Effects
of Cold Temperature and Ethanol Content on
VOC Emissions from Light-Duty Gasoline Vehicles
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Abstract
Emissions
of speciated volatile organic compounds (VOCs), including
mobile source air toxics (MSATs), were measured in vehicle exhaust
from three light-duty spark ignition vehicles operating on summer
and winter grade gasoline (E0) and ethanol blended (E10 and E85) fuels.
Vehicle testing was conducted using a three-phase LA92 driving cycle
in a temperature-controlled chassis dynamometer at two ambient temperatures
(−7 and 24 °C). The cold start driving phase and cold
ambient temperature increased VOC and MSAT emissions up to several
orders of magnitude compared to emissions during other vehicle operation
phases and warm ambient temperature testing, respectively. As a result,
calculated ozone formation potentials (OFPs) were 7 to 21 times greater
for the cold starts during cold temperature tests than comparable
warm temperature tests. The use of E85 fuel generally led to substantial
reductions in hydrocarbons and increases in oxygenates such as ethanol
and acetaldehyde compared to E0 and E10 fuels. However, at the same
ambient temperature, the VOC emissions from the E0 and E10 fuels and
OFPs from all fuels were not significantly different. Cold temperature
effects on cold start MSAT emissions varied by individual MSAT compound,
but were consistent over a range of modern spark ignition vehicles