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Atmospheric Environment (v.40, #38)
Data assimilation for short-range dispersion of radionuclides: An application to wind tunnel data by Monika Krysta; Marc Bocquet; Bruno Sportisse; Olivier Isnard (pp. 7267-7279).
This work contributes to improvement in consequences evaluation for a release of radioactivity to the atmosphere at local scale. An investigation of how such an improvement could be achieved with the help of variational data assimilation is presented. The measurements collected in a wind tunnel experiment are coupled to a Gaussian puff model. Capacity of finding the true source emission rate is tackled in the first place. Secondly, data assimilation is employed to accommodate the computed concentration profiles to the measured ones. Benefit from data assimilation is subject to the quantity of information contained in the measurements. Therefore, posterior analysis of the monitoring network is carried out and its quality assessed.
Keywords: Data assimilation; Dispersion; Radionuclides
Plume-in-grid modeling for particulate matter by Prakash Karamchandani; Krish Vijayaraghavan; S.-Y. Shu-Yun Chen; Christian Seigneur; Eric S. Edgerton (pp. 7280-7297).
Three-dimensional grid models are now being commonly used to simulate particulate matter (PM) concentrations, especially fine PM (PM2.5), which includes a significant fraction of secondary species formed in the atmosphere. These models usually do not address the subgrid-scale effects associated with emissions from large elevated point sources. This can lead to errors in the calculation of PM2.5 concentrations downwind of these sources because of unrealistic representations of the dispersion and transformation processes that govern PM2.5 formation. Here, we describe the development, application and evaluation of a plume-in-grid (PiG) model for PM. The model, based on an existing PiG model for ozone, is extended to include in the plume component state-of-the-science treatments of aerosol chemistry and dynamics as well as aqueous chemistry that are consistent with the treatments used in the host grid model. Application of this model to several SO2 and NO x emitting power plants in the southeastern United States shows that the PiG treatment leads to significant differences in sulfate and total inorganic nitrate concentrations. Comparisons of model results, with and without PiG treatment, against measurements characterizing specific plume events, show that the PiG treatment captures the plume events more often and generally better than the standard grid-based approach.
Keywords: PM; 2.5; Subgrid-scale; Plume chemistry; CMAQ; SCICHEM; SEARCH
CH3OCF2CHFCl and CHF2OCF2CHFCl: Reaction with Cl atoms, atmospheric lifetimes, ozone depletion and global warming potentials by Pablo R. Dalmasso; R.A. Raúl A. Taccone; Jorge D. Nieto; Mariano A. Teruel; Silvia I. Lane (pp. 7298-7307).
The relative rate technique has been used to determine the rate constants of the reactions of Cl atoms with 2-chloro-1,1,2-trifluoroethyl-methyl-ether (CH3OCF2CHFCl) and 2-chloro-1,1,2-trifluoroethyl-difluoromethyl-ether (CHF2OCF2CHFCl). Experiments were carried out at 296±2K and atmospheric pressure using nitrogen or synthetic air as bath gases. The decay rates of the organic species were measured relative to those of 1,2-dichloroethane, dichloromethane and 1,1,1,2-tretrafluoroethane. The following rate coefficients were derived for the reaction of Cl atoms (in units of cm3molecule−1s−1) with CH3OCF2CHFCl, k=(3.24±0.49)×10−13 and CHF2OCF2CHFCl, k=(3.20±0.32)×10−15. The rate constants obtained are compared with previous literature data to establish reactivity trends and used to estimate the atmospheric lifetimes for the studied ethers. From the calculated lifetimes, using average global concentrations of Cl atoms and OH radicals, the atmospheric loss of CH3OCF2CHFCl and CHF2OCF2CHFCl is determined by the OH-initiated oxidation.The atmospheric implications of these reactions are discussed based on the calculated ozone depletion potential (ODP) and global warming potential (GWP) of the ethers.
Keywords: Chlorine atoms; Rate coefficient; Relative method; Tropospheric chemistry
Surface ozone mixing ratio increase with altitude in a transect in the Catalan Pyrenees by Àngela Ribas; Penuelas Josep Peñuelas (pp. 7308-7315).
Tropospheric ozone mixing ratios and their phytotoxicity and NO2 mixing ratios were measured along an altitudinal gradient at the Meranges valley in the Catalan Pyrenees. Biweekly measurements using Radiello passive samplers were taken along a transect of seven stations ranging from 1040 to 2400m ASL from May to December 2004. As well, at each station biweekly evaluations were made of the visual symptoms of ozone damage in Bel-W3 and Bel-B tobacco cultivars. Whereas ozone mixing ratios increased with altitude, NO2 mixing ratios decreased from the valley floor upwards. Ozone damage rates were found to vary with time and space depending on local environmental and meteorological conditions, although the highest ozone damage to foliage was found in the stations at greatest altitude, especially wherever altitudinal micrometeorological conditions enhanced plant sensitivity.
Keywords: Altitudinal gradient; Mediterranean region; Nitrogen oxides; Ozone; Phytotoxicity; Tobacco plants
Single imputation method of missing values in environmental pollution data sets by A. Plaia; A.L. Bondì (pp. 7316-7330).
Missing data represent a general problem in many scientific fields above all in environmental research. Several methods have been proposed in literature for handling missing data and the choice of an appropriate method depends, among others, on the missing data pattern and on the missing-data mechanism. One approach to the problem is to impute them to yield a complete data set. The goal of this paper is to propose a new single imputation method and to compare its performance to other single and multiple imputation methods known in literature. Considering a data set of PM10 concentration measured every2h by eight monitoring stations distributed over the metropolitan area of Palermo, Sicily, during 2003, simulated incomplete data have been generated, and the performance of the imputation methods have been compared on the correlation coefficient(Ï?), the index of agreement ( d), the root mean square deviation (RMSD) and the mean absolute deviation (MAD). All the performance indicators agree to evaluate the proposed method as the best among the ones compared, independently on the gap length and on the number of stations with missing data.
Keywords: Missing at random; Time series; Environmental pollutant; Single imputation
Mixing ratios and sources of halocarbons in urban, semi-urban and rural sites of the Pearl River Delta, South China by C.Y. Chan; J.H. Tang; Y.S. Li; L.Y. Chan (pp. 7331-7345).
The pearl river delta (PRD) region is one of the most important industrial and manufacturing centers of China and the world. In order to explore the regional mixing ratios of halocarbons in the PRD atmosphere and to reconcile the major halocarbon emission sources, air samples were collected in an urban site in Guangzhou City, a semi-urban site in Panyu and a rural site on Dinghu Mountain, as well as roadside sites and vehicular tunnels of the PRD in 2001 and 2004. The samples were analyzed for a variety of carbon-containing compounds. The results revealed elevated regional mixing ratios of most halocarbons, especially trichloroethene (C2HCl3), methyl iodide (CH3I), tetrachloroethene (C2Cl4), bromochlorodifluoromethane (Halon-1211, CBrClF2), 1-dichloro-1,1-fluoroethane (HCFC-142b, CH3CClF2) and trichloromethane (CHCl3) when compared with the background levels of the western Pacific and East Asian coast, and the Northern Hemisphere suggesting that there are significant sources of halocarbons in the PRD region. Higher dichlorodifluoromethane (CFC-12, CCl2F2), 1,1,1-trichlorotrifluoroethane (CFC-113, CCl2FCClF2), dibromomethane (CH2Br2) and tribromomethane (CHBr3) mixing ratios were found in the tunnels and roadside samples when compared with the ambient samples. In these samples, CH2Br2 and CHBr3 correlated well with each other and methyl bromide (CH3Br) suggesting they are associated with exhaust emissions from vehicles running on leaded gasoline. High levels of methyl halides: methyl chloride (CH3Cl), CH3Br and CH3I, and CH2Br2, bromodichloromethane (CHBrCl2), CHBr3 and dimethyl sulfide (C2H6S, DMS) were simultaneously observed in the oceanic air masses that originated from the coastal areas of southeast China and had passed over the Pearl River Estuary. Good correlations were found between CH2Br2 and CHBr3 with linear regression slopes of 0.17 and 0.15 for the Dinghu Mountain and Guangzhou City samples, respectively, and between CH3I and CHBr3, and DMS suggesting that emissions from the coastal territorial ecosystems of the PRD are important sources of the methyl halides, CH2Br2, CHBrCl2, CHBr3 and DMS observed.
Keywords: Halocarbons; Montreal Protocol; Air pollutant emissions; Pearl River Delta and China
Spatial and temporal distributions of mercury emissions from forest fires in Mediterranean region and Russian federation by Sergio Cinnirella; Nicola Pirrone (pp. 7346-7361).
Mercury emissions from forest fires in Europe and in North African countries bordering the Mediterranean Sea were estimated on the basis of ground-based forest fires data, forests phytomass and measured emission factors. Satellite observations were used to assess mercury emissions in Russian Federation through the assessment of spatial and temporal distributions of forest phytomass content and forest burnt areas. Annual mercury emissions in Europe were in the range of 0.9–3.6Mgyr−1, Italy and Portugal have the highest emissions with an average of 821 and 459kgyr−1 respectively, followed by Spain (394kgyr−1), France (247kgyr−1) and Poland (191kgyr−1). On regional scale, Hg emissions from this particular source in the Mediterranean region is 2.3Mgyr−1 (in the range 0.4–4.0Mgyr−1) on average, while emissions from African and Middle East countries bordering the Mediterranean Sea are not significant. Mercury emissions in the Russian Federation are in the range of 3.4–24.8Mgyr−1 (16Mgyr−1 on average).
Keywords: Remote sensing; GIS; Europe; Russian federation; Mediterranean; Forest fires; Emissions; Mercury
Validation of road traffic urban emission inventories by means of concentration data measured at air quality monitoring stations in Europe by Giorgos Mellios; Roel Van Aalst; Zissis Samaras (pp. 7362-7377).
A method has been developed to validate inventories of urban emissions from road transport using air quality measurements. To this aim atmospheric concentration data for CO, NO x and PM10 measured at urban traffic stations in five European countries, retrieved from the European Air Quality Information System AirBase, have been analysed. Traffic emission ratios as derived from this analysis were compared to estimates of emission ratios as provided by a suitable emissions model (TRENDS).The comparison shows a fair agreement for the CO over NO x ratio on a country level, suggesting that the measured concentrations indeed dominantly originate from traffic-related emissions. On the other hand, the NO x over PM10 and PM10 over CO emission ratios estimated by TRENDS are over- and underestimated, respectively, as compared to the respective average measured ratio. These discrepancies may be attributed to the fact that modelled PM10 emissions do not account for particles originating from non-exhaust sources. Modelled ratios have confirmed the observed weekday and year dependence of the ratios.A sensitivity analysis on the CO over NO x ratio has shown that small changes in the share of mileage allocated to urban driving by different vehicle categories result in significant changes in the emission ratio. Appropriate re-allocations of the urban shares, especially for diesel vehicles, enabled the calibration of the TRENDS model against air quality data collected at various monitoring sites in different countries. In order to further improve the consistency of the method, more information on ambient air PM2.5 mass concentrations needs to be collected from the monitoring stations and PM10 emission factors from primary non-exhaust sources (including gasoline-fuelled vehicles) need to be incorporated into TRENDS.
Keywords: Air quality measurements; Urban emission inventories; Traffic emissions
Spatiotemporal analysis of air conditions as a tool for the environmental management of a show cave (Cueva del Agua, Spain) by A. Fernandez-Cortes; J.M. Calaforra; F. Sanchez-Martos (pp. 7378-7394).
We recorded the air temperature and carbon dioxide concentration within the Cueva del Agua, a cave in Spain, under natural conditions prior to the cave being opened to tourists. Geostatistical tools are useful techniques for characterizing microclimate parameters with the aim of adopting measures to ensure the conservation and sound environmental management of tourist caves. We modelled the spatial distribution of these microclimatic parameters over an annual cycle using iterative residual kriging, revealing the stratification of air related to the cave's topography. Replenishment of the cave air is activated by convective circulation that accompanies the development of inversions in the thermal gradient of the air. Comparison of the spatial distribution of each microclimatic parameter over time enables us to characterize the exchange of air between the cave interior and the outside, as well as identify potential areas that could be opened to tourists and determine suitable visiting schedules.
Keywords: Show cave; Environmental management; Kriging; Convective air circulation; Karst
High222Rn levels in a show cave (Castañar de Ibor, Spain): Proposal and application of management measures to minimize the effects on guides and visitors by J. Lario; Sanchez-Moral S. Sánchez-Moral; S. Cuezva; M. Taborda; V. Soler (pp. 7395-7400).
Castañar de Ibor (Caceres, Spain) is a low energy cave showing very high micro-environmental stability throughout the annual cycle and minimum rates of energy exchange with the atmosphere. The radon (222Rn) levels monitored inside Castañar cave reached 50,462Bqm−3 in April 2005 and had an annual average of 32,246Bqm−3. Annual variations in Rn concentration seem mainly related to differences in internal and external temperature. The highest values of222Rn concentration occur during winter and early spring when air-cave temperature surpasses the external air temperature, evidencing very low air exchange rate. These values are the highest recorded in any Spanish cave, either natural or show, and are much higher than the average in most caves around the world. The calculation of the effective dose received by guides during 2004 showed values higher than the maximum effective dose recommended by authorities. Two management measurements were applied to reduce these doses: reduction of the time of visit to a maximum of 60min, and opening the cave door 1hour before the entrance of the guides and visitors. These management measures were effective, as they led to a decrease of 10–12% in222Rn in the cave atmosphere during visits and prevented the guides from being exposed to higher than recommended doses of radiation.
N2O5 hydrolysis on the components of mineral dust and sea salt aerosol: Comparison study in an environmental aerosol reaction chamber by Praveen K. Mogili; Paul D. Kleiber; Mark A. Young; Vicki H. Grassian (pp. 7401-7408).
The kinetics of the heterogeneous hydrolysis of N2O5 on some of the major components of mineral dust and sea salt aerosol have been investigated in an environmental aerosol chamber. Gas-phase N2O5 undergoes heterogeneous reaction to form HNO3 on carbonate, clay and oxide minerals. The nitric acid hydrolysis product was promptly detected in the gas phase concomitant with the decay of N2O5 over time. The N2O5 decay kinetics were measured and analyzed assuming first-order reaction kinetics. When normalized for surface area, heterogeneous decay of N2O5 on the different minerals followed the reactivity trend; kaolinite > hematite > montmorillonite > calcite>quartz. N2O5 decay was faster on all of the mineral dust aerosol components relative to NaCl, a major component of sea salt, at a relative humidity (RH) below the NaCl deliquescence point. The measured heterogeneous uptake coefficients were over an order of magnitude larger on several of the mineral dust aerosol compared to NaCl. The uptake coefficient was found to increase with RH.
Keywords: Mineral dust aerosol; Heterogeneous chemistry; N; 2; O; 5; hydrolysis; Atmospheric chemistry; Laboratory study
Determination of seasonal and regional variation in the provenance of dissolved cations in rain in Japan based on Sr and Pb isotopes by Takanori Nakano; Satomi Morohashi; Hiroshi Yasuda; Masaharu Sakai; Shuhei Aizawa; Koji Shichi; Takeshi Morisawa; Masamichi Takahashi; Masaru Sanada; Yojiro Matsuura; Hisao Sakai; Akio Akama; Naoki Okada (pp. 7409-7420).
We determined the elemental and Pb and Sr isotopic compositions of monthly wet precipitation at five sites in Japan (Sapporo, Morioka, Toyama, Tsukuba, and Kumamoto) to elucidate the seasonal and regional variation in the provenance of water-soluble materials. The concentrations of As, Cd, and Pb in the precipitation became high in winter to spring when the prevailing winds are westerly, but those of some metals (Mn, Cu, Ni) did not show distinct seasonal variations. Comparison of Pb isotopic ratios of the precipitation with those of aerosols from the Asian region showed (1) a geographical trend such that precipitation at Sapporo and Morioka in northeastern Japan contained Pb from aerosols from Russia and Mongolia, whereas that at Kumamoto in southwestern Japan contained Pb from aerosols from southern China, and (2) a seasonal variation in that precipitation in winter and spring became enriched in the airborne Pb from northern China, but the degree of the enrichment differed geographically. The sea-salt component (Cl, Na, and Mg) was high in winter and low in summer, particularly at Sapporo and Toyama, which face the Sea of Japan, whereas the non-sea-salt content of Ca and Sr and the87Sr/86Sr tended to become high in spring and low in summer to autumn. The pH was low in winter and became high in spring and summer, except at Tsukuba, which faces the Pacific Ocean. These results show that spring precipitation was partly neutralized by the dissolution of calcium carbonate in the Asian dust with high87Sr/86Sr and Ca/Sr. Summer and autumn precipitation, which was less affected by the Asian aerosols, had distinct Pb and Sr isotopic ratios depending on the site, suggesting that there are several Japanese sources of the base cations and heavy metals in the atmosphere over Japan.
Keywords: Acid rain; Asian dust; Sr isotope; Pb isotope; Provenance; Base cation; Terrestrial source
Investigation of geographical and temporal distribution of tropospheric ozone in Catalonia (North-East Spain) during the period 2000–2004 using multivariate data analysis methods by M. Felipe-Sotelo; L. Gustems; Hernà ndez I. Hernà ndez; M. Terrado; R. Tauler (pp. 7421-7436).
Multivariate data analysis methods were applied to study the geographical and temporal distribution of tropospheric ozone in Catalonia (North-East Spain). Ozone data were collected during the period 2000–2004 in 41 sampling stations. Data analysis by multivariate curve resolution alternating least squares (MCR-ALS) allowed the recognition of three sub-regions within Catalonia according to their ozone variation patterns. Representation of loadings by means of geographical information systems (GIS) allowed a better visualisation of these areas. Daily, weekly and annual ozone profiles were determined for each sub-region. Principal component analysis (PCA) was applied within each sub-region to unravel the relationship between ozone variation and some other parameters, such as atmospheric pollutants (SO2, H2S, NO, NO2, CO and particulate matter), as well as meteorological variables (temperature, relative humidity, solar radiation, pressure, precipitation and wind speed).
Keywords: Chemometrics; Multivariate data analysis; Multivariate curve resolution
Ozone pollution and ozone biomonitoring in European cities Part II. Ozone-induced plant injury and its relationship with descriptors of ozone pollution by Andreas Klumpp; Wolfgang Ansel; Gabriele Klumpp; Phillippe Vergne; Nicolas Sifakis; M.J. MarÃa José Sanz; Stine Rasmussen; Ro-Poulsen Helge Ro-Poulsen; A. Àngela Ribas; Penuelas Josep Peñuelas; Harry Kambezidis; Shang He; Jean Pierre Garrec; Vicent Calatayud (pp. 7437-7448).
Within the scope of a biomonitoring study conducted in twelve urban agglomerations in eight European countries, the ozone-sensitive bioindicator plant Nicotiana tabacum cv. Bel-W3 was employed in order to assess the occurrence of phytotoxic ozone effects at urban, suburban, rural and traffic-exposed sites. The tobacco plants were exposed to ambient air for biweekly periods at up to 100 biomonitoring sites from 2000 to 2002. Special emphasis was placed upon methodological standardisation of plant cultivation, field exposure and injury assessment. Ozone-induced leaf injury showed a clearly increasing gradient from northern and northwestern Europe to central and southern European locations. The strongest ozone impact occurred at the exposure sites in Lyon and Barcelona, while in Edinburgh, Sheffield, Copenhagen and Düsseldorf only weak to moderate ozone effects were registered. Between-site differences within local networks were relatively small, but seasonal and inter-annual differences were strong due to the variability of meteorological conditions and related ozone concentrations.The 2001 data revealed a significant relationship between foliar injury degree and various descriptors of ozone pollution such as mean value, AOT20 and AOT40. Examining individual sites of the local monitoring networks separately, however, yielded noticeable differences. Some sites showed no association between ozone pollution and ozone-induced effects, whereas others featured almost linear relationships. This is because the actual ozone flux into the leaf, which is modified by various environmental factors, rather than ambient ozone concentration determines the effects on plants. The advantage of sensitive bioindicators like tobacco Bel-W3 is that the impact of the effectively absorbed ozone dose can directly be measured.
Keywords: Air quality; Bioindicators; Tobacco Bel-W3; AOT40; Urban air pollution
Comparison of peak and average nitrogen dioxide concentrations inside homes by Peter Franklin; Tina Runnion; Drew Farrar; Peter Dingle (pp. 7449-7454).
Most health studies measuring indoor nitrogen dioxide (NO2) concentrations have utilised long-term passive monitors. However, this method may not provide adequate information on short-term peaks, which may be important when examining health effects of this pollutant. The aims of this study were to investigate the relationship between short-term peak (peak) and long-term average (average) NO2 concentrations in kitchens and the effect of gas cookers on this relationship. Both peak and average NO2 levels were measured simultaneously in the kitchens of 53 homes using passive sampling techniques. All homes were non-smoking and sampling was conducted in the summer months. Geometric mean (95% confidence interval (CI)) average NO2 concentrations for all homes were 16.2μgm−3 (12.7–20.6μgm−3). There was no difference between homes with and without gas cookers ( p=0.40). Geometric mean (95%CI) peak NO2 concentrations were 45.3μgm−3 (36.0–57.1μgm−3). Unlike average concentrations, peak concentrations were significantly higher in homes with gas cookers (64.0μgm−3, 48.5–82.0μgm−3) compared to non-gas homes (25.1μgm−3, 18.3–35.5μgm−3) ( p<0.001). There was only a moderate correlation between the peak and average concentrations measured in all homes ( r=0.39, p=0.004). However, when the data were analysed separately based on the presence of gas cookers, the correlation between peak and average NO2 concentrations was improved in non-gas homes ( r=0.59, p=0.005) but was not significant in homes with gas cookers ( r=0.19, p=0.33). These results suggest that average NO2 concentrations do not adequately identify exposure to short-term peaks of NO2 that may be caused by gas cookers. The lack of peak exposure data in many epidemiological studies may explain some of the inconsistent findings.
Keywords: Nitrogen dioxide; Indoor air; Passive monitoring; Peak concentrations; Long-term average concentrations
Corrigendum to “Results from a pilot-scale air quality study in Addis Ababa, Ethiopia�
by V. Etyemezian; M. Tesfaye; A. Yimer; M. Ali; J.C. Chow; D. Mesfin; T. Nega; G. Nikolich; J.G. Watson; M. Wondmagegn (pp. 7455-7455).