Oxidative Stress from PM Emitted by Various Light-Duty Vehicle Engine Technologies and Fuels

Chris Ruehl, John Collins, Satya Sardar, Chandan Misra, & Jorn Herner

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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

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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

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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

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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

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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

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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)

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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