USDA Forest Service

Pacific Southwest Research Station


Pacific Southwest Research Station
800 Buchanan Street
Albany, CA 94710-0011

(510) 559-6300

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Distribution of ozone, ozone precursors and gaseous components of atmospheric nitrogen deposition in the Lake Tahoe Basin

Proposal [pdf]

Lead Researchers:

Andrzej Bytnerowicz, Haiganoush Preisler and Mark Fenn, US Forest Service, Pacific Southwest Research Station; Alan Gertler and Barbara Zielinska, Desert Research Institute


The proposed study will characterize ozone, precursors of ozone (O3) formation, and gaseous pollutants that are important contributors to atmospheric nitrogen (N) deposition in the Lake Tahoe Basin. We will use passive samplers for monitoring of O3, nitric oxide (NO), nitrogen dioxide (NO2), ammonia (NH3), nitric acid (HNO3) and volatile organic compounds (VOCs) on a network of 32 sites inside and outside of the Basin. Using statistical and geostatistical models we will create distribution maps of the measured compounds for the entire Basin. On a subset of 10 monitoring sites, we will also measure real-time O3 concentrations with active UV absorption monitors to evaluate diurnal changes of the pollutant, calibrate passive O3 samplers, and use that data for evaluation of the exceedances of O3 air pollution standards in the Basin. At the same sites we will also measure N deposition with ion exchange resin (IER) collectors placed in forest clearings (bulk precipitation) and under tree canopies (throughfall). In these bulk and throughfall samples from the IER collectors we will measure the stable isotope composition (15N and 18O) of NO3 and of NH3 (15N) from passive sampler extracts to evaluate the origin of N deposition in the Basin. Results of this study will help to evaluate the present and future potential of O3 formation as well as the biological/ecological effects of N air pollutants and the resulting N deposition in the Lake Tahoe Basin. These results will also help to develop science-based management strategies aimed at improving air quality and ecological sustainability of the Basin.

This research will be conducted by a collaborative team consisting of researchers and air quality specialists of the US Forest Service, Desert Research Institute, the San Francisco State University and St. Mary's College. We will establish a large-scale field monitoring network with dense and well-distributed sites allowing for generation of reliable maps of the distribution of key pollutants and O3 precursors (for O3, NO, NO2, NH3, HNO3 and selected VOCs). We will be also able to produce maps of exceedances of the air pollution standards for O3 and of atmospheric N deposition. Results of the proposed study supported by the best-available meteorological data sets will improve our understanding of the role of biogenic and anthropogenic VOCs and NOx in O3 formation within the Basin. Such improved knowledge will lead to science-based recommendations regarding management strategies that could be recommended for effective control of O3 levels in the Basin. The established monitoring network will allow for cost-effective measurements of N deposition and stable isotopic analyses of atmospheric N needed for a better understanding of N deposition sources and empirically-based estimates of N deposition in the Basin. All these efforts will help in creating a knowledge base for future investigations of potential ecological impacts of ambient O3 and N deposition in the Tahoe Basin under various scenarios of the changing climate for California and Nevada.

Relation to Other SNPLMA Projects

The proposed research is a logical continuation of previous efforts focusing on understanding air quality and its effects on the human health-based national and state air pollution standards, and also on potential ecological impacts of air pollution and atmospheric deposition in the Lake Tahoe Basin. We are hoping to utilize meteorological data that may be collected as part of proposed SNPLMA Round 10 science projects, including "The Tahoe Climate Information Management System (TahoeClim)" and "Improving meteorological data and forecasts for prescribed fire burn day decisions for the Lake Tahoe Basin".

Expected date of final products:

June 2012

Last Modified: Mar 28, 2013 02:52:07 PM