Local and regional components of aerosol in a heavily trafficked street canyon in central London derived from PMF and cluster analysis of single-particle ATOFMS spectra.

Positive matrix factorization (PMF) has been applied to single particle ATOFMS spectra collected on a six lane heavily trafficked road in central London (Marylebone Road), which well represents an urban street canyon. PMF analysis successfully extracted 11 factors from mass spectra of about 700,000 particles as a complement to information on particle types (from K-means cluster analysis). The factors were associated with specific sources and represent the contribution of different traffic related components (i.e., lubricating oils, fresh elemental carbon, organonitrogen and aromatic compounds), secondary aerosol locally produced (i.e., nitrate, oxidized organic aerosol and oxidized organonitrogen compounds), urban background together with regional transport (aged elemental carbon and ammonium) and fresh sea spray. An important result from this study is the evidence that rapid chemical processes occur in the street canyon with production of secondary particles from road traffic emissions. These locally generated particles, together with aging processes, dramatically affected aerosol composition producing internally mixed particles. These processes may become important with stagnant air conditions and in countries where gasoline vehicles are predominant and need to be considered when quantifying the impact of traffic emissions.This is the author accepted manuscript. The final version is available via ACS at http://pubs.acs.org/doi/abs/10.1021/es506249z

Fine particle emission factors from vehicles in a highway tunnel: Effects of fleet composition and season

In-use, fuel-based motor vehicle emission factors were determined using measurements made in a highway tunnel in Pittsburgh, Pennsylvania. Concentrations Of PM2.5 mass, CO, CO2, and NO, were measured continuously. Filter-based measurements included PM2.5 mass, organic and elemental carbon (OC and EQ, inorganic ions and metals. Fuel-based emission factors for each pollutant were calculated using a fuel-carbon balance. The weekday traffic volume and fleet composition varied in a consistent diurnal pattern with the estimated fraction of fuel consumed by heavy-duty diesel ve ' hicle (HDDV) traffic ranging from 11% to 36%. The emission rate of most species showed a significant dependence on sample period. NOx, PM2.5, EC and OC emission factors were significantly larger during the early morning, truckdominated period. Emissions of particulate metals associated with brake wear (Cu, Sb, Ba and potentially Ga) were emitted at higher rates during the rush-hour period, which is characterized by slower, stop-and-go traffic. Emission rates of crustal elements (Fe, Ca, Mg, Li), Zn and Mn were highest during the early-morning period when there was more heavytruck traffic. A seasonal shift in average OC/EC ratio for the rush-hour period was observed; fall and summer OC/EC ratios are 1.0+0.6 and 0.26+0.06, respectively. Potential causes for this shift are increased partitioning of semi-volatile organic compounds into the gas phase during the summer months and/or effects of seasonal changes in fuel formulation. Emission factors for HDDV and light-duty vehicles (LDV) classes were estimated using a linear regression of emission factor as a function of fleet composition. The extrapolated emission factors generally agree with previously published measurements, though a substantial range in published values is noted. (c) 2006 Elsevier Ltd. All rights reserved

A national estimate of U.S. underground natural gas storage incident emissions

The 2015 Aliso Canyon storage well blowout was widely reported as the worst natural gas leak in the history of the United States (U.S.) and released ∼0.1 million metric tons of methane (CH _4 ), a potent greenhouse gas. Although storage well fugitive emissions are estimated in the U.S. Environmental Protection Agency’s annual Greenhouse Gas Inventory, the inventory does not include historical estimates of anomalous large emission events other than Aliso Canyon or smaller incident related CH _4 releases. A total of 129 underground natural gas storage (UGS) incident-related events between 1940 and 2016 were compiled from various federal/state agencies and literature reviews. Incident emissions were estimated based on best available information, such as direct operator reports, the monetary cost of gas lost, or modeling of the escaping gas at sonic speeds. There are 387 active UGS fields in three types of reservoirs: salt caverns, aquifers, and depleted oil and gas (O&G) fields. 65% of events were in the depleted O&G fields, which account for 79% of storage fields. Texas recorded the highest number of incidents (20), 14 of which were in salt dome reservoirs. The incident emissions showed a heavy-tailed emission pattern with CH _4 releases up to 29 billion cubic feet (8.2 × 10 ^8 m ^3 ). The top seven events contributed 98% of the total estimated/measured CH _4 emissions