TY - JOUR
T1 - Characteristics of cabin air quality in school buses in Central Texas
AU - Rim, Donghyun
AU - Siegel, Jeffrey
AU - Spinhirne, Jarett
AU - Webb, Alba
AU - McDonald-Buller, Elena
N1 - Funding Information:
We express our deepest gratitude to Hazel Barbour of the Central Texas Adopt-A-School Bus Program, and Dan Roberts, Director of Transportation for the Round Rock Independent School District (RRISD). We thank Ron Seres, the bus driver for all of the tests, as well as Dennis Thompson and the RRISD bus maintenance staff who provided in-kind support for the installation of the retrofits. We thank Gabriel Beko of the Technical University of Denmark, David Allen of The University of Texas at Austin and Ramon Alvarez of Environmental Defense Fund for their insights and assistance. We also express our appreciation to the Donaldson Company, Inc. and to David Hitchcock of the Houston Advanced Research Center. Although preparation of this manuscript is based on work supported by the State of Texas through a Grant from the Houston Advanced Research Center, Texas Environmental Research Consortium and Texas Commission on Environmental Quality, it does not necessarily reflect the views of these agencies and no official endorsement should be inferred.
PY - 2008/8
Y1 - 2008/8
N2 - This study assessed in-cabin concentrations of diesel-associated air pollutants in six school buses with diesel engines during a typical route in suburban Austin, Texas. Air exchange rates measured by SF6 decay were 2.60-4.55 h-1. In-cabin concentrations of all pollutants measured exhibited substantial variability across the range of tests even between buses of similar age, mileage, and engine type. In-cabin NOx concentrations ranged from 44.7 to 148 ppb and were 1.3-10 times higher than roadway NOx concentrations. Mean in-cabin PM2.5 concentrations were 7-20 μg m-3 and were generally lower than roadway levels. In-cabin concentrations exhibited higher variability during cruising mode than frequent stops. Mean in-cabin ultrafine PM number concentrations were 6100-32,000 particles cm-3 and were generally lower than roadway levels. Comparison of median concentrations indicated that in-cabin ultrafine PM number concentrations were higher than or approximately the same as the roadway concentrations, which implied that, by excluding the bias caused by local traffic, ultrafine PM levels were higher in the bus cabin than outside of the bus. Cabin pollutant concentrations on three buses were measured prior to and following the phased installation of a Donaldson Spiracle Crankcase Filtration System and a Diesel Oxidation Catalyst. Following installation of the Spiracle, the Diesel Oxidation Catalyst provided negligible or small additional reductions of in-cabin pollutant levels. In-cabin concentration decreases with the Spiracle alone ranged from 24 to 37% for NOx and 26 to 62% and 6.6 to 43% for PM2.5 and ultrafine PM, respectively. Comparison of the ranges of PM2.5 and ultrafine PM variations between repetitive tests suggested that retrofit installation could not always be conclusively linked to the decrease of pollutant levels in the bus cabin.
AB - This study assessed in-cabin concentrations of diesel-associated air pollutants in six school buses with diesel engines during a typical route in suburban Austin, Texas. Air exchange rates measured by SF6 decay were 2.60-4.55 h-1. In-cabin concentrations of all pollutants measured exhibited substantial variability across the range of tests even between buses of similar age, mileage, and engine type. In-cabin NOx concentrations ranged from 44.7 to 148 ppb and were 1.3-10 times higher than roadway NOx concentrations. Mean in-cabin PM2.5 concentrations were 7-20 μg m-3 and were generally lower than roadway levels. In-cabin concentrations exhibited higher variability during cruising mode than frequent stops. Mean in-cabin ultrafine PM number concentrations were 6100-32,000 particles cm-3 and were generally lower than roadway levels. Comparison of median concentrations indicated that in-cabin ultrafine PM number concentrations were higher than or approximately the same as the roadway concentrations, which implied that, by excluding the bias caused by local traffic, ultrafine PM levels were higher in the bus cabin than outside of the bus. Cabin pollutant concentrations on three buses were measured prior to and following the phased installation of a Donaldson Spiracle Crankcase Filtration System and a Diesel Oxidation Catalyst. Following installation of the Spiracle, the Diesel Oxidation Catalyst provided negligible or small additional reductions of in-cabin pollutant levels. In-cabin concentration decreases with the Spiracle alone ranged from 24 to 37% for NOx and 26 to 62% and 6.6 to 43% for PM2.5 and ultrafine PM, respectively. Comparison of the ranges of PM2.5 and ultrafine PM variations between repetitive tests suggested that retrofit installation could not always be conclusively linked to the decrease of pollutant levels in the bus cabin.
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U2 - 10.1016/j.atmosenv.2008.04.030
DO - 10.1016/j.atmosenv.2008.04.030
M3 - Article
AN - SCOPUS:50849094197
SN - 1352-2310
VL - 42
SP - 6453
EP - 6464
JO - Atmospheric Environment
JF - Atmospheric Environment
IS - 26
ER -