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Atmospheric Environment (v.41, #21)
Wet deposition of mercury at a New York state rural site: Concentrations, fluxes, and source areas by S.-o Soon-onn Lai; T.M. Thomas M. Holsen; Philip K. Hopke; Peng Liu (pp. 4337-4348).
Event-based mercury (Hg) precipitation samples were collected with a modified MIC-B sampler between September 2003 and April 2005 at Potsdam, NY to investigate Hg in wet deposition and identify potential source areas using the potential source contribution function (PCSF) and residence time weighted concentration (RTWC) models. The volume-weighted mean (VWM) concentration and wet deposition flux were5.5ngL-1 and7.6μgm-2 during the study period, and5.5ngL-1 and5.9μgm-2 in 2004, respectively, and show seasonal trends with larger values in the spring and summer. The PSCF model results matched known source areas based on an emission inventory better than did the RTWC results based on the spatial correlation index. Both modeling results identified large Hg source areas that contain a number of coal-fired power plants located in the Upper Ohio River Valley and in southeastern Michigan, as well as in Quebec and Ontario where there are metal production facilities, waste incinerators and paper mills. Emissions from the Atlantic Ocean were also determined to be a potential source.
Keywords: Wet deposition; Mercury; Potential source contribution function (PCSF); Residence time weighted concentration (RTWC)
The influence of tropical cyclone Melor on PM10 concentrations during an aerosol episode over the Pearl River Delta region of China: Numerical modeling versus observational analysis by Yerong Feng; Anyu Wang; Dui Wu; Xiangde Xu (pp. 4349-4365).
In this article, numerical simulations and observational analyses have been made for the aerosol episode that occurred over the Pearl River Delta (PRD) region in China during 1–3 November 2003. An air quality modeling system that consisted of the mesoscale model MM5, chemical transport model MODELS-3/CMAQ, and air pollutant emission model SMOKE, was employed. Studies have shown that this particulate matter (PM) pollution episode was apparently associated with the activity of tropical cyclone (TC) Melor. Model simulations revealed that Melor spawned this PM episode through dynamic and thermodynamic processes. The strong compensating subsidence induced by Melor's peripheral circulations created favorable meteorological conditions that enhanced local aerosol pollution. This strong downward motion produced significant adiabatic warming (2–4°C daily) and dramatic drying in the low-level troposphere over the PRD. As a result, the PRD region was blanketed with a dry and warm air layer that strengthened the static stability of the lower troposphere. The descending motion also tended to dramatically lower the heights of the planetary boundary layer (PBL) through its dynamic effect. The fair weather created by this synoptic pattern further intensified the nocturnal temperature inversions through enhanced radiative cooling. All of these factors promoted a stagnant local atmosphere with very light winds near the surface. The horizontal and vertical dispersions of locally emitted aerosol particles were largely suppressed, leading to the accumulation of large amounts of PMs near local emission sources in the PRD region. As Melor drew near, changes in surface winds strengthened the horizontal transport of aerosol particles from inland sources to the area of Hong Kong downstream. This horizontal advection greatly contributed to the high PM10 (particulate matters less than 10μm in diameters) concentrations in Hong Kong.
Keywords: PM; 10; Aerosol; Air quality modeling; Tropical cyclone; PRD region
Quantifying Asian and biomass burning sources of mercury using the Hg/CO ratio in pollution plumes observed at the Mount Bachelor observatory by Peter Weiss-Penzias; Dan Jaffe; Phil Swartzendruber; William Hafner; Duli Chand; Eric Prestbo (pp. 4366-4379).
Total airborne mercury (TAM) and carbon monoxide (CO) were measured in 22 pollution transport “events” at Mt. Bachelor Observatory (MBO), USA (2.8km asl) between March 2004 and September 2005. Submicron particulate scattering (σsp), ozone (O3), and nitrogen oxides (NOy) were also measured and enhancement ratios for each chemical and aerosol species with CO were calculated. Events were categorized based on their source regions, which were determined by a combination of back trajectories, satellite fire detections, chemical and aerosol enhancement ratios, and meteorology. The meanΔTAM/ΔCO values for each source region are: East Asian industrial (0.0046±0.0013ngm-3ppbv-1,n=10 events, 236h), Pacific Northwest U.S. (PNW) biomass burning (0.0013±0.008ngm-3ppbv-1,n=7 events, 173h), and Alaska biomass burning (0.0014±0.0006ngm-3ppbv-1,n=3 events, 96h). TheΔTAM/ΔCO means from Asian long-range transport (ALRT) and biomass burning events are combined with previous estimates of CO emissions from Chinese anthropogenic, global biomass burning, and global boreal biomass sources in order to estimate the emissions of gaseous elemental mercury (GEM) from these sources. The GEM emissions that we calculate here are: Chinese anthropogenic (620±180ty-1), global biomass burning(670±330ty-1), and global boreal biomass burning(168±75ty-1), with errors estimated from propagating the uncertainty in the mean enhancement ratios and CO emissions. A comparison of our results with published mercury (Hg) emissions inventories reveals that the Chinese GEM emissions from this study are higher by about a factor of two, while our estimate for global biomass burning is consistent with previous studies.
Keywords: Mercury; Long-range transport; Emissions; CD; Biomass burning; China
Airborne cadmium in the major monitoring locations in Korea between 1991 and 2004 by Ki-Hyun Kim (pp. 4380-4395).
Air quality monitoring data for cadmium (Cd) collected in 13 cities in Korea over a 14-year period (1991–2004) have been analyzed. In the course of this study, variation of Cd was examined over time and with location to learn about its sources, transport, and removal processes and to help improve air quality control. The results of this study indicate that the spatial distribution of Cd is clearly distinguishable between different cities and that such a pattern is sensitively reflected by such a factor as the level of industrialization. Comparison of the Cd data sets between different cities indicated that its concentration levels observed in highly industrialized cities approached or exceeded 10ngm−3, while those of urban background cities were found to lie in a narrow range of 1–3ngm−3. As such, Cd values determined from the polluted areas were notably higher than the relatively clean ones, at least by several times. The Cd data collected from all study sites were also evaluated with respect to temporal behavior. Inspection of seasonal patterns generally showed the occurrences of the highest Cd value during spring (and winter) and the lowest one during summer. When the long-term pattern of Cd was assessed across all study years, the results differed greatly between different cities in relation to their pollution status. Although Cd concentrations tended to decrease rather abruptly in highly industrialized cities, its patterns for most cities were too variable to project a definitive trend. The results of this analysis thus suggest that Cd concentration levels in most urban areas of Korea are fairly comparable with those commonly seen in the urban background areas of western countries. Considering that most urban areas are affected by various pollution sources and that Cd concentrations have been reduced significantly through the years, more deliberate efforts are needed to further control Cd concentrations in the atmosphere.
Keywords: Cadmium (Cd); Atmosphere; Industrial; Urban background; Long-term trend
Distribution of ions of marine origin in Galicia (NW Spain) as a function of distance from the sea by B. Silva; T. Rivas; García-Rodeja E. García-Rodeja; B. Prieto (pp. 4396-4407).
In order to know how far marine salts can be transported inland, bulk deposition was collected periodically at 9 sites located at increasing distances from the Atlantic coast in Galicia (NW Spain) and water samples taken from 16 streams, along a similar transect, were also analysed.In bulk deposition samples Cl− and Na+ were the ions that presented maximum concentrations especially until 57km from the sea. Chloride appeared as the best marker of marine influence in the studied area, whereas Na+ showed variations attributable to other sources. On the other hand, Ca2+ and SO42− were more related to non-marine sources. From a factorial analysis of ion concentrations and deposition volumes, the ions with dominant marine origin appeared to be associated to precipitation.Ions analysed in stream waters after heavy rain events showed similar trends than those in bulk deposition, especially in the case of Cl−. Therefore, this methodological approach can be very useful to determine marine influence as it implies a great simplification in sampling.
Keywords: Atmospheric deposition; Bulk deposition; Marine salts; Stream water composition
Features of the multimodal aerosol size distribution depending on the air mass origin in the Baltic region by Anna Pugatshova; Aivo Reinart; Eduard Tamm (pp. 4408-4422).
The purpose of this research is to study the dependence of the characteristics of the atmospheric aerosol size distribution (SD), especially its modal structure on the type and origin of the air mass using multivariate analysis. A large amount of the data of measurement campaigns of different duration, which were held all over Estonia from 1992 to 2001, was collected and systematized. The data were collected using the original electrical aerosol spectrometer, designed at the Institute of Environmental Physics of the University of Tartu. The dependence of aerosol particle size spectra on the air mass origin can be analyzed by means of air mass trajectories. The measurement data were classified according to the air mass origin taking into account of the starting point, climatic conditions and different kinds of pollution sources the air mass trajectory overpasses. The particle size mean spectra over all measurement campaigns were calculated for all selected air mass types. These mean spectra curves are quite smooth, so that their modal structure is visually not clearly seen. Therefore, their modal structure was identified by means of the factor analysis for most of the separated air masses. The retained factors were interpreted as the lognormally distributed components (modes) of the particle size spectrum. With the help of graphs that show the factor loadings as the functions of particle size, the modal diameter and the width of these modes were roughly assessed. Then, using the iterative least squares method, the parameters of the lognormal components were specified to obtain the best fit of the measured spectrum with the sum of lognormal components.
Keywords: Atmospheric aerosol; Particle size spectrum; Spectrum modes; Multivariate analysis
Mass transfer effects on the hygroscopic growth of ammonium sulfate particles with a water-insoluble coating by Man Nin Chan; Chak K. Chan (pp. 4423-4433).
Organic coatings have been commonly found in atmospheric particles and can affect the hygroscopicity of atmospheric particles. In this paper, we examine the effect of a water-insoluble coating on the hygroscopic growth and phase transformation properties of ammonium sulfate ((NH4)2SO4) particles using an electrodynamic balance. Octanoic acid was utilized as a model compound for water-insoluble coating. (NH4)2SO4 particles coated with octanoic acid (9 and 34wt% octanoic acid) were subjected to relative humidity (RH) cycling to effect two cycles of deliquescence and crystallization. The coated particles exhibited very similar hygroscopicity in two cycles. Octanoic acid was likely present on the surface of solid (NH4)2SO4 cores and (NH4)2SO4 solution droplets throughout the RH cycling. Mass transfer effects were found in the deliquescence and evaporation of the heavily coated (34wt%) particles. The mass transfer of water molecules to and through octanoic acid coating led to a significant delay in the deliquescence and crystallization of the coated particles, an increase in the observed deliquescence RH and a decrease in observed crystallization RH as compared to that of uncoated (NH4)2SO4 particles. A water accommodation coefficient in the order of 10−3 can explain these observations. When sufficient time was given to ensure equilibrium, the coating had no effect in altering the equilibrium phase transitions and hygroscopic growth of the (NH4)2SO4 particles. It is important to allow sufficient time for equilibration in hygroscopic measurements of aerosol particles coated with organic coatings.
Keywords: Organic coating; Hygroscopicity; Electrodynamic balance; Multicomponent aerosol; Mass transfer; Deliquescence
Analysis of long-range transport influences on urban PM10 using two-stage atmospheric trajectory clusters by Rafael Borge; Julio Lumbreras; Sotiris Vardoulakis; Pavlos Kassomenos; Rodriguez Encarnacion Rodríguez (pp. 4434-4450).
There is evidence that long-range transport of natural and/or anthropogenic particles can have a negative impact on urban air quality. Certain European cities may fail to comply with the currently implemented 24-h PM10 limit value due to the additional impact of remote sources of particles, which are not controllable at local level. For that reason, reliable methodologies identifying long-range transport patterns and quantifying their contribution to urban PM10 levels are required. In this study, a two-stage clustering methodology was developed and applied to back trajectories arriving in three European cities: Athens, Madrid and Birmingham, which experience large, moderate and small numbers of daily PM10 episodes, respectively. The atmospheric trajectories used in this analysis were computed with HYSPLIT model (NOAA) for a 3-year period. The two-stage cluster analysis has the advantage of providing highly disaggregated trajectory clusters, which proved to correspond to significantly different PM10 levels. In the case of Madrid and Birmingham, clusters of trajectories originating from North Africa and continental Europe, respectively, were strongly associated with the highest PM10 levels recorded in selected monitoring stations. In Athens, long-range transport patterns and trans-boundary influences were less evident, which highlighted the more substantial impact of local emission sources. Finally, two simple statistical indexes were proposed for assessing PM10 episodes associated with different clusters of trajectories. This study has established a practical methodology for examining the impact of long-range atmospheric transport on local air quality, without resorting to high resource-demanding source apportionment techniques.
Keywords: Two-stage cluster analysis; Back trajectories; Urban air quality; Long-range transport; PM; 10
Influence of dense surface meteorological data assimilation on the prediction accuracy of ozone pollution in the southeastern coastal area of the Korean Peninsula by Soon-Hwan Lee; Yoo-Keun Kim; Heon-Sook Kim; H.-W. Hwa-Woon Lee (pp. 4451-4465).
In order to clarify the influence of surface meteorological data assimilation with various resolutions on the photochemical ozone concentration in the southeastern Korean Peninsula, several numerical experiments were conducted. The meteorological and photochemical reaction models used in this study are the fifth-generation mesoscale model (MM5) and the three-dimensional photochemical urban airshed model (UAM-V), respectively. Dense meteorological data make it easier to obtain accurate estimates and surface characteristics than coarse-resolution data. As a result, the estimated temperature obtained from high resolution surface data assimilation in the Busan and Ulsan metropolitan areas is higher than that obtained from coarse resolution surface data assimilation. These high temperatures resulted in strong winds from the sea and a significant dispersion of ozone. In analyses involving an index of agreement (IOA) and root mean square deviation (RMSD), the temperature and wind speed estimated with dense surface data assimilation agreed well with those obtained from observations.However, the influence of dense surface data assimilation tends to be stronger in the flat Ulsan metropolitan area than in the mountainous Busan metropolitan area. This is caused by the heterogeneity of the surface characteristics, including the topography. If the surface parameters induced by regional circulation, such as the topography and land use, are complex and heterogeneous, the efficiency of observational data on data assimilation has to be verified before air pollution is assessed.
Keywords: Urban air quality; Spatial measurement density; Numerical assessment; Data assimilation; Ozone concentration
Comparison of the MURA and an improved single-receptor (SIRA) trajectory source apportionment (TSA) method using artificial sources by Stephanie Lee; Lowell Ashbaugh (pp. 4466-4481).
Two trajectory source apportionment methods were tested using an artificially generated data set to determine their ability to detect the known sources. The forward-looking step from the multi-receptor trajectory analysis (MURA) method was added to the conditional probability (CP)method of Ashbaugh et al. [1985. A residence time probability analysis of sulfur concentrations at Grand Canyon National Park. Atmospheric Environment 19(8), 1263–1270] to develop the single-receptor forward CP (SIRA) method. The multi-receptor (MURA) and the SIRA methods were tested with three simulations using artificially generated sources. The ability of the methods to detect the sources was quantified for each simulation. The first simulation showed that the SIRA method is an improvement over the original CP method. The MURA trajectory method proved to be superior at identifying sources for the simulation located in the west and comparable to the SIRA method for the two simulations located in the east.
Keywords: Residence time analysis; Trajectory analysis; HYSPLIT; Source apportionment; MURA
Citronellal reactions with ozone and OH radical: Rate constants and gas-phase products detected using PFBHA derivatization by J.C. Harrison; J.E. Ham; J.R. Wells (pp. 4482-4491).
The bimolecular rate constants, kOH+citronellal, (150±40)×10−12cm3molecule−1s−1 and,kO3+citronellal, (3.5±1.2)×10−16cm3molecule−1s−1, were measured using the relative rate technique for the reactions of the hydroxyl radical (OH) and ozone (O3) with 3,7-dimethyl-6-octen-1-al ((R)-(+)-citronellal) at (297±3)K and 1atm total pressure. To more clearly define part of citronellal's indoor environment degradation mechanism, the products of the citronellal+OH and citronellal+O3 reactions were also investigated. The positively identified citronellal/OH and citronellal/O3 reaction products were: 3-methylhexanedial HC(O)CH2CH2CH(CH3)CH2C(O)H and 2-oxopropanal (methylglyoxal, CH3C(O)C(O)H). The use of derivatizing agent O-(2,3,4,5,6-pentafluorobenzyl)hydroxylamine (PFBHA) was used to propose 3-methylhexanedial as a major citronellal/OH and citronellal/O3 reaction product. The elucidation of this reaction product was facilitated by mass spectrometry of the derivatized reaction products coupled with plausible citronellal/OH and citronellal/O3 reaction mechanisms based on previously published volatile organic compound/OH and volatile organic compound/O3 gas-phase reaction mechanisms.
Keywords: Citronellal; 3, 7-Dimethyl-6-octen-1-al; Reaction products; Kinetics; Oxygenated organic compounds
An empirical relationship between PM2.5 and aerosol optical depth in Delhi Metropolitan by Naresh Kumar; Allen Chu; Andrew Foster (pp. 4492-4503).
Atmospheric remote sensing offers a unique opportunity to compute indirect estimates of air quality, which are critically important for the management and surveillance of air quality in megacities of developing countries, particularly in India and China, which have experienced elevated concentration of air pollution but lack adequate spatial–temporal coverage of air pollution monitoring. This article examines the relationship between aerosol optical depth (AOD) estimated from satellite data at 5km spatial resolution and the mass of fine particles ⩽2.5μm in aerodynamic diameter (PM2.5) monitored on the ground in Delhi Metropolitan where a series of environmental laws have been instituted in recent years.PM2.5 monitored at 113 sites were collocated by time and space with the AOD computed using the data from Moderate Resolution Imaging Spectroradiometer (MODIS onboard the Terra satellite). MODIS data were acquired from NASA's Goddard Space Flight Center Earth Sciences Distributed Active Archive Center (DAAC). Our analysis shows a significant positive association between AOD and PM2.5. After controlling for weather conditions, a 1% change in AOD explains 0.52±0.202% and 0.39±0.15% change in PM2.5 monitored within ±45 and 150min intervals of AOD data. This relationship will be used to estimate air quality surface for previous years, which will allow us to examine the time–space dynamics of air pollution in Delhi following recent air quality regulations, and to assess exposure to air pollution before and after the regulations and its impact on health.
Keywords: PM; 2.5; Aerosol optical depth (AOD); Air pollution; Remote sensing
Improving bioaerosol exposure assessments of composting facilities — Comparative modelling of emissions from different compost ages and processing activities by M.P.M. Taha; G.H. Drew; A. Tamer; G. Hewings; G.M. Jordinson; P.J. Longhurst; S.J.T Pollard (pp. 4504-4519).
We present bioaerosol source term concentrations from passive and active composting sources and compare emissions from green waste compost aged 1, 2, 4, 6, 8, 12 and 16 weeks. Results reveal that the age of compost has little effect on the bioaerosol concentrations emitted for passive windrow sources. However emissions from turning compost during the early stages may be higher than during the later stages of the composting process. The bioaerosol emissions from passive sources were in the range of 103–104cfum−3, with releases from active sources typically 1-log higher. We propose improvements to current risk assessment methodologies by examining emission rates and the differences between two air dispersion models for the prediction of downwind bioaerosol concentrations at off-site points of exposure. The SCREEN3 model provides a more precautionary estimate of the source depletion curves of bioaerosol emissions in comparison to ADMS 3.3. The results from both models predict that bioaerosol concentrations decrease to below typical background concentrations before 250m, the distance at which the regulator in England and Wales may require a risk assessment to be completed.
Keywords: Bioaerosols; Compost; Dispersion modelling; Emission rate; Exposure
Global backtracking of anthropogenic radionuclides by means of a receptor oriented ensemble dispersion modelling system in support of Nuclear-Test-Ban Treaty verification by Andreas Becker; Gerhard Wotawa; L.-E. Lars-Erik De Geer; Petra Seibert; Roland R. Draxler; Craig Sloan; Real D’Amours; Matthew Hort; Hubert Glaab; Philippe Heinrich; Yves Grillon; Vyacheslav Shershakov; Keiichi Katayama; Yuetang Zhang; Paul Stewart; Marcus Hirtl; Michel Jean; Peter Chen (pp. 4520-4534).
In this paper, we introduce a methodology for quality assessment of backtracking models. We present results illustrating the level of agreement between the backtracking models, and the accuracy of each model and the ensemble model in resolving the geo-temporal reference of a single point source. Both assessments are based on an ensemble of 12 different Lagrangian particle dispersion modelling (LPDM) systems utilized in receptor oriented (adjoint) mode during an international numerical experiment dedicated to source region estimation.As major result, we can confirm that the findings of Galmarini et al. [2004b. Ensemble prediction forecasting—Part II: application and evaluation. Atmospheric Environment 38, 4619–4632] and Delle Monache and Stull [2003. An ensemble air-quality forecast over Europe during an ozone episode. Atmospheric Environment 37, 3469–3474], regarding the superiority of the ensemble dispersion forecast over a single forecast, do also apply to LPDM when utilized for backtracking purposes, in particular if only vague a priori knowledge of the source time is available. This, however, is a likely situation in the context of the global nuclear monitoring performed by the Provisional Technical Secretariat (PTS) of the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO), where quick but reliable source location identification is required. We introduce a simple methodology as a template for a future electronic emergency response system in the field of dispersion modelling.
Keywords: Long-range Lagrangian dispersion models; Multi-model backward ensemble dispersion modelling; Inversion model evaluation; Global nuclear monitoring
Real-world emissions of carbonyl compounds from in-use heavy-duty diesel trucks and diesel Back-Up Generators (BUGs) by Aniket A. Sawant; Sandip D. Shah; Xiaona Zhu; J. Wayne Miller; David R. Cocker (pp. 4535-4547).
Emissions of carbonyl compounds such as formaldehyde, acetaldehyde, and acrolein are of interest to the scientific and regulatory communities due to their suspected or likely impacts on human health. The present work investigates emissions of carbonyl compounds from nine Class 8 heavy-duty diesel (HDD) tractors and also from nine diesel-powered backup generators (BUGs); the former were chosen because of their ubiquity as an emission source, and the latter because of their proximity to centers of human activity. The HDD tractors were operated on the ARB 4-Mode heavy heavy-duty diesel truck (HHDDT) driving cycle, while the BUGs were operated on the ISO 8178 Type D2 5-mode steady-state cycle and sampled using a mobile emissions laboratory (UCR MEL) equipped with a full-scale dilution tunnel. Samples were analyzed using the SAE930142 (Auto/Oil) method for 11 aldehydes, from formaldehyde to hexanaldehyde, and 2 ketones (acetone and methyl ethyl ketone). Although absolute carbonyl emissions varied widely by BUG, the relative contributions of the different carbonyls were similar (e.g., median: 56% for formaldehyde). A slight increasing trend with engine load was observed for relative formaldehyde contribution, but not for acetaldehyde contribution, for the BUGs. On-road per-mile carbonyl emission factors were a strong function of operating mode of the ARB HHDDT cycle, and found to decrease in the order Creep>Transient>Cruise. This order is qualitatively similar to emission factors for PAHs and n-alkanes determined for the same set of Class 8 diesel tractors in an earlier work. In general, relative carbonyl contributions for the HDD tractors were similar to those for BUGs (e.g., median: 54% for formaldehyde). These results indicate that while engine operating mode and application appear to exert a strong influence on the total absolute mass emission rate of the carbonyls measured, they do not appear to exert as strong an influence on the relative mass emission rates of individual carbonyls.
Keywords: Formaldehyde; Carbonyl; Back-up generator; On-road; Heavy-duty diesel; Truck
Are fuel additives a viable contrail mitigation option? by Klaus Gierens (pp. 4548-4552).
Fuel additives have been proposed as a potential mitigation option for contrails. They could change the thermodynamic conditions necessary for contrail formation in a way that makes contrail formation more difficult than with standard kerosene fuel. Here I show how additives could affect contrail formation, and I conclude that fuel additives are not a useful way to avoid contrails.
Keywords: Aviation; Contrails; Fuel additives; Alternative fuels; Mitigation
A simple and inexpensive dilution system for the TSI 3007 condensation particle counter by Luke D. Knibbs; Richard J. de Dear; Lidia Morawska; Peter M. Coote (pp. 4553-4557).
The aim of this study was to develop a dilution system which would permit the TSI 3007 condensation particle counter (CPC) to operate within its maximum detectable concentration threshold, even when sampling extremely high submicron particle concentrations. The intention of this was to provide a better alternative to coincidence correction factors, which have several limitations; the most significant of which being that they are only applicable to a comparatively low concentration and also that the components of the unit are exposed to concentrations beyond their operating specifications. To achieve the aim, a bifurcation-based system was developed and tested repeatedly at concentrations of unleaded petrol combustion particles up to ∼8.5×106pcm−3. The benchmark particle concentration was measured by a TSI 3022A CPC. The results of the tests showed that the nominal dilution ratio based on flow partitioning was applicable up to ∼3.5×105pcm−3, after which particle losses to a capillary tube primarily caused a large increase in apparent dilution. These losses were consistent throughout all tests and allowed the unit to remain below the maximum detection threshold, even under the extreme challenge concentrations encountered. This work represents a useful extension of the operating range of the TSI 3007, without significantly compromising either the quality of data collected or the internal components of the unit.
Keywords: TSI 3007; Condensation particle counter; Dilution; Submicron; Particle measurement