Dry PM Research Articles

Remote sensing of atmospheric particulate mass of dry PM2.5 near the ground: Method validation using ground-based measurements

Abstract The satellite-based estimation of dry PM 2.5 mass concentration near the surface is a big challenge in the aerosol remote sensing fields, but urgently needed by the environmental monitoring. We present an experimental validation of a physical PM 2.5 remote sensing (PMRS) method which is not dependent on geographical location, based on ground-based remote sensing measurements at Jinhua City, a typical middle size city in East of China. The PMRS method is designed to employ currently available satellite remote sensing parameters as many as possible, including aerosol optical depth (AOD), fine mode fraction (FMF), planetary boundary layer height (PBLH) and atmospheric relative humidity (RH), and thus be capable of deriving PM 2.5 from instantaneous remote sensing measurements under different pollution levels. The key processes of the PM 2.5 method including size cutting, volume visualization, bottom isolation and particle drying are directly validated by comparing with reference parameters. We found that the size cutting of the PMRS method has a significant bias (about 0.86) resulting from the use of fine mode fraction to estimate PM 2.5 among all size of aerosol particles, which should be systematically corrected. The validation results of the volume visualization and particle drying of the PMRS method are quite satisfied while the bottom isolation procedure brings currently the maximum uncertainty to the PM 2.5 remote sensing. The improved PMRS method shows good performance on the remote sensing of hourly PM 2.5 with an average error of about 38 μg/m 3 and relative error of about 31%. The correlation coefficient between remote sensing and in situ hourly PM 2.5 is about 0.67 with a linear slope of 1.03 and intercept of 11 μg/m 3 while the means are very close (110.7 μg/m 3 versus 118.6 μg/m 3 ). The validation study also helps find out future improvement directions and demonstrates the possible application to ground-based remote sensing data.

A measurement of summertime dry deposition of ambient air particulates and associated metallic pollutants in Central Taiwan.

The purpose of this study is to characterize metallic elements associated with atmospheric particulate matter in the dry deposition plate, total suspended particulate, fine particles, and coarse particles at Taichung Harbor and Gong Ming Junior High School (airport) in central Taiwan at a sampling site from June 2013 to August 2013. The results indicated that: (1) the average concentrations of the metallic elements Cr and Cd were highest at the Gong Ming Junior High School (airport), and the average concentrations of the metallic elements Ni, Cu, and Pb were highest at the Taichung Harbor sampling site. (2) The high smelting industry density and export/import rate of heavily loaded cargos were the main reasons leading to these findings. (3) The average metallic element dry deposition and metallic element PM(2.5-10) all followed the order of Pb > Cr > Cu > Ni > Cd at the two sampling sites. However, the average metallic elements Cu and Pb were found to have the highest dry deposition velocities and concentrations in PM(2.5) for the two sampling sites in this study. (4) The correlation coefficients of ambient air particle dry deposition and concentration with wind speed at the airport were higher than those from the harbor sampling site. The wind and broad open spaces at Taichung Airport were the possible reasons for the increasing correlation coefficients for ambient air particle concentration and dry deposition with wind speed at the Taichung Airport sampling site.

Fine Scale Modeling of Agricultural Air Quality over the Southeastern United States Using Two Air Quality Models. Part I. Application and Evaluation

Two air quality models, the U.S. EPA Community Multiscale Air Quality (CMAQ) model and ENVIRON’s Comprehensive Air Quality Model with extensions (CAMx), are evaluated for their applications in simulating ambient air quality, in particular, the fate and transport of agriculturally-emitted NH3 over an area in the southeastern U.S. in January and July 2002 using a fine-scale horizontal grid resolution of 4-km. Both models moderately overpredict maximum 1-hr and 8-hr ozone (O3) and fine particulate matter (PM2.5) in January, due likely to a weaker vertical mixing and insufficient dry and wet removal of PM2.5 species simulated by the models. They either slightly underpredict or overpredict O3 but significantly underpredict PM2.5 in July. The large underprediction in PM2.5 is due to an excess wet deposition removal of sulfate, an excess dry deposition removal of precursors, and an underestimation of emissions of primary PM and precursors of secondary PM and secondary organic aerosol concentrations. Both models show large biases in the simulated concentrations of several gases (e.g., CO in CAMx, NO in CMAQ, NO2 in both models in both months and NH3 by both models in July) and PM species (in particular, nitrate in both months and carbonaceous PM in July), visibility indices, and dry and wet deposition fluxes. They also show some inaccuracies in reproducing temporal variations of NH3, PM2.5, dry and wet deposition fluxes. Differences in model performance between the two models are attributed to different model treatments such as vertical mixing, wet and dry deposition, SOA formation, and PM size representations. These results indicate a need to improve accuracies of the emissions and measurements of NH3, the emissions of primary PM and precursors of secondary PM, as well as model treatments of vertical mixing and dry and wet removal processes.

직장인의 직무스트레스가 구강건조감에 미치는 영향

Objectives : The purpose of this study was to examine the effect between job stress in jobholders and xerostomia. Methods : 250 jobholders living in Jecheon city were the subjects of this questionnaire. The questionnaire was made up of three contents and 37 items: general characteristic(13), job stress(14), degree & behavior of xerostomia(10). The data were analyzed by two-sample t-test, one-way ANOVA to examine the subjects general characteristics, job stress and degree of xerostomia and were analyzed by Chi-square test to examine the subjects general characteristics, job stress and behavior of xerostomia. Results : Only 215 jobholders were evaluated due to inadequate responses. The results were as follow. 1. As general characteristic of jobholder, male(83.7%) were more than women(16.3%), 30~39 year-old(47%) in age variable, university graduation(63.7%) in the last educational background variable, 2~3 million won(31.2%) in the month average income variable, 1~5 year(33.5%) in tour of duty variable, non-smoker(47.9%) in smoking variable were most. Married(58.6%) were more than unmarried(39.5%). Alcoholic(69.8%) were more than non-alcoholic(30.2%). 2. As classification of job stress, high strain group was 28.4%, active group was 26%, low strain group was 24.2%, passive group was 21.4%. 3. Analysis of effect between general characteristic and degree & behavior of xerostomia showed smoker were statistical significantly higher than non-smoker on 'dry eat', 'Am-sal', 'Night awake', 'Slip-liq'and 'Gumcandy'(p<0.05) and showed alcoholic were statistical significantly higher than non-alcoholic on 'Dry PM', 'Night awake, <TEX>$H_2O$</TEX>-bed'(p<0.05). 4. Analysis of effect between job stress and degree & behavior of xerostomia showed hight strain group were statistical significantly higher than low strain group on 'Dry PM', 'Dry-day', 'Am-sal', 'Eff-life'and 'Night awake'(p<0.05). Conclusions : As high strain group were higher than other groups on degree & behavior of xerostomia, stress would be factor that have an effect on xerostomia. Thus consider and management of stress is necessary for diagnosis and treatment of xerostomia.

Evaluating Relative Contribution of Atmospheric Mercury Species to Mercury Dry Deposition in Japan

In this study, we evaluated the relative contribution of atmospheric particulate mercury (Hg(p)) and divalent reactive gaseous mercury (RGM) to mercury dry deposition in Japan. The dry deposition fluxes (on a water surface sampler) and atmospheric PM concentrations of Hg, Cd, Cu, Mn, Ni, Pb and V, which were measured concurrently from April 2004 to March 2006 at 10 sites across the nation, were used in this evaluation. We considered that Hg(p) and RGM, but not Hg0, are deposited on the water surface, and that our method of sampling Hg(p) without the use of KCl-coated annular denuders enables the exclusion of a significant amount of RGM artifact. The monthly average dry deposition velocities (= deposition flux/atmospheric PM concentration) of Cd and Pb were found to be similar to each other (Cd/Pb deposition velocities = 1.06 ± 0.58). It was assumed that the deposition velocity of Hg(p) is identical to the mean deposition velocity of Cd and Pb, because the particle size distribution of Hg(p) is likely similar to those of both elements. Using this deposition velocity, the monthly dry deposition flux of Hg(p) was calculated. The average contribution (±1σ) of Hg(p) to the annual deposition flux at ten sites was 26 ± 15%. The mercury dry deposition flux increased generally from spring to early summer, which was attributed mostly to the deposition of RGM. This seasonal change correlated to that in photochemical oxidant (primarily O3) concentration in air at most sites. These suggest that mercury dry deposition in Japan is predominantly deposition of RGM, which was formed via oxidation of Hg0 by O3 in the atmosphere.

Adapting CMAQ to investigate air pollution in North Sea coastal regions

The Models-3 Community Multiscale Air Quality (CMAQ) model is setup on a 54 × 54 km 2 grid for Europe and on a nested smaller domain with a 18 × 18 km 2 grid for the North Sea region. This paper concentrates on the models ability to represent the transport and deposition of atmospheric pollution in North Sea coastal areas. Comparisons to NO 2 and PM 10 measurements at selected sites of the Co-operative Program for Monitoring and Evaluation of the Long-range Transmission of Air Pollutants in Europe (EMEP) are used for quality control for atmospheric concentrations. We use modeled nitrogen deposition fields and EMEP wet deposition measurements during January and July 2001 as a measure to evaluate the deposition schemes. Close agreement between the model and the measurements was found for the oxidised nitrogen compounds in January, when on average NO 2 was overestimated by 18% (measured: 3.52 μg N/m 3, modeled: 4.16 μg N/m 3) and nitrate deposition was only slightly underestimated by 2%. However, ammonia was underestimated by 44%. In July, NO 2 levels are much lower than in January and the model underestimates the mean concentration by 35% (measured 1.49 μg N/m 3, modeled 0.97 μg N/m 3). Wet deposition is also underestimated, but again the results for nitrate (−38%) were in better agreement with the measurements than for ammonium (−57%). PM 10 concentrations are largely underestimated in January and July (by about 65% on average), but this result was expected, because only anthropogenic emissions were considered. Nevertheless, especially in January high daily correlations (0.69–0.84) between the modeled dry PM 10 and the measurements in Germany were found. This indicates that the aerosol transport pathways are captured quite well by the model. CMAQ has been expanded to represent also persistent organic pollutants (POPs). In this paper first results of deposition fields of the carcinogenic benzo(a)pyrene (B(a)P) are shown. Preliminary comparisons to air concentration and deposition measurements show that the model results are in the right order of magnitude. In particular the observed strong seasonal cycle of B(a)P in air was also present in the model.

Characterisation of bio-aerosols during dust storm period in N–NW India

Bio-investigations for pollen and spores were performed on dry free-fall dust and PM 10 aerosol samples, collected from three different locations separated by a distance of 600 km, situated in dust storm hit region of N–NW India. Presence of pollen of trees namely Prosopis ( Prosopis juliflora and Prosopis cinearia), Acacia, Syzygium, Pinus, Cedrus, Holoptelea and shrubs namely Ziziphus, Ricinus, Ephedra and members of Fabaceae, Oleaceae families was recorded but with varying proportions in the samples of different locations. Poaceae, Chenopodiaceae/Amaranthaceae, Caryophyllaceae, Brassicaceae and Cyperaceae (sedges) were some of the herb pollen identified in the samples. Among the fungal spores Nigrospora was seen in almost all samples. Nigrospora is a well known allergen and causes health problems. The concentration of trees and shrubs increases in the windward direction just as the climate changes from hot arid to semiarid. The higher frequency of grasses (Poaceae) or herbs could either be a result of the presence of these herbs in the sampling area and hence the higher production of pollen/spores or due to the resuspension from the exposed surface by the high-intensity winds. But we cannot ascertain the exact process at this stage. The overall similarity in the pollen and spore assemblage in our dust samples indicates a common connection or source(s) to the dust in this region. Presence of the pollen of the species of Himalayan origin in our entire samples strongly point towards a Himalayan connection, could be direct or indirect, to the bioaerosols and hence dust in N–NW India. In order to understand the transport path and processes involved therein, present study needs further extension with more number of samples and with reference to meteorological parameters.

To what extent can aerosol water explain the discrepancy between model calculated and gravimetric PM&amp;lt;sub&amp;gt;10&amp;lt;/sub&amp;gt; and PM&amp;lt;sub&amp;gt;2.5&amp;lt;/sub&amp;gt;?

Abstract. Inter-comparisons of European air quality models show that regional transport models, including the EMEP (Co-operative Programme for monitoring and evaluation of the long-range transmission of air pollutants in Europe) aerosol model, tend to underestimate the observed concentrations of PM10 and PM2.5. Obviously, an accurate representation of the individual aerosol constituents is a prerequisite for adequate calculation of PM concentrations. On the other hand, available measurements on the chemical characterization of ambient particles reveal that full chemical PM mass closure is rarely achieved. The fraction unaccounted for by chemical analysis can comprise as much as 30-40% of gravimetric PM10 or PM2.5 mass. The unaccounted PM mass can partly be due to non-C atoms in organic aerosols and/or due to sampling and measurement artefacts. Moreover, a part of the unaccounted PM mass is likely to consist of water associated with particles. Thus, the gravimetrically measured particle mass does not necessarily represent dry PM10 and PM2.5 mass. This is thought to be one of the reasons for models under-prediction of observed PM, if calculated dry PM10 and PM2.5 concentrations are compared with measurements. The EMEP aerosol model has been used to study to what extent particle-bound water can explain the chemically unidentified PM mass in filter-based particle samples. Water content of PM2.5 and PM10 has been estimated with the model for temperature 20°C and relative humidity 50%, which are conditions required for equilibration of dust-loaded filters according to the Reference method recommended by the European Committee for Standardization (CEN). Model calculations for Europe show that, depending on particle composition, particle-bound water constitutes 20-35% of the annual mean PM10 and PM2.5 concentrations, which is consistent with existing experimental estimates. At two Austrian sites, in Vienna and Streithofen, where daily measurements of PM2.5 mass and chemical composition are available, calculated PM2.5 water content is found to be about 75-80% of the undetermined PM2.5 mass and there is correlation between them. Furthermore, accounting for aerosol water has improved the agreement between modelled and measured daily PM2.5 concentrations, whilst model calculated dry PM2.5 concentrations appear to agree quite well with the total identified PM2.5 mass. No information on the composition of PM measured at EMEP sites is presently available. Given that PM10 and PM2.5 concentrations are measured at EMEP stations with gravimetric methods they are likely to contain water. We show that the levels of modelled PM10 and PM2.5 concentrations with aerosol water included agree with measurements better than dry PM concentrations. As expected, the spatial correlation has not changed significantly, whereas the temporal correlation of daily PM10 and PM2.5 with monitoring data has slightly improved at most of the EMEP sites. Our results suggest that aerosol water should be accounted for in modelled PM10 and PM2.5 when compared with filter-based gravimetric measurements.

An Analysis of Four Models Predicting the Partitioning of Semivolatile Inorganic Aerosol Components

A comparison is conducted between 4 atmospheric equilibrium mod els: GFEMN, ISORROPIA, SCAPE2, and SEQUILIB. While ISORROPIA, SCAPE2, and SEQUILIB simplify the problem at hand in an effort to reduce computational rigor, GFEMN does not employ many of the simplifying assumptions used in previous models, thus allowing it to accurately predict multistage aerosol behavior and deliquescence depression. We examine model performance for representative atmospheric environments over an extended composition, temperature, and RH domain and against observations in Southern California. The predictions of GFEMN, ISORROPIA, SCAPE2, and SEQUILIB are in general agreement, but the latter 3 do not adequately reproduce multistage deliquescence behavior for multi component systems. The most notable differences in model predictions occur for H+ and aerosol water concentrations; discrepancies in predictions of aerosol nitrate and total dry inorganic PM concentrations are not as significant. The models predict different deliquescence relative humidities for multicomponent systems, but for ammonia poor environments, these discrepancies do not introduce differences in total dry inorganic PM predictions. Against measurements taken during the Southern California Air Quality Study (SCAQS), all models qualita tively reproduce but generally underpredict aerosol nitrate concentrations. Finally, based on its overall agreement with GFEMN and its computational efficiency, ISORROPIA appears to be the model of choice for use in large-scale aerosol transport models. In places where crustal material comprises a significant portion of total PM, SCAPE2 is an alternative.

99/02807 In-stack condensible particulate matter measurement and permitting issues

Based on the results of recent epidemiological studies and assessments of the causes of visibility degradation, EPA is proposing to regulate PM2.5 emissions. PM can be classified as either filterable or condensible PM. Condensible PM includes sulfates, such as sulfuric acid. Sulfates typically account for at least half of the total dry fine PM mass in the atmosphere. Power plant SO{sub x}-based emissions make a significant contribution to ambient fine PM levels in the eastern US. Although much of this mass is derived from secondary chemical reactions in the atmosphere, a portion of this sulfate is emitted directly from stacks as condensible PM. The potential condensible PM fraction associated with coal-burning boiler emissions is somewhat uncertain. The characterization of PM emissions from these sources has been, until recently, based on in-stack filterable PM measurements only. To determine the relative magnitude of condensible PM emissions and better understand condensible PM measurement issues, a review and analysis of actual EPA Method 202 results and state-developed hybrid condensible PM methods were conducted. A review of available Method 202 results for several coal-burning boilers showed that the condensible PM, on average, comprises 60% of the total PM10. A review of recent results for state-developedmore » measurement methods for condensible PM for numerous coal-burning boilers indicated that condensible PM accounted for, on average, approximately 49% of total PM. Caution should be exercised in the use of these results because of the seemingly unresolved issue of artifact formation, which may bias the Method 202 and state-developed methods results on the high side. Condensible PM10 measurement results and issues, and potential ramifications of including condensible PM10 emissions in the PSD permit review process are discussed. Selected power plants in Maryland are discussed as examples.« less