USDA Forest Service

Pacific Southwest Research Station


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

(510) 559-6300

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Refining estimates of atmospheric deposition for sediment particles and particulate nutrients in the Lake Tahoe Basin

Proposal [pdf]

Lead Researchers:

Antony Chen, John Watson, and Xiaoliang Wang, Desert Research Institute
Wen-Ming Chien, University of Nevada-Reno


Deposition of sediment particles and particulate nutrients into Lake Tahoe seriously influences the Total Maximum Daily Load (TMDL) and threatens lake clarity. The current deposition estimates derived from inferential methods with limited temporal and size resolution need to be improved. This project will employ innovative multi-channel deposition samplers to collect dry and wet deposition particles at sites representative of offshore, nearshore, and upper watershed environments in the Lake Tahoe Basin for a full year. Samples of 24-hr duration will be analyzed in the laboratory by a scanning electron microscopy/energy-dispersion X-ray spectroscopy (SEM/EDX) method to determine the number count, size distribution, and chemical composition of deposited particles, which are in turn translated into the deposition fluxes and annual loads of particles and particulate nutrients. Contrasts between different environments and chemical information should reveal the significance of nearshore activities and inland pollutants on particulate deposition, which leads to best management practices (BMPs) for mitigating the impact. Simultaneous measurements of PM10 and TSP (particulate matter with aerodynamic diameter <10 μm and total suspended particles, respectively) concentration by DustTrak at the monitoring sites will evaluate their use as an indicator for particulate deposition on a routine, cost-effective basis.

Relation to Other Research Including SNPLMA Science Projects

This project complements the benchmark Lake Tahoe Atmospheric Deposition Study by providing an independent assessment of dry and wet PM deposition. The two studies are based on different but both scientifically sound methods; their discrepancies may quantify the level of uncertainty and identify areas for further research. Several PM monitoring and source apportionment studies, including the Lake Tahoe Source Characterization Study (Kuhns et al., 2004), the SNPLMA Round 9 study, "Lake Tahoe visibility impairment source apportionment analysis," (Green et al., 2011), and biomass burning studies funded in SNPLMA Round 10 ("Particulate emissions from biomass burning: quantification of the contributions from residential wood combustion, forest fires, and prescribed fires") and Round 11 ("Evaluation of prescribed burning impacts on air quality and visibility in the Lake Tahoe Basin") have been conducted to understand the origins of PM and particulate nutrients in the Lake Tahoe atmosphere. This study seeks to perform similar source attribution analysis by examining chemical signature and morphology of deposited particles. This study will also complement other air quality research efforts funded in SNPLMA Round 7, "Lake Tahoe source attribution study: receptor modeling study to determine the sources of observed ambient particulate matter in the Lake Tahoe Basin," Round 9, "Impacts of vehicle activity on airborne particle deposition to Lake Tahoe," and Round 10, "Distribution of ozone, ozone precursors and gaseous components of atmospheric deposition in the Lake Tahoe Basin."

Expected date of final products:

October 2014

Last Modified: Mar 28, 2013 02:52:08 PM