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Oxidative Stress from PM Emitted by Various Light-Duty Vehicle Engine Technologies and Fuels
Chris Ruehl, John Collins, Satya Sardar, Chandan Misra, & Jorn Herner
1
CA Air Resources Board Mobile Source Air Toxics workshopFebruary 18, 2015
Today’s talk
1. Introduction / background material
2. Overview of emissions by all 8 vehicle configurations
3. Oxidative Stress (OS) induced by emitted PM
4. Relationship between OS and PM chemistry
2Intro Emissions overview PM OS PM chemistry
Fuels and vehicles tested5 fuels:
1) Gasoline2) E85 (85% Ethanol)3) CNG (Natural Gas)4) Diesel5) Biodiesel
3Intro Emissions overview PM OS PM chemistry
5 vehicles, w/mileage:
1) 1998 Mercedes 420SEL (“High-emitter”), 240k
2) 2008 Chevy Impala flex (E85/gasoline), 35k
3) 2010 VW Jetta GDI, 10k
4) 2007 Honda Civic CNG, 15k
5) 2012 Chevy Silverado (diesel), 10k
UC cycle (hot and cold start), Highway cruise
4
8 total LDV configurations
Gasoline, E85: 2008 Chevy Impala
Biodiesel, Diesel: 2012 Chevy Silverado (w/DPF)
CNG: 2007 Honda Civic GDI, GDI+GPF: 2010 VW Jetta
High-emitter: 1988 Mercedes 420SEL
B: Biodiesel
C: CNG
D: Diesel
E: Ethanol (E85)
F: GDI + GDF
G: Gasoline (PFI)
H: “High-emitter”
I: GDI
Intro Emissions overview PM OS PM chemistry
5
ROS assayROS = “Reactive Oxygen Species”
In vitro assay using rat macrophage cells
Done at UWM (Martin Shafer)
Filters are extracted in DI water: sonication, overnight shaking, sonication (all dark)
Intro Emissions overview PM OS PM chemistry
EST, 48(13): 7576-7583, 2014
Overview of gaseous emissions
6Intro Emissions overview PM OS PM chemistry
This study
Full VEDS database (Haagen-Smit Lab)
Overview of particulate emissions
7Intro Emissions overview PM OS PM chemistry
Full VEDS databaseThis study (log)
• Median PM emitted per mile: High emitter > GDI > PFI > GDI + GPF > E85 > Biodsl > CNG > Dsl
• Biodiesel and Diesel are skewed towards larger EFs (probably regeneration)
This study (linear)
PM mostly OC/EC
8Intro Emissions overview PM OS PM chemistry
• Among all 8 LDVs, 67±5% of gravimetric PM was detected as OC + EC
• GDI had most EC (78±5% of TC)
• High-emitter had most OC• E85 highest OC/TC (78±5%) • CNG EC below MDL
All LDVsGDI
High-emitter
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Per mg:• Diesel and
Biodiesel highest and most variable – probably due to regeneration
• Warm start ROS similar to or greater than cold start
• Highway ROS lower for all LDVs
• Ethanol, GDI higher than gasoline
Per mile:• Diesel and Biodiesel UC
cycle highest• Highway ROS still low• Ethanol, GDI lower
than gasoline
ROS results
Intro Emissions overview PM OS PM chemistry
10
Sonicated aqueous extracts were run w/ and w/o filtering (0.2 μm polypropylene)
ROS response decreased with filtering for most vehicles
GDI: 99% reduction
ROS removed by filtering extracts
Intro Emissions overview PM OS PM chemistry
Diesel – greater WSOC contribution
E85 – only UC cold start ROS removed by filtration, and only 40% toxicity due more to WSOC
11
ROS-elemental correlation (1/2)
Intro Emissions overview PM OS PM chemistry
Among most abundant elements (ICPMS), six had r2 > 0.50: S, Cu, Ba, Cr, Sb, Sr
12
ROS-elemental correlation (2/2)
Intro Emissions overview PM OS PM chemistry
diesel/biodiesel ROS > gasoline ROS
higher r2 for elements in diesel but not gasoline
Fe (0.11)S (0.89)
Cu (0.78)
(r2 in parentheses)
13
Conclusions5 LDV vehicles using 5 fuels tested 8 LDV vehicle configurations
Although PM was greatest in gasoline LDVs, PM was skewed high for diesel
ROS per mile was greatest for diesel/biodiesel
E85, GDI ROS greater than PFI per PM mass, but less than PFI per mile
Filtering extracts removed much of the ROS activity: 99% for GDI, but much less (<50%) for diesel and ~0% for warm E85
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