratio ofNH4+ to(SO42−+NO3−). Thus, ion m/ z −195 alone is not an indicator of acidic sulphate aerosol. The combined approach using the ATOFMS and the GPIC found that cloud-processing formed incompletely-neutralized acidic sulphate aerosol in 2 out of 35 days sampled in winter in Toronto, Canada. It is interesting that the two episodes both occurred at night. Formation of incompletely-neutralized acidic sulphate aerosol caused a decrease in the concentration of particulate nitrate. This can be explained by acidic sulphate aerosol reacting with ammonium nitrate, leading to the release of HNO 3 to the gas phase. It was also found that the GPIC results occasionally suffered a positive artifact ofNH4+ concentration caused by the clogging-induced high back-pressure in the instrument.► This work provides laboratory data on incompletely-neutralized sulphate aerosol and m/ z −195 ion. ► Field measurements are used to evaluate reliability of using m/ z −195 ion as a marker of acidity. ► This study improves reliability in interpreting atmospheric processes associated with acid aerosols.
Keywords: Extent of neutralization; NH; 4; +; SO; 4; 2−; NO; 3; −; ATOFMS
Turbulent diffusion with gravitational settling in a capped atmospheric boundary layer – An analytical solution by William A. Hoppel; Peter F. Caffrey (pp. 6257-6260).
The general solution of the turbulent diffusion equation for a capped atmospheric boundary layer and including gravitational settling of large particles is examined. A revised analytical solution that corrects problems with the earlier work of is presented.
Keywords: Diffusion; Aerosol; Boundary layer; Gravitational settling
Effect of drought stress on isoprene emission from two major Quercus species native to East Asia by Akira Tani; Daisuke Tozaki; Motonori Okumura; Susumu Nozoe; Takashi Hirano (pp. 6261-6266).
Effect of drought on isoprene emission from 2 major Quercus species native to East Asia is investigated. Three individuals of Quercus serrata and 2 individuals of Quercus crispula continued to emit isoprene under moderate and severe drought conditions, although the emission rates were lower than under normal conditions. Diurnal variation in the isoprene emission rates was monitored in real-time when temperature and light intensity were changed stepwise to imitate natural conditions. Under normal and moderate drought conditions, isoprene emission showed hysteresis with regard to the environmental parameters, but generally followed the common G93 model. Under severe drought conditions, isoprene emission rates were not explained using given coefficients in the G93 model, probably due to a depletion of isoprene substrate.
Keywords: Quercus crispula; Quercus serrata; PTR-MS; G93 model; Light; Temperature