Variation of mass scattering efficiencies in IMPROVE

Area of Science:

• Atmospheric Science
• Environmental Chemistry
• Aerosol Science

Background:

• The Interagency Monitoring of Protected Visual Environments (IMPROVE) equation is crucial for U.S. Environmental Protection Agency (EPA) Haze Rule compliance.
• This equation assumes constant dry mass scattering efficiencies for aerosol chemical components.

Purpose of the Study:

• To investigate the variability of aerosol scattering efficiencies.
• To determine if aerosol properties change with increasing particle light scattering and mass concentration.

Main Methods:

• Analysis of aerosol size distributions and chemical composition from the Big Bend Regional Aerosol and Visibility Observational Study and the Southeastern Aerosol and Visibility Study.
• Examination of the relationship between scattering efficiencies and aerosol properties.

Main Results:

• Aerosol volume and mass scattering efficiencies were found to vary directly with increasing particle light scattering and aerosol mass concentration.
• Particle size distributions shifted towards larger sizes under more polluted conditions.
• Aerosol aging during transport to remote locations appears to influence scattering efficiencies.

Conclusions:

• The assumption of constant scattering efficiencies in the IMPROVE equation may not accurately reflect real-world conditions.
• Variations in scattering efficiencies are linked to aerosol pollution levels, particle size, and atmospheric aging.
• Further research is needed to refine atmospheric haze models for improved accuracy.