Pacific Southwest Research Station

Lake Tahoe Visibility Impairment Source Apportionment Analysis

Final Report [pdf]

Abstract

The project will provide a comprehensive analysis of causes of visibility impairment in the Lake Tahoe Basin. We will gather and review existing aerosol, optical, emissions, and meteorological data and summarize past source apportionment analyses as well as conducting new source apportionment receptor modeling. We will provide a thorough analysis of chemically speciated aerosol data, especially the IMPROVE data collected at Bliss State Park and data collected in South Lake Tahoe. Nephelometer light scattering data, including diurnal and seasonal patterns, and trends will analyzed and summarized. We will review source and receptor modeling results for the area from the Western Regional Air Partnership (WRAP) and conduct additional receptor modeling using Chemical Mass Balance (CMB) and Positive Matrix Factorization (PMF). PMF factors will be weighted by backward air trajectory residence time frequency to shed light on the likely sources identified by PMF. Receptor modeling results will be compared to emissions inventories (e.g. WRAP inventory) for consistency. The conclusions will be based on a weight-of-evidence approach considering the 2 receptor models applied here, meteorological patterns, source oriented modeling for the WRAP, emissions inventories, and other relevant information.

Relation to Other SNPLMA Projects

The project was coordinated with the proposed SNPLMA Round 10 science project, "Visibility Monitoring and Standards for Lake Tahoe Basin: Assessment of Current and Alternative Approaches".