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PM2.5 mass and light extinction reconstruction in IMPROVE
Douglas H Lowenthal1, Naresh Kumar
1Division of Atmospheric Sciences, Desert Research Institute, Reno, Nevada 89512, USA. dougl@dri.edu
Journal of the Air & Waste Management Association (1995)
|September 19, 2003
Summary
The IMPROVE aerosol mass and light extinction models underestimate PM2.5 and overestimate light scattering, impacting Regional Haze Rule compliance. These biases stem from formula limitations and hygroscopic growth factor assumptions.
Area of Science:
- Environmental Science
- Atmospheric Chemistry
- Air Quality Monitoring
Background:
- The Regional Haze Rule of 1999 relies on Interagency Monitoring of Protected Visual Environments (IMPROVE) protocols for assessing air quality.
- IMPROVE protocols reconstruct aerosol mass and light extinction from chemical concentration data.
Purpose of the Study:
- To evaluate the accuracy, consistency, and potential biases of IMPROVE formulations for aerosol mass and light extinction.
- To assess the impact of these formulations on Regional Haze Rule compliance.
Main Methods:
- Analysis of IMPROVE aerosol chemistry and light extinction data from 1988-1999.
- Examination of the IMPROVE mass reconstruction formula, including the impact of excluded elements and organic carbon measurement artifacts.
- Assessment of light scattering measurements and the IMPROVE particle scattering (Bsp) reconstruction formula, including the role of hygroscopic growth factors.
Main Results:
- The IMPROVE mass reconstruction formula underestimated particulate matter with an aerodynamic diameter < 2.5 microm (PM2.5) by an average of 12%.
- This underestimation is linked to the exclusion of elements like sodium and chlorine and organic carbon measurement artifacts.
- Light scattering was systematically overestimated by an average of 34% using the IMPROVE Bsp formula.
- The use of climatologically based hygroscopic growth factors significantly contributed to light scattering overestimation.
Conclusions:
- IMPROVE formulations exhibit significant biases in reconstructing aerosol mass and light extinction.
- These biases, particularly the overestimation of light scattering, can affect the accuracy of Regional Haze Rule compliance assessments.
- Refinements to the IMPROVE protocols, especially concerning hygroscopic growth factors and aerosol composition, are necessary for accurate air quality management.