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We quantify the contributions of long-range and regionally transported aerosols to ambient primary PM(2.5) and PM(10) in a representative United States industrialized/urban atmosphere via detailed elemental analysis and chemical mass balance (CMB) modeling after identifying their presence using a variety of publicly available satellite data/information, software products, and synoptic-scale aerosol models. A year-long study in Houston, Texas identified North African dust as the principal long-range global source of primary particulate matter (PM). CMB estimated transatlantic dust from the Sahara-Sahel region to be dominant in the summer months contributing an average of 3.5 μg m(−3) to PM(2.5) and 7.9 μg m(−3) to PM(10) during May–August, i.e., the active Saharan dust season. Biomass burning was the chief source of regionally transported PM impacting air quality on different occasions throughout the year depending on the fire location. Four major biomass combustion events affecting air quality in Texas were calculated to contribute an average of 1.3 μg m(−3) to PM(2.5) and 1.4 μg m(−3) to PM(10) in corresponding samples whose origins were tracked to Canada, southeastern states of USA, and Central America using fire maps, HYSPLIT back trajectories, and the Navy Aerosol Analysis and Prediction System global aerosol model. Elemental concentrations and signature ratios revealed significant mixing of potassium, rare earth metals, and vanadium from proximal and distal crustal (natural) sources with anthropogenically emitted PM. This demonstrates the need to isolate the non-mineral components of these metals to employ them as tracers for primary PM emitted by biomass burning, petroleum refineries, and oil combustion. Transboundary contributions to primary PM(2.5) were 1.5 μg m(−3) and 3.1 μg m(−3) to PM(10) adding 16% to annual average mass concentration of both size fractions demonstrating that local sources were primarily responsible for ambient air quality with non-trivial contributions from international and interstate sources. Rigorously identifying and quantifying aerosol sources assists in improving air quality management policies designed to protect public health and comply with ever-decreasing federal PM standards that allow state agencies to exclude contributions that are not reasonably controllable or preventable from regulatory decisions and actions.

Paired PM10 and fine particulate matter (PM2.5) samples were collected indoor and outdoor at a fully mechanically ventilated high school in the ultraindustrialized ship channel region of Houston, Texas over a two-month period. The primary foci of this research are to measure the elemental composition of ambient outdoor and indoor coarse particulate matter (PM10-2.5), characterize aerosol infiltration/ventilation, and obtain clues to their origins. Several metallic hazardous air pollutants were detected inside the school but at concentrations lower than even the most rigorous indoor air quality benchmarks. Only chromium may have potentially posed a hazard based on indoor air quality standards set by the California Environmental Protection Agency. Indoor-to-outdoor (I/O) mass abundance ratios for some metals (Li, Be, Si, Ti, Cr, Co, Ni, Zn, As, Se, Zr, Cd, Sn, Sb, Hf, and Pb) were significantly greater than 1 in PM10-2.5, suggesting corresponding indoor sources in the PM10-2.5 size range. Some other metals (Al, K, Ca, V, Mn, Fe, Cu, Ga, Rb, Sr, Y, Mo, Ce, Pr, Nd, Sm, Gd, Dy, Yb, and U) in PM10-2.5 had I/O ratios close to one suggesting they had predominantly outdoor origins. Enrichment factors of several metals including light rare earths (e.g. Cu, Sb, Pb, Mo, Cd, La, Ce, Pr, Nd, and Sm) with respect to local soil were overall the highest both indoors and outdoors, illustrating their anthropogenic origins. Several lines of evidence including light lanthanoid ratios, simultaneous La–Ce-Sm variations (ternary diagrams), and correlations with cracking catalysts indicated that petroleum refineries are principally responsible for the elevated lanthanoid concentrations. Rare earth element analysis revealed shifts between transient catalyst releases from petroleum refining operations and windblown soil resuspension as their dominant sources.

A series of field sampling and controlled laboratory experiments were undertaken to quantify the role of trace metals found in ambient fine particulate matter and metal-rich primary sources in the heterogenous catalytic conversion of SO2 gas into sulfate particulate matter (PM) in the atmosphere. Analysis produced source profiles of three primary source materials, fluidized-bed catalytic cracking catalyst, coal-fired combustion fly ash, and paved road dust, featuring 33 elements including rare earth metals, which are not commonly reported in the literature. Subsequently three sets of experiments were conducted exposing 1) source materials, 2) ambient PM, and 3) ambient PM augmented with approximately an equal amount of source material to SO2 gas and measuring sulfate formation. Source material experiments revealed that the greatest extent of reaction was on the surface of coal fly ash with sulfate formation of 19 ± 5 mg sulfate g−1 material. Ambient fine particulate matter (PM) experiments showed sulfate formation ranging from negligible amounts to 180 ± 10 mg sulfate g−1 PM. It was much more difficult to quantify the sulfate formation on ambient filters augmented with the source materials. In these experiments, sulfate formation ranged from negligible amounts to 40 ± 8 mg sulfate g−1 of particles (ambient + augmented material). These three sets of experiments shows that heterogenous sulfate formation is often negligible but, under some conditions can contribute 10% or more to the total sulfate concentrations when exposed to high SO2 concentrations such as those found in plumes. Factor analysis of the source material experiments grouped metals into two categories, crustal components and anthropogenically emitted metals representative of catalyst material, with the former showing the strongest correlation with sulfate formation. Subsequent analysis of data collected from the ambient PM experiments showed a much weaker correlation of sulfate formation with the crustal components, including iron and titanium, remaining clustered with sulfate formation. Independent research has been previously reported in the literature establishing mechanisms for the iron and titanium catalyzed conversion of S(IV) to S(VI) suggesting there may be other metals within these crustal type metal components that behave similarly. Additional experiments spanning a wider range of variables including more sources, SO2 concentrations and exposure times, ambient PM locations, as well as more individual samples may be necessary to obtain more conclusive evidence into the role of various metals in catalyzing the conversion of S(IV) to S(VI).

Petroleum refineries may emit large quantities of pollutants during non-routine operations that include start-ups and shutdowns, planned maintenance, and unplanned equipment failures. The Texas Commission on Environmental Quality (TCEQ) tracks such events by requiring industries to self-report estimates of these emissions because they often have a detrimental impact on local air quality and potentially, public health. An inventory of non-routine episodic emission events is available via TCEQ's website. However, there is on-going concern that such episodic emissions are sometimes under-reported or even not cataloged. Herein, we present concentrations of 42 main group, transition, and lanthanoid elements in 114 time-resolved (3 or 6 h) samples collected over a 1-month period. We also develop strategies to identify aerosol sources using elemental tracers and compare source apportionment (performed by positive matrix factorization) based on ambient measurements to inventoried non-routine emission events. Through interpretation of key marker elements, five sources impacting concentrations of metals in PM10 were identified and calculated to contribute 73% of the measured PM10 mass. On average, primary emissions from fluidized-bed catalytic cracking (FCC) units negligibly contributed to apportioned PM10 mass. However, 35 samples were identified as impacted by transient PM10 emissions from FCC units because of elevated levels of lanthanoid metals and their ratios. Only 31 of these 35 samples coincided with self-reported non-routine emission events. Further, roughly half of the emission event self-reports detailed only emissions of gaseous pollutants. Based on this, we posit that not all PM10 emission events are reported and even self-reported emission events are incomplete - those that only catalog gaseous pollutants may also include unreported PM emissions. (C) 2012 Elsevier Ltd. All rights reserved.

A study was conducted in Houston, TX focusing on rare earth elements (REEs) in atmospheric fine particles and their sources. PM2.5 samples were collected from an ambient air quality monitoring site (HRM3) located in the proximity of a large number of oil refineries and petrochemical industries to estimate the potential contributions of emissions from fluidized-bed catalytic cracking operations to ambient fine particulate matter. The elemental composition of ambient PM2.5, several commercially available zeolite catalysts, and local soil was measured after microwave assisted acid digestion using inductively coupled plasma—mass spectrometry. Source identification and apportionment was performed by principal component factor analysis (PCFA) in combination with multiple linear regression. REE relative abundance sequence, ratios of La to light REEs (Ce, Pr, Nd, and Sm), and enrichment factor analysis indicated that refining and petrochemical cat cracking operations were predominantly responsible for REE enrichment in ambient fine particles. PCFA yielded five physically meaningful PM2.5 sources: cat cracking operations, a source predominantly comprised of crustal material, industrial high temperature operations, oil combustion, and sea spray. These five sources accounted for 82% of the total mass of atmospheric fine particles (less carbon and sulfate). Factor analysis confirmed that emissions from cat cracking operations primarily contributed to REE enrichment in PM2.5 even though they comprised only 2.0% of the apportioned mass. Results from this study demonstrate the need to characterize catalysts employed in the vicinity of the sampling stations to accurately determine local sources of atmospheric REEs.