Urban Outdoor?Indoor PM2.5 Concentrations and Personal Exposure in the Deep South. Part II. Inorganic Chemistry

Abstract

This paper reports the results of an exploratory inorganic chemical characterization of PM_{2 . 5}. The particle samples exemplify the personal exposure of nine healthy, nonsmoking individuals living and working in the metropolitan area of Birmingham, Alabama, in comparison with stationary outdoor and indoor sampling at their homes. The samples were taken by filtration in two seasons, summer and winter of 1997?1998. The chemical analyses were performed on water soluble extracts for sulfate, nitrate, ammonium, chloride, and potassium and x-ray fluorescence spectroscopy for elements of atomic number > 13. The results indicate that a sulfate mixture, calculated to be either ammonium sulfate or letovicite, dominated the mass concentration of all samples. Small contributions also derived from nitrate as ammonium nitrate, chloride, aluminum silicates, and metals such as iron, copper, and zinc. Potentially toxic elements such as chromium, nickel, arsenic, and selenium were present only at the ng/m3 level or less. Most of the unaccounted for mass fraction is hypothesized to be carbonaceous material. Correlation was found between sulfate concentration data from outdoor, indoor, and personal samples. Sulfate concentrations also correlated with outdoor PM_{2 . 5} gravimetric mass concentrations. However, minor or trace contaminant concentrations were not correlated with outdoor mass concentrations. Indoor sulfate levels can be explained by infiltration of outdoor particles into the buildings, while evidence was found for sources of PM_{2 . 5} particles indoors in four of eight residences in summer and two of eight in winter.     

Size-Resolved Concentrations of Particulate Matter and Bioaerosols Inside versus Outside of Homes

Size-resolved airborne particulate matter samples (PM _2.5 , PM ₁₀ , and TSP) collected inside ten northern California homes over four days and one night (9–12 h/sample, spanning a 3.5 week period) were analyzed for protein, endotoxin, and (1 → 3)-β-D-glucan concentrations. Some simultaneous size-resolved outdoor samples were also collected. The associations of residential characteristics and occupant behavior with the indoor airborne levels were investigated. In addition, the relation between these chemical biomarkers and the more traditional culturing approaches was studied. Most of the indoor mass concentration of airborne particles and protein was in the fine fraction (PM _2.5 ), while the mass of airborne endotoxin and (1 → 3)-β-D-glucan was mainly in the coarser fractions (PM _10–2.5 and PM _TSP–10 ). No strong correlations were seen between short-term (3–6 min) culturable bacteria and fungi counts and the corresponding longer-term (9–12 h) biomarker levels. Daytime indoor levels of the biomarkers tended to be higher than outdoors, especially for the PM _10–2.5 fraction, but only in a few cases were the indoor/outdoor relationships statistically significant. Indoor pets were associated with elevated airborne PM and bioaerosols inside homes. Two other factors, wall-to-wall carpet and older houses, also appear to be associated with some elevations in indoor levels.     

An Experimental Study of Indoor and Outdoor Concentrations of Fine Particles Through Nonisothermal Cracks

It has been shown that a substantial proportion of indoor exposure is from particles originating outdoors. Idealized cracks have been used to study penetration under laboratory settings and all previous studies assumed isothermal conditions. There can be 10–20°C difference between indoor and outdoor temperatures even in mild climate zones. This is the first study to investigate the influence of thermophoresis on the penetration of particles through cracks. A sandwich design consisting of two chambers (each 0.325 [W] × 0.125 [L] × 0.11 [H] m³) and a crack module was used to measure indoor-to-outdoor particle concentrations under practical indoor and outdoor conditions. An idealized aluminum smooth crack of 90 mm crack length was tested under three different pressures ranging from 4 to 8 Pa. Submicron sodium chloride particles were generated and a scanning mobility particle sizer was used to scan the concentration in outdoor and indoor chambers. To mimic summer and winter conditions in temperate climatic zones, two sets of temperature differences (indoor–outdoor) were used: +18°C and ?10°C. I/O ratio and relative difference of I/O ratio compared to the isothermal condition were calculated. Inferring from the results, it can be observed that the I/O ratios under the winter scenario are substantially higher than those under the summer and isothermal scenarios for particle sizes less than 100 nm and the influence of temperature on I/O ratios diminishes with increasing particle sizes.

Copyright 2013 American Association for Aerosol Research     

Contributions of Foot Traffic and Outdoor Concentrations to Indoor Airborne Aspergillus

Aspergillus is a mold genus that can cause allergies, asthma, and pulmonary infections in sensitive people; its particles are common in indoor air. Two potential contributors to indoor Aspergillus particles were examined in this field study: human activity (walking over carpet), and outdoor Aspergillus concentrations. Filtered air samples were collected outdoors and inside two carpeted hallways in public buildings, while measuring indoor foot traffic. Aspergillus concentrations were analyzed using quantitative Polymerase Chain Reaction (qPCR). A bivariate model was used to predict indoor Aspergillus concentrations based on foot traffic and outdoor Aspergillus concentrations. For 3 of 4 scenarios, most of the variation in indoor Aspergillus could be explained by the combined effect of outdoor Aspergillus concentrations and foot traffic, with particularly strong correlations during peak traffic times. In addition, indoor Aspergillus was significantly associated with outdoor Aspergillus in 2 of 4 scenarios, and with foot traffic in 2 of 4 scenarios. For 2 of 3 sampling campaigns, Aspergillus did not have a significant association either with gravimetric particulate matter ≤5 μm (PM₅), or with optically measured PM of 0.75–1 μm, 1–2 μm, 2–3.5 μm, or 3.5–5 μm. Controlled experiments, examining whether the foot traffic contribution was due to resuspension from carpeting or to shedding from clothing and/or human bodies, saw a significant increase in Aspergillus levels from resuspension. Although an increase was also seen for clothing over Tyvek suits, it was not statistically significant.     

Chemical Characteristics of Fine Particles (PM1) from Xi'an,China

Daily mass concentrations of water-soluble inorganic (WS-i) ions, organic carbon (OC), and elemental carbon (EC) were determined for fine particulate matter (PM₁, particles < 1.0 μm in diameter) collected at Xi'an, China. The annual mean PM₁ mass concentration was 127.3 ± 62.1 μg m^–3: WS-i ions accounted for ～38% of the PM₁ mass; carbonaceous aerosol was ～30%; and an unidentified fraction, probably mostly mineral dust, was ～32%. WS-i ions and carbonaceous aerosol were the dominant species in winter and autumn, whereas the unidentified fraction had stronger influences in spring and summer. Ion balance calculations indicate that PM₁ was more acidic than PM_2.5 from the same site. PM₁ mass, sulfate and nitrate concentrations followed the order winter > spring > autumn > summer, but OC and EC levels were higher in autumn than spring. Annual mean OC and EC concentrations were 21.0 ± 12.0 μg m^?3 and 5.1 ± 2.7 μg m^–3 with high OC/EC ratios, presumably reflecting emissions from coal combustion and biomass burning. Secondary organic carbon, estimated from the minimum OC/EC ratios, comprised 28.9% of the OC. Positive matrix factorization (PMF) analysis indicates that secondary aerosol and combustion emissions were the major sources for PM₁.     

Reconstructing Primary and Secondary Components of PM2.5 Composition for an Urban Atmosphere

Total 360 samples (of 8 h each) of PM_2.5 were collected from six sampling sites for summer and winter seasons in Kanpur city, India. The collected PM_2.5 mass was subjected to chemical speciation for: (1) ionic species (NH⁺ ₄, SO^2– ₄, NO^– ₃, and Cl^–), (2) carbon contents (EC and OC), and (3) elemental contents (Ca, Mg, Na, K, Al, Si, Fe, Ti, Mn, V, Cr, Ni, Zn, Cd, Pb, Cu, As, and Se). Primary and secondary components of PM_2.5 were assessed from speciation results. The influence of marine source to PM_2.5 was negligible, whereas the contribution of crustal dust was significant (10% in summer and 7% in winter). A mass reconstruction approach for PM_2.5 could distinctly establish primary and secondary components of measured PM_2.5 as: (1) Primary component (27% in summer and 24% in winter): crustal, elemental carbon, and organic mass, (2) Secondary component (45% in summer and 50% in winter): inorganic and organic mass, and (3) others: unidentified mass (27% in summer and 26% in winter). The secondary inorganic component was about 34% in summer (NH⁺ ₄: 9%; SO^2– ₄: 16%; NO^– ₃: 9%) and 32% in winter (NH⁺ ₄: 8%; SO²⁺ ₄: 13%; NO^– ₃: 11%). The secondary organic component was 12% in summer and 18% in winter. In conclusion, secondary aerosol formation (inorganic and organic) accounted for significant mass of PM _2.5 (about 50%) and any particulate control strategy should also include control of primary precursor gases.     

Calibration,Intersampler Comparison,and Field Application of a New PM-10 Personal Air-Sampling Impactor

The MS&T personal impactor is designed to provide a particle size cut (d _50%) of 10 μm in aerodynamic diameter (PM-10) at a flow rate of 4 L/min. Data are presented that verify the designed particulate mass cut specifications of this impactor for personal sampling. These data are derived from three different analyses', laboratory calibration, intersampler comparison, and field application. Laboratory calibration using monodispersed liquid aerosol shows a sharp 10-μm particle cut size.

The performance of the personal impactor was tested using ambient and combustion-generated aerosols. Established PM-10 samplers (the Sierra/Andersen dichotomous and the MS&T indoor air sampler impactor) were run side by side with the personal impactor. The intra- and intersampler vari-abilities in PM-10 measurements were evaluated. Results showed good precision among personal impactors (CV = 3.2%). The PM-10 sampled by the personal impactor was found to be highly correlated with measurements made with the indoor air sampler impactor (r ² = 0.99) and the dichotomous sampler (r¹ = 0.97).

The impactor was subsequently employed for personal air sampling in the Total Human Environmental Exposure Study (THEES). The THEES sampling protocol entailed 24-hour sampling during a 14-day study interval. THEES field measurements included indoor, outdoor, and personal PM-10 samples. The personal impactor measurements for 13 participants were predicted by a time-weighted exposure model using indoor and outdoor PM-10 and specific activity variables (p < 0.01).     

Characterizing Indoor and Outdoor 15 Minute Average PM 2.5 Concentrations in Urban Neighborhoods

While a number of studies have looked at the relationship between outdoor and indoor particulate levels based on daily (24 h) average concentrations, little is known about the within-day variability of indoor and outdoor PM levels. It has been hypothesized that brief airborne particle excursions on a time scale of a few minutes to several hours might be of health significance. This article reports variability in measurements of daily (24 h) average PM 2.5 concentrations and short-term (15 min average) PM 2.5 concentrations in outdoor and indoor microenvironments. Daily average PM 2.5 concentrations were measured using gravimetry, while measurements of 15 min average PM 2.5 mass concentrations were made using a light scattering photometer whose readings were normalized using the gravimetric measurements. The measurements were made in 3 urban residential neighborhoods in the Minneapolis-St. Paul metropolitan area over 3 seasons: spring, summer, and fall of 1999. Outdoor measurements were made at a central monitoring site in each of the 3 communities, and indoor measurements were made in 9-10 residences (with nonsmoking occupants) in each community. Residential participants completed a baseline questionnaire to determine smoking status, sociodemographics, and housing characteristics. Outdoor PM 2.5 concentrations across the Minneapolis-St. Paul metropolitan area appear to be spatially homogeneous on a 24 h time scale as well as on a 15 min time scale. Short-term average outdoor PM 2.5 concentrations can vary by as much as an order of magnitude within a day. The frequency distribution of outdoor 15 min averages can be described by a trimodal lognormal distribution, with the 3 modes having geometric means of 1.1 w g/m 3 (GSD = 2.1), 6.7 w g/m 3 (GSD = 1.6), and 20.8 w g/m 3 (GSD = 1.3). There is much greater variability in the within-day 15 min indoor concentrations than outdoor concentrations (as much as ～40-fold). This is most likely due to the influence of indoor sources and activities that cause high short-term peaks in concentrations. The indoor 15 min averages have a bimodal lognormal frequency distribution, with the 2 modes having geometric means of 8.3 w g/m 3 (GSD = 1.66) and 35.9 w g/m 3 (GSD = 1.8), respectively. The correlation between the matched outdoor and indoor 15 min average PM 2.5 concentrations showed a strong seasonal effect, with higher values observed in the spring and summer ( R 2 adj = 0.49 - 0.33) and lower values in the fall ( R 2 adj = 0.13 - 0.13).     

Temporal and Spatial Variation of Fungal Concentrations in Indoor Air

The aim of this study was to determine temporal and spatial variation of airborne concentrations of viable fungi in 2 single-family houses during the period of the year that such levels are mostly determined by indoor sources. One of the subject residences had moisture problems (the index residence), the other did not have any moisture problems (the reference residence). The concentrations of viable fungi in indoor air were determined a total of 6 times during the winter with 2 six-stage impactors (Andersen 10-800) in 2 rooms in both of the houses. The total concentrations of viable fungi and concentrations of Penicillium, Aspergillus, and Aspergillus versicolor     

The Measurement of Ambient Bioaerosol Exposure

Monitoring of ambient bioaerosol concentrations through the characterization of outdoor particulate matter (PM) has only been performed on a limited basis in North Carolina (NC) and was the goal of this research. Ambient samples of PM _2.5 (fine) and PM _10?2.5 (coarse) were collected for a six-month period and analyzed for mold, endotoxins and protein. PM _2.5 and PM _10?2.5 concentrations of these bioaerosols were reported as a function of PM mass, as well as volume of air sampled. The mass of PM _2.5 was almost twice that of the PM _10?2.5 ; however, the protein and endotoxin masses were greater in the coarse than the fine PM indicating an enrichment in the coarse PM. The protein and mold results demonstrated a seasonal pattern, both being higher in the summer than in the winter. Except for an occasional excursion, the endotoxin data remained fairly constant throughout the six months of the study.     

Fine particles sampled at an urban background site and an industrialized coastal site in Northern France—Part 2: Comparison of offline and online analyses for carbonaceous aerosols

Particulate matter was sampled in Northern France during two summer and winter periods at both an urban background site (Douai, DO) and an industrialized coastal site (Grande-Synthe, GS). Ambient levels of particulate carbonaceous species and Polycyclic Aromatic Hydrocarbons (PAH) were measured by real-time measurements and via collection and analysis of offline filters (F). The comparison between online organic matter (OM) measured by an Aerosol Mass Spectrometer (AMS) and organic carbon (OC) determined by an offline thermal-optical method showed good linear trends in wintertime GS (r² = 0.82 while only 0.50 in summer), and DO (r² = 0.86 in summer and 0.92 in winter). However, significant differences were observed between analytical methods and sites with OC_AMS/OC_F ratios decreasing from 0.80 in DO during winter to ≈0.20 for GS in summer, suggesting that a large part of OM could be in the PM₁–PM_2.5 fraction. The simultaneous measurements of Black Carbon (BC) and Elemental Carbon (EC) concentrations in PM_2.5 were also well correlated at both sites with r² = 0.61–0.97 and slopes between 0.6 and 0.8. PAHs were analyzed in PM_2.5 and also measured online by AMS in PM₁. Their wintertime concentrations were highly correlated in DO (r² = 0.98) and to a lesser degree in GS (r² = 0.67). r² values determined for comparison between online and offline parameters (OC and PAHs) in GS were lower than in DO, probably due to a more complex aerosol composition and a higher variability of the physical and chemical properties resulting from the coastal situation and diversity of emission sources in the vicinity of GS.

Copyright © 2018 American Association for Aerosol Research     

Penetration of freeway ultrafine particles into indoor environments

High concentrations of ultrafine particles have been reported to exist near major freeways. Many urban residences are located in close proximity to high-density roadways. Consequently, indoor environments near freeways may experience significant concentrations of outdoor ultrafine particles. Given that people spend over 80% of their time indoors, understanding transport of ultrafine particles from outdoor to indoor environments is important for assessing the impact of exposure to outdoor particulate matter on human health. Four two-bedroom apartments within 60 m from the center of the 405 Freeway in Los Angeles, CA were used for this study. Indoor and outdoor ultrafine particle size distributions in the size range of 6–220 nm were measured concurrently under different ventilation conditions without indoor aerosol generation sources. The size distributions of indoor aerosols showed less variability than the adjacent outdoor aerosols. Indoor to outdoor ratios for ultrafine particle number concentrations depended strongly on particle size. Indoor/outdoor (I/O) ratios also showed dependence on the nature of indoor ventilation mechanisms. Under infiltration conditions with air exchange rates ranging from 0.31 to 1.11  ${\mathrm{h}}^{-1}$, the highest I/O ratios (0.6–0.9) were usually found for larger ultrafine particles (70–100 nm), while the lowest I/O ratios (0.1–0.4) were observed for particulate matter of 10–20 nm. Data collected under infiltration conditions were fitted into a dynamic mass balance model. Size-specific penetration factors and deposition rates were determined for all studied residences. Results from this research have implications concerning personal exposure to freeway-related ultrafine particles and possible associated health consequences.     

Time and Space Uniformity of Indoor Bacteria Concentrations in Chicago Area Residences

The objective of this article is to assess spatial and temporal variation of indoor gram-positive bacteria and Staphylococcus sp. in 20 urban residences. At each residence, air was sampled at one outdoor site and four indoor sites (rooms) to assess spatial variation and once each season for five consecutive seasons to assess temporal variation. All temporal and spatial comparisons were performed using data obtained by the Andersen sampling technique. A secondary objective of this study is to evaluate relationships among several sampling methods used to measure bacteria levels; since differences in the measured concentrations are expected, the focus is to discern if corresponding measurements relate to each other. Not surprisingly, comparisons among the four sampling systems revealed statistically significant differences, although levels correlated relatively well. Using data only from the Andersen samplers, we conclude that seasonal variation is residence dependent with typically higher summer levels, but a clear pattern of variation could not be established. Room-to-room difference is not statistically significant, but the basement levels render the basement a distinct microenvironment. Indoor concentrations exceeded corresponding outdoor concentrations 75% of the time. Staphylococcus accounts for approximately 27% of the average indoor bacteria levels. The highest levels of gram-positive bacteria are found in the kitchen. The presence of multiple indoor sources with variable emission rates in multiple indoor locations results in bacteria levels that vary with time and space.     

The PAH and Nitro-PAH Concentration Profiles in Size-Segregated Urban Particulate Matter and Soil in Traffic-Related Sites in Catania,Italy

Polycyclic aromatic hydrocarbons (PAHs) and nitrated polycyclic aromatic hydrocarbons (nitro-PAHs) were identified from both air particulate matter and soils. For air sampling, a six-stage cascade impactor was situated in an urban area (Catania, Italy) that is recognized for its high traffic volume. The soil samples were collected every 1.5 km from under the grass by the side of the median of a Catania road along its full length (8.2 km). HPLC in electrochemical-fluorescence detection mode was used for selective separation, identification and quantification of analytes in air and soil samples, providing both good selectivity and sensitivity. The seasonal trends, effects of urban traffic, and source profiles are discussed herein. Higher PM₁₀ concentrations were observed for summer (43 μg m^?3) in comparison to winter (24 μg m^?3). Conversely, the PAHs contained in PM₁₀ were higher in winter (0.48 ng m^?3 for fluoranthene) than in summer (0.14 ng m^?3 for fluoranthene). Analysis of the size-segregated urban particulate matter showed that the amount of PM_0.5 (stage 6) was always higher than the amount of other particles (stages 1–5). Furthermore, the PM_0.5 was always higher in summer (about 40%, m/m) than in winter (about 30%, m/m). Finally, the amounts of PAH and nitro-PAH in PM_0.5 (stage 6) were always higher, by a maximum of one order of magnitude, than that of other particles (stages 1–5). This result is crucial because ultrafine particles have a tendency to move into the blood through the alveolar epithelial barrier. Moreover, the air and soil pollution levels agree with those found in other cities with similar levels of pollution. Supplemental materials are available for this article. Go to the publisher's online edition of Polycyclic Aromatic Compounds to view the supplemental file.     

Using Regional Data and Building Leakage to Assess Indoor Concentrations of Particles of Outdoor Origin

Time-resolved fine particle concentrations of nitrate, sulfate, and black carbon were examined to assess the appropriateness of using regional data and calculated air exchange rates to model indoor concentrations of particles from outdoor sources. The data set includes simultaneous, sub-hourly aerosol composition measurements at three locations: a regional monitoring site in Fresno, California, inside of an unoccupied residence in Clovis, California, located 6 km northeast of the regional site, and immediately outside of this same residence. Indoor concentrations of PM_2.5 nitrate, sulfate, and black carbon were modeled using varying sets of inputs to determine the influence of three factors on model accuracy: the constraints of the simplified indoor-outdoor model, measured versus modeled air exchange rates, and local versus regional outdoor measurements.

Modeled indoor concentrations captured the lag and attenuation in indoor concentrations as well as the differences among chemical constituents in the indoor-outdoor concentration relationships. During periods when the house was closed and unoccupied, use of air exchange rates calculated from the LBNL infiltration model in place of those directly measured did not contribute significantly to the error in the estimated indoor concentrations. Differences between ambient concentrations at the regional monitoring site and the immediate neighborhood contributed to estimation errors for sulfate and black carbon. Evaporation was the dominant factor affecting indoor nitrate concentrations. Even when limiting the model inputs to concentrations and meteorological parameters measured at the regional monitoring station, the modeled concentrations were more highly correlated with measured indoor concentrations than were the regional measurements themselves.     

Analysis of Aerosolized Particulates of Feedyards Located in the Southern High Plains of Texas

The objective of this study was to quantify, size, and examine the composition of particulates found in ambient aerosolized dust of four large feedyards in the Southern High Plains. Ambient air samples (concentration of dust) were collected upwind (background) and downwind of the feedyards. Aerosolized particulate samples were collected using high volume sequential reference ambient air samplers, PM ₁₀ and PM _2.5 , laser strategic aerosol monitors, cyclone air samplers, and biological cascade impactors. Weather parameters were monitored at each feedyard. The overall (main effects and estimable interactions) statistical (P < 0.0001) general linear model statement (GLM) for PM ₁₀ data showed more concentration of dust (μg/m ³ of air) downwind than upwind and more concentration of dust in the summer than in the winter. PM _2.5 concentrations of dust were comparable for 3 of 4 feedyards upwind and downwind, and PM _2.5 concentrations of dust were lower in the winter than in the summer. GLM (P < 0.0001) data for cascade impactor (all aerobic bacteria, Enterococcus spp, and fungi) mean respirable and non-respirable colony forming units (CFU) were 676 ± 74 CFU/m ³ , and 880 ± 119 CFU/m ³ , respectively. The PM ₁₀ geometric mean size (±GSD) of particles were analyzed in aerosols of the feedyards (range 1.782 ± 1.7 μm to 2.02 ± 1.74μm) and PM _2.5 geometric mean size particles were determined (range 0.66 ± 1.76 μm to 0.71 ± 1.71 μm). Three of 4 feedyards were non-compliant for the Environmental Protection Agency (EPA) concentration standard (150 μg/m ³ /24 h) for PM ₁₀ particles. This may be significant because excess dust may have a negative impact on respiratory disease.     

Inter- and Intra-Community Variability in Continuous Coarse Particulate Matter (PM10-2.5) Concentrations in the Los Angeles Area

Continuous coarse particulate matter (CPM, PM _10?2.5 ) concentrations were measured hourly at three different sites in the Los Angeles area from April 2008 through May 2009 as part of a larger study of the characteristics and toxicology of CPM. Mean hourly concentrations calculated seasonally ranged from less than 5 μg m ^–3 to near 70 μg m ^–3 at the three sites depending upon the CPM source variability and prevailing meteorology. Different diurnal concentration profiles were observed at each site. Correlation analysis indicates that CPM concentrations can generally be explained by wind-induced road dust re-suspension, particularly in drier seasons. CPM concentrations between the sites were not appreciably correlated and metrics used to assess variability between the sites—the coefficients of divergence—indicated that CPM concentrations were heterogeneous. The relative CPM contribution to observed PM ₁₀ concentrations varied by season and between sites. Additional concurrent CPM data available within a few km of the three sites indicate that intra-community variability can be on the same order as that observed for inter-community variability, although a similar analysis using PM ₁₀ data yielded reduced heterogeneity. The results indicate that accurate exposure assessment to CPM in the Los Angeles area requires measurements of CPM concentrations at different sites with higher temporal resolution than a single daily mean value.     

Seasonal Variation of Airborne Particle Deposition Efficiency in the Human Respiratory System

Particulate matter (PM) is associated with human health effects but the apparent toxicity of PM in epidemiological studies varies with season. PM toxicity may change due to seasonal shifts in composition or particle size distributions that in turn affect respiratory deposition efficiencies. In the current study, size-resolved PM composition was measured in the largest city (Fresno) in California's heavily polluted San Joaquin Valley during the summer (30 days) and winter (20 days) between 2006 and 2009 for 21 metals, organic carbon, elemental carbon, and 7 water-soluble ions. The Multiple-Path Particle Dosimetry model was applied to determine if seasonal variation in size-resolved composition influences respiratory deposition patterns. Mg, Al, S, V, Mn, Fe, Ni, Ba, SO₄ ^2-, Na⁺, and Ca²⁺ had larger total deposition efficiencies (p < 0.004) during the summer versus the winter in all three regions of the respiratory tract. This trend results from increased relative concentrations of the target analytes per μg m^?3 ambient PM_1.8 concentration and would be detected with routine PM_2.5 filter samples. V, Zn, Se, NO₃ ^-, SO₄ ^2-, and NH₄ ⁺ also experienced seasonal size distribution shifts that enhanced the specific deposition efficiency in the tracheobronchial and pulmonary regions during the summer months (p < 0.05). This enhanced deposition would not be detected by routine filter samples because all of the size distribution changes occur at particle diameters <2.5 μm. This study demonstrates that changes to the particle size distributions (<2.5 μm) can enhance respiratory deposition efficiencies for trace metals and/or water-soluble ions and this may contribute to seasonal shifts in PM toxicity.     

The 2003/2004 Libby,Montana PM2.5 Source Apportionment Research Study

Except for areas in California, Libby, Montana is the only designated EPA nonattainment area for fine particulate matter (PM _2.5 ) in the mid and western states. During the winter of 2003/2004, PM _2.5 speciated data (mass, elements, ions, organic/elemental carbon) were collected every six days from November 11, 2003 through February 27, 2004. Using a Chemical Mass Balance computer model (Version 8.0), these data were used to apportion the sources of PM _2.5 in the Libby valley. In support of the source apportionment program, a comprehensive evaluation of the particulate matter associated organic compounds (including polar organics, phenolics, polycyclic aromatic hydrocarbons, and ¹⁴ C) present in the airshed was also conducted.

CMB modeling results revealed that emissions from residential wood combustion was the major source of PM _2.5 throughout the winter months in Libby, contributing an average of 82% of the measured PM _2.5 . Levoglucosan, a well-known chemical marker for wood smoke, had the highest measured concentrations of any of the 95 polar organic compounds quantified from the fine fraction, accounting for over 15.5% of the measured organic carbon fraction. Other semi-volatile organic compounds with high measured concentrations during the program were four phenolic compounds commonly found in wood smoke, including phenol, 2-methylphenol ( o -cresol), 4-methylphenol ( p -cresol), and 2,4-dimethylphenol. Results from ¹⁴ C analysis indicate that as much as 82% of the measured ¹⁴ C results from a wood smoke source. These indicators support modeling results that residential wood combustion was the major source of PM _2.5 in Libby, Montana throughout the winter months.     

Development and evaluation of a palm-sized optical PM2.5 sensor

A new palm-sized optical PM_2.5 sensor has been developed and its performance evaluated. The PM_2.5 mass concentration was calculated from the distribution of light scattering intensity by considering the relationship between scattering intensity and particle size. The results of laboratory tests suggested that the sensor can detect particles with diameters as small as ～0.3 µm and can measure PM_2.5mass concentrations as high as ～600 µg/m³. Year-round ambient observations were conducted at four urban and suburban sites in Fukuoka, Kadoma, Kasugai, and Tokyo, Japan. Daily averaged PM_2.5 mass concentration data from our sensors were in good agreement with corresponding data from the collocated standard instrument at the Kadoma site, with slopes of 1.07–1.16 and correlation coefficients (R) of 0.90–0.91, and with those of the nearest observatories of the Ministry of the Environment of Japan, at 1.7–4.1 km away from our observation sites, with slopes of 0.97–1.23 and R of 0.89–0.95. Slightly greater slopes were observed in winter than in summer, except at Tokyo, which was possibly due to the photochemical formation of relatively small secondary particles. Under high relative humidity conditions (>70%), the sensor has a tendency to overestimate the PM_2.5 mass concentrations compared to those measured by the standard instruments, except at Fukuoka, which is probably due to the hygroscopic growth of particles. This study demonstrates that the sensor can provide reasonable PM_2.5 mass concentration data in urban and suburban environments and is applicable to studies on the environmental and health effects of PM_2.5.

Copyright © 2018 American Association for Aerosol Research