Candis Claiborn

Monitoring of particulate matter outdoors

Recent studies of the size and composition of atmospheric particulate matter (PM) have demonstrated the usefulness of separating atmospheric PM into its fine and coarse components. The need to measure the mass and composition of fine and coarse PM separately has been emphasized by research in exposure, epidemiology, and toxicology of atmospheric PM. This paper provides a background on the size distribution and properties of PM relevant to the differences between fine and coarse particles. Various decisions that must be made when deciding how to separate, collect, and measure PM are discussed. Techniques for monitoring fine and coarse particles, including the US Federal Reference Method for PM2.5 and several techniques for PM10-2.5, are presented. Problems encountered in collecting semivolatile PM and in weighing atmospheric PM collected on a filter are described. Continuous monitoring methods for PM mass and for PM components (carbon, nitrate, and sulfate) are described and brief descriptions are given of analytical techniques for the chemical characterization of collected PM. This information should be especially useful for environmental workers familiar with monitoring methods for total suspended particles or PM10 but who will need to measure PM2, and PM10-2.5 in the future.

Source identification of PM2.5 in an arid Northwest U.S. City by positive matrix factorization

Spokane, WA is prone to frequent particulate pollution episodes due to dust storms, biomass burning, and periods of stagnant meteorological conditions. Spokane is the location of a long-term study examining the association between health effects and chemical or physical constituents of particulate pollution. Positive matrix factorization (PMF) was used to deduce the sources of PM2.5 (particulate matter V2.5 Am in aerodynamic diameter) at a residential site in Spokane from 1995 through 1997. A total of 16 elements in 945 daily PM2.5 samples were measured. The PMF results indicated that seven sources independently contribute to the observed PM2.5 mass: vegetative burning (44%), sulfate aerosol (19%), motor vehicle (11%), nitrate aerosol (9%), airborne soil (9%), chlorinerich source (6%) and metal processing (3%). Conditional probability functions were computed using surface wind data and the PMF deduced mass contributions from each source and were used to identify local point sources. Concurrently measured carbon monoxide and nitrogen oxides were correlated with the PM2.5 from both motor vehicles and vegetative burning. D 2003 Elsevier Science B.V. All rights reserved.

WIND EROSION AND FUGITIVE DUST FLUXES ON AGRICULTURAL LANDS IN THE PACIFIC NORTHWEST

With recent emphasis of agricultural wind erosion and associated dust emissions impacting downwind air quality, there is an increased need for a prediction method to estimate dust emissions and ambient particle concentrations on a wind event basis. Most current wind erosion methods predict average annual or seasonal erosion amounts, and only very approximate estimates of suspended dust emissions are available. A project in the Columbia Plateau of eastern Washington State was initiated to develop an empirical method to estimate dust emissions for this region. Field measurements, wind tunnel tests, and laboratory analyses were combined to provide an empirical wind erosion equation and a related vertical flux dust emission model. While based on measured data, the model has not been independently verified. When combined with a transport-dispersion model and calibrated, estimates of downwind particulate concentrations compared reasonably with those measured.

Association between particulate matter and emergency room visits, hospital admissions and mortality in Spokane, Washington.

There is conflicting evidence regarding the association between different size fractions of particulate matter (PM) and cardiac and respiratory morbidity and mortality. We investigated the short-term associations of four size fractions of particulate matter (PM1, PM2.5, PM10, and PM10–2.5) and carbon monoxide with hospital admissions and emergency room (ER) visits for respiratory and cardiac conditions and mortality in Spokane, Washington. We used a log-linear generalized linear model to compare daily averages of PM and carbon monoxide with daily counts of the morbidity and mortality outcomes from January 1995 to June 2001. We examined pollution lags ranging from 0 to 3 days and compared our results to a similar log-linear generalized additive model. Effect estimates tended to be smaller and have larger standard errors for the generalized linear model. Overall, we saw no association with respiratory ER visits and any size fraction of PM. However, there was a suggestion of greater respiratory effect from fine PM when compared to coarse fraction. Carbon monoxide was associated with both all respiratory ER visits and visits for asthma at the 3-day lag. We feel that carbon monoxide may be serving as a marker for combustion-derived pollutants, which is one large component of the diverse air pollutant mixture. We also found no association with any size fraction of PM or CO with cardiac hospital admissions or mortality at the 0- to 3-day lag. We found no consistent associations between any size fraction of PM and cardiac or respiratory ER visits or hospital admissions.

Source Apportionment of Indoor, Outdoor, and Personal PM2.5 in Seattle, Washington, Using Positive Matrix Factorization

Abstract As part of a large exposure assessment and health-effects panel study, 33 trace elements and light-absorbing carbon were measured on 24-hr fixed-site filter samples for particulate matter with an aerodynamic diameter <2.5 μm (PM2.5) collected between September 26, 2000, and May 25, 2001, at a central outdoor site, immediately outside each subjects residence, inside each residence, and on each subject (personal sample). Both two-way (PMF2) and three-way (PMF3) positive matrix factorization were used to deduce the sources contributing to PM2.5. Five sources contributing to the indoor and outdoor samples were identified: vegetative burning, mobile emissions, secondary sulfate, a source rich in chlorine, and a source of crustal-derived material. Vegetative burning contributed more PM2.5 mass on average than any other source in all microenvironments, with average values estimated by PMF2 and PMF3, respectively, of 7.6 and 8.7 μg/m3 for the outdoor samples, 4 and 5.3 μg/m3 for the indoor samples, and 3.8 and 3.4 μg/m3 for the personal samples. Personal exposure to the combustion-related particles was correlated with outdoor sources, whereas exposure to the crustal and chlorine-rich particles was not. Personal exposures to crustal sources were strongly associated with personal activities, especially time spent at school among the child subjects.

Evaluation of PM10 emission rates from paved and unpaved roads using tracer techniques

Spokane, WA, is a nonattainment area for airborne particulate matter smaller than 10μm (PM10), so that a detailed emission inventory for PM10 is needed to evaluate various control strategies. It is thought that emissions from paved and unpaved roads in Spokane contribute three-fourths of the anthropogenic PM10 (neglecting wind-blown dust from agricultural areas). A study was conducted in the summer and fall of 1992 and again in the spring and summer of 1994 to measure PM10 emission rates from paved and unpaved roads in Eastern Washington state using a novel tracer technique. A known amount of an inert tracer (SF6) was released and concentrations of PM10 and SF6 downwind of the road, along with meteorological parameters and traffic volume, were measured. The results of the tracer experiments showed that within experimental uncertainties the PM10 and the tracer gas disperse in the same manner, suggesting that the use of a tracer in a line source to simulate roadway PM10 emissions can provide a tool for improving the existing emission inventories from roads. The emission factors obtained from two unpaved road experiments (136 g per vehicle per kilometer traveled, or g VKT−1, and 336 g VKT−1) were similar in magnitude to those predicted using currently accepted empirical algorithms. The factors determined from six paved road experiments were approximately 80% higher than that predicted using current formulae (6.7 ± 3.7 g VKT−1 compared to 3.7 g VKT−1) for two-lane roads with daily traffic less than 10,000 vehicles. For major highways (4 + lanes and traffic in excess of 10,000 vehicles per day) the emission factors obtained from the tracer experiments were, on average, 44% lower than those predicted using standard formulae (1.0 ± 0.5 g VKT−1 compared to 1.8 g VKT−1). The calculated emission factors for paved roads exhibited a wide range of variability, suggesting that in order to quantify PM10 emission rates from paved roads, more investigation is warranted.

An Analysis of the Association Between Respiratory Symptoms in Subjects with Asthma and Daily Air Pollution in Spokane, Washington

The association between respiratory symptoms and ambient levels of particulate matter (PM) air pollution has been the focus of several panel studies. The majority of studies focused only on PM10, were conducted for relatively short periods, reported peak flow data, and involved children with asthma. The goal of our study was to evaluate the effect of particulate matter of various size fractions (PM10, PM2.5, PM1.0, and PM coarse fraction) on respiratory symptoms in both adults and children with asthma monitored over many months. Daily diary data on respiratory symptoms and medication use were collected. Air pollution data were collected by the local air agency and Washington State University. Data were collected in Spokane, WA, a semiarid city with diverse sources of particulate matter, including motor vehicles, woodstoves, agricultural burning, resuspended road dust, and dust storms. Sixteen adults and nine children living in Spokane participated in the study. The majority of adult subjects participated for over 1 yr and the children were studied for over 8 mo. In the children, we found a strong association between cough and PM10, PM2.5, PM coarse fraction, and PM1.0 (p <. 05). Sputum production and runny nose were associated with PM10 and coarse fraction. However, no association was found between the presence of any respiratory symptom any PM metric in the adult subjects. These positive associations between various metrics of PM and respiratory symptoms in children suggest that children are more sensitive than adults to the effects of increased levels of PM air pollution or that the central site monitor was more representative for children who spend more time outdoors than adults. These findings also suggest that both larger and smaller particles can aggravate asthma symptoms.

Hydrocarbon emissions from spruce species using environmental chamber and branch enclosure methods

Abstract Isoprene emission rates from Engelmann ( Picea engelmannii ), red ( Picea rubens ), and black ( Picea mariana ) spruce were measured from groups of seedlings in a controlled environmental chamber. Standard isoprene emission rate factors, obtained from measurements over an array of light and temperature conditions, ranged from 1 to 16 μgCg −1 h −1 at 30°C and 1000 μmolm −2 s −1 photosynthetically active radiation. Emission measurements were also collected using a dynamic enclosure technique from branches of a mature white spruce ( Picea glauca ) through a complete growing season. These data indicate that isoprene emissions, normalized to standard conditions, are moderate in spring and fall (∼ 7 μgC g −1 h −1 at 30°C, 1000 μmol m −2 s −1 ) with a maximum in mid-summer (∼ 12 μgCg −1 h −1 at 30°C, 1000 μmolm −2 s −1 ) Isoprene from white spruce represented more than 90% of the total identified hydrocarbons. Branch enclosure measurements from limited survey samples for blue spruce ( Picea pungens ) yielded a standard emission rate of 12 μgC g −1 h −1 while samples for Norway spruce ( Picea abies ) indicated very little isoprene emitted ( −1 h −1 ). The wide range of isoprene emissions from these different spruce species suggest that improvements in hydrocarbon emission inventories may require detailed species distribution data. On a regional basis, this may be especially true in Europe where 22% of isoprene emissions are estimated to be from spruce and in boreal regions where spruce is a dominant part of the ecosystem.

Windblown dust contributes to high PM2.5 concentrations.

ABSTRACT The revised National Ambient Air Quality Standards for PM include fine particulate standards based upon mass measurements of PM25. It is possible in arid and semi-arid regions to observe significant coarse mode intrusion in the PM2.5 measurement. In this work, continuous PM10, PM2.5, and PM1.0 were measured during several windblown dust events in Spokane, WA. PM2 5 constituted ~30% of the PM10 during the dust event days, compared with ~48% on the non-dusty days preceding the dust events. Both PM10 and PM2.5 were enhanced during the dust events. However, PM1.0 was not enhanced during dust storms that originated within the state of Washington. During a dust storm that originated in Asia and impacted Spokane, PM1.0 was also enhanced, although the Asian dust reached Washington during a period of stagnation and poor dispersion, so that local sources were also contributing to high particulate levels. The “intermodal” region of PM, defined as particles ranging in aerodynamic size from 1.0 to 2.5 um, was found to represent a significant fraction of PM25 (~51%) during windblown dust events, compared with 28% during the non-dusty days before the dust events.

Asthma aggravation, combustion, and stagnant air

BACKGROUND The relationship between current concentrations of ambient air pollution and adverse health effects is controversial. We report a meteorological index of air stagnation that is associated with daily visits to the emergency department for asthma in two urban areas. METHODS Data on daily values of a stagnation persistence index and visits to the emergency department for asthma were collected for approximately two years in Spokane, Washington, USA and for 15 months in Seattle, Washington, USA. The stagnation persistence index represents the number of hours during the 24 hour day when surface wind speeds are less than the annual hourly median value, an index readily available for most urban areas. Associations between the daily stagnation persistence index and daily emergency department visits for asthma were tested using a generalised additive Poisson regression model. A factor analysis of particulate matter (PM2.5) composition was performed to identify the pollutants associated with increased asthma visits. RESULTS The relative rate of the association between a visit to the emergency department for asthma and the stagnation persistence index was 1. 12 (95% CI 1.05 to 1.19) in Spokane and 1.21 (95% CI 1.09 to 1.35) in Seattle for an increase of 11 and 10 hours, respectively, of low wind speed in a given day. The stagnation persistence index was only correlated with one set of factor loadings; that cluster included the stagnation persistence index, carbon monoxide, and organic/elemental carbon. CONCLUSION Increased air stagnation was shown to be a surrogate for accumulation of the products of incomplete combustion, including carbon monoxide and fine particulate levels of organic and elemental carbon, and was more strongly associated with asthma aggravation than any one of the measured pollutants.