Project at a Glance

Title: Transport of acidic air pollutants to forests and alpine regions of the Sierra Nevada (TAAPS).

Principal Investigator / Author(s):

Contractor: Tracer Technologies, Inc

Contract Number: A932-141

Research Program Area: Atmospheric Processes

Topic Areas: Acid Deposition, Chemistry & Reactivity, Monitoring, Transport


Two separate atmospheric tracer experiments were conducted in the summer and fall season of 1990 to study the transport of air pollutants from the San Joaquin Valley (SJV) into the Sierra Nevada Range. The experiments involved the release of three perfluorocarbon chemicals, used as atmospheric tracer gases, to track air mass movement during the breakdown of ozone episodes in the SJV. Forecasting and the determination of when to perform each test was made by ARB personnel. Sequential two-hour averaged concentration levels were sampled simultaneously at 31 preselected locations situated throughout the SJV and the Sierra Nevada Range. The summer test was performed during August 12-14, 1990 and the fall test was performed during October 24- 27, 1990. Each test was designed to last 48 hours following the release of tracer gases from Stockton, Fresno and Bakersfield. The Autumn test, however, involved a longer sampling time period due to unexpected equipment problems. This study has provided some important findings concerning the transport of pollutants from the SJV. First, because air pollutant transport is dominated by winds aloft within the mixing layer, surface winds are a poor indicator of air mass transport. Secondly, pollutants born in the SJV are eventually transported into the upper Sierra. Return flow during nocturnal periods has little effect in removing pollutants from the Sierra foothill regions. Finally, transport mechanisms of air pollutants into the Sierra are not a simple process. In most instances, the pollutants are trapped along the foothill regions and slowly seep into the upper Sierra through major canyons and valleys. This decreases the peak pollutant concentration levels which impact the upper Sierra but can substantially prolong episodes of elevated concentrations.

For questions regarding this research project, including available data and progress status, contact: Research Division staff at (916) 445-0753

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