Source Identification of PM_2.5 in Steubenville, Ohio Using a Hybrid Method for Highly Time-Resolved Data

A new source-type identification method, Reduction and Species Clustering Using Episodes (ReSCUE), was developed to exploit the temporal synchronicity typically observed between ambient species in high time resolution fine particulate matter (PM_2.5) data to form clusters that vary together. High time-resolution (30 min) PM_2.5 sampling was conducted for a month during the summer of 2006 in Steubenville, OH, an EPA designated nonattainment area for the U.S. National Ambient Air Quality Standards (NAAQS). When the data were evaluated, the species clusters from ReSCUE matched extremely well with the source types identified by EPA Unmix demonstrating that ReSCUE is a valuable tool in identifying source types. Results from EPA Unmix show that contributions to PM_2.5 are mostly from iron/steel manufacturing (36% ± 9%), crustal matter (33% ± 11%), and coal combustion (11% ± 19%). More importantly, ReSCUE was useful in (i) providing objective data driven guidance for the number of source factors and key fitting species for EPA Unmix, and (ii) detecting tenuous associations between some species and source types in the results derived by EPA Unmix

Behavior of Mercury Emissions from a Commercial Coal-Fired Power Plant: The Relationship between Stack Speciation and Near-Field Plume Measurements

The reduction of divalent gaseous mercury (Hg^II) to elemental gaseous mercury (Hg⁰) in a commercial coal-fired power plant (CFPP) exhaust plume was investigated by simultaneous measurement in-stack and in-plume as part of a collaborative study among the U.S. EPA, EPRI, EERC, and Southern Company. In-stack continuous emission monitoring data were used to establish the CFPP’s real-time mercury speciation and plume dilution tracer species (SO₂, NO_X) emission rates, and an airship was utilized as an airborne sampling platform to maintain static position with respect to the exhaust plume centerline for semicontinuous measurement of target species. Varying levels of Hg^II concentration (2.39–3.90 μg m^–3) and percent abundance (∼87–99%) in flue gas and in-plume reduction were observed. The existence and magnitude of Hg^II reduction to Hg⁰ (0–55%) observed varied with respect to the types and relative amounts of coals combusted, suggesting that exhaust plume reduction occurring downwind of the CFPP is influenced by coal chemical composition and characteristics

Summary of PM_2.5 Measurement Artifacts Associated with the Teledyne T640 PM Mass Analyzer Under Controlled Chamber Experimental Conditions Using Polydisperse Ammonium Sulfate Aerosols and Biomass Smoke

Particulate matter (PM) is a major primary pollutant emitted during wildland fires that has the potential to pose significant health risks to individuals/communities who live and work in areas impacted by smoke events. Limiting exposure is the principle measure available to mitigate health impacts of smoke and therefore the accurate determination of ambient PM concentrations during wildland fire events is critical to protecting public health. However, monitoring air pollutants in smoke impacted environments has proven challenging in that measurement interferences or sampling conditions can result in both positive and negative artifacts. The EPA has performed research on methods for the measurement of PM2.5 in a series of laboratory based studies including evaluation in smoke. This manuscript will summarize the results of the laboratory based evaluation of federal equivalent method (FEM) analyzers for PM2.5 with particular attention being given to the Teledyne-API Model T640 PM Mass analyzer, as compared to the filter-based federal reference method (FRM). The T640 is an optical-based PM analyzer and has been gaining wide use by state and local agencies in monitoring for PM2.5 U.S. National Ambient Air Quality Standards (NAAQS) attainment. At present, the T640 (includes both T640 and T640X) comprises ~40% of the PM2.5 FEM monitors in U.S. regulatory monitoring networks. In addition, the T640 has increasingly been employed for the higher time resolution comparison/evaluation of low-cost PM sensors including during smoke impacted events. Results from controlled non-smoke laboratory studies using generated ammonium sulfate aerosols, demonstrated a generally negative T640 measurement artifact that was significantly related to the PM2.5 concentration and particle size distribution. Results from biomass burning chamber studies demonstrated positive and negative artifacts significantly associated with PM2.5 concentration and optical wavelength dependent absorption properties of the smoke aerosol. Implications The results detailed in this product will provide state and local air monitoring agencies with the tools and knowledge to address PM2.5 measurement challenges in areas frequently impact by wildland fire smoke. The observed large positive and negative artifacts in the T640 PM mass determination has the potential to result in false exceedances of the PM2.5 NAAQS or in the disqualification of monitoring data through an exceptional event designation. In addition, the observed artifacts in smoke impacted air will have a detrimental effect on providing reliable public information when wildfires occur and also in identifying reference measurements for small sensor evaluation studies. Other PM2.5 FEMs such as the BAM-1022 perform better in smoke and are comparable to the filter based FRM. Care must be taken in choosing high time resolution FEM monitors that will be operated at smoke impacted sites. Accurate methods, such as the FRM and BAM-1022 will reduce the burden of developing and reviewing exceptional event request packages, data loss/disqualification, and provide states with tools to adequately evaluate public exposure risks and provide accurate public health messaging during wildfire/smoke events. Implications The results detailed in this product will provide state and local air monitoring agencies with the tools and knowledge to address PM2.5 measurement challenges in areas frequently impact by wildland fire smoke. The observed large positive and negative artifacts in the T640 PM mass determination has the potential to result in false exceedances of the PM2.5 NAAQS or in the disqualification of monitoring data through an exceptional event designation. In addition, the observed artifacts in smoke impacted air will have a detrimental effect on providing reliable public information when wildfires occur and also in identifying reference measurements for small sensor evaluation studies. Other PM2.5 FEMs such as the BAM-1022 perform better in smoke and are comparable to the filter based FRM. Care must be taken in choosing high time resolution FEM monitors that will be operated at smoke impacted sites. Accurate methods, such as the FRM and BAM-1022 will reduce the burden of developing and reviewing exceptional event request packages, data loss/disqualification, and provide states with tools to adequately evaluate public exposure risks and provide accurate public health messaging during wildfire/smoke events.</p

Physical and Chemical Characterization of Residual Oil-Fired Power Plant Emissions

Although the toxicity of oil combustion emissions is a significant public health concern, few studies characterize the emissions from plant-scale utility boilers firing residual oil. This study remedies that deficiency by diluting, sampling, and monitoring stack emissions from a 432 gigajoules (GJ) front-fired fossil fuel steam generator burning residual oil. Over a 3-day test period, continuous CO₂, SO₂, and NO_<i>x</i> emissions monitoring confirms a steady fuel feed rate, high combustion efficiency (3.4 kg of CO₂/kg of fuel oil burned), and evidence of a nocturnal soot-blowing event. The utility boiler emits fine aerosol (PM_2.5) at a rate of 53 ± 2 μg/kJ (2 g/kg of oil burned). Vesicular coarse particles composed of C and S and spherical Al silicates with V and Ni inclusions are identified in a cyclone rinse using scanning electron microscopy and backscatter analysis. Ion chromatography results establish that the fine aerosol is predominantly sulfate (44% ± 0.2%, w/w) which is likely coordinated to transition metals. From thermal optical transmittance measurements, less than 1% (w/w) of the fine aerosol is surmised to be carbonaceous. Low emissions of particle-phase carbon and contaminants interfered with the gas chromatography−mass spectrometry (GC-MS) analysis of polcyclic aromatic hydrocarbons and certain other semivolatile organic compounds. However, trace levels of branched-, cyclic-, and <i>n</i>-alkanes and organic acids are observed in the particle emissions. Sterane and hopane molecules are below the picogram level GC-MS detection limits. Future research determining the individual organic species in the particles emitted from this source will require real-time single particle measurements. Finally, application of EPA methods TO-11 and TO-15 shows that the total volatile nonmethane organic gas emissions from the plant-scale boiler vary between 6 and 28 mg/kg of fuel oil burned; greater than 50% of this mass is ascribed to oxygenated matter

Differential Effects of Particulate Matter Upwind and Downwind of an Urban Freeway in an Allergic Mouse Model

Near-road exposure to air pollutants has been associated with decreased lung function and other adverse health effects in susceptible populations. This study was designed to investigate whether different types of near-road particulate matter (PM) contribute to exacerbation of allergic asthma. Samples of upwind and downwind coarse, fine, and ultrafine PM were collected using a wind direction-actuated ChemVol sampler at a single site 100 m from Interstate-96 in Detroit, MI during winter 2010/2011. Upwind PM was enriched in crustal and wood combustion sources while downwind PM was dominated by traffic sources. Control and ovalbumin (OVA)-sensitized BALB/cJ mice were exposed via oropharyngeal (OP) aspiration to 20 or 100 μg of each PM sample 2 h prior to OP challenge with OVA. In OVA-allergic mice, 100 μg of downwind coarse PM caused greater increases than downwind fine/ultrafine PM in bronchoalveolar lavage neutrophils, eosinophils, and lactate dehydrogenase. Upwind fine PM (100 μg) produced greater increases in neutrophils and eosinophils compared to other upwind size fractions. Cytokine (IL-5) levels in BAL fluid also increased markedly following 100 μg downwind coarse and downwind ultrafine PM exposures. These findings indicate coarse PM downwind and fine PM upwind of an interstate highway promote inflammation in allergic mice