Particle size evaluations using multiwavelength extinction measurements

Area of Science:

• Environmental Science
• Atmospheric Science
• Optical Engineering

Background:

• Accurate measurement of particulate matter size is crucial for environmental monitoring and industrial process control.
• Remote sensing methods offer advantages for evaluating emissions from stationary sources.

Purpose of the Study:

• To develop and validate a lidar-based method for remote estimation of mean particle size in stationary source emissions.
• To establish a foundational dataset correlating extinction coefficients with particle sizes for various aerosols.

Main Methods:

• Experimental data collection using a 10-m aerosol tunnel and multi-wavelength transmissometers.
• Generation of aerosols including fly ash, silica, and other particulate materials across different size fractions.
• Particle size characterization using multistage impactors and air permeability analysis.

Main Results:

• A single-laser lidar system at 1.06 and 0.53 micrometers effectively estimates particle sizes below 1 micrometer.
• Extinction ratios approach unity for larger particles, necessitating longer wavelengths.
• A two-laser lidar system (10.6 and 0.53 micrometers) can estimate mean particle sizes up to 6 micrometers.

Conclusions:

• Lidar technology shows promise for remote monitoring of particle size in industrial emissions.
• Wavelength selection is critical for accurate particle size estimation across different size ranges.
• Further development of multi-wavelength lidar systems can enhance remote sensing capabilities for aerosols.