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Atmospheric Environment (v.42, #29)
Characterizations of ozone, NO x, and VOCs measured in Shanghai, China by Fuhai Geng; Xuexi Tie; Jianmin Xu; Guangqiang Zhou; Li Peng; Wei Gao; Xu Tang; Chunsheng Zhao (pp. 6873-6883).
Shanghai Meteorological Bureau (SMB) has established a VOC laboratory and an observational station network for VOC, NO x and O3 measurements in the Shanghai region. The measurements became operational since 2005. In this study, we investigate spatial and temporal variability of O3 and its precursors (NO x and VOCs), and impacts of the precursors on O3 formation. A chemical mechanism model (NCAR-MM) is applied to assess the sensitivity of the O3 formation to NO x and VOC concentrations. The results show that O3 concentrations are higher in rural area than in center of the city, suggesting that there are O3 depression processes in center of city and air pollutant emissions are not favorable for the O3 chemical formation. The analysis suggests that the NO and NO2 concentrations in center of the city are lower during weekend than weekday due to less traffic and industrial activities. By contrast, the O3 concentrations are higher during weekend than weekday. During weekend, the reduction of NO2 leads to enhancement in OH radicals, resulting in the higher O3 production. This enhancement of weekend O3 is off-set by decrease in VOC concentrations. The chemical model study suggests that the decrease of NO x alone could result in a larger weekend O3 enhancement than the measured result. The model sensitivity study also suggests that O3 concentration decreases when NO x concentration is enhanced. Both model and measurement results indicate that the O3 formation is clearly under VOC-sensitive regime in the city of Shanghai. As a result, in the urban area, the O3 production is strongly depressed by high NO x concentrations, resulting in lower O3 concentration in center of the city than in rural area of the city. This study further shows that the highly reactive VOCs (aromatics) play important roles in determining the O3 formation. The ratio of toluene/benzene suggests that automobiles play important roles in the O3 formation in the city of Shanghai. Further increase in automobiles in Shanghai could lead to potential high O3 concentration in the future.
Keywords: Ozone; NO; x; VOCs; Shanghai
Study on an intense dust storm over Greece by D.G. Kaskaoutis; H.D. Kambezidis; P.T. Nastos; P.G. Kosmopoulos (pp. 6884-6896).
Springtime constitutes the most favorable period for Sahara dust outbreaks and transport over Eastern Mediterranean. This study investigates the aerosol properties during April 2005 using remote-sensing and ground-based measurements. Three dust events with high aerosol optical depth (AOD) values have been observed during the measuring period, with duration of two days, i.e. 11–12, 16–17 and 25–26 April 2005. In this paper we mainly focus on the intense dust event of 16–17 April 2005, when a thick dust layer transported from Libya affected the whole Greek territory. Very high AOD values obtained from Aqua-MODIS sensor were observed over Greece (mean 2.42±1.25) on 17 April, while the respective mean April value was 0.31±0.09. The AOD at 550 nm (AOD550) values over Crete were even larger, reaching ∼4.0. As a consequence, the PM10 concentrations over Athens dramatically increased reaching up to 200μgm−3. On the other hand, the fine-mode fraction values obtained from Terra-MODIS showed a substantial decrease in the whole Greek area on 17 April with values below 0.2 in the Southern regions. The intense dust layer showed a complex behavior concerning its spatial and temporal evolution and allowed us to study the changes in the optical properties of the desert dust particles along their transport routes due to the mixing processes with other aerosol types. The results from different measurements (ground-based and remote-sensing) did not contradict each other and, therefore, are adequate for monitoring of dust load over the Eastern Mediterranean.
Keywords: Saharan dust event; MODIS; Sunphotometer; PM; 10; Eastern Mediterranean; Greece
Evaluation of the CMB and PMF models using organic molecular markers in fine particulate matter collected during the Pittsburgh Air Quality Study by Kerry R. Bullock; Rachelle M. Duvall; Gary A. Norris; Stephen R. McDow; Michael D. Hays (pp. 6897-6904).
This analysis investigated different possible strategies for source apportionment of airborne fine particulate matter (PM2.5) using data collected as part of the Pittsburgh Air Quality Study (PAQS). More specifically, we apportioned the organic fraction of the winter and summer season PM2.5 using two source–receptor models – the EPA Chemical Mass Balance 8.2 (CMB) and EPA Positive Matrix Factorization 1.1 (PMF) models – and tested several case scenarios with each model by varying either the chemical species or source profiles used as model input. Moreover, we added the constraint of selecting only individual molecular marker species with concentrations above their minimum quantitative limits. Model results suggest that the molecular marker and source profile selection can strongly affect the model, as reflected in the source contribution estimates determined by both CMB and PMF. Biomass burning and mobile emissions sources were identified by both models as being major source contributors in Pittsburgh. A third source was consistent with a meat cooking profile but was more likely a combination of cooking and secondary organic aerosol.As expected, the relative proportion of each source's contribution depended on both the season and on whether the CMB or PMF model was applied. Selecting fewer species in CMB resulted in less mass being apportioned, and an unrealistically large wood burning contribution estimate. Swapping a wildfire profile for one of the two wood burning profiles also resulted in less mass being apportioned in the winter. The results suggest that CMB can distinguish between fireplace burning and wildfire contributions when appropriate species are included. The gasoline/diesel split also varied by up to an order of magnitude, depending on which model was applied and which species were fit.
Keywords: Chemical mass balance model; Positive matrix factorization; Source apportionment; Organic tracers; Pittsburgh Air Quality Study
Mercury dynamics of a northern hardwood canopy by Joseph T. Bushey; Alexei G. Nallana; Mario R. Montesdeoca; Charles T. Driscoll (pp. 6905-6914).
Atmospheric emissions have led to widespread concern over mercury (Hg) contamination in aquatic and terrestrial ecosystems. Plant litter is an important pathway of Hg inputs to forest ecosystems. We investigated the role of the canopy in Hg accumulation, transport and deposition in an upland forest ecosystem. The total Hg content of leaf tissue increased approximately 10-fold over the growing season across all species, from 4.4±2.7 to 37.3±12.4ngg−1, with estimated average linear Hg accumulation rates of 0.22, 0.23, and 0.35ngg−1day−1 for yellow birch ( Betula alleghaniensis), sugar maple ( Acer saccharum), and American beech ( Fagus grandifolia), respectively. This linear concentration relationship suggests that the accumulation is regulated by mass transfer processes between the atmosphere and leaf tissue. Conversely, the methyl Hg content (0.17±0.18ngg−1) and accumulations were low. Concentrations of total Hg were also 42% higher in understory (∼1m), compared to overstory (∼10m), beech. Such disparities in leaf Hg content may result from within-canopy variation in environmental variables, a canopy Hg0(g) concentration gradient, or species-specific growth strategies. Annual Hg litterfall was 17.9 and 16.4mgm−2yr−1 for 2004 and 2005, respectively, representing the largest input of Hg to this forest ecosystem. Methyl Hg litter input was <0.12mgm−2yr−1 for 2005. Modeling estimates of transpiration uptake and Hg0(g) deposition suggest that Hg in leaf tissue is largely derived from atmospheric sources. Thus, litter Hg represents largely a new, rather than recycled, input to the forest ecosystem.
Keywords: keywords; Deposition; Forest; Leaf tissue; Mercury; Plants; UplandAbbreviations; ANC; acid neutralizing capacity; CVAFS; cold vapor atomic fluorescence spectroscopy; HFNY; Huntington Experimental Forest, NY; Hg; mercury; MeHg; methylmercury; THg; total mercury
Identification of dust transport pathways from Lake Eyre, Australia using Hysplit by Hamish McGowan; Andrew Clark (pp. 6915-6925).
The HYbrid Single-Particle Lagrangian Integrated Trajectory model (HYSPLIT_4) is used to create seasonal climatologies (1980–2000) of air parcel trajectories from the Southern Hemisphere's most active dust source Lake Eyre, Australia. Daily trajectories were computed forward for eight days from an origin centered over Lake Eyre at 500m above the ground surface. Trajectory density maps were then created within a GIS for five levels; 0–500magl., 500–1000magl., 1000–1500magl., 1500–2000magl. and 2000–5000magl. These show that air parcel trajectories originating from Lake Eyre can affect regions many thousands of kilometers from the Australian continent in a relatively short period of time. Importantly, under favourable atmospheric conditions these air parcels have the potential to transport dust and other aerosols. During the austral winter, trajectories extended north to the southern Philippines highlighting the potential for dust from central Australia to affect most of Indonesia. This includes the tropical rainforests of Borneo and New Guinea, and the coral reefs of northern Australia and the Indonesian archipelago. We also show the potential for transport of dust from Lake Eyre to the Antarctic and much of the South Pacific and Southern Oceans. Accordingly, dust from Lake Eyre may affect biogeochemical cycles, sediment budgets, atmospheric processes and a wide range of ecosystems over a region much larger than previously thought. This highlights the need for further research to confirm the deposition of dust in the areas mapped by the present study.
Keywords: Dust transport; Lake Eyre; Air parcel trajectories; Hysplit; Antarctic; Coral Reefs; Australia
Quantification of total emission of air pollutants from Beijing using mobile mini-DOAS by Mattias Johansson; Bo Galle; Tong Yu; Lin Tang; Deliang Chen; Haijun Li; Jin Xiang Li; Yan Zhang (pp. 6926-6933).
This paper presents a novel method for quantification of the total emission of gases from area sources using the mobile mini-DOAS (Differential Optical Absorption Spectroscopy) instrument, a ground based optical remote sensing technique. The presented method has been applied to measure the emission of SO2 and NO2 from the city of Beijing, P.R. China, on a time scale of approximately 2h. The measurements have been performed during two field campaigns, in April and in August 2005. The estimated emission of NO2 is roughly the same during the two field campaigns with an average emission of 189tonsd−1 during April and 174tonsd−1 during August. The estimated emission of SO2 varies greatly between the two periods, with an average emission of 293tonsd−1 during April and 52tonsd−1 during August.
Keywords: Total emission; Air pollution; Ground based optical remote sensing; DOAS; Beijing; China
Sensitivity and uncertainty analysis of the mechanism of gas-phase chlorine production from NaCl aerosols in the MAGIC model by Paul Nissenson; Jennie L. Thomas; Barbara J. Finlayson-Pitts; Donald Dabdub (pp. 6934-6941).
This paper presents a global sensitivity and uncertainty analyses of the chlorine chemistry included in the Model of Aqueous, Gaseous and Interfacial Chemistry (MAGIC). Uncertainty ranges are established for input parameters (e.g. chemical rate constants, Henry's law constants, etc.) and are used in conjunction with Latin hypercube sampling and multiple linear regression to conduct a sensitivity analysis which determines the correlation between each input parameter and the model output. The contribution of each input parameter to the uncertainty in the model output is calculated by combining the results of the sensitivity analysis with the input parameters' uncertainty ranges. The peak concentration of molecular chlorine, [Cl2(g)]peak, is used to compare model runs since MAGIC has demonstrated previously the importance of an interfacial reaction between OH(g) and Cl−(aq,surface) in the production of Cl2(g). Results indicate that the interface reaction rate is most strongly correlated with [Cl2(g)]peak and is most responsible for the uncertainty in MAGIC's ability to calculate precisely [Cl2(g)]peak. In addition, the mass accommodation coefficient for OH and the aqueous-phase reaction rate for Cl2+OH−→HOCl+Cl− and 2CO3−+O2+2H2O→2CO2·H2O+2O2− also contribute significantly to the uncertainty in [Cl2(g)]peak.
Keywords: Interface chemistry; Sea-salt aerosol; Sensitivity analysis; Chlorine chemistry
Temporal variation in atmospheric ammonia concentrations above seabird colonies by T.D. Blackall; L.J. Wilson; J. Bull; M.R. Theobald; P.J. Bacon; K.C. Hamer; S. Wanless; M.A. Sutton (pp. 6942-6950).
Recent studies have shown that seabirds are an important source of ammonia (NH3) emissions in remote coastal ecosystems. Nesting behaviour, which varies between seabird species, is likely to be a major factor in determining the proportion of excreted nitrogen (N) volatilised to the atmosphere as NH3. A long-term NH3 monitoring programme was implemented at a Scottish seabird colony with a range of species and associated nesting behaviours. The average monthly NH3 concentration was measured at 12 locations over a 14-month period, to infer spatial (i.e. species-specific) and temporal (seasonal) changes in NH3 emissions from different seabird species. An emissions model of seabird NH3, based on species-specific bioenergetics and behaviour, was applied to produce spatial estimates for input to a dispersion model.Atmospheric NH3 concentrations demonstrated spatial variability as a result of differing local populations of breeding seabirds, with the highest concentrations measured above cliff nesting species such as Common guillemot Uria aalge, Razorbill Alca torda and Black-legged kittiwake Rissa tridactyla. NH3 concentrations above a colony of burrow nesting Atlantic puffin Fratercula arctica were low, considering the high number of birds. Emission of NH3 from excreted N exhibits a time lag of approximately a month. It is likely that all excreted N is lost from the colony by volatilisation as NH3 or surface run-off between breeding seasons. Modelled NH3 emissions and concentrations correlated with measured concentrations, but were much higher, reflecting uncertainties in the local turbulent characteristics. The results allow multi-species seabird population data to be used for the calculation of regional and global NH3 emission inventories, whilst improving understanding of N budgets of remote coastal ecosystems.
Keywords: Ammonia; Emission; Seabird; Nitrogen; Guano; Model
Airborne study of ozone formation over Dallas, Texas by Menachem Luria; Ralph J. Valente; Solomon Bairai; William J. Parkhurst; Roger L. Tanner (pp. 6951-6958).
Twelve research fights were performed during August 2005 over the Dallas (Texas) metropolitan area. The primary objective was to estimate the relative contribution of primary emissions from large point sources, i.e., major power plants, compared with mobile sources in terms of O3 production. The distinction between the source types was derived from concurrent measurements of SO2 (tracer for point sources) and CO (tracer for mobile sources) relative to levels of O3 and NO x (the O3 precursor). The flights also examined the vertical structure of the atmosphere and its effect on the dispersion/dilution of the trace gases. During the first half of the study the O3 levels in the Dallas area were relatively low and only during the second half were significantly elevated O3 levels observed. For the latter period the relationship between maximum O3 levels, the air mass chemical age and the O3 yield are evaluated. The results also revealed that mobile sources are the main contributors to the elevated O3 levels in the Dallas area.
Keywords: Ozone; Ozone production efficiency; Chemical age; Carbon monoxide; Nitrogen oxides; Urban air pollution
Near real time monitoring of biomass burning particulate emissions (PM2.5) across contiguous United States using multiple satellite instruments by Xiaoyang Zhang; Shobha Kondragunta; Christopher Schmidt; Felix Kogan (pp. 6959-6972).
Biomass burning is a major source of aerosols that affect air quality and the Earth's radiation budget. Current estimates of biomass burning emissions vary markedly due to uncertainties in biomass density, combustion efficiency, emission factor, and burned area. This study explores the modeling of biomass burning emissions using satellite-derived vegetative fuel loading, fuel moisture, and burned area across Contiguous United States (CONUS). The fuel loading is developed from Moderate-Resolution Imaging Spectroradiometer (MODIS) data including land cover type, vegetation continuous field, and monthly leaf area index. The weekly fuel moisture category is retrieved from AVHRR (Advanced Very High Resolution Radiometer) Global Vegetation Index (GVIx) data for the determination of fuel combustion efficiency and emission factor. The burned area is simulated using half-hourly fire sizes obtained from the GOES (Geostationary Operational Environmental Satellites) Wildfire Automated Biomass Burning Algorithm (WF_ABBA) fire product. By integrating all these parameters, quantities of PM2.5 (particulate mass for particles with diameter <2.5μm) aerosols are calculated for each individual fire at an interval of half hour from 2002–2005 across CONUS. The PM2.5 estimates indicate that the annual PM2.5 emissions are 3.49×105, 3.30×105, 1.80×105, and 2.24×105 tons for 2002 (April to December), 2003, 2004, and 2005, respectively. Among various ecosystems, forest fires release more than 44% of the emissions although the related burned areas only account for less than 30%. Spatially, PM2.5 emissions are larger in California for all these years, but only for some individual years in Oregon, Montana, Arkansas, Florida, Arizona, Louisiana, and Idaho. Finally, the calculated PM2.5 emissions are evaluated using national wildfire emission inventory data (NWEI) and compared with estimates from different fuel loadings. The difference between NWEI and GOES fire-based estimate is less than 20% if the same fuel data are used. The evaluation suggests that the biomass burning emissions derived from multiple satellite data provide realistic spatiotemporal patterns and can be assimilated into air quality models for forecasts in real or near real time.
Keywords: Biomass burning emissions; Particulate matter; Multiple satellite instruments; GOES; Near real time
Variability of ozone depleting substances as an indication of emissions in the Pearl River Delta, China by Chih-Chung Chang; Cheng-Hsun Lai; Chieh-Heng Wang; Ying Liu; Min Shao; Yuanhang Zhang; Jia-Lin Wang (pp. 6973-6981).
The continued production and consumption of five major chlorocarbons, i.e., CFC-11 (CCl3F), CFC-12 (CCl2F2), CFC-113 (CCl2FCClF2), CH3CCl3, and CCl4, as allowed by developing nations including China under the Montreal Protocol, were assessed by a method employing concentration variability. Measurements of the five ozone depleting substances (ODS) were measured in downtown Guangzhou and a rural site in the Pearl River Delta (PRD), China by both in situ and flask measurements. In order to post a contrast to PRD with a referencing environment of minimal emissions, in situ measurements were also conducted in Taipei, Taiwan, where a decade long phase-out of CFCs has been implemented.In general, the variability of chlorocarbons in the PRD sites was significantly greater than that of Taipei. While the abundance of the five ODSs in Taipei was relatively uniform with a relative standard deviation (RSD) varying between 3% and 16%, their variability in PRD with the exception of CFC-113 was significantly more pronounced, clearly indicating the significant usage of ODSs. The variability of CFC-113 in both cities, however, was nearly indiscernible from the instrumental precision, suggesting little usage of CFC-113 in China. Methyl chloroform in Guangzhou exhibited a strong link to solvent evaporation as it showed a tight correlation with ambient toluene. Alarmingly, CCl4 was the most variable of the five major chlorocarbons in Guangzhou, which should arouse a serious concern for public health due to its carcinogenicity.
Keywords: Montreal Protocol; Chlorofluorocarbons (CFCs); Volatile organic compounds (VOCs)
Pollutant roses for daily averaged ambient air pollutant concentrations by Guido Cosemans; Jan Kretzschmar; Clemens Mensink (pp. 6982-6991).
Pollutant roses are indispensable tools to identify unknown (fugitive) sources of heavy metals at industrial sites whose current impact exceeds the target values imposed for the year 2012 by the European Air Quality Daughter Directive 2004/207/EC. As most of the measured concentrations of heavy metals in ambient air are daily averaged values, a method to obtain high quality pollutant roses from such data is of practical interest for cost-effective air quality management.A computational scheme is presented to obtain, from daily averaged concentrations, 10° angular resolution pollutant roses, called PRP roses, that are in many aspects comparable to pollutant roses made with half-hourly concentrations.The computational scheme is a ridge regression, based on three building blocks:1.ordinary least squares regression;2.outlier handling by weighting based on expected values of the higher percentiles in a lognormal distribution;3.weighted averages whereby observed values, raised to a power m, and daily wind rose frequencies are used as weights. Distance measures are used to find the optimal value for m.The performance of the computational scheme is illustrated by comparing the pollutant roses, constructed with measured half-hourly SO2 data for 10 monitoring sites in the Antwerp harbour, with the PRP roses made with the corresponding daily averaged SO2 concentrations. A miniature dataset, made up of 7 daily concentrations and of half-hourly wind directions assigned to 4 wind sectors, is used to illustrate the formulas and their results.
Keywords: Pollutant roses; Averaging time; Outliers; Weighted averages; Least squares regression; Lognormal distribution
Micrometeorological measurements of nitrous oxide exchange above a cropland by Jun Li; Xiaojuan Tong; Qiang Yu; Yunshe Dong; Changhui Peng (pp. 6992-7001).
N2O fluxes in a wheat/maize rotation system were measured using flux gradient methods combined with gas chromatograph (GC) technique. The mean precision of two repeated GC analyses for N2O concentration achieved to 0.27–0.46ppbv, which could resolve N2O concentration differences in a low range of 0.39–0.65ppbv. To maximize measurable N2O concentration differences, gradient measurements were conducted only after fertilization or under low wind conditions. During observation period, N2O flux ranged from −4.41 to 4.84mgN2Om−2h−1 for maize field, and from −2.82 to 3.59mgN2Om−2h−1 for wheat field. When gradient observation changed from two layers to four layers, the temporal variation of N2O flux reduced but the mean value changed less. Many negative N2O fluxes were found in maize and wheat fields even after fertilization. Nearly all of them were caused by negative N2O concentration differences. During four days' observation in maize field, a mean N2O flux of −0.75mgN2Om−2h−1 was found in the daytime and could not be simply attributed to the temporal variation of N2O flux. N2O flux determined by the aerodynamic method ( Fa) and the Bowen ratio/energy balance method ( Fb) were in a good agreement and statistically significant. The ratio of Fa to Fb increased linearly with energy balance ratio (EBR) obtained by the aerodynamic method in the daytime when EBR is larger than 0.3. It is the first time to give a quantitative description for the impact of energy closure on N2O flux, and show a possible way to improve the data quality under the condition of poor energy balance.
Keywords: N; 2; O flux; N; 2; O concentration gradient; Available N; 2; O concentration difference; Aerodynamic method; Bowen ratio/energy balance method; Energy balance ratio; Winter wheat; Summer maize
A hybrid model for ozone forecasting by Erez Weinroth; William Stockwell; Darko Koračin; Julide Kahyaoglu-Koračin; Menachem Luria; Travis McCord; Domagoj Podnar; Alan Gertler (pp. 7002-7012).
Significant uncertainties in the prediction of pollutant transport and dispersion limit the accuracy of air quality in areas with complex terrain, such as along the California coastline, which suffers from elevated air pollutant concentrations. Typical Lagrangian air quality models treat the dispersion of plumes better than Eulerian models but the chemical interactions induced by the mixing of intersecting plumes are ignored. In contrast, Eulerian models treat the emissions as well mixed within each grid box. To address these limitations, an air quality model with in-line chemistry and meteorology that combines the advantages of the Eulerian and Lagrangian approach to air quality modeling has been developed. In order to evaluate the model, simulation results of ozone concentrations were compared against a commonly used photochemical model (CAMx) and with airborne data from a field study made in the San Diego area of southwestern California.
Keywords: Air quality modeling; Coastal meteorology; Atmospheric chemistry; Model validation; Lagrangian dispersion
Identification and estimation of the biomass burning contribution to Beijing aerosol using levoglucosan as a molecular marker by Ting Zhang; Magda Claeys; Hélène Cachier; Shuping Dong; Wan Wang; Willy Maenhaut; Xiande Liu (pp. 7013-7021).
Two series of size-selective aerosol samples, PM2.5 and PM10, were collected in Beijing from July 2002 to July 2003. The samples were analyzed for levoglucosan and related saccharidic compounds, organic and elemental carbon, and ionic species. Levoglucosan and related saccharidic compounds were mostly present in the fine size fraction. The contribution from biomass burning to the carbonaceous aerosol in Beijing was estimated; biomass burning was responsible for 18–38% of the PM2.5 organic carbon and for 14–32% of the PM10 organic carbon. The biomass burning marker levoglucosan was present all year round in Beijing. High levoglucosan concentrations in October and November were attributed to corn field burning and burning of fallen leaves, while the high level observed on 7 May 2003 was tracked back to a boreal forest fire more than 1000km away in northeastern China. The biomass burning contribution to the Beijing aerosol is made up of two parts, a background component, which is due to biofuel burning all year round in the neighboring countryside households, and a superimposed component from seasonal crop burning events and wild fires.
Keywords: Levoglucosan; Marker; Biomass burning; Beijing; Aerosols
A combination of size-resolved particle samplers and XRF microprobe technique for single particle study by Chang-Jin Ma; Ki-Hyun Kim (pp. 7022-7026).
It is important to understand the properties of individual airborne particulates that are determined by the processes of various physicochemical reactions occurring in their generation, transformation, and transport. This study describes the application of the X-ray fluorescence (XRF) microprobe technique to the analysis of size-resolved individual particles as well as the results of an experimental study on the comparison of three different particle collection instruments for single particle analysis: a two-stage filter pack, a low pressure Andersen impactor (LPAI), and a micro-orifice uniform deposit impactor (MOUDI). Though LPAI and MOUDI are relatively suitable for multisize-segregated particles sampling compared with the two-stage filter pack sampler, they can easily form particle clusters and finally these particle clusters impede single particle analysis. Even though more particle mass can be collected without overloading on the substrate using MOUDI, by stage rotating, particles are still deposited and form clusters on the concentric circles. When particles are forming a spot (or other shapes of particle cluster), single particle analysis using the XRF micro-beam technique is restricted to individual particles deposited at the edge of the spot. Thus, the sampling duration time depending on the sampler stage should be adjusted for single particle study.
Keywords: Single particle; Andersen sampler; MOUDI; XRF microprobe