Steven S. Cliff

Real-World Emission Factors for Antimony and Other Brake Wear Related Trace Elements: Size-Segregated Values for Light and Heavy Duty Vehicles

Hourly trace element measurements were performed in an urban street canyon and next to an interurban freeway in Switzerland during more than one month each, deploying a rotating drum impactor (RDI) and subsequent sample analysis by synchrotron radiation X-ray fluorescence spectrometry (SR-XRF). Antimony and other brake wear associated elements were detected in three particle size ranges (2.5-10, 1-2.5, and 0.1-1 microm). The hourly measurements revealed that the effect of resuspended road dust has to be taken into account for the calculation of vehicle emission factors. Individual values for light and heavy duty vehicles were obtained for stop-and-go traffic in the urban street canyon. Mass based brake wear emissions were predominantly found in the coarse particle fraction. For antimony, determined emission factors were 11 +/- 7 and 86 +/- 42 microg km(-1) vehicle(-1) for light and heavy duty vehicles, respectively. Antimony emissions along the interurban freeway with free-flowing traffic were significantly lower. Relative patterns for brake wear related elements were very similar for both considered locations. Beside vehicle type specific brake wear emissions, road dust resuspension was found to be a dominant contributor of antimony in the street canyon.

Measurement of multioxygen isotopic (δ18O and δ17O) fractionation factors in the stratospheric sink reactions of nitrous oxide

Nitrous oxide is an important component in the Earths atmosphere with a global budget that shows significant imbalance between known sources and sinks. A recent isotopic analysis of atmospheric nitrous oxide has suggested that back fluxing from the stratosphere could be an important source of N2O to the troposphere. To quantitatively determine the potential magnitude of this process, the relevant isotopic fractionations must be known. We have measured the isotopic fractionation factors associated with the two known stratospheric sink reactions of N2O: photolysis and photooxidation. It is observed that nitrous oxide photolysis produces no fractionation in δ18O and δ17O, while photooxidation produces a small mass-dependent enrichment in 18O and 17O in the residual N2O.

First measurement of the 18O/16O and 17O/16O ratios in stratospheric nitrous oxide: A mass‐independent anomaly

The first multi-oxygen isotopic analysis of nitrous oxide samples from the lower stratosphere has a mass-independent composition. This study extends the results from tropospheric nitrous oxide samples. Measurements are reported from two 8–12 km altitude airplane flights from New Zealand to the Antarctic in June and October 1993. The observed isotopic results strengthen the previous argument that an atmospheric process, source, sink, or exchange reaction, involving nitrous oxide must exist in the atmosphere, and they further define its signature.

CHARACTERISTICS OF ION COMPONENTS AND TRACE ELEMENTS OF FINE PARTICLES AT GOSAN, KOREA IN SPRING TIME FROM 2001 TO 2002

Size-segregated measurements of the composition of an aerosol are used to determine the transport of natural and anthropogenic aerosols to the Gosan site in springtime from 2001 to 2002. Although the transport of Asian dust is a well-known phenomenon in springtime, this study shows that not only is soil dust transported into Gosan each spring but so are anthropogenic aerosols, including sulfur, enriched trace metals such as Pb, Zn, Ni, K, S. This study also combines the size- and time-resolved aerosol composition measurements with isentropic, backward air-mass trajectories in order to identify some potential source regions of the anthropogenic aerosols. Finally, four types of transport episodes were identified: (1) anthropogenic pollutants, (2) dust storm mixed with the anthropogenic aerosols, (3) typical dust storms, (4) some sea salt with clean air mass. Overall, in addition to typical soil dust, a large amount of anthropogenic aerosols, whether mixed with the soil dust or not, are transported to Gosan each spring.

Pb Isotopes as an Indicator of the Asian Contribution to Particulate Air Pollution in Urban California

During the last two decades, expanding industrial activity in east Asia has led to increased production of airborne pollutants that can be transported to North America. Previous efforts to detect this trans-Pacific pollution have relied upon remote sensing and remote sample locations. We tested whether Pb isotope ratios in airborne particles can be used to directly evaluate the Asian contribution to airborne particles of anthropogenic origin in western North America, using a time series of samples from a pair of sites upwind and downwind of the San Francisco Bay Area. Our results for airborne Pb at these sites indicate a median value of 29% Asian origin, based on mixing relations between distinct regional sample groups. This trans-Pacific Pb is present in small quantities but serves as a tracer for airborne particles within the growing Asian industrial plume. We then applied this analysis to archived samples from urban sites in central California. Taken together, our results suggest that the analysis of Pb isotopes can reveal the distribution of airborne particles affected by Asian industrial pollution at urban sites in northern California. Under suitable circumstances, this analysis can improve understanding of the global transport of pollution, independent of transport models.

Analysis of aerosols from the World Trade Center collapse site, New York, October 2 to October 30, 2001

The collapse of the World Trade Center (WTC) buildings #2 (South Tower), #1 (North Tower), and #7 created an enormous collapse pile which emitted intense plumes of acrid smoke and dust until roughly mid-December, when the last spontaneous surface fire occurred. We collected particles by size (8 modes, ≈12 to 0.09 micrometers diameter) and time (typical resolution of 1 to 3 h) from October 2 until late December at the EML 201 Varick Street site roughly 1.8 km NNE of the collapse site and 50 m above ground level. Here we show some of the 70,000 mass and elemental data from the time period October 2 through October 30. Identification of a WTC collapse pile source for aerosols seen at the receptor site were based upon the simultaneous presence of finely powdered concrete, gypsum, and glass with intense very fine combustion mode mass episodes concurrent with winds from the southwest quadrant. The results, derived from seven independent beam-based analytical techniques, showed that while PM10 and PM2.5 24 h values rarely, if ever, violated federal air quality standards, WTC-derived plumes swept over lower Manhattan Island, resulting in intense aerosol impacts of duration a few hours at any one site. The WTC plume resembled in many ways those seen from municipal waste incinerators and high temperatures processes in coal-fired power plants. The size fractions above 1 micrometer contained finely powdered concrete, gypsum, and glass, with sootlike coatings and anthropogenic metals, but little asbestos. Composition in the very fine size range (0.26 > Dp > 0.09 μm) was dominated by sulfuric acid and organic matter, including polycyclic aromatic hydrocarbons (PAHs) and their derivatives, and glasslike silicon-containing aerosols. Many metals were seen in this mode, most, but not all, at low concentrations. The concentrations of very fine silicon, sulfur, and many metals, as well as coarse anthropogenic metals, decreased markedly during October, probably in association with the cooling of the collapse piles. Values of very fine elements seen in May, 2002 at the WTC site were only a few percent of October values.

Phenol Groups in Northeastern U.S. Submicrometer Aerosol Particles Produced from Seawater Sources

Atmospheric particles collected during the ICARTT 2004 field experiment at ground based sites at Appledore Island (AI), New Hampshire, Chebogue Point (CP), Nova Scotia, and aboard the R/V Ronald Brown (RB) were analyzed using Fourier transform infrared (FTIR) spectroscopy to quantify organic mass (OM) and organic functional groups. Several of these spectra contain a unique absorbance peak at 3500 cm(-1). Laboratory calibrations identify this peak with phenol functional groups. The phenol groups are associated with seawater-derived emissions based on correlations with tracer volatile organic compounds (VOCs) and ions, and potential source contribution function (PSCF) analysis. On the basis of the measured absorptivities, the project average phenol group concentrations are 0.24 +/- 0.18 microg m(-3) (4% of the total OM) at AI, 0.10 +/- 0.6 microg m(-3) (5% of the total OM) at CP, and 0.08 +/- 0.09 microg m(-3) (2% of the total OM) on board the RB, with detection limits typically between 0.06 and 0.11 microg m(-3). The spectra were partitioned into three primary factors using positive matrix factorization (PMF) sufficient to explain more than 95% of the measured OM. The fossil fuel combustion factor contributed 40% (AI), 34% (CP), and 43% (RB) of the total OM; the terrestrial biogenic factor contributed 20% (AI), 30% (CP), and 27% (RB). The seawater-derived factor contributed 40% (AI), 36% (CP) and 29% (RB) of the OM and showed similar correlations to tracers as the phenol group.

Development of PIXE, PESA and transmission ion microscopy capability to measure aerosols by size and time

Abstract We describe a new capability that consists of a combination of proton induced X-ray emission (PIXE), proton elastic scattering analysis (PESA) and transmission ion microscopy (all performed at the same location on the sample) techniques to address some of the research needs associated with time series and size-dependent composition of atmospheric aerosols. Simultaneous measurements of PIXE and PESA can be performed on aerosols collected using 3 stage improved rotating DRUM impactor by size (Stage A: 2.5–1.15 μm; Stage B: 0.34–1.15 μm; Stage C: 0.07–0.34 μm) with time resolution set by the rotation rate from 1 mm every 4 h to 1 mm every 6 min on a 16.8 cm long impaction strips that can be coated with Mylar, stretched Teflon, or aluminum, depending on the analysis method chosen. Preliminary measurements carried out using a 1 mm diameter proton beam were made on industrial test samples, yielding promising results at a time resolution of only 6 min.

Direct surface analysis of time-resolved aerosol impactor samples with ultrahigh-resolution mass spectrometry.

Aerosol particles in the atmosphere strongly influence the Earths climate and human health, but the quantification of their effects is highly uncertain. The complex and variable composition of atmospheric particles is a main reason for this uncertainty. About half of the particle mass is organic material, which is very poorly characterized on a molecular level, and therefore it is challenging to identify sources and atmospheric transformation processes. We present here a new combination of techniques for highly time-resolved aerosol sampling using a rotating drum impactor (RDI) and organic chemical analysis using direct liquid extraction surface analysis (LESA) combined with ultrahigh-resolution mass spectrometry. This minimizes sample preparation time and potential artifacts during sample workup compared to conventional off-line filter or impactor sampling. Due to the high time resolution of about 2.5 h intensity correlations of compounds detected in the high-resolution mass spectra were used to identify groups of compounds with likely common sources or atmospheric history.

Guidance for Quantifying the Contribution of Airport Emissions to Local Air Quality

This report is a guide for airport operators on effective procedures for using air quality models in combination with on-site measurement equipment to prepare a comprehensive assessment of air pollutant concentrations in the vicinity of airports. It is designed to help practitioners generate information desired by local communities as they seek to develop more detailed local air quality assessments as well as respond to regulatory needs, including those of the National Environmental Policy Act (NEPA). The guide provides in-depth information on the capabilities and limitations of modeling and measurement tools, adding to an increasing knowledge base concerning preparation of air quality assessments near airports. Starting with the Federal Aviation Administrations (FAAs) regulatory EDMS/AEDT, it describes how best to use available models, in combination with potential on-site monitoring programs, to conduct air quality assessments. Detailed information on the monitoring campaigns and modeling assessments is included in a set of appendices that accompany the guide. The appendices (available in CRP-CD-115) describe the models tested and the various equipment used to collect data, the rationale behind the selection of Washington Dulles International Airport as a case study application, and the components and steps involved in the measurement campaigns, and include an assessment of the various model outputs.