# Presentation: 528639

## LIDAR DETECTION OF PARTICULATE MATTER:OVERVIEW AND APPLICATION TO AUTOMOTIVE EMISSIONS

- Hans Moosmüller
- hansm@dri.edu
- Desert Research Institute
- University of Nevada System
- Reno, NV 89512

## LIDAR Principle

- Spatially Resolved Measurement Along Line (1-D)
- r = c/2 t
- Scanning => 2-D or 3-D Measurements

## LIDAR Equation

**LIDAR Equation**

- For each distance r, there are two unknownsT(r) and (r), but only one measurement S(r)
- If extinction and backscatter can be related, and C is known, equation may be solved (Klett Inversion)
- If either T(r) or (r) are well known, the other quantity can be determined

## Distributed Backreflection

**Distributed Backreflection**

**Particle Scattering** Particle Concentration, Shape , Size(?), Wind Velocity
**Rayleigh Scattering**Atmospheric Density, Temperature, Wind Velocity
**Raman Scattering**Gas Density, Temperature
**Fluorescence (Quenching!)**Atoms, Molecules, Biological Material?

## Distributed Return

**Distributed Return**

**Terra-Watt Femtosecond Laser** 1012W, 10 - 100 fs = 10-13- 10-15 s
**Nonlinear Effects in Atmosphere**1 - 20 km distance
**Plasma Channel (several 100 m)**Self-Focusing, Filamenting
**White Light Source**DOAS in the Sky

## Transmission

**Transmission**

**Atmospheric Extinction** Visibility, Radiative Transfer, Aerosol Size Distribution, Concentration
**Differential Absorption Lidar **Gas Concentrations: e.g., O3, NO2, SO2, Hg, H2OTemperaturePressure

## Automotive Emissions

**Automotive Emissions**

**Dynamometer Testing** Few vehicles under a large range of operating conditions_Applications:_ I&M, Emission Factors for Inventories and Modeling (e.g., MOBILE, EMFAC)_Missing:_ Real Time PM Measurements
**Remote Sensing **Large (10,000/day) number of vehicles under a limited number of operating conditions_Applications:_ I&M (Clean Screening & Gross Emitter Identification), Emission Factors for Inventories and Modeling (e.g., MOBILE, EMFAC)_Missing:_ PM Measurements

## Gaseous Remote Sensing

**Gaseous Remote Sensing**

- Pioneered by Stedman & Bishop (DU)** **
- Commercially Available
- Measures Gaseous Column Content across Road behind Vehicle
- CO2, CO, NO, HC by IR, UV Absorption
- Ratio to CO2 (& CO, HC) to Obtain Fuel-Based Emission Factor (i.e., g/kg fuel)
- Ancillary Measurements: Speed, Acceleration, License Plate

## PM Emissions

**PM Emissions**

- PM Mass Nearly Exclusively Elemental (EC) & Organic (OC) Carbon
- EC: Strongly Light Absorbing (i.e., Black Smoke)
- OC: No Light Absorption (i.e., White Smoke)
- Mass Mean Diameter 0.1-0.2m
- Not Covered by I&M Programs(Exceptions: no visible emissions, Diesel opacity) Why is there no PM I&M?

## Visible PM Emissions?

**Visible PM Emissions?**

## Remote Sensing of PM

**Remote Sensing of PM**

- _IR Extinction:_ Insensitive Measure of EC
- _UV Backscatter:_ Sensitive to both EC & OCAssume Transmission = 1
- _UV Extinction:_ Insensitive Measure of both EC & OC
- Lidar System helps to discriminate against Road Dust and Beam Terminus Signal

## LORAX Lidar On-Road Aerosol eXperiment

**LORAX**** ****L**idar **O**n-**R**oad **A**erosol e**X**periment

- Bob Keislar (Operation)
- Claudio Mazzoleni (Grad. Student)
- Peter Barber (Theory)
- Hampden Kuhns (CEO)
- John Watson (PI)

## LORAX Lidar On-Road Aerosol eXperiment

**LORAX**** ****L**idar **O**n-**R**oad **A**erosol e**X**periment

- _Transmitter:_ 266-nm Passively Q-Switched, All Solid-State Nd:YAG Laser (6 kHz PRF)
- _Receiver:_ 2” Telescope with Compact PMT
- _Data Acquisition:_ 8 GS/s, 1.5 GHz Oscilloscope, IEEE 488 Interface to PC Running LabView
- _Spatial Resolution:_ 20 cm

## SCHEMATIC

**SCHEMATIC**

## Main System & Beam Terminus

**Main System & Beam Terminus**

## Main System

**Main System**

## Beam Terminus

**Beam Terminus**

## On-Road Operation

**On-Road Operation**

## Lidar Calibration (1)

**Lidar Calibration (1)**

- 6-m Calibration Tube Filled with Filtered Air (25.5 Mm-1/sr) or CO2 (75.5 Mm-1/sr)
- Calibration Similar to Nephelometer Calibration for each Range Gate
- Results in Absolute Calibration Including Lidar Overlap Correction
- Calibrates LORAX for Measuring PM Backscatter in Units of Rayleigh (1 Rayleigh = 25.5 Mm-1/sr)

## Example Gas Calibration 

## Lidar Calibration (2)

**Lidar Calibration (2)**

- Convert from PM Backscatter (Rayleigh) to PM Mass Density (g/m3)
- Define Calibration PMLogNormal Size Distribution, Density = 1250 kg/m3, (Mass Mean Diameter = 0.1m, Geometric Standard Deviation = 1.5 m)Refractive Index: nOC = 1.5, nEC = 1.5 + i 0.5PMSI:	OC Sphere, PMDiesel:	Sphere with EC Core & OC Shell of Equal Volume
- Calibration CoefficientsCSI = 0.16 mg/(m3 Rayleigh)CDiesel = 0.18 mg/(m3 Rayleigh)

## LORAX Use

**LORAX Use**

- Initial Small Scale Use for Instrument Testing and Debugging
- First Large Scale Use During Summer 2002 in Las Vegas
- Measurement of 150,000 Vehicles
- Southern Nevada Air Quality Study (SNAQS)(Sponsored by Federal Transit Administration)
- Clark County Remote Sensing Study(Sponsored by Clark County Division of Air Quality Management and Department of Comprehensive Planning)

## Some High PM Emitters (>500 mg/mi)Las Vegas, May 2002

## Example: CO2 and Backscatter Signals

## Example Correlation:CO2 and Backscatter

## Future Work

**Future Work**

- Full Analysis of Las Vegas Study
- Dissemination of Results (Papers & Conferences)
- Use for Off-Road Military Diesel Vehicles
- Build Next Generation Instrument:Higher SensitivityIntegrated PM & Gas MeasurementsEasier Use
- Commercialization

## Conclusions

**Conclusions**

- Lidar used to add PM channel to on-road remote sensing system
- Measure PM emissions for large number (104-106) of vehicles under a limited number of operating conditions
- Get PM emission statistics for SIPs in PM non-attainment areas
- Use for PM I&M (Clean Screening & Gross Emitter Identification)
- Lots of interest from ARB, BAR, and CRC