Source apportionment of atmospheric trace gases and particulate matter--Comparison of log-ratio and traditional approaches
No abstract available.
Conference Paper↗
Geology topics
Mark A. Engle
Publications and source records attributed to Mark A. Engle.
Comparison of atmospheric mercury speciation and deposition at nine sites across central and eastern North America
This study presents >5 cumulative years of tropospheric mercury (Hg) speciation measurements, over the period of 2003–2009, for eight sites in the central and eastern United States and one site in coastal Puerto Rico. The purpose of this research was to identify local and regional processes that impact Hg speciation and deposition (wet + dry) across a large swath of North America. Sites sampled were selected to represent both a wide range of mercury exposure and environmental conditions. Seasonal mean concentrations of elemental Hg (1.27 ± 0.31 to 2.94 ± 1.57 ng m−3; x ± s), reactive gaseous mercury (RGM; 1.5 ± 1.6 to 63.3 ± 529 pg m−3), and fine particulate Hg (1.2 ± 1.4 to 37.9 ± 492 pg m−3) were greatest at sites impacted by Hg point sources. Diel bin plots of Hgo and RGM suggest control by a variety of local/regional processes including impacts from Hg point sources and boundary layer/free tropospheric interactions as well as from larger‐scale processes affecting Hg speciation (i.e., input of the global Hg pool, RGM formed from oxidation of Hgo by photochemical compounds at coastal sites, and elemental Hg depletion during periods of dew formation). Comparison of wet Hg deposition (measured), RGM and fine particulate Hg dry deposition (calculated using a multiple resistance model), and anthropogenic point source emissions varied significantly between sites. Significant correlation between emission sources and dry deposition was observed but was highly dependant upon inclusion of data from two sites with exceptionally high deposition. Findings from this study highlight the importance of environmental setting on atmospheric Hg cycling and deposition rates.
Journal of Geophysical Research↗
Patterns of mercury dispersion from local and regional emission sources, rural Central Wisconsin, USA
Simultaneous real-time changes in mercury (Hg) speciation-reactive gaseous Hg (RGM), elemental Hg (Hg??), and fine particulate Hg (Hg-PM 2.5 ), were determined from June to November 2007, in ambient air at three locations in rural Central Wisconsin. Known Hg emission sources within the airshed of the monitoring sites include: 1) a 1114 megawatt (MW) coal-fired electric utility generating station; 2) a Hg-bed chlor-alkali plant; and 3) a smaller (465 MW) coal-burning electric utility. Monitoring sites, showing sporadic elevation of RGM, Hg o and Hg-PM 2.5 , were positioned at distances of 25, 50 and 100 km northward of the larger electric utility. A series of RGM events were recorded at each site. The largest, on 23 September, occurred under prevailing southerly winds, with a maximum RGM value (56.8 pg m -3 ) measured at the 100 km site, and corresponding elevated SO 2 (10.41 ppbv; measured at 50 km site). The finding that RGM, Hg o , and Hg-PM 2.5 are not always highest at the 25 km site, closest to the large generating station, contradicts the idea that RGM decreases with distance from a large point source. This may be explained if: 1) the 100 km site was influenced by emissions from the chlor-alkali facility or by RGM from regional urban sources; 2) the emission stack height of the larger power plant promoted plume transport at an elevation where the Hg is carried over the closest site; or 3) RGM was being generated in the plume through oxidation of Hg o . Operational changes at each emitter since 2007 should reduce their Hg output, potentially allowing quantification of the environmental benefit in future studies.
Atmospheric Chemistry and Physics Discussions↗
CO 2 , CO, and Hg emissions from the Truman Shepherd and Ruth Mullins coal fires, eastern Kentucky, USA
Carbon dioxide (CO 2 ), carbon monoxide (CO), and mercury (Hg) emissions were quantified for two eastern Kentucky coal-seam fires, the Truman Shepherd fire in Floyd County and the Ruth Mullins fire in Perry County. This study is one of the first to estimate gas emissions from coal fires using field measurements at gas vents. The Truman Shepherd fire emissions are nearly 1400 t CO 2 /yr and 16 kg Hg/yr resulting from a coal combustion rate of 450–550 t/yr. The sum of CO 2 emissions from seven vents at the Ruth Mullins fire is 726 ± 72 t/yr, suggesting that the fire is consuming about 250–280 t coal/yr. Total Ruth Mullins fire CO and Hg emissions are estimated at 21 ± 1.8 t/yr and > 840 ± 170 g/yr, respectively. The CO 2 emissions are environmentally significant, but low compared to coal-fired power plants; for example, 3.9 × 10 6 t CO 2 /yr for a 514-MW boiler in Kentucky. Using simple calculations, CO 2 and Hg emissions from coal-fires in the U.S. are estimated at 1.4 × 10 7 – 2.9 × 10 8 t/yr and 0.58–11.5 t/yr, respectively. This initial work indicates that coal fires may be an important source of CO 2 , CO, Hg and other atmospheric constituents.
Kentucky↗
The Tiptop coal-mine fire, Kentucky: Preliminary investigation of the measurement of mercury and other hazardous gases from coal-fire gas vents
The Tiptop underground coal-mine fire in the Skyline coalbed of the Middle Pennsylvanian Breathitt Formation was investigated in rural northern Breathitt County, Kentucky, in May 2008 and January 2009, for the purpose of determining the concentrations of carbon dioxide (CO2), carbon monoxide (CO), and mercury (Hg) in the vent and for measuring gas-vent temperatures. At the time of our visits, concentrations of CO2 peaked at 2.0% and > 6.0% (v/v) and CO at 600 ppm and > 700 ppm during field analysis in May 2008 and January 2009, respectively. For comparison, these concentrations exceed the U.S. Occupational Safety & Health Administration (OSHA) eight-hour safe exposure limits (0.5% CO2 and 50 ppm CO), although the site is not currently mined. Mercury, as Hg0, in excess of 500 and 2100 μg/m3, in May and January, respectively, in the field, also exceeded the OSHA eight-hour exposure limit (50 μg/m3). Carbonyl sulfide, dimethyl sulfide, carbon disulfide, and a suite of organic compounds were determined at two vents for the first sampling event. All gases are diluted by air as they exit and migrate away from a gas vent, but temperature inversions and other meteorological conditions could lead to unhealthy concentrations in the nearby towns. Variation in gas temperatures, nearly 300 °C during the January visit to the fire versus < 50 °C in May, demonstrates the large temporal variability in fire intensity at the Tiptop mine. These preliminary results suggest that emissions from coal fires may be important, but additional data are required that address the reasons for significant variations in the composition, flow, and temperature of vent gases.
Kentucky↗
Summary of mercury and trace element results in precipitation from the Culpeper, Virginia, Mercury Deposition Network Site (VA-08), 2002-2006
The VA-08 Mercury Deposition Network (MDN) site, southwest of Culpeper, Virginia, was established in autumn of 2002. This site, along with nearby VA-28 (~31 km west) at Big Meadows in Shenandoah National Park, fills a spatial gap in the Mid-Atlantic region of the MDN network and provides Hg deposition data immediately west of the Washington, D.C., metropolitan area. Results for the Culpeper site from autumn of 2002 to the end of 2006 suggest that the highest mercury (Hg) deposition (up to 5.0 µg/m 2 per quarter of the 6.5-12.6 µg/m 2 annual Hg deposition) is measured during the second and third quarters of the year (April-September). This is a result of both elevated Hg precipitation concentrations (up to 27 ng/L) and greater precipitation during these months. The data also exhibit a general statistically significant (p<0.05) negative correlation between weekly total precipitation and Hg concentrations, suggesting a dilution effect during larger precipitation events, especially during winter and spring. Comparison of results between the Culpeper and Big Meadows sites indicates that although quarterly Hg deposition was not significantly different (p<0.05) between sites, quarterly volume-averaged Hg precipitation concentrations were statistically larger (p<0.05) and precipitation was significantly lower (p<0.05) at VA-08. Lower Hg concentrations at the VA-28 site relative to VA-08 are likely a result of greater total precipitation and thus additional dilution of Hg in precipitation. Results from concomitant trace elements in precipitation collected from July, 2005, to December, 2006, were used to better identify possible sources of Hg at the Culpeper MDN site. Principal component analysis of the Hg and trace metal data identified 3 primary source categories, each with large loadings of characteristic elements: 1) Ca, Al, Mg, Sr, La, and Ce (crustal sources); 2) V, Na, and Ni (local wintertime heating oil); and 3) Zn, Cd, Mn, and Hg (regional anthropogenic emission sources). HYSPLIT air mass trajectory modeling and enrichment factor calculations are consistent with this interpretation. A preliminary source attribution model suggests that ~51% of the Hg in wet deposition is due to regional anthropogenic sources, while crustal sources and local oil combustion account for 9.5% and <1%, respectively. This calculation implies that the global Hg burden accounts for ~40% of the Hg in wet deposition.
Virginia↗