P061: Lake Tahoe Visibility Impairment Source Apportionment Analysis

The EPA Regional Haze Regulations require the use of reconstructed light extinction from aerosol data to track trends in haze at mandatory Class I areas. Long-term monitoring conducted at Bliss State Park and South Lake Tahoe has found that the thresholds were met and visibility has improved since monitoring began. However, the TRPA 2006 Threshold Evaluation report noted concerns over backsliding. This study interpreted 20 years of chemically speciated PM2.5 aerosol data at Bliss SP and 15 years-worth of data at South Lake Tahoe to determine the effects of light scattering and absorption by particles on visibility impairment in the Lake Tahoe Basin.