Jay R. Turner

Source identification of airborne PM2.5 at the St. Louis‐Midwest Supersite

Daily 24-hour integrated PM 2.5 (particulate matter <2.5 μm aerodynamic diameter) mass and species concentrations were measured at the St. Louis-Midwest Supersite in East St. Louis, Illinois, during the sampling period from June 2001 to May 2003. The PM 2.5 speciation data were analyzed using a receptor model, positive matrix factorization (PMF), to identify sources contributing to the observed PM 2.5 burdens. Species profiles for the identified sources and their contributions to the observed mass concentration at the receptor were derived from the PMF modeling. These source-specific contributions were then coupled with on-site wind data to identify the directionality of the identified sources which are compared to known point source locations. Overall, ten source categories were resolved (study average contribution to the PM 2.5 mass in parentheses): secondary sulfate (33%), carbon-rich sulfate (20%), gasoline exhaust (16%), secondary nitrate (15%), steel processing (7%), airborne soil (4%), diesel emissions/railroad traffic (2%), zinc smelting (1.3%), lead smelting (1.3%), and copper production (0.5%). Temperature-resolved organic and elemental carbon fractions enhanced the source separation between secondary sulfate and carbon-rich sulfate and between gasoline exhaust and diesel emissions/railroad traffic. A major Saharan dust plume observed throughout the Midwestern U.S. in July 2002 was also observed in this study. Overall, about half (48%) of PM 2.5 mass concentration measured at this site was distinctly apportioned to secondary sulfate and secondary nitrate. Contributions from distinct primary emissions included local industrial sources (9%), transportation (gasoline/diesel/railroad, 19%), and airborne dust (4%). The remaining 20% of the PM 2.5 mass was apportioned to a carbon-rich sulfate factor which is likely an admixture of primary emissions and secondary formation. More work is needed to identify the distinct sources contributing to this factor.

Hourly and Daily Patterns of Particle-Phase Organic and Elemental Carbon Concentrations in the Urban Atmosphere

Abstract Two semicontinuous elemental and organic carbon analyzers along with daily integrated samplers, which were used for laboratory elemental and organic carbon analysis, were operated to measure PM2.5 organic carbon (OC) and elemental carbon (EC) for the entire year of 2002 at the St. Louis Midwest Supersite. The annual-average denuded OC and EC concentrations were 3.88 and 0.7 μg/m3, respectively. A comparison of the 24-hr average denuded and undenuded OC measurements showed a positive bias for the undenuded OC measurement that was best represented by a positive intercept of 0.34 ± 0.1 μg/m3 and a slope of 1.06 ± 0.02, with an R2 of 0.91. The full year of daily EC and OC measurements was used to demonstrate that a one-in-six-day sampling strategy at this site accurately represents the annual average concentrations. Although fine particle OC concentrations did not correlate with day of the week, EC concentrations showed a significant weekly pattern, with the highest concentration during the middle of the workweek and the lowest concentration on Sundays. Hourly EC and OC measurements yielded average diurnal patterns for the EC to OC ratio that peaked during morning rush hour traffic on weekdays but not on weekends.

Estimation of the Monthly Average Ratios of Organic Mass to Organic Carbon for Fine Particulate Matter at an Urban Site

Two independent methods are used to estimate the seasonality of the ratio of fine particulate organic matter (OM) to fine particulate organic carbon (OC) for atmospheric particulate matter collected at the St. Louis—Midwest Supersite. The first method assumes that all of the fine particulate matter mass that cannot be attributed to sulfate ion, nitrate ion, ammonium ion, elemental carbon and metal oxides is organic matter. Using this method, 98 daily samples were used to estimate the annual average fine particulate matter OM/OC ratio to be 1.81 ± 0.07 with a summer average of 1.95 ± 0.17 and a winter average of 1.77 ± 0.13. The second approach to estimating fine particle OM/OC employed OC source apportionment results and estimates of source specific OM/OC, including primary sources and secondary organic aerosol. The OM/OC estimate that was based on 98 daily source apportionment calculations over a two year period yielded an annual average ratio of 1.96 ± 0.03. Methods used in the study yielded a relatively stable annual average estimate of the OM/OC ratio for fine particulate matter in the St. Louis area. The source apportionment results indicate that the similar OM/OC ratio for St. Louis in the summer and winter results from an increased relative contribution of secondary organic aerosol in the summer months that is balanced by the higher woodsmoke in the winter. Although the estimated OM/OC ratios that were determined for St. Louis cannot be directly applied to other locations, the methodologies used to estimate OM/OC can be broadly applied given the necessary data for these calculations.

How fragmentation and corridors affect wind dynamics and seed dispersal in open habitats

Significance Understanding how widespread human-induced global changes are affecting the movement and dispersal of organisms is critical for maintaining species diversity and making sound land management decisions. In contrast with animal-dispersed species, little is known about how wind-dispersed species are affected by conservation strategies such as corridors. We use a combination of mechanistic models and field data to show that habitat corridors alter wind dynamics in a way that promotes seed dispersal and appears to increase plant diversity. Wind direction also interacts with landscape orientation to determine when corridors can provide connectivity. Determining how widespread human-induced changes such as habitat loss, landscape fragmentation, and climate instability affect populations, communities, and ecosystems is one of the most pressing environmental challenges. Critical to this challenge is understanding how these changes are affecting the movement abilities and dispersal trajectories of organisms and what role conservation planning can play in promoting movement among remaining fragments of suitable habitat. Whereas evidence is mounting for how conservation strategies such as corridors impact animal movement, virtually nothing is known for species dispersed by wind, which are often mistakenly assumed to not be limited by dispersal. Here, we combine mechanistic dispersal models, wind measurements, and seed releases in a large-scale experimental landscape to show that habitat corridors affect wind dynamics and seed dispersal by redirecting and bellowing airflow and by increasing the likelihood of seed uplift. Wind direction interacts with landscape orientation to determine when corridors provide connectivity. Our results predict positive impacts of connectivity and patch shape on species richness of wind-dispersed plants, which we empirically illustrate using 12 y of data from our experimental landscapes. We conclude that habitat fragmentation and corridors strongly impact the movement of wind-dispersed species, which has community-level consequences.

Use of the Electrical Aerosol Detector as an Indicator of the Surface Area of Fine Particles Deposited in the Lung

Abstract Because of recent concerns about the health effects of ultrafine particles and the indication that particle toxicity is related to surface area, we have been examining techniques for measuring parameters related to the surface area of fine particles, especially in the 0.003- to 0.5-µm size range. In an earlier study, we suggested that the charge attached to particles, as measured by a prototype of the Electrical Aerosol Detector (EAD, TSI Inc., Model 3070), was related to the 1.16 power of the mobility diameter. An inspection of the pattern of particle deposition in the lung as a function of particle size suggested that the EAD measurement might be a useful indicator of the surface area of particles deposited in the lung. In this study, we calculate the particle surface area (micrometer squared) deposited in the lung per cubic centimeter of air inhaled as a function of particle size using atmospheric particle size distributions measured in Minneapolis, MN, and East St. Louis, IL. The correlations of powers of the mobility diameter, DX, were highest for X = 1.1–1.6 for the deposited surface area and for X = 1.25 with the EAD signal. This overlap suggested a correspondence between the EAD signal and the deposited surface area. The correlation coefficients of the EAD signal and particle surface area deposited in the alveolar and tracheobronchial regions of the lung for three breathing patterns are in the range of Pearson’s r = 0.91–0.95 (coefficient of determination, R2 = 0.82–0.90). These statistical relationships suggest that the EAD could serve as a useful indicator of particle surface area deposited in the lung in exposure and epidemiologic studies of the human health effects of atmospheric particles and as a measure of the potential surface area dose for the characterization of occupational environments.

Transport of Atmospheric Fine Particulate Matter: Part 2-Findings from Recent Field Programs on the Intraurban Variability in Fine Particulate Matter

Abstract Air quality field data, collected as part of the fine particulate matter Supersites Program and other field measurements programs, have been used to assess the degree of intraurban variability for various physical and chemical properties of ambient fine particulate matter. Spatial patterns vary from nearly homogeneous to quite heterogeneous, depending on the city, parameter of interest, and the approach or method used to define spatial variability. Secondary formation, which is often regional in nature, drives fine particulate matter mass and the relevant chemical components toward high intraurban spatial homogeneity. Those particulate matter components that are dominated by primary emissions within the urban area, such as black carbon and several trace elements, tend to exhibit greater spatial heterogeneity. A variety of study designs and data analysis approaches have been used to characterize intraurban variability. High temporal correlation does not imply spatial homogeneity. For example, there can be high temporal correlation but with spatial heterogeneity manifested as smooth spatial gradients, often emanating from areas of high emissions such as the urban core or industrial zones.

Fine Particulate Matter Components and Emergency Department Visits for Cardiovascular and Respiratory Diseases in the St. Louis, Missouri–Illinois, Metropolitan Area

Background: Given that fine particulate matter (≤ 2.5 μm; PM2.5) is a mixture of multiple components, it has been of high interest to identify its specific health-relevant physical and/or chemical features. Objectives: We conducted a time-series study of PM2.5 and cardiorespiratory emergency department (ED) visits in the St. Louis, Missouri–Illinois metropolitan area, using 2 years of daily PM2.5 and PM2.5 component measurements (including ions, carbon, particle-phase organic compounds, and elements) made at the St. Louis-Midwest Supersite, a monitoring site of the U.S. Environmental Protection Agency Supersites ambient air monitoring research program. Methods: Using Poisson generalized linear models, we assessed short-term associations between daily cardiorespiratory ED visit counts and daily levels of 24 selected pollutants. Associations were estimated for interquartile range changes in each pollutant. To allow comparison of relationships among multiple pollutants and outcomes with potentially different lag structures, we used 3-day unconstrained distributed lag models controlling for time trends and meteorology. Results: Considering results of our primary models, as well as sensitivity analyses and models assessing co-pollutant confounding, we observed robust associations of cardiovascular disease visits with 17α(H),21β(H)-hopane and congestive heart failure visits with elemental carbon. We also observed a robust association of respiratory disease visits with ozone. For asthma/wheeze, associations were strongest with ozone and nitrogen dioxide; observed associations of asthma/wheeze with PM2.5 and its components were attenuated in two-pollutant models with these gases. Differential measurement error due to differential patterns of spatiotemporal variability may have influenced patterns of observed associations across pollutants. Conclusions: Our findings add to the growing field examining the health effects of PM2.5 components. Combustion-related components of the pollutant mix showed particularly strong associations with cardiorespiratory ED visit outcomes. Citation: Sarnat SE, Winquist A, Schauer JJ, Turner JR, Sarnat JA. 2015. Fine particulate matter components and emergency department visits for cardiovascular and respiratory diseases in the St. Louis, Missouri–Illinois, metropolitan area. Environ Health Perspect 123:437–444; http://dx.doi.org/10.1289/ehp.1307776

Daily Variation in Particle-Phase Source Tracers in an Urban Atmosphere

One full year of daily 24-hour fine particulate matter samples collected in East St. Louis, IL at the EPA funded St. Louis-Midwest Supersite were analyzed for organic carbon (OC), elemental carbon (EC) and non-polar organic tracers including polycyclic aromatic hydrocarbons (PAH(s)), hopanes, and alkanes. Two different analytical methods were used for analysis, solvent extraction gas chromatography/mass spectrometry (GCMS) and thermal desorption GCMS (TD-GCMS). The TD-GCMS method was equivalent to the solvent extraction GCMS method for key molecular markers. Select PAH(s) and alkanes were found to have extreme events within the annual study which had daily 24-hour concentrations that were 10 to 22 times higher than the annual average daily concentration. The OC and EC maxima were only 3 to 5 times higher than the annual average. To further assess the impact of point sources and to evaluate the compatibility of the two organic speciation methods, the six potential every sixth day annual averages were calculated and compared. The extreme concentration days were large enough, in the case of benzo[a]pyrene, to make every sixth day analysis not representative of the true annual average even with events greater than the 99th percentile of the annual distribution removed. The final analysis calculated day of the week averages for select representative organic tracers and revealed that gasoline motor vehicle tracers and OC do not have a distinct day of the week trend. EC, believed to be largely impacted by diesel exhaust, had a midweek concentration peak. These trends cannot necessarily be extrapolated to other urban areas or other events.

Seasonal variations of elemental carbon in urban aerosols as measured by two common thermal-optical carbon methods.

Two commonly employed laboratory-based elemental carbon (EC) and organic carbon (OC) thermal/optical methods for the analysis of ambient particulate matter were used to analyze 709 twenty-four hour integrated PM(2.5) samples along with 76 field blanks from the St. Louis-Midwest Supersite in East St. Louis, Illinois. The two laboratory ECOC methods were the Aerosol Characterization Experiment-Asia (ACE-Asia) method based on National Institute of Occupational Safety and Health (NIOSH 5040) method and the Interagency Monitoring of Protected Visual Environments (IMPROVE) protocol. As in previous intercomparisons between these two methods, there was excellent agreement for total carbon (i.e. sum of EC and OC), but significant differences were observed in the split between the measured EC and OC. The 709 daily PM(2.5) samples spanned a time series of two years that allowed an assessment of seasonal relationships between the EC reported by the two methods. Seasonal average ACE-Asia and IMPROVE EC concentration values were highest in the fall and lowest in the spring. Differences between the seasonal average IMPROVE and ACE-Asia EC concentration values were about 40% greater in summer compared to winter. While IMPROVE EC values were always larger than ACE-Asia EC, the EC difference between these methods exhibited a strong seasonal variation with largest differences occurring in the spring and especially summer with the smallest differences in the fall and winter. Seasonal average EC differences (IMPROVE-ACE-Asia) were anti-correlated with molecular markers for biomass burning and mobile source emissions that had wintertime maximum concentrations. The EC difference between methods did have a moderate positive correlation with indicators of secondary organic aerosol and sulfate suggesting that oxidized organic aerosol associated with atmospheric processing or other secondary components of ambient aerosol could be associated with the seasonal differences between these EC measurements.

Transport of Atmospheric Fine Particulate Matter: Part 1—Findings from Recent Field Programs on the Extent of Regional Transport within North America

Abstract Air quality field data, collected as part of the fine particulate matter Supersites program and other field measurements programs, have been used to assess the role of aerosol transport, over length scales of approximately 100–1000 km, on fine particulate matter concentrations. Assessment of data from New York, NY; Baltimore, MD; Pittsburgh, PA; Atlanta, GA; Houston, TX; St. Louis, MO; and Fresno, CA, indicates that in virtually all of the regions, transport of aerosol over distances of 100-1000 km has a significant impact on urban particulate matter concentrations and a dominant role in determining rural particulate matter concentrations, though the nature of the regional contributions differs from region to region. This assessment is generally consistent with previous conceptual models of fine particulate matter formation and accumulation in these regions. The nature of the transported aerosol is largely sulfate in Eastern and Midwestern cities and nitrate in the Central Valley of California. In addition to physical transport of aerosol over distances of 100–1000 km, regional transport of aerosol precursors may lead to conditions conducive to large-scale nucleation events. Regional nucleation events have been reported in the East, Midwest, and in California. The events occurred in the morning soon after surface layers coupled with layers aloft, and the events generate ultrafine particles. In some cases, these nucleation events have been correlated with availability of sulfur dioxide and, therefore, may be sulfate formation events.