Inorganic and Organic Aerosols Downwind of California's Roseville Railyard

Abstract

Inorganic and organic constituents of aerosols from a major railyard and repair facility were characterized to develop a profile of emissions from railyard activities. The railyard has very consistent downslope winds blowing laterally across the railyard for about 8 hours each night, so two sampling stations were used, one just upwind of the railyard and one downwind adjacent to the railyard fence line. Aerosol samples were collected by rotating drum impactors (DRUM and Lundgren) in up to 9 size modes for 5 weeks in summer and fall of 2005 in tandem with the Roseville Railyard Aerosol Monitoring Project (RRAMP), which measured, black carbon (BC) PM₂, as well as NO and NO₂. The DRUM aerosol samples were analyzed for mass, optical absorption, and elemental content in 3 h time resolution to allow separation of day and night. Organic analysis was conducted on another set of time integrated size-segregated samples taken by a Lundgren impactor during nighttime hours. The ratio between the downwind versus upwind sites at night was as high as 21.9 (NO, RRAMP) and 6.4 (optical absorption, DRUM) but many species had ratios greater than 2, demonstrating which aerosols arose from railyard activities. The main emissions from the railyard consisted of very fine (0.26 > D _p > 0.09 μm) and ultrafine (<0.1 μm) aerosols associated with diesel exhaust such as mass, organic matter, transition metals, and sulfur, the latter 3.3% of the mass since locomotive diesel fuel still contained sulfur. There were also coarse soil aerosols contaminated with anthropogenic metals and petroleum-derived n-alkanes. The aerosol PAH (polycyclic aromatic hydrocarbons) profile showed higher proportions of the heavier PAHs, such as benzo[a]pyrene, compared to diesel truck exhaust on a per unit mass. These aerosols were mostly in the ultrafine (<0.1 μm) size mode, enhancing lung capture. These results and those of Roseville Railyard Aerosol Monitoring Project (RRAMP) largely confirm earlier California Air Resources Board's (ARB) model estimates of health impacts downwind of the railyard based on diesel exhaust, while adding data on very fine transition metals and contaminated soils, potentially important to human health.

Acknowledgments

The authors wish to acknowledge the continual support, encouragement, and expert scientific guidance of the Health Effects Task Force (HETF) of Breathe California of Sacramento-Emigrant Trails, its Chair, Jan Sharpless, and its Consultant, Betty Turner. HETF is a long term (1994) standing committee of volunteer experts from state and local agencies, universities and medical organizations. It provides high level technical expertise to Breath California of Sacramento Emigrant Trails, a local NGO that has focused on protecting lungs from disease, smoking, and air pollution since 1917. (http://www.sacbreathe.org).The Detection and Evaluation of Long-range Transport of Aerosols (DELTA) Group is a primarily global climate research association headquartered at UC Davis (http://delta.ucdavis.edu) that lends its samplers, analytical capabilities, and expertise to problems of human health. The staff of the Placer County APCD, especially Yushuo Chang, Kurt Schreiber, and Mike Sims, who were exemplary in their support of our field analyses and their provision of meteorology and data from RRAMP. We would like to gratefully acknowledge EPA Region IX for funding the organic analysis (Meredith Kurpius, project manager).The authors also gratefully acknowledge the NOAA Air Resources Laboratory (ARL) for the provision of the HYSPLIT transport and dispersion model and/or READY website (http://www.arl.noaa.gov/ready.html) used in this publication. This report has benefited greatly from the comments and suggestions of the RRAMP Technical Advisory Committee, but the opinions expressed herein are solely those of the authors.

[Supplementary materials are available for this article. Go to the publisher's online edition of Aerosol Science and Technology to view the free supplementary files.]

Notes

^aUnable to quantify compound due to analytical problem, namely excessive enrichment of chrysene-d ₁₂ that saturated the ion trap mass spectrometer.