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Atmospheric Environment (v.44, #20)
Assessing the spatial and temporal variability of fine particulate matter components in Israeli, Jordanian, and Palestinian cities by Jeremy A. Sarnat; Tamar Moise; Jacob Shpund; Yang Liu; Jorge E. Pachon; Radwan Qasrawi; Ziad Abdeen; Shmuel Brenner; Khaled Nassar; Rami Saleh; James J. Schauer (pp. 2383-2392).
This manuscript presents results from an extensive, multi-country comparative monitoring study of fine particulate matter (PM2.5) and its primary chemical components in Israeli, Jordanian and Palestinian cities. This study represented the first time that researchers from these countries have worked together to examine spatial and temporal relationships for PM2.5 and its major components among the study sites. The findings indicated that total PM2.5 mass was relatively homogenous among many of the 11 sites as shown from strong between-site correlations. Mean annual concentrations ranged from 19.9 to 34.9 μg m−3 in Haifa and Amman, respectively, and exceeded accepted international air quality standards for annual PM2.5 mass. Similarity of total mass was largely driven by SO42− and crustal PM2.5 components. Despite the close proximity of the seven, well correlated sites with respect to PM2.5, there were pronounced differences among the cities for EC and, to a lesser degree, OC. EC, in particular, exhibited spatiotemporal trends that were indicative of strong local source contributions. Interestingly, there were moderate to strong EC correlations ( r > 0.65) among the large metropolitan cities, West Jerusalem, Tel Aviv and Amman. For these relatively large cities, (i.e., West Jerusalem, Tel Aviv and Amman), EC sources from the fleet of buses and cars typical for many urban areas predominate and likely drive spatiotemporal EC distributions. As new airshed management strategies and public health interventions are implemented throughout the Middle East, our findings support regulatory strategies that target integrated regional and local control strategies to reduce PM2.5 mass and specific components suspected to drive adverse health effects of particulate matter exposure.
Keywords: Fine particulate matter; Sulfate; Elemental carbon; Organic carbon; Middle East; Correlation; Spatial; Temporal; Variability
Temporal distribution and potential sources of atmospheric mercury measured at a high-elevation background station in Taiwan by Guey-Rong Sheu; Neng-Huei Lin; Jia-Lin Wang; Chung-Te Lee; Chang-Feng Ou Yang; Sheng-Hsiang Wang (pp. 2393-2400).
Measurements of gaseous elemental mercury (GEM), reactive gaseous mercury (RGM), and particulate mercury (PHg) have been conducted at Lulin Atmospheric Background Station (LABS) in Taiwan since April 2006. This was the first long-term free tropospheric atmospheric Hg monitoring program in the downwind region of East Asia, which is a major Hg emission source region. Between April 13, 2006 and December 31, 2007, the mean concentrations of GEM, RGM, and PHg were 1.73 ng m−3, 12.1 pg m−3, and 2.3 pg m−3, respectively. A diurnal pattern was observed for GEM with afternoon peaks and nighttime lows, whereas the diurnal pattern of RGM was opposite to that of GEM. Spikes of RGM were frequently observed between midnight and early morning with concurrent decreases in GEM and relative humidity and increases in O3, suggesting the oxidation of GEM and formation of RGM in free troposphere (FT). Upslope movement of boundary layer (BL) air in daytime and subsidence of FT air at night resulted in these diurnal patterns. Considering only the nighttime data, which were more representative of FT air, the composite monthly mean GEM concentrations ranged between 1.06 and 2.06 ng m−3. Seasonal variation in nighttime GEM was evident, with lower concentrations usually occurring in summer when clean marine air masses prevailed. Between fall and spring, air masses passed the East Asian continent prior to reaching LABS, contributing to the elevated GEM concentrations. Analysis of GEM/CO correlation tends to support the argument. Good GEM/CO correlations were observed in fall, winter, and spring, suggesting influence of anthropogenic emission sources. Our results demonstrate the significance of East Asian Hg emissions, including both anthropogenic and biomass burning emissions, and their long-range transport in the FT. Because of the pronounced seasonal monsoon activity and the seasonal variation in regional wind field, export of the Asian Hg emissions to Taiwan occurs mainly during fall, winter, and spring.
Keywords: Biomass burning; Long-range transport; Gaseous elemental mercury; Reactive gaseous mercury; Particulate mercury
Provenances of atmospheric dust over Korea from Sr–Nd isotopes and rare earth elements in early 2006 by Min Kyung Lee; Yong Il Lee; Hi-Il Yi (pp. 2401-2414).
Sr and Nd isotopic composition of pre- and syn-Asian dust (Hwangsa) particles collected from three different water depths at two different offshore sites, western Korea and rare earth elemental composition of syn-Asian dust particles collected from three islands around the Korean Peninsula in late April 2006 were analyzed to interpret their provenance. The dust Sr–Nd isotopic compositions vary spatiotemporally, but they show specific values when the Hwangsa event occurred. Satellite images, airmass backward trajectory modeling, and comparison with Sr–Nd isotopic ratios and rare earth elements compositions of soils and desert sands of northern China all suggest the major source of dust particles for the late April 2006 Hwangsa event to be the Mu Us Desert in northern China. Dust particles of the pre-Hwangsa period include both background dusts and the previous Hwangsa event dust particles, and they are interpreted to have been originated from various arid regions of China such as the Hobq Desert, the Mu Us Desert, and the Taklamakan Desert in different times. Different background dust sources during pre-Hwangsa period in early 2006 resulted from the changing route of the westerlies.
Keywords: Asian dust; Hwangsa; Backward trajectory; Sr–Nd isotopes; REE; Provenance
Understanding of regional air pollution over China using CMAQ, part I performance evaluation and seasonal variation by Xiao-Huan Liu; Yang Zhang; Shu-Hui Cheng; Jia Xing; Qiang Zhang; David G. Streets; Carey Jang; Wen-Xing Wang; Ji-Ming Hao (pp. 2415-2426).
The U.S. EPA Models-3 Community Multiscale Air Quality (CMAQ) modeling system with the process analysis tool is applied to China to study the seasonal variations and formation mechanisms of major air pollutants. Simulations show distinct seasonal variations, with higher surface concentrations of sulfur dioxide (SO2), nitrogen dioxide (NO2), and particulate matter with aerodynamic diameter less than or equal to 10 μm (PM10), column mass of carbon monoxide (CO) and NO2, and aerosol optical depth (AOD) in winter and fall than other seasons, and higher 1-h O3 and troposphere ozone residual (TOR) in spring and summer than other seasons. Higher concentrations of most species occur over the eastern China, where the air pollutant emissions are the highest in China. Compared with surface observations, the simulated SO2, NO2, and PM10 concentrations are underpredicted throughout the year with NMBs of up to −51.8%, −32.0%, and −54.2%, respectively. Such large discrepancies can be attributed to the uncertainties in emissions, simulated meteorology, and deviation of observations based on air pollution index. Max. 1-h O3 concentrations in Jan. and Jul. at 36-km are overpredicted with NMBs of 12.0% and 19.3% and agree well in Apr. and Oct. Simulated column variables can capture the high concentrations over the eastern China and low values in the central and western China. Underpredictions occur over the northeastern China for column CO in Apr., TOR in Jul., and AODs in both Apr. and Jul.; and overpredictions occur over the eastern China for column CO in Oct., NO2 in Jan. and Oct., and AODs in Jan. and Oct. The simulations at 12-km show a finer structure in simulated concentrations than that at 36-km over higher polluted areas, but do not always give better performance than 36-km. Surface concentrations are more sensitive to grid resolution than column variables except for column NO2, with higher sensitivity over mountain and coastal areas than other regions.
Keywords: CMAQ; Model evaluation; Seasonality; China; Sensitivity to horizontal grid resolution
Atmospheric methanethiol emitted from a pulp and paper plant on the shore of Lake Baikal by Kei Toda; Tomoaki Obata; Vladimir A. Obolkin; Vladimir L. Potemkin; Kazutoshi Hirota; Masaki Takeuchi; Shou Arita; Tamara V. Khodzher; Michael A. Grachev (pp. 2427-2433).
On-site measurement of methanethiol (CH3SH) was performed for three years on ships and cars near a pulp and paper plant standing on the shore of Lake Baikal in Siberia, Russia, to investigate the behavior and impact of atmospheric CH3SH emitted from a point source. Despite its strong odor, there are few reports on atmospheric CH3SH, while many investigations have been carried out on dimethyl sulfide (DMS). In this work, CH3SH and DMS were measured every 15 min by a recently developed automated instrument based on single column trapping/separation and chemiluminescence measurement. Hydrogen sulfide, sulfur dioxide and ozone were also measured simultaneously by individual instruments. Of these sulfur compounds, CH3SH was dominant and its concentration sometimes reached several tens of ppbv. The concentration of CH3SH was high at night, because of the lack of photodecomposition and local winds from the mountain to the lake. Such time variation was marked in the summer. The CH3SH level decreased significantly downwind, while decreases in concentrations of other compounds such as DMS and SO2 were relatively small. From these temporal and spatial variations, the behavior of CH3SH is described in this paper. The impact of CH3SH near the Siberian big sources is discussed with the presented data.
Keywords: Methanethiol (methyl mercaptan); Pulp and paper plant; Lake Baikal; Spatial and daily variations
Sea salt concentrations across the European continent by A.M.M. Manders; M. Schaap; X. Querol; M.F.M.A. Albert; J. Vercauteren; T.A.J. Kuhlbusch; R. Hoogerbrugge (pp. 2434-2442).
The oceans are a major source for particles that play an important role in many atmospheric processes. In Europe sea salt may contribute significantly to particulate matter concentrations. We have compiled sodium concentration data as a tracer for sea salt for 89 sites in Europe to provide more insight in the distribution of sea salt across Europe. The annual average sea salt concentrations above land were estimated to range between 0.3 and almost 13 μg m−3. Maximum concentrations are found at the Irish coast. At coastal sites along the Atlantic and North Sea coast concentrations tend to be around 5 μg m−3. More inland locations up to about 300 km away from the coast tend to show concentrations between 2 and 5 μg m−3, whereas sites further away from the coast are characterized by lower concentrations. An analysis of the representativity of the data with respect to a long term average showed that the long average is associated with a standard deviation of around 15%. The compilation of observations provides an improved overview of sea salt concentrations in Europe as well as an improved basis for model validation. Verification of the results of the LOTOS-EUROS model learned that the model represents well the spatial variability of the observed sea salt concentrations very well. However, the absolute concentrations are significantly overestimated due to large uncertainties in the emission and dry deposition parameterizations. Using the high explained variability in the gradients across Europe, the bias-corrected modelled distribution serves as a best estimate of the sea salt distribution across Europe for 2005.
Keywords: Sodium; Sea salt; Regional modelling; PM10
Responses of future air quality to emission controls over North Carolina, Part I: Model evaluation for current-year simulations by Xiao-Huan Liu; Yang Zhang; Kristen M. Olsen; Wen-Xing Wang; Bebhinn A. Do; George M. Bridgers (pp. 2443-2456).
The prediction of future air quality and its responses to emission control strategies at national and state levels requires a reliable model that can replicate atmospheric observations. In this work, the Mesoscale Model (MM5) and the Community Multiscale Air Quality Modeling (CMAQ) system are applied at a 4-km horizontal grid resolution for four one-month periods, i.e., January, June, July, and August in 2002 to evaluate model performance and compare with that at 12-km. The evaluation shows skills of MM5/CMAQ that are overall consistent with current model performance. The large cold bias in temperature at 1.5m is likely due to too cold soil initial temperatures and inappropriate snow treatments. The large overprediction in precipitation in July is due likely to too frequent afternoon convective rainfall and/or an overestimation in the rainfall intensity. The normalized mean biases and errors are −1.6% to 9.1% and 15.3–18.5% in January and −18.7% to −5.7% and 13.9–20.6% in July for max 1-h and 8-h O3 mixing ratios, respectively, and those for 24-h average PM2.5 concentrations are 8.3–25.9% and 27.6–38.5% in January and −57.8% to −45.4% and 46.1–59.3% in July. The large underprediction in PM2.5 in summer is attributed mainly to overpredicted precipitation, inaccurate emissions, incomplete treatments for secondary organic aerosols, and model difficulties in resolving complex meteorology and geography. While O3 prediction shows relatively less sensitivity to horizontal grid resolutions, PM2.5 and its secondary components, visibility indices, and dry and wet deposition show a moderate to high sensitivity. These results have important implications for the regulatory applications of MM5/CMAQ for future air quality attainment.
Keywords: MM5/CMAQ; Fine-scale modeling; Model evaluation; Sensitivity to horizontal grid resolution
Source characteristics of hazardous Chihuahuan Desert dust outbreaks by Nancy I. Rivera Rivera; Thomas E. Gill; Max P. Bleiweiss; Jenny L. Hand (pp. 2457-2468).
The Chihuahuan Desert region is an important contributor to atmospheric dust loading and transport in North America; however, specific dust sources in this region are poorly characterized. Major dust events frequently are characterized by multiple dust plumes developing nearly simultaneously over a large region. Remote sensing data were used to identify the source locations and associated land cover for the most extreme dust events in the Chihuahuan Desert since 2002. Analysis of infrared channels utilizing brightness temperature differences was used to analyze data from geostationary and polar-orbiting satellites, from which dust sources were determined and located. This methodology was applied to the five dust events in the region that resulted in “hazardous” PM10 levels in Texas per the USEPA’s Air Quality Index. Source locations determined from satellite images were used in conjunction with LANDSAT data and Google Earth™ images to determine the corresponding land-surface features. Agricultural lands, playas, and their edges are pointed out as focus areas for dust emission, at least during the most intense events. The 130 dust plume initiation sites were relatively uniformly spaced over the landscape, not clumped into a few “hotspots,” suggesting the role of spatiotemporally random meteorological factors in determining major points of emission within and between dust storms. These findings provide an initial characterization of Chihuahuan Desert dust source locations and establish a baseline for continued research in determining potential locations for future dust outbreaks in the southwestern U.S. and northwestern Mexico.
Keywords: Dust; Remote sensing; Chihuahuan Desert; Land cover; AVHRR
Formation of oxidized products from the reaction of gaseous phenanthrene with the OH radical in a reaction chamber by JiYi Lee; Douglas A. Lane (pp. 2469-2477).
The reaction of gas phase phenanthrene (Phen) with the OH radical in the presence of NOx was studied in a reaction chamber. A number of oxidation products were identified by two dimensional gas chromatography–time of flight mass spectrometry (GC × GC–TOFMS). Identified products included 9-fluorenone, 1,2-naphthalic anhydride, 2,2′-diformylbiphenyl, dibenzopyranone, 1, 2, 3, 4 and 9-phenanthrols, 2, 3, 4 and 9-nitrophenanthrenes, 1,4-phenanthrenequinone, 9,10-phenanthrenequinone, and 2- and 4-nitrodibenzopyranones. This is the first study to identify 1,2-naphthalic anhydride and 1,4-phenanthrenequinone as products of the gas phase reaction of Phen with the OH radical. Eight more products were tentatively identified by their mass spectral fragmentation patterns and based on the typical OH radical initiated photochemical reaction mechanisms of simple aromatic compounds and naphthalene. In the reaction chamber, particle formation of products as a function of irradiation time was measured. Phenanthrenequinones, phenanthrol, nitrophenanthrene and nitrobenzopyranone were observed predominantly in the particle phase. This implies that these oxidized products formed from the reaction of Phen with the OH radical in the chamber would be associated with particles in the atmosphere and may, therefore, have an impact on human health. Possible pathways for the formation of these products are suggested and discussed.
Keywords: Phenanthrene; OH radical reaction; Oxidized products; Particle formation
Impact of an exceptional Saharan dust outbreak in France: PM10 and artificial radionuclides concentrations in air and in dust deposit by Olivier Masson; Damien Piga; Rodolfo Gurriaran; Donato D’Amico (pp. 2478-2486).
The present study focuses on the exceptional Saharan dust event that affected most of France in February 2004. Activity levels of various artificial radionuclides (90Sr,137Cs, uranium, thorium and plutonium isotopes,241Am) were examined. Activity or isotopic ratios are discussed in the context of atmospheric nuclear weapons tests, among them French tests performed in Sahara in the 1960s. The daily evolution of137Cs activity levels in the atmosphere was compared to daily PM10 change. A link between airborne137Cs and PM10, is given. It is estimated that this 2-day event deposited as much137Cs as would be deposited on average over a 10-month period. The amount of deposited137Cs and239+240Pu represents respectively about 0.1 and 1% of the activity already present in the soil. Such Saharan dust events correspond to an extreme type of “feeder” process of artificial radionuclides in the atmosphere. Therefore, they contribute to the long term background level of artificial radionuclides kept at trace levels in the atmosphere.
Keywords: Saharan dust; PM; 10; Radionuclide; Deposition
Global emission of mercury to the atmosphere from anthropogenic sources in 2005 and projections to 2020 by E.G. Pacyna; J.M. Pacyna; K. Sundseth; J. Munthe; K. Kindbom; S. Wilson; F. Steenhuisen; P. Maxson (pp. 2487-2499).
This paper presents the 2005 global inventory of anthropogenic emissions to the atmosphere component of the work that was prepared by UNEP and AMAP as a contribution to the UNEP report Global Atmospheric Mercury Assessment: Sources, Emissions and Transport ().It describes the methodology applied to compile emissions data on the two main components of the inventory – the ‘by-product’ emissions and the ‘intentional use’ emissions – and to geospatially distribute these emissions estimates to produce a gridded dataset for use by modelers, and the results of this work.It also presents some initial results of work to develop (simplified) scenario emissions inventories for 2020 that can be used to investigate the possible implications of actions to reduce mercury emissions at the global scale.
Keywords: Mercury; Global emissions; Anthropogenic sources; Current levels; Future scenarios