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Abstract: Cooling tower emissions are harmful for several reasons such as air polluting, wetting, icing and solid particle deposition, but mainly due to human health hazards (i.e. Legionella). There are several methods for measuring drift drops. This paper is focussed on the sensitive paper technique, which is suitable in low drift scenarios and real conditions. The lack of an automatic classification method motivated the development of a digital image process algorithm for the Sensitive Paper method. This paper presents a detailed description of this method, in which, drop-like elements are identified by means of the Canny edge detector combined with some morphological operations. Afterwards, the application of a J48 decision tree is proposed as one of the most relevant contributions. This classification method allows us to discern between stains whose origin is a drop and stains whose origin is not a drop. The method is applied to a real case and results are presented in terms of drift and PM10 emissions. This involves the calculation of the main features of the droplet distribution at the cooling tower exit surface in terms of drop size distribution data, cumulative mass distribution curve and characteristic drop diameters. The Log-normal and the Rosin–Rammler distribution functions have been fitted to the experimental data collected in the tests and it can been concluded that the first one is the most suitable for experimental data among the functions tested (whereas the second one is less suitable). Realistic PM10 calculations include the measurement of drift emissions and Total Dissolved Solids as well as the size and number of drops. Results are compared to the method proposed by the U.S. Environmental Protection Agency assessing its overestimation. Drift emissions have found to be 0.0517% of the recirculating water, which is over the Spanish standards limit (0.05%). [Copyright &y& Elsevier]

Several emission inventories exist for Europe, which include emissions originating from ship traffic in European sea areas. However, few comparisons of these inventories, in particular focusing on specific emission sectors like shipping, exist in literature. Therefore, the aim of this paper is to review and compare commonly used, and freely available, emission inventories available for the European domain, specifically for shipping and its main pollutants (NOx, SOx and PM10). Five different inventories were considered which include shipping activity: 1) EMEP; 2) TNO-MACC_III; 3) E-PRTR; 4) EDGAR and 5) STEAM. The inventories were initially compared in terms of total emission values and their spatial distribution. The total emission values are largely in agreement (with the exception of E-PRTR), however, the spatial representation shows significant differences in the emission distribution, in particular over the Mediterranean region. As for the contribution of shipping to overall emissions, this sector represent on average 16%, 11% and 5% of total NOx, SOx and PM10 emissions, respectively. Recommendations are given regarding the specific use of each available inventory. [ABSTRACT FROM AUTHOR]

Source term estimation for atmospheric dispersion deals with estimation of the emission strength and location of an emitting source using all available information, including site description, meteorological data, concentration observations and prior information. In this paper, Bayesian methods for source term estimation are evaluated using Prairie Grass field observations. The methods include those that require the specification of the likelihood function and those which are likelihood free, also known as approximate Bayesian computation (ABC) methods. The performances of five different likelihood functions in the former and six different distance measures in the latter case are compared for each component of the source parameter vector based on Nemenyi test over all the 68 data sets available in the Prairie Grass field experiment. Several likelihood functions and distance measures are introduced to source term estimation for the first time. Also, ABC method is improved in many aspects. Results show that discrepancy measures which refer to likelihood functions and distance measures collectively have significant influence on source estimation. There is no single winning algorithm, but these methods can be used collectively to provide more robust estimates. [ABSTRACT FROM AUTHOR]

Abstract: In this paper a custom-developed model of dispersion of pollutants is presented. The proposed approach is based on both a Lagrangian particle model and an urban-scale diagnostic model of the air velocity field. Both models constitute a part of an operational air quality assessment system. The proposed model is validated by comparing its computed results with the results of measurements obtained in a wind tunnel reflecting conditions of the Mock Urban Setting Test (MUST) experiment. Commonly used measures of errors and model concordance are employed and the results obtained are additionally compared with those obtained by other authors for CFD and non-CFD class models. The obtained results indicate that the validity of the model presented in this paper is acceptable. [Copyright &y& Elsevier]

Abstract: This paper, which focuses on diesel trucks, is the third in a series of three papers published in Atmospheric Environment to understand vehicle emissions in China by conducting on-board emission measurements. Diesel trucks are a significant source of emissions in ambient air, especially for NOx. Recently, China announces an aggressive target to reduce national NOx emissions by 10% from 2010 to 2015 in the “Twelfth Five-Year Plan (2011–2015)” and diesel vehicles are identified as a key target for NOx control. However, the understanding of the real-world emissions of diesel trucks is limited. In this study, we measured HC, CO, NOx, and PM2.5 emissions from 175 diesel trucks of different sizes and technologies in five Chinese cities during 2007 and 2011, and generated emission factors on the basis of the measurements. The results show that the HC, CO, and PM2.5 emission factors have been reduced significantly as the emission standards become more stringent from Euro 0 to Euro IV, but the NOx emission factors change differently. Euro II trucks have 3–6% higher NOx emission levels than Euro I technologies and Euro III trucks fail to show a reduction as regulated by the standards. More stringent NOx requirements (e.g. Euro IV) for diesel vehicles need to be enforced. The comparison with the emission factors used in recent emission inventory studies shows that these inventories may have overestimated or underestimated diesel emissions for the years after 2006. This study emphasizes the importance of conducting local measurement research to improve the accuracy of the estimates of mobile emissions in China. [Copyright &y& Elsevier]

Abstract: This paper highlights the similarities and differences in how emission inventories and datasets were developed and processed across North America and Europe for the Air Quality Model Evaluation International Initiative (AQMEII) project and then characterizes the emissions for the two domains. We focus specifically on the creation of “model-ready” gridded emission datasets for 2006 across the two continental study domains. The practice of creating and processing the two inventories is discussed with a focus on emission factors, spatial allocation, temporal variability, speciation of PM and VOCs, and the mechanics of distributing the data and supporting emission algorithms to the modeling community. The spatial and temporal distribution on common scales is compared for the pollutants of primary concern: NOx, VOCs, SO2, PM2.5, CO, and NH3. Because of differences of population distribution, emissions across North America tend to be more heterogeneous in spatial coverage than in Europe. The temporal patterns in the estimated emissions are largely the result of assumptions used to characterize human activity, with the exception of “natural” emissions, which are modulated by meteorological variability, and emissions from large electric generating units in the U.S., which have the benefit of continuous emission monitors that provide hourly resolved profiles. Emission estimates in both study domains are challenged by several important but poorly characterized emission source sectors, notably road dust, agricultural operations, biomass burning, and road transport. Finally, this paper provides insight on the strengths and weaknesses of emission inventory preparation practices on both continents. One important outcome of this comparison of 2006 emissions between Europe and North America is the greater understanding provided into how the emission estimates developed for the AQMEII project impact regional air quality model performance. [Copyright &y& Elsevier]

Abstract: Halocarbons are powerful greenhouse gases capable of significantly influencing the radiative forcing of the Earth’s atmosphere. Halocarbons are monitored in several stations which are globally distributed in order to assess long term atmospheric trends and to identify source regions. However, to achieve these aims the definition of background mixing ratios, i.e. the mixing ratio in a given air mass when the recent contribution of local sources is absent, is necessary. This task can be accomplished using different methods. This paper presents a statistical methodology that has been devised specifically for a mountain site located in Continental Europe (Monte Cimone, Italy), characterised by the vicinity of strong sources. The method involves the decomposition of the observed data distribution into a Gaussian distribution, representative of background values, and a Gamma distribution, ascribable to contribution from stronger sources. The method has been applied to a time series from a European marine remote station (Mace Head, Ireland) as well as to time series from Monte Cimone. A comparison of the methodology described in this paper with a well-established meteorological filtering procedure at Mace Head has shown an excellent agreement. A comparison of the baselines at Mace Head, Mt. Cimone and the Swiss alpine station of the Jungfraujoch highlighted the occurrence of a specific background concentration. Although this paper presents the application of the method to three hydrofluorocarbons, the proposed methodology can be extended to any long lived atmospheric component for which a long term time series is available and at any location even if affected by strong source regions. [Copyright &y& Elsevier]

The Air Quality Model Evaluation International Initiative Phase2 aims to intercompare online coupled regional-scale models over North America and Europe. The NMMB/BSC Chemical Transport Model (NMMB/BSC-CTM) is a fully online integrated system for meso- to global-scale applications under development at the Barcelona Supercomputing Center. The NMMB/BSC-CTM is applied to Europe for the year 2010 in the framework of the AQMEII-Phase2 intercomparison exercise. This paper presents a spatial, temporal and vertical evaluation of the gas-phase model results. This is the first time that the model has been evaluated on a regional scale over a whole annual cycle. The model is compared with available ground-based monitoring stations for relevant reactive gases, ozonesondes, and OMI and MOPITT satellite retrievals of NO 2 and CO. A comparative analysis of the present results and several European model evaluations is also presented here. The seasonal cycle for O 3 , NO 2 , SO 2 and CO is successfully reproduced by the model. The O 3 daily mean and daily maximum correlations for the analysed period are r = 0.68 and r = 0.75, respectively. The OMI tropospheric NO 2 column retrievals are well reproduced, capturing the most polluted areas over Europe throughout the whole year. Modelled SO 2 and CO surface concentrations are generally underestimated, especially during the winter months. Two different vertical configurations of the model (24 and 48 vertical layers) are also analysed. Although model results are very similar, the simulation configured with 48 vertical layers provides better results regarding surface O 3 concentrations during summer. Compared to previous model evaluations, the NMMB/BSC-CTM's performance corresponds to state-of-the-art regional air quality models. [ABSTRACT FROM AUTHOR]

In the framework of the AQMEII initiative WRF-Chem has been applied over Europe adopting two chemical configurations for the calendar year 2010. The first one employed the RADM2 gas-phase chemistry and MADE/SORGAM aerosol module, while the second one implemented the CBM-Z gaseous parameterization and MOSAIC aerosol chemistry. Configurations shared the same domain, meteorological setups and input data. The Comparison demonstrated that CBM-Z has a more efficient ozone-NO titration than RADM2 in regions with sufficiently high levels of NOx and VOCs. At the same time, CBM-Z is found to have a more effective NO 2 + OH reaction. The parameterization of the relative humidity of deliquescence point has a strong impact on HNO 3 and NO 3 concentrations over Europe, particularly over the sea. The MADE approach showed to be more efficient than MOSAIC. Differently, particulate sulfate and SO 2 ground concentrations proved to be more influenced by the heterogeneous SO 2 cloud oxidation. PM10 and PM2.5 have shown similar results for MOSAIC and MADE/SORGAM, even though some differences were found in the dust and sea salt size partitioning between modes and bins. Indeed, in MADE the sea salt was distributed only in the coarse fraction, while the dust emissions were distributed mainly in the fine fraction. Finally, different chemical mechanisms give different Aerosol Optical Depths (AOD). WRF-Chem is found to under predict the AODs in both configurations because of the misrepresentation of the dust coarse particle, as shown by the analysis of the relationship between the Angström exponent and the AOD bias. Differently, when the AOD is dominated by fine particles, the differences in model performance are more evident, with MADE/SORGAM generally performing better than MOSAIC. Indeed the higher availability of both sulfate and nitrate has a significant influence on reconstruction of the AOD estimations. This paper shows the great importance of chemical mechanisms in both gaseous and aerosols predictions, as well as in the calculation of aerosol optical properties. [ABSTRACT FROM AUTHOR]

In this paper, we studied concentrations of cloud condensation nuclei (CCN) and CCN activity measured at a suburb site of Qingdao in the North China during a non-heating period from 19 May to 3 June 2013 and a heating period from 6 November to 6 December 2013. Concentrations of CCN during the non-heating period were 3.1 ± 1.9 (mean ± standard deviation), 4.9 ± 3.4, 5.6 ± 3.9, 6.1 ± 4.3 and 6.5 ± 4.6 in unit of ×10 3 cm −3 at supersaturation (SS) of 0.2%, 0.4%, 0.6%, 0.8% and 1.0%, respectively. The corresponding CCN activities of atmospheric particles were 0.28 ± 0.17, 0.43 ± 0.24, 0.48 ± 0.26, 0.52 ± 0.27 and 0.54 ± 0.28, respectively. Concentrations of CCN during the heating period were 3.1 ± 1.3, 6.4 ± 2.3, 8.5 ± 2.9, 9.6 ± 3.5 and 10 ± 3.9 in unit of ×10 3 cm −3 at SS of 0.2%, 0.4%, 0.6%, 0.8% and 1.0%, respectively. The corresponding CCN activities were 0.11 ± 0.06, 0.24 ± 0.11, 0.31 ± 0.14, 0.35 ± 0.15 and 0.37 ± 0.15, respectively. At SS ≥ 0.4%, concentrations of CCN were significantly larger during the heating period than during the non-heating period with 95% confidence because of larger particle number concentrations associated. However, CCN activities were significantly lower during the heating period than during the non-heating period at each SS. The lower CCN activities during the heating period were analyzed in terms of origins, median mobility diameter and possible chemical composition of atmospheric particles. However, when new particle formation events during the heating and the non-heating periods were considered alone, CCN activities of grown new particles at the same size range sometimes appeared to be constant regardless of the heating or non-heating periods. [ABSTRACT FROM AUTHOR]

In this paper, we conducted a comparative study of new particle formation (NPF) events occurring between Qingdao and Toronto during spring. The extent of air pollution in Qingdao was much severer than that in Toronto, but the occurrence frequency of NPF events in Qingdao (41%) was almost same as that (42%) in Toronto. The geometric median diameter of new particles (D pg,1 ) increased up to >40 nm in 15 days out of the total 16 NPF days in Qingdao, the D pg,1 at least in eight days increased up to >60 nm and even reached >80 nm in two days. Two-stage growth was generally observed in these eight NPF events. The first-stage growth occurred in daytime and it was likely associated with formation of secondary organic aerosol (SOA) on basis of the modeling results. The second-stage growth was generally observed at nighttime when the modeling results showed increases of NH 4 + and NO 3 − in concentration together with SOA, implying that NH 4 NO 3 possibly played a role in the growth. In Toronto, the maximum D pg,1 of the observed new particles in all 13 NPF events was less than 50 nm. A slight second-stage growth of new particles was observed only in four days when either the increase of NH 4 + and NO 3 − in concentration or the increase of relative humidity occurred. The NPF events in Toronto less likely had a significant contribution to cloud condensation nuclei due to the small size of the observed new particles. [ABSTRACT FROM AUTHOR]

Abstract: Modeling the behavior of suspended particles in gaseous phase is important for diverse reasons; e.g. aerosol is usually the main subject of CFD simulations in clean rooms. Additionally, to determine the rate and sites of deposition of particles suspended in inhaled air, the motion of the particles should be predicted in lung airways. Meanwhile there are two basically different approaches to simulate the behavior of particles suspension, Lagrangian and Eulerian approaches. This study compares the results of these two approaches on simulating the same problem. An in-house particle tracking code was developed to simulate the motion of particles with Lagrangian approach. In order to simulate the same problem with Eulerian approach, the solution to the transport equation with appropriate initial and boundary conditions was used. In the first case study, diffusion of particles, initially positioned homogeneously on an infinite plane was modeled with both approaches and the results were compared and the mismatch between Lagrangian and Eulerian approaches was analyzed for different concentrations. In the second case study, airflow with parabolic velocity profile moving between two parallel plates was modeled with two approaches. The airflow initially contained a homogeneous suspension of particles and the plates were maintained at zero concentration. The concentration along the plates was compared between the two approaches and the differences in the performance of each approach were investigated, again for different initial concentrations. The overall results confirm that as particle concentration falls below a minimum amount, approximately 105 m−2, the results of the two approaches deviate considerably from each other and hence the Eulerian approach cannot be taken as an alternative for Lagrangian approach for low concentrations. For the third problem, we investigated the 3D particle flow in an expanding lung alveolus. It is shown that when the number of total released particles increases, the results of Eulerian approach can be used as an alternative to Lagrangian simulation. Since the number of particles existing in the lung alveolus in normal condition is much lower than this value, we concluded that Eulerian method cannot be applied to problems involving low concentration of particles. Although, the results of the Lagrangian problem may converge to the Eulerian one by increasing simulation time, but it is a hypothetical situation which not really exist in short time scale problems such as third case study in this paper. [Copyright &y& Elsevier]

Abstract: Resuspension of particles indoors increases the risk of consequent exposure through inhalation and non-dietary ingestion. Studies have been conducted to characterize indoor particle resuspension but results do not always agree, and there are still many open questions in this field. This paper reviews the recent research of indoor resuspension and summarizes findings to answer six critical questions: 1) How does the resuspension sources compared to other indoor sources; 2) How is resuspension determined and how does the resuspension measure change as a function of particle size; 3) What are the primary resuspension mechanisms; 4) What are the factors affecting resuspension; 5) What are the knowledge gaps and future research directions in this area; and 6) How can what we know about resuspension guide better exposure mitigation strategies? From synthesized results, we conclude that resuspension is an important source for indoor particulate matter, compared with other indoor sources. Among all existing quantification terms of resuspension, resuspension fraction has the least variation in its estimates by explicitly defining surface loading and walking frequency, and thus is recommended to be adopted in future research over other terms. Resuspension increases with particle size in the range of 0.7–10 μm, although differences exist in resuspension estimates by orders of magnitude. The primary mechanism of particle resuspension involves rolling detachment, and the adhesive forces can be greatly reduced by microscopic surface roughness. Particle resuspension is by nature complicated, affected by various factors and their interactions. There are still many open questions to be answered to achieve an understanding of resuspension fundamentals. Given the complex and multidisciplinary nature of resuspension, understanding indoor particle resuspension behavior requires cross-disciplinary participation from experts in aerosol science, textile science, surface chemistry, electrostatics, and fluid mechanics. [Copyright &y& Elsevier]

Abstract: This paper provides an account of observed variations in Black carbon (BC) mass concentrations and BC induced radiative forcing for the first time over a background Global Atmosphere Watch (GAW) site, Anmyeon in South Korea. BC concentrations were continuously measured over the site during January 2003–December 2004 periods using an Aethalometer. BC showed higher concentrations during 2003 in majority of the months (except in January, August and October). BC found to be showing higher concentrations in September 2003, with values reaching up to 3μgm−3 over the site. It also showed higher peaks in May and December in 2003. BC values were found to be comparatively less during wet season (July–August; especially august), which could be associated with the rainout and washout associated with the Changma season (summer monsoon). Optical Properties of Aerosols and Clouds (OPAC) model in combination with a radiative transfer model (SBDART) were used to estimate aerosol radiative forcing separately for composite aerosols (total aerosols) and solely for BC aerosols using chemical composition data sets of Total Suspended Particulates (TSP) and BC. The atmospheric forcing for composite aerosols found to be +14.9 to +25.9Wm−2 during spring, +13.4 to +20.4Wm−2 in summer, +12.9 to +19.1Wm−2 in autumn and +16 to +18.2Wm−2 during winter,respectively. The respective BC atmospheric forcings were +8.1 to +11.8Wm−2, +8.4 to +11.1Wm−2, +8.7 to +11.4Wm−2 and +8.8 to +11.7Wm−2 during spring, summer, autumn and winter. The study suggests that BC induced atmospheric forcing can contribute up to 88% of total aerosol induced atmospheric warming. [Copyright &y& Elsevier]

Abstract: Air–water partition coefficient (K AW) is one of the key parameters determining environmental behavior of Persistent Organic Pollutants (POPs). Experimentally measured values of K AW are still unavailable for majority of POPs, thus alternative methods of supplying data, including Quantitative Structure–Property Relationships (QSPR) modeling, are often in use. In this paper, applicability of two QSPR methods of predicting K AW were compared with each other in the context of further application of the predicted data in environmental transport and fate studies. According to the first (indirect) method, K AW is calculated from previously predicted values of octanol–water (K OW) and octanol–air (K OA) partition coefficients. In the second (direct) approach, K AW is calculated, based on the estimated value of Henry's law constant (K H) and then adjusted to ensure its consistency with the other two partition coefficients (K OW and K OA). Although the indirect method carries theoretically twice as much error as the direct method, when the predicted values of K AW are then utilized as an input to the environmental fate model The OECD P OV and LRTP Screening Tool, ver. 2.2, the indirect method elicits much higher and therefore much more restrictive values of overall persistence (P OV) and transfer efficiency (TE) than its equivalent (direct method). High uncertainties related to the application of the direct method result mainly from the necessary adjustment procedure. [Copyright &y& Elsevier]

Abstract: Accidental pollution events often threaten people's health and lives, and it is necessary to identify a pollutant source rapidly so that prompt actions can be taken to prevent the spread of pollution. But this identification process is one of the difficulties in the inverse problem areas. This paper carries out some studies on this issue. An approach using single sensor information with noise was developed to identify a sudden continuous emission trace pollutant source in a steady velocity field. This approach first compares the characteristic distance of the measured concentration sequence to the multiple hypothetical measured concentration sequences at the sensor position, which are obtained based on a source-three-parameter multiple hypotheses. Then we realize the source identification by globally searching the optimal values with the objective function of the maximum location probability. Considering the large amount of computation load resulting from this global searching, a local fine-mesh source search method based on priori coarse-mesh location probabilities is further used to improve the efficiency of identification. Studies have shown that the flow field has a very important influence on the source identification. Therefore, we also discuss the impact of non-matching flow fields with estimation deviation on identification. Based on this analysis, a method for matching accurate flow field is presented to improve the accuracy of identification. In order to verify the practical application of the above method, an experimental system simulating a sudden pollution process in a steady flow field was set up and some experiments were conducted when the diffusion coefficient was known. The studies showed that the three parameters (position, emission strength and initial emission time) of the pollutant source in the experiment can be estimated by using the method for matching flow field and source identification. [Copyright &y& Elsevier]

Abstract: In this paper, starting from a multivariate spatio-temporal array, containing air pollution data collected for the main pollutants at different monitoring sites over a 1-year period, a new approach is proposed to get a Multipollutant-Multisite Air Quality Index (AQI) time series. A two steps aggregation, related to space and to pollutants, is considered. For the first aggregation (spatial synthesis) a PCA is performed on data array opportunely rearranged, while the index I 2, proposed in Ruggieri and Plaia (2011), is used for the second aggregation (pollutant synthesis), obtaining the new index . Daily data of four air pollutants from the city of Palermo (Italy) are analyzed to test the performance of the new index. The index overcomes the main issues presented by other indices, many of which based on AQI computed by US EPA, considering the highest pollutant concentration adequately standardized. The comparison carried out shows that the index here proposed has a better performance than the synthesis by median-maximum (Bruno and Cocchi, 2002) and the synthesis by PCA along both space and pollutant dimensions, if the conjoint effect on air quality of the different pollutants has to be taken into account. [Copyright &y& Elsevier]

Abstract: Biogenic volatile organic compounds (BVOCs) are known to play an important role in atmospheric chemistry due to their high reactivity and high emission rates. Therefore, in recent decades, many efforts have been made to estimate the emission rates, composition and allocation of the BVOCs. Monoterpenes (MNTs) and sesquiterpenes (SQTs) are major groups of BVOCs and mainly emitted from coniferous trees. There is quite a few reports discussing the seasonality of basal emission rate, which is a normalized emission rate at a set of standard conditions (e.g. temperature, light intensity), of the BVOCs. Three field measurements were conducted using branch enclosure techniques to determine MNTs and SQTs emission measured from mature trees of Cryptomeria japonica and Chamaecyparis obtusa, which are the most dominant trees in Japan and account for about 40–50% of Japanese forest in leaf amount throughout the four seasons in southern Japan in 2010. The results are compared with the measurements for the same compound classes obtained at a suburban area of Tokyo, Japan in 2009. The seasonal variation in the basal emissions of MNTs from both tree species at Shiiba did not show significant seasonal changes. For both tree species, the variations in the basal emission of MNTs differ in the two sites, while those of SQTs showed relatively similar variations. Chemical composition of SQTs showed clear and continued seasonal variations, while MNTs did not show any clear seasonal variation for these tree species at both sites. It can be hypothesized that the emissions of BVOC classes (e.g. MNTs and SQTs) depend on leaf age. In this paper, we discuss about the seasonal variations in the basal emission rates and chemical compositions of BVOCs obtained from the two dominant coniferous tree species in Japan based on nine field measurement campaigns conducted at two different sites. [Copyright &y& Elsevier]

Abstract: Atmospheric deposition is one of the most important pathways of urban stormwater pollution. Atmospheric deposition, which can be in the form of either wet or dry deposition have distinct characteristics in terms of associated particulate sizes, pollutant types and influential parameters. This paper discusses the outcomes of a comprehensive research study undertaken to identify important traffic characteristics and climate factors such as antecedent dry period and rainfall characteristics which influences the characteristics of wet and dry deposition of solids and heavy metals. The outcomes confirmed that Zinc (Zn) is correlated with traffic volume whereas Lead (Pb), Cadmium (Cd), Nickel (Ni), and Copper (Cu) are correlated with traffic congestion. Consequently, reducing traffic congestion will be more effective than reducing traffic volume for improving air quality particularly in relation to Pb, Cd, Ni, and Cu. Zn was found to have the highest atmospheric deposition rate compared to other heavy metals. Zn in dry deposition is associated with relatively larger particle size fractions (>10 μm), whereas Pb, Cd, Ni and Cu are associated with relatively smaller particle size fractions (<10 μm). The analysis further revealed that bulk (wet plus dry) deposition which is correlated with rainfall depth and contains a relatively higher percentage of smaller particles compared to dry deposition which is correlated with the antecedent dry period. As particles subjected to wet deposition are smaller, they disperse over a larger area from the source of origin compared to particles subjected to dry deposition as buoyancy forces become dominant for smaller particles compared to the influence of gravity. Furthermore, exhaust emission particles were found to be primarily associated with bulk deposition compared to dry deposition particles which mainly originate from vehicle component wear. [Copyright &y& Elsevier]

Abstract: Tracking of an atmospheric release of pollution is usually based on measurements provided by stationary networks, occasionally complemented with deployment of mobile sensors. In this paper, we extend the existing concept to the case where the sensors are carried onboard of unmanned aerial vehicles (UAVs). The decision theoretic framework is used to design an unsupervised algorithm that navigates the UAVs to minimize the selected loss function. A particle filter with a problem-tailored proposal function was used as the underlying data assimilation procedure. A range of simulated twin experiments was performed on the problem of tracking an accidental release of radiation from a nuclear power plant in realistic settings. The main uncertainty was in the released activity and in parametric bias of the numerical weather forecast. It was shown that the UAVs can complement the existing stationary network to improve the accuracy of data assimilation. Moreover, two autonomously navigated UAVs alone were shown to provide assimilation results comparable to those obtained using the stationary network with more than thirty sensors. [Copyright &y& Elsevier]

Abstract: A number of recent toxicity studies have highlighted the increased potency of oxygen analogs (oxons) of several organophosphorus (OP) pesticides. These findings were a major concern after environmental oxons were identified in environmental samples from air and surfaces following agricultural spray applications in California and Washington State. This paper reports on the validity of oxygen analog measurements in air samples for the OP pesticide, chlorpyrifos. Controlled environmental and laboratory experiments were used to examine artificial formation of chlorpyrifos-oxon using OSHA Versatile Sampling (OVS) tubes as recommended by NIOSH method 5600. Additionally, we compared expected chlorpyrifos-oxon attributable to artificial transformation to observed chlorpyrifos-oxon in field samples from a 2008 Washington State Department of Health air monitoring study using non-parametric statistical methods. The amount of artificially transformed oxon was then modeled to determine the amount of oxon present in the environment. Toxicity equivalency factors (TEFs) for chlorpyrifos-oxon were used to calculate chlorpyrifos-equivalent air concentrations. The results demonstrate that the NIOSH-recommended sampling matrix (OVS tubes with XAD-2 resin) was found to artificially transform up to 30% of chlorpyrifos to chlorpyrifos-oxon, with higher percentages at lower concentrations (<30 ng m−3) typical of ambient or residential levels. Overall, the 2008 study data had significantly greater oxon than expected by artificial transformation, but the exact amount of environmental oxon in air remains difficult to quantify with the current sampling method. Failure to conduct laboratory analysis for chlorpyrifos-oxon may result in underestimation of total pesticide concentration when using XAD-2 resin matrices for occupational or residential sampling. Alternative methods that can accurately measure both OP pesticides and their oxygen analogs should be used for air sampling, and a toxicity equivalent factor approach should be used to determine potential health risks from exposures. [Copyright &y& Elsevier]

Abstract: The paper analyzes PM10 data from Mt. Cimone observatory (44°11′ N, 10°42′ E) in the period 1998–2011. Mt. Cimone is the highest peak of the Italian northern Apennines (2165 m asl) which hosts a high altitude background station in Southern Europe. The dataset is discussed in the framework of the main atmospheric meteorological and territorial features, representative of the central Mediterranean free troposphere. The overall geometric mean of PM10 mass concentration in the period investigated is 6.0 μg m−3 (arithmetic mean 8.8 ± 8.0 μg m−3), with large variability at the synoptic time-scale. At Mt. Cimone station the PM10 mass load features a strong seasonal fluctuation with a winter minimum (0.1 μg m−3, average winter value: 4.1 ± 4.8 μg m−3) and a summer maximum (45.7 μg m−3, average summer value: 13.7 ± 7.2 μg m−3). Influence of surface source areas upon PM10 is discussed by comparison of simultaneous PM10 data collected at ground stations to the north and south of the Northern Apennine range in order to investigate transport connections at the regional scale. PM10 data collected from the Environmental Protection Agencies networks of Emilia Romagna and Tuscany mostly cover urban stations and a few rural and semirural stations usually at ground level. In general PM10 mass load exhibits a vertical negative gradient with altitude, with Mt. Cimone displaying the least average value. Nevertheless exceptions can be observed on an event basis, while direct comparison of concentration data is not advisable due to the remoteness of Mt. Cimone as compared even to rural or semirural stations. Analysis of PM10 time series in conjunction with fine and coarse particle number densities reveals the influence of transports from source regions such as the Northern African desert, the Po valley and the European continent including the Balkan area. Source apportionment of PM10 is achieved applying a methodology based on Hysplit back-trajectories calculation. [Copyright &y& Elsevier]

Abstract: This paper discusses the development and validation of passenger car emission factors, using real world operation data. In total, six passenger cars of different technologies were studied. The tested vehicles were operated under various driving conditions and over two different routes in the region of Lombardia, Italy. These routes were specifically defined in order to provide a range of driving conditions, including urban, rural and highway driving. Tailpipe emissions and exhaust gas flows were measured on-board the vehicle, using a portable emissions measurement system (PEMS). In addition, all vehicles were tested over the European type-approval driving cycle (NEDC) with the same PEMS equipment. The testing of gasoline vehicles showed that emissions are well below the emission standards and do not raise any concern. However, the testing of diesel vehicles both under real-world driving conditions and over the NEDC brought to the surface important concerns regarding the actual NO x emissions of modern diesel vehicles, since they seem to comply with the corresponding emission standard over the type-approval cycle, but they constantly exceed the specified limit when tested under real-world driving conditions. Results from real-world operation revealed that there is a significant deviation from the NO x emission standard limit (especially for the newly introduced Euro 5 technology). These observations raise concerns regarding the actual NO x emissions of modern vehicles and their impact on urban air-quality. The emission factors originally measured on the road are also compared to the corresponding COPERT average speed emission factors. In general, emissions of CO2, THC and CO correlate fairly well with COPERT, for all vehicles. In the case of NO x emissions, emission levels of the two tested Euro 5 diesel passenger cars are consistently higher in urban, rural, and highway driving compared to the corresponding COPERT emission factor. Thus, leading to the conclusion that more experimental data are necessary, especially for post-Euro 4 compliant diesel vehicles of different engine capacities particularly when it comes to NO x emissions from diesel vehicles. [Copyright &y& Elsevier]

Abstract: Fungal spores are the dominant biological component of air. Although ubiquitous in outdoor air, they are scarcely measured due to the inadequacy of measurement methods. The use of biomarkers as tools for the determination of fungal contribution to bioaerosol has often been suggested, and ergosterol, arabitol and mannitol have been associated to fungal spores as tracers. In the present paper, the fungal component of aerosol was studied at suburban/rural and at urban sites. Ergosterol, arabitol, and mannitol contents in airborne particulate matter, even at different sizes, were determined. Literature conversion factors and calculated conversion factors correlating ergosterol, arabitol, and mannitol masses to fungi mass were applied and compared to each other. The obtained fungal spore concentrations were different depending on the marker utilized both with the conversion factors found in literature and the calculated ones. Size-segregated marker distribution suggested different sources for the three tracers indicating ergosterol as the only reliable biomarker at our latitudes. The fungal spore concentrations were higher at the suburban/rural location and respectively inversely and directly proportional to temperature and relative humidity. [Copyright &y& Elsevier]

Abstract: This paper presents a computational investigation of the residence of atmospheric contaminants in the wake of an isolated cubical building under different stability conditions, using the computational fluid dynamics code ADREA-HF. Characteristic concentration decay times describing the detrainment behaviour of gas in the near-wake are assessed for different atmospheric stability conditions and the results are compared with experiments conducted in the field (Mavroidis et al., 1999). The flow and concentration fields are also investigated computationally. Two building orientations are examined, with the mean wind direction normal to or at 45° to the leading face of the cubical building. Characteristic decay time patterns calculated by the model agree in general with the experimental ones, while there is a tendency for the model to overestimate dilution rates for the wind direction normal to the face of the building. The residence time (T d), defined as the time it takes for gas concentration to decay to 1/e of its original value, depends on atmospheric stability, with higher values observed in general under stable conditions; T d is especially influenced by the prevailing wind speeds, with a tendency for higher values under lower wind speeds. On the other hand, the non-dimensional residence time (τ = UT d/H) is to a large extent independent of the atmospheric stability conditions, as also indicated by the experimental measurements. Residence times are in general larger when the cube is oriented at 45° to the wind than when it is normal to the wind. Finally, the spatial variability of the calculated residence time T d is also presented and discussed. [Copyright &y& Elsevier]

Abstract: Volcanic air pollution, known as vog (volcanic smog) has recently become a major issue in the Hawaiian islands. Vog is caused when volcanic gases react with oxygen and water vapor. It consists of a mixture of gases and aerosols, which include sulfur dioxide and other sulfates. The source of the volcanic gases is the continuing eruption of Mount Kilauea. This paper studies predicting vog using statistical methods. The data sets include time series for SO2 and SO4, over locations spanning the west, south and southeast coasts of Hawaii, and the city of Hilo. The forecasting models include regressions and neural networks, and a frequency domain algorithm. The most typical pattern for the SO2 data is for the frequency domain method to yield the most accurate forecasts over the first few hours, and at the 24 h horizon. The neural net places second. For the SO4 data, the results are less consistent. At two sites, the neural net generally yields the most accurate forecasts, except at the 1 and 24 h horizons, where the frequency domain technique wins narrowly. At one site, the neural net and the frequency domain algorithm yield comparable errors over the first 5 h, after which the neural net dominates. At the remaining site, the frequency domain method is more accurate over the first 4 h, after which the neural net achieves smaller errors. For all the series, the average errors are well within one standard deviation of the actual data at all the horizons. However, the errors also show irregular outliers. In essence, the models capture the central tendency of the data, but are less effective in predicting the extreme events. [Copyright &y& Elsevier]

Abstract: This paper presents the ground based comparison of solar UV index at three major cities in Nepal (Kathmandu, Pokhara and Biratnagar). Kathmandu (27.72° N, 85.32° E), Pokhara (28.22° N, 83.22° E) and Biratnagar (26.45° N, 87.27° E) are located at an elevation of 1350 m, 800 m and 72 m respectively from the sea level. This comparison was performed from January to December 2009 for Kathmandu (KTM) and Pokhara (PKR) and from February to December 2009 for Biratnagar (BRT). The measurement instruments used are the NILU-UV irradiance meter and the Moderate Resolution Imaging Spectroradiometer (MODIS). The NILU-UV irradiance meter records the UV radiation whereas the MODIS estimates AOD. During this study, the monthly mean UV Index (UVI) in July were found to be 7.5 ± 2.5 in KTM, 8.6 ± 3.5 in PKR and 7.2 ± 3.1 in BRT. Meanwhile, the hourly mean UVI during monsoon at 7UT was found to be 5.7 ± 2.5 in KTM, 6.4 ± 2.6 in PKR and 5.8 ± 2.5 in BRT. The highest values of these hourly mean UVI was found at or around noon. The UVI values between KTM and PKR was slightly more correlated with its correlation coefficient being 0.73 than that between KTM and BRT whose correlation coefficient was 0.65. Similarly, the mean bias difference for KTM, BRT and KTM, PKR was found to be 4.8% and −38.1% respectively. This higher and lower mean bias difference indicates large and small deviation in UV data. The study also showed that besides solar elevation, the fluctuation in UVI was also influenced by the variation in ozone, aerosols and clouds. Furthermore, a year long comparison of UVI indicated that the UVI in Pokhara was higher than that in Kathmandu and Biratnagar. This analysis also showed that the extreme values of UVI were not found during the study period. [Copyright &y& Elsevier]

Abstract: In this paper we investigate the added value of assimilation of ozone in-situ measurements for both re-analysis and forecasting purposes. Various simulations were performed using the LOTOS-EUROS chemical transport model and an Ensemble Kalman Filter (EnKF) to assimilate measured ozone surface concentrations over Europe, for spring and summer of 2007. The results for the re-analysis of ozone show a significant improvement in the LOTOS-EUROS performance score when compared to measurements. The average correlation coefficient for the daily maximum ozone concentration improves from 0.72 to 0.83. Similarly, the average Root Mean Square Error (RMSE) for the daily maximum ozone concentration is reduced from 20.8 to 16.9 μg m−3. The free running model performs well in forecast mode and the agreement between in-situ and modeled ozone concentration is good. The average temporal correlation coefficient ranges from 0.62 for the first day forecast to 0.61 for the third day forecast. Based on these results, assimilated fields were used to initialize the forecast. As for the re-analysis a better comparison between model and observation was observed. The mean correlation coefficient increased by 0.07 and the averaged RMSE decreased by 0.65 μg m−3. However, the addition of an inheritance scheme to import additional information from the data assimilation to the forecast did not significantly improve the concentration fields. [Copyright &y& Elsevier]

Abstract: This research aims to determine the overall effects that a vehicle''s short-term operating history has on its subsequent emissions, and how Vehicle Specific Power (VSP)-based vehicle emission models could be improved to account for these effects. Current VSP-based emission models, such as the U.S. EPA''s MOtor Vehicle Emission Simulator (MOVES), only predict emissions based on instantaneous vehicle activity and the corresponding VSP value; the past short-term vehicle operational activity is not taken into account (e.g., the last 10–20 s of operation). For example, instantaneous vehicle emissions could be affected by a hard acceleration vs. a deceleration event at that particular point in time. This paper attempts to determine the accuracy of VSP-based emission models, which may suffer due to the fact that the history effects are being overlooked. A number of experiments were carried out in order to determine the anomalies resulting from instantaneous estimation as opposed to taking short-term vehicle operating history into account. These experiments compare model estimates with actual emission measurements. A quantitative analysis shows that the higher power operating modes (such as modes 33, 35, 37, 38, and 40 in MOVES) had the greatest variability – sometimes in the range of 60–100% – due to the effects that vehicle operating history has on carbon monoxide (CO). Hydrocarbons (HC) in higher power operating modes also vary 40–60% depending on the driving cycle. For lower power operating modes (e.g., MOVES modes 1–30), the uncertainty for all pollutants was significantly less. It was also established that the carbon dioxide (CO2) and nitrogen oxide (NO x ) estimations conducted by MOVES were least affected by the vehicle operational history effects compared with other emissions. As such, MOVES emission results are more accurate for mild to normal driving cycles, but there is greater uncertainty for higher power driving cycles. [Copyright &y& Elsevier]

Abstract: APOLLO2 is a new version of the long range Lagrangian particle dispersion model integrated into ARIES (Accidental Release Impact Evaluation System), the system that I.S.P.R.A. (Italian National Institute for Environmental Protection and Research) developed to provide prognosis about the dispersion of radioactive clouds in case of nuclear accidents. In this paper the theoretical aspects of the APOLLO2 formulation are briefly described. Moreover, the model performances have been evaluated qualitatively and quantitatively against the observations of the first release of the European Tracer Experiment (ETEX). The global analysis showed a FA2 = 56%, a FA5 = 78%, and a good agreement for intermediate values within the Q–Q plot. Considering a total of 126 stations, the number of locations where NMSE < 10, PCC > 0.7 and FMT > 20% is respectively 91, 65 and 86. The number of stations where the performance evaluation criteria are satisfied is 33. The capability of APOLLO2 to predict arrival time, cloud duration and time of peak is comparable to the one shown by similar models. Finally, the sensitivity of the model to some input variables has also been investigated. [Copyright &y& Elsevier]

Abstract: Particulate matter remains a challenging pollutant for air pollution control in the UK and across much of Europe. Particulate matter is a complex mixture of which secondary inorganic compounds (sulphates, nitrates) are a major component. This paper is concerned with taking a basic version of the UK Photochemical Trajectory Model and enhancing a number of features in the model in order to better represent boundary layer processes and to improve the description of secondary inorganic aerosol formation. The enhancements include an improved treatment of the boundary layer, deposition processes (both wet and dry), attenuation of photolysis rates by cloud cover, and inclusion of the aerosol thermodynamic model ISORROPIA II to account both for chemistry within the aerosol and between the particles and gas phase. Emissions inventories have been updated and are adjusted according to season, day of the week and hour of the day. Stack emissions from high level sources are now adjusted according to the height of the boundary layer and a scheme for generating marine aerosol has been included. The skill of the improved model has been evaluated through predictions of the concentrations of particulate chloride, nitrate and sulphate and the results show increased accuracy and lower mean bias. There is a much higher proportion of the values lying within a factor of 2 of the observed values compared to the basic model and Normalised Mean Bias has reduced by at least 89% for nitrate and sulphate. Similarly, the Index of Agreement between calculated and measured values has improved by ∼10%. Considering the contribution of each enhancement to the improvement in the performance metrics, the most significant enhancement was the replacement of the parameterisation of the boundary layer height, relative humidity and temperature by HYSPLIT values calculated for each trajectory. The second most significant enhancement was the parameterisation of the photolysis rates by values calculated by an off line database accounting for the dependence of photolysis rates on zenith angle, cloud cover, land surface type and column ozone. The inclusion of initial conditions which were dependent on the starting point of the trajectory and the modulation of stack emissions made the most significant improvement to sulphate. Furthermore, in order to assess the model''s response to abatement scenarios, 30% abatements of either NH3, NOx or SO2 showed a reduction in the sum of chloride, nitrate and sulphate of between 3.1% and 8.5% (with a corresponding estimated reduction of 1.6–3.7% reduction in PM10). The largest reduction in this contribution is due to the abatement of NOx. [Copyright &y& Elsevier]

Abstract: This paper presents a study of the evolution of particles and gases downwind of a highway, with a focus on the diurnal variation of pollutant gradients and its controlling variables. A mobile laboratory was used to measure the concentration gradients of ultra-fine particles (UFP), black carbon (BC), CO2, NO, and NO2 at varying distances up to 850 m from a major highway. The horizontal distributions of pollutants show a strong diurnal pattern. Results suggest that the horizontal gradients are predominantly influenced by traffic levels, friction velocity, and atmospheric stability. The results were compared to a dispersion model, which showed good agreement with the measurements and was able to qualitatively capture the observed diurnal cycles. Emission rates [g km−1] calculated from the model fits are within 10% of the Mobile 6.2C inventory for CO2 and demonstrate good agreement for NOx, but are higher than the inventory by a factor between 2.0 and 5.9 for black carbon. Hourly NOx emission rates correlate with the fraction of heavy-duty vehicles in the total fleet and agree with inventory values based on maximum vehicle emission rates. [Copyright &y& Elsevier]

Abstract: Traffic related emissions have been recognised as one of the main sources of air pollutants. In the research study discussed in this paper, variability of atmospheric total suspended particulate matter (TSP), polycyclic aromatic hydrocarbons (PAH) and heavy metal (HM) concentrations with traffic and land use characteristics during weekdays and weekends were investigated. Data required for the study were collected from a range of sampling sites to ensure a wide mix of traffic and land use characteristics. The analysis undertaken confirmed that zinc has the highest concentration in the atmospheric phase during weekends as well as weekdays. Although the use of leaded gasoline was discontinued a decade ago, lead was the second most commonly detected heavy metal. This is attributed to the association of previously generated lead with roadside soil and re-suspension to the atmosphere. Soil related particles are the primary source of TSP and manganese to the atmosphere. The analysis further revealed that traffic sources are dominant in gas phase PAHs compared to the other sources during weekdays. Land use related sources become important contributors to atmospheric PAHs during weekends when traffic sources are at their minimal levels. [Copyright &y& Elsevier]

Abstract: The paper presents the results of a field test carried out in Gdańsk region between 01-01-2010 and 31-12-2010 in order to demonstrate equivalence of the Eberline FH 62-1 sampler to the reference gravimetric method of suspended PM10 dust measurement. The differences in PM10 dust concentration provided by both methods have been discussed for different seasons of the year. A method of estimation of the correction factors/correction equations has been described based on the European Union guide “Demonstration of Equivalence of Ambient Air Monitoring Methods. EC Working Group on Guidance for the Demonstration of Equivalence”. The results obtained from Eberline sampler are equivalent to the ones from gravimetric method, but after application of data correction. The investigation revealed different correction factors/correction equations for winter and summer season. The winter season is characterized by higher PM10 concentration and bigger discrepancies between both methods. A lack of equivalence has been found for PM10 dust concentration higher than 30μgm−3. [Copyright &y& Elsevier]

Abstract: In this paper we have compared detailed road traffic NOx emissions with the equivalent trends in ambient roadside NOx measurements. This was undertaken separately in Great Britain and London, for all of the major roads, and by road type and location. The emissions trends were created using different emissions factors, those used in UK emissions inventories (Base case), the Swiss-German handbook (HBEFA), and those created from recent remote sensing measurements in the UK (RSD). An alternative assumption for use of Selective Catalytic Reduction (SCR) in the articulated Heavy Goods Vehicle (HGV) fleet was also tested. For all scenarios traffic flows, speeds and vehicle age were kept constant. Comparison between the emissions scenarios in Great Britain showed that by 2009, NOx emissions estimates from road traffic could be as much as 25% greater than current UK estimates and 31% greater in London. The RSD emissions inventory gave the smallest downward trend in NOx emissions, from 2004 to 2009, of between 3 and 4%/year and this compared with a reduction of ∼6%/year from the Base Case and HBEFA scenarios. All scenarios compared poorly with roadside NOx measurement trends from UK sites, which typically reduce by between 1% and 2%/year. We have shown that the differences in NOx emissions trends were driven, partially at least, by the relative contribution from light duty diesel vehicles. An analysis from 2700 NOx measurement sites throughout Europe has shown that this problem is unlikely to be limited to the UK, and identifies a difficulty in meeting EU limit values for NO2, obligations under the National Emission Ceilings Directive () and the Gothenburg Protocol () and for forecasting future changes in PM2.5. [Copyright &y& Elsevier]

Abstract: Over twenty modeling groups are participating in the Air Quality Model Evaluation International Initiative (AQMEII) in which a variety of mesoscale photochemical and aerosol air quality modeling systems are being applied to continental-scale domains in North America and Europe for 2006 full-year simulations for model inter-comparisons and evaluations. To better understand the reasons for differences in model results among these participating groups, each group was asked to use the same source of emissions and boundary concentration data for their simulations. This paper describes the development and application of the boundary concentration data for this AQMEII modeling exercise. The European project known as GEMS (Global and regional Earth-system Monitoring using Satellite and in-situ data) has produced global-scale re-analyses of air quality for several years, including 2006 (http://gems.ecmwf.int). The GEMS trace gas and aerosol data were made available at 3-hourly intervals on a regular latitude/longitude grid of approximately 1.9° resolution within 2 “cut-outs” from the global model domain. One cut-out was centered over North America and the other over Europe, covering sufficient spatial domain for each modeling group to extract the necessary time- and space-varying (horizontal and vertical) concentrations for their mesoscale model boundaries. Examples of the impact of these boundary concentrations on the AQMEII continental simulations are presented to quantify the sensitivity of the simulations to boundary concentrations. In addition, some participating groups were not able to use the GEMS data and instead relied upon other sources for their boundary concentration specifications. These are noted, and the contrasting impacts of other data sources for boundary data are presented. How one specifies four-dimensional boundary concentrations for mesoscale air quality simulations can have a profound impact on the model results, and hence, this aspect of data preparation must be performed with considerable care. [Copyright &y& Elsevier]

Abstract: Aerosol and cloud play important roles in the atmosphere and climate system. Accurately detecting their presence, altitude, and properties using satellite radiance measurements is a very important task. This paper presents a comparative analysis of the Cloud–Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) Level 2 Vertical Feature Mask (VFM) product with the Ozone Monitoring Instrument (OMI) UV Aerosol Index (UVAI) and reflectivity datasets for a full year of 2007 from regional to global scales. Based on CALIPSO and OMI observations, the vertical and horizontal extent of clouds and aerosols are determined and effects of aerosol type, load and cloud fraction on aerosol identification are discussed. It was found that the spatial–temporal correlation found between CALIPSO and OMI observations, is strongly dependent on aerosol types and cloud contamination. CALIPSO is more sensitivity to cloud and often misidentifies aerosol as cloud, while some small scale aerosol layers as well as some pollution aerosols are unidentified by OMI UVAI. Large differences in aerosol distribution patterns between CALIPSO and OMI are observed, especially for the smoke and pollution aerosol dominated areas. In addition, the results found a significant correlation between CALIPSO lidar 1064 nm backscatter and the OMI UVAI over the study regions. [Copyright &y& Elsevier]

Abstract: An ambient air monitoring campaign was performed in six counties (Sacramento, CA; Maricopa, AZ; Anoka, MN; Jefferson, KY; Harris, TX; and Pinellas, FL) between January 2008 and September 2009. The purpose of this paper is to compare the spatial and temporal variability of black carbon (BC) and particle-bound polycyclic aromatic hydrocarbons (p-PAHs), across these counties using continuous monitoring instruments – an Aethalometer and a Photoelectric Aerosol Sensor reporting in units of μg m−3 and fA, respectively. We explored temporal trends in these measurements to assess the potential impact of local combustion sources on air quality. Median BC concentrations ranged from 0.13 to 0.53 μg m−3; and median p-PAH values ranged from 0.31 to 4.18 fA. Hourly BC and p-PAH were elevated during morning rush hour and rapidly decreased later in the morning. Nighttime increases in BC and p-PAH were also observed in most counties. Diurnal patterns of BC and p-PAH were different on weekdays compared to weekends. Profiles of hourly ratios of p-PAH/BC in combination with meteorological data can provide insight into potential sources across the sites. Hourly ratios of p-PAH/BC which peaked during early morning and late afternoon hours suggest a dominating contribution of motor vehicle sources in four of the six counties. In two counties, hourly ratios remained elevated for several hours after rush hour and did not show a distinctive peak suggesting additional sources of BC and p-PAH. Such profiles were seen in both Jefferson KY and Harris TX, and may be attributed to coal combustion, petro-chemical industry and shipping activities, respectively. These results suggest that measurements of BC and p-PAH, combined with meteorological information and emission data are potentially useful to identify combustion sources impacting air quality. More research combining BC and p-PAH measurements with detailed source apportionment data is needed to more fully evaluate the utility of these real-time measures. [Copyright &y& Elsevier]

Abstract: A case study designed to investigate indoor and outdoor air quality in naturally ventilated homes near the US-Mexico border was conducted in Nogales, Sonora, Mexico from 14–30 March 2009. To better understand resident’s actual exposure to various sizes of particulate matter (PM), we compare measured concentrations in homes using different household stove cooking fuels (gas versus biomass) and investigate the spatial distribution of outdoor PM. Data from two home locations, one with a gas stove and one with both biomass and gas stoves are evaluated. In each home, continuous PM concentrations were sampled over a range of particle sizes. Indoor and outdoor concentration measurements were facilitated using a valve switching system. PM 2.5 was also sampled on quartz filters located inside and outside of the two homes for carbon analysis. This paper will present a subset of the field data to compare time resolved indoor PM concentrations and carbon content for the two homes; specifically, comparing cooking versus non-cooking time periods. Results indicate that indoor elemental carbon concentrations are dominated by indoor sources during biomass burning, and outdoor sources at all other times. The data indicate that the influence of indoor sources on organic carbon concentrations increases during both gas and biomass stove use; this information is correlated to continuous indoor PM concentrations and home activities. The mean 24 h indoor PM 10 concentration was 408 μg m−3 for the gas stove home and 648 μg m−3 for the home with biomass and gas stoves, while the outdoor concentrations were 609 μg m−3 and 381 μg m−3, respectively. The average 24 h PM 10 Indoor/Outdoor ratio was 0.71 for the gas stove home and 1.79 for the home with both gas and biomass stoves. These ratios should be interpreted with caution as they appear to underestimate the indoor source contribution due to high outdoor PM levels. [Copyright &y& Elsevier]

Abstract: Aerosol Robotic Network (AERONET) aerosol optical depth (AOD) and almucantar retrievals (single scattering albedo (SSA) and aerosol size distribution) from 2005–2009 in Beijing and Kanpur are used to analyze differences and similarities in aerosol optical properties over these two regions. The examination of monthly mean AOD (440 nm) shows that maximum and minimum values occurred in summer and winter, respectively, for Beijing, while the range in AOD in Kanpur was lower. Precipitation in both Beijing and Kanpur peaked in summer; however, the columnar water vapor (CWV) exhibited a high correlation with AOD in Beijing (R 2 = 0.79) but had a weak relationship with AOD in Kanpur (R 2 = 0.13). The Angstrom exponent (α, 440–870 nm) generally increased linearly as the fine mode fraction (FMF) of AOD (500 nm) increased for FMF < 90% in both regions, with a high correlation of R 2 > 0.96. However a clear decrease in α for FMF > 90% found in Beijing is not shown distinctly in Kanpur, and is mainly due to the higher aerosol loading in this FMF bin at Beijing (AOD at 440 nm > 2.2) which results in a stronger coagulation of fine mode particles. Bimodal seasonally-averaged size distributions reveals similar aerosol mixtures composed of fine pollution particles and coarse dust particles in both regions. The analysis of spectral SSA as a function of α is emphasized in this paper. The average SSA at 440 nm in both regions shows a similar low dynamic range of ∼0.03 for α < 1.4. The obvious increase in SSA at 440 nm for α > 1.4 in both regions can be attributed to a higher FMF leading to fine mode coagulation. However, the distinctly smaller increase in Kanpur suggests that fine mode aerosols at Beijing are less absorbing than those at Kanpur. The visibly lower SSA at 675 nm at Kanpur compared to that at Beijing for α > 0.4 is due to a larger find-coarse mode separation radius of ∼0.76 μm in Beijing versus a value lower than ∼0.58 μm in Kanpur. Another reason lies in the weaker absorption by fine mode aerosols in Beijing. The distinctly lower near-infrared SSA in Kanpur when α < 1.4, compared to Beijing, may be attributed to lower aerosol concentrations in all α bins, resulting in less aggregation of absorbing black carbon particles on coarse particles in Kanpur. The classification of aerosol properties shows that the AOD accumulation mode in all seasons, even including spring, in Beijing and in post-monsoon and winter seasons in Kanpur can be attributed to fine particle coagulation or hygroscopic growth; during pre-monsoon and monsoon seasons in Kanpur, it is due to coarse mode particle accumulation or cloud contamination. [Copyright &y& Elsevier]

Abstract: Landfills are important anthropogenic sources of methane (CH4) emission especially in fast urbanizing countries. This paper presents the CH4 emission estimations carried out using the in-situ CH4 measurements, IPCC 1996 Default methodology (DM), Modified Triangular Method (MTM) and First Order Decay (FOD) method for the three landfills currently operational in the capital city Delhi of India. The in-situ methodology has yielded the landfills specific methane emission factors (EFs). The annual average methane emission rates from three landfills namely, Ghazipur (GL), Bhalswa (BL) and Okhla (OL) are 14.6, 23.6 & 7.5 Gg y−1 by DM; 13.3, 10.6 & 7.2 Gg y−1 by the FOD; 17.0, 13.7 and 10.7 Gg y−1 by the MTM; and 4.6, 4.2 and 1.4 Gg y−1 by the in-situ measurement method respectively. The CH4 EFs have been found to be 9.7 ± 2.6, 5.5 ± 1.6 and 5.5 ± 1.7 g kg−1 of waste respectively for the GL, BL and OL landfills in Delhi. The study reveals that in-situ methodology seems to provide better representative emission estimation compared to other methods. The FOD method also yields comparable results with that of in-situ methodology in cases where good waste composition data is available. [Copyright &y& Elsevier]

Abstract: The development of geographical information system techniques has opened up a wide array of methods for air pollution exposure assessment. The extent to which these provide reliable estimates of air pollution concentrations is nevertheless not clearly established. Nor is it clear which methods or metrics should be preferred in epidemiological studies. This paper compares the performance of ten different methods and metrics in terms of their ability to predict mean annual PM10 concentrations across 52 monitoring sites in London, UK. Metrics analysed include indicators (distance to nearest road, traffic volume on nearest road, heavy duty vehicle (HDV) volume on nearest road, road density within 150 m, traffic volume within 150 m and HDV volume within 150 m) and four modelling approaches: based on the nearest monitoring site, kriging, dispersion modelling and land use regression (LUR). Measures were computed in a GIS, and resulting metrics calibrated and validated against monitoring data using a form of grouped jack-knife analysis. The results show that PM10 concentrations across London show little spatial variation. As a consequence, most methods can predict the average without serious bias. Few of the approaches, however, show good correlations with monitored PM10 concentrations, and most predict no better than a simple classification based on site type. Only land use regression reaches acceptable levels of correlation (R 2 = 0.47), though this can be improved by also including information on site type. This might therefore be taken as a recommended approach in many studies, though care is needed in developing meaningful land use regression models, and like any method they need to be validated against local data before their application as part of epidemiological studies. [Copyright &y& Elsevier]

Abstract: In order to provide consistency for PM2.5 carbon data across urban and rural areas in the United States the Chemical Speciation Network (CSN) carbon sampling and analysis protocols were changed to resemble those of the Interagency Monitoring of Protected Visual Environments (IMPROVE). The “new” CSN carbon sampler, the URG-3000N, was introduced into the network in May 2007. In this paper collocated carbon measurements are used to (1) check for equivalency between the URG-3000N and the IMPROVE and (2) compare the URG-3000N and IMPROVE data with other collocated measurements. A sufficiently extensive dataset (over several years) enabled comparisons to be performed on a seasonal basis. The URG-3000N provided consistent measurements of PM2.5 carbon with the IMPROVE at both urban and rural locations. In contrast measurements by the CSN MetOne were higher by approximately 20–30% for total carbon at the urban location and 40–50% at the rural location. This information is important for assessing discontinuities in time series data due to changes in the method as occurred to the CSN carbon in 2007. [Copyright &y& Elsevier]

Abstract: The U.S. EPA periodically evaluates ambient concentrations, human exposures, and health risks for 180 hazardous air pollutants plus diesel particulate matter using modeled estimates from the National-Scale Air Toxics Assessment (NATA). NATA publishes estimates at the spatial resolution of U.S. Census tracts, which are subdivisions of a county. These local scale, model-predicted estimates from NATA are used extensively in community-based assessments; however, evaluation of NATA’s ambient concentrations and human exposure estimates against measurement data has been limited to date. This paper compares modeled annual average benzene results from the 2002 NATA with measured results from the 2004 to 2007 Detroit Exposure and Aerosol Research Study (DEARS) as a case study of the quality of NATA results. NATA model estimates support community-scale characterization and assessment. Benzene is particularly important as it was estimated by the 2002 NATA as the largest single air toxic pollutant in terms of cancer risk in the U.S. We found that the average ambient concentrations of benzene predicted by NATA were within 5 percent, on average, of the 24-h integrated average ambient concentrations measured in DEARS. The NATA human exposure estimates, which include only outdoor sources for benzene, were, on average, approximately half the measured breathing zone concentrations from DEARS. Our analyses support that the factors driving higher DEARS personal benzene concentrations relative to the NATA predicted exposure values are likely due, at least in part, to indoor sources. This work points to further community-scale modeling research to improve characterizations and assessments of human exposures. [Copyright &y& Elsevier]

Abstract: In this paper, we examine the extent to which an ensemble generated from a single air quality model correctly represents the global uncertainty of ozone simulations with a regional scale chemistry-transport model and whether it is suitable for ozone data assimilation. An ensemble of 30 members is constructed from a reference simulation in which the model parameters that are the most uncertain for determining ozone concentrations are randomly perturbed. Comparisons of the simulated ensemble using the model CHIMERE with observations are examined over the summer season both at the surface and higher in the troposphere. Although the ensemble overestimates vertical and horizontal correlation between errors, the average model error is well represented both at the surface and in the vertical dimension (after an adjustment for the latter). A variability of about 7–8ppb is found. The results found in this study with respect to tropospheric ozone model errors and error correlation lengths both from ensemble simulations and model to observation comparisons are of particular interest for data assimilation when constructing model error covariance matrices. [ABSTRACT FROM AUTHOR]

Abstract: HVAC filters are in place for extended periods of time and can serve as integrated air samplers. This paper presents a comparison of bacterial and fungal concentrations and communities in HVAC filter dust and other sampling locations in occupied residences and in the unoccupied UTest House. A DNA-based, culture-independent approach was utilized to characterize the microbial communities. Microbial concentrations and communities in HVAC filter dust samples were not statistically different from those in high surface dust samples in occupied homes. Despite the general similarity in the communities, Proteobacteria were present in greater proportion in HVAC filter dust samples than in surface dust samples suggesting the air origin of this phylum. Gram-positive bacteria were present in greater proportion in occupied residences than in an unoccupied test house, confirming the potential association of this group with occupants. HVAC filter microbial communities were not different from those present in a composited month-long indoor air sample providing preliminary evidence that filters could be a viable option for long-term investigation of airborne biological contaminants. [ABSTRACT FROM AUTHOR]

Abstract: Rather surprisingly, urban atmospheric particulate levels in West Africa compare with measured concentrations in Europe and Asia megacities (Liousse, C., Galy-Lacaux, C., Assamoi, E.-M., Ndiaye, A., Diop, B., Cachier, H., Doumbia, T., Gueye, P., Yoboue, V., Lacaux, J.-P., Guinot, B., Guillaume, B., Rosset, R., Castera, P., Gardrat, E., Zouiten, C., Jambert, C., Diouf, A., Koita, O., Baeza, A., Annesi-Maesano, I., Didier, A., Audry, S., Konare, A., 2009. Integrated Focus on West African Cities (Cotonou, Bamako, Dakar, Ouagadougou, Abidjan, Niamey): Emissions, Air Quality and Health Impacts of Gases and Aerosols. Third International AMMA Conference on Predictability of the West African Moosoon Weather, Climate and Impacts. Ouagadougou, Burkina Faso. July 20–24). This pollution mainly derives from road traffic emissions with, in some capitals (e.g. Cotonou), the strong contribution of two-wheel vehicles. Two key questions arise: are presently available emission inventories (e.g. Junker, C., Liousse, C., 2008. A global emission inventory of carbonaceous aerosol from historic records of fossil fuel and biofuel consumption for the period 1860–1997. Atmospheric Chemistry Physics, 8, 1–13; Bond, T.C., Streets, D.G., Yarber, K.F., Nelson, S.M., Woo, J.H., Klimont, Z., 2004. A technology-based global inventory of black and organic carbon emissions from combustion. Journal of Geophysical Research, 1009, D14203, DOI:10.1029/2003JD003697) able to account for these emissions? And, if not, how can we remedy this? The aim of this paper is to develop a methodology to estimate emissions produced by two-wheel vehicles in West Africa for 2002 in a context where reliable information is hardly available. Fuel consumption ratios between two-wheel engines (in this work) and all vehicles issued from UN database (http://data.un.org/Data.aspx?d=EDATA&f=cmID%3aMO%3btrID%3a1221) are as high as 169%, 264% and 628%, for Burkina Faso, Mali and Chad respectively, indicating that this global database does not properly account for regional specificities. Moreover, emission factors for black carbon (BC) and primary organic carbon (OCp) have been measured for two-stroke engines in Benin (Guinot, B., Liousse, C., Cachier, H., Guillaume, B., et al. New emission factor estimates for biofuels and mobile sources. Atmospheric Environment, in press.), giving significantly higher values than in Europe. This is particularly true for OCp, and consequently the calculated emissions for two-stroke engines are also significantly larger than total road traffic previously estimated in global inventories ( with United Nations database for 2002; ). The ensuing discussion illustrates the importance of two-stroke engines in the West Africa transport sector and the strong need for inventory updating. [Copyright &y& Elsevier]

Abstract: This paper presents an evaluation of the consistency of an urban state-of-the-art hydrocarbon (HC) emission inventory. The evaluation was conducted through the comparison of this inventory with hourly HC measurements during two summer months in the centre of Marseille, on the Mediterranean French coast. Factors of under or overestimation could be calculated for each compound on the basis of a systematic HC to HC ratio analysis. These results, associated with a deep analysis of the speciation profiles, show that most of the common and highly concentrated hydrocarbons (such as butanes) are too much predominant in the emission speciation, while the heavy and less common species (branched alkanes, substituted aromatics) are under-represented in the inventory. The urban diffuse sources appear here as one critical point of the inventories. The disagreements were shown to have a strong incidence on the representation of the air mass reactivity. In a last step, the identified uncertainties in emissions were implemented in an air-quality model for sensitivity studies. It was shown that the observed biases in the inventory could affect the regional ozone production, with a probable impact on ozone peaks of 2–10 ppbv over the area. [ABSTRACT FROM AUTHOR]

Abstract: In this paper we address two important aspects of micro-scale urban airflow model evaluation: (a) the identification of key flow features as dictated by the physics of the problem and as captured by the simulations, and (b) the comparison of important model output parameters (mean flows and fluctuations) with experimental data. A series of mesh-adaptive large eddy simulations (LES) was carried out for the study of air flows within two intersecting street canyons with varying building configurations. The novelty of the approach lies in the combination of LES with mesh adaptivity, which allows a variable-filter length and the implementation of an anisotropic eddy-viscosity model. Both coarse and fine-mesh simulations were carried out, using single and parallel-processor systems respectively. The simulations showed clearly that the expected flow patterns such as the street canyon recirculation and the street-mouth vortices, as well as the exchange of air flow at the street intersections, can readily be captured by the mesh-adaptive LES. In addition, the detailed comparisons of mean flows and fluctuations of the resolved velocity field with the measured data showed that the simulation results agreed well with the patterns and trends of the wind tunnel measurements. In most cases the finer-mesh simulations improved considerably the accuracy of the mean flows, especially for the symmetrical configuration. The improvement in the predicted fluctuations was less obvious, with several detector locations underpredicting the measured values, although the overall comparison was also satisfactory. The typical errors for the mean flows for all three building configurations were less than 30%, whilst for the velocity fluctuations less that 40%. Both the simulated means flows and turbulence levels were generally more accurate in the streets parallel to the wind (streamwise direction) than in the streets normal to the wind. [Copyright &y& Elsevier]

Abstract: In this paper we describe and quality assure the sampling system of a mobile research laboratory SNIFFER which was shown to be a useful tool for studying emission levels of respirable dust from street surfaces. The dust plume had bimodal structure; another mode rising to higher altitudes whereas the other mode remained at lower altitudes. The system was tested on a route in Helsinki, Finland, during spring 2005 and 2006. The PM2.5 and PM10 were positively correlated and the PM levels increased with the vehicle speed. SNIFFER was able to identify the characteristic emission levels on different streets. A clear downward trend in the concentrations was observed in all street locations between April and June. The composition of the street dust collected by SNIFFER was compared with springtime PM10 aerosol samples from the air quality monitoring stations in Helsinki. The results showed similarities in the abundance and composition of the mineral fraction but contained significantly more salt particles. [Copyright &y& Elsevier]