Environmental Sciences and Health

Student Name: Sandra L. Carroll
Major Professor and Institutional Affiliation: Dr. Glenn C. Miller, Natural Resources and Environmental Science, University of Nevada, Reno
Graduate Program: Environmental Sciences and Health (Environmental Toxicology)
Graduation Date: May 2005
Title of Research Project: Complex Mixtures of Polycyclic Aromatic Hydrocarbons in Motorized Watercraft Emissions: Phototoxic Effects at Very Low (ng/L) Concentrations
Key Findings of Research Project: Polycyclic aromatic hydrocarbon (PAH) compounds found in Lake Tahoe waters were the lower molecular weight
compounds with higher aqueous solubilities, and the phototoxic PAHs detected most often were: acenaphthylene, anthracene, fluoranthene and pyrene. Mortalities of
Ceriodaphnia dubia were observed in bioassay treatments containing 900 ng/L total phototoxic PAH with UV exposure, approximately one-half the concentration seen in UV-filtered treatments. Ultraviolet radiation exposure and emission sources (two-stroke and four-stroke marine engines) were significant indicators of daphnid survival and reproductive success.

Current Position: Senior Toxicologist, Tetra Tech, Inc., Reno, Nevada


Student Name: Veronica Edirveerasingam
Major Professor and Institutional Affiliation: Dr. Glenn C. Miller, Natural Resources and Environmental Science, University of Nevada, Reno
Graduate Program: Environmental Sciences and Health
Graduation Date: December 2006

Title of Research Project: Implications of vehicle emissions to Lake Tahoe soils and sediments

Key Findings of Research Project: Petroleum hydrocarbon input into Tahoe soils and sediments are high, catchment basins are preventing the pollutants from entering the Lake to a certain degree. Engine oil is a source of phosphorus input to Lake Tahoe

Publications from Graduate Research: Implications of vehicle emissions to Lake Tahoe soils and sediments

Student Name: Mary Fiore-Wagner
Major Professor and Institutional Affiliation: Dr. Glenn C. Miller, Natural Resources and Environmental Science, University of Nevada, Reno
Graduate Program: Environmental Science and Health
Graduation Date: December 1999

Title of Research Project: Quantifying the Dissolved Phase of MTBE and BTEX Exhausted from Marine Engines – Lake Tahoe Motorized Watercraft Study

Key Findings of Research Project: The seasonal distribution of MTBE and BTEX observed in the reconnaissance study conducted during 1997 suggested that gasoline concentrations found in Lake Tahoe were associated with motorized watercraft activity. Additional studies conducted during the summer of 1998 revealed that all six types of watercraft tested, regardless of operating cycle (two- or four-stroke) and induction system (carbureted or fuel injection), released measurable amounts of gasoline into Lake Tahoe. However, the amounts of soluble gasoline constituents (MTBE and BTEX) discharged into the water from motorized watercraft exhaust were largely dependent on marine engine type. Field experiments demonstrated that the two-stroke carbureted engines had the greatest amount of unburned gasoline passing through the engine and into the water. In a localized area, the average concentrations of gasoline constituents (MTBE and BTEX) released by a two-stroke engine were over an order of magnitude greater than concentrations measured for four-stroke carbureted and two-stroke direct injected technologies. In open water,
the carbureted two-stroke engines released at least seven times more gasoline (using toluene as the surrogate gasoline constituent) than the four-stroke carbureted and newer two-stroke fuel injected engines. This study provided scientific evidence to assist regulators at Lake Tahoe in making educated decisions about preventing pollution of Lake Tahoe by watercraft exhaust. The findings from this thesis project and other related watercraft studies were used to support the Tahoe Regional Planning Agency’s decision to ban watercraft powered by two-stoke engines, a regulation that was a very controversial issue in the Lake Tahoe Basin at the time.

Subsequent to the watercraft ban, water quality monitoring of Lake Tahoe indicated that the levels of gasoline pollutants present in the Lake during the boating season had decreased significantly compared to pre-ban levels of pollutants.

Current Position: Environmental Scientist with the California Regional Water Quality Control Board

Publications from Graduate Research:

  • Quantifying the Dissolved Phase of MTBE and BTEX Exhausted from Marine Engines – Lake Tahoe Motorized Watercraft Study (December 1999)

Student Name: Lynell M. Garfield
Major Professor and Institutional Affiliation: Dr. Mark Walker, Natural Resources and Environmental Science, funded through USDA Cooperative State Research, Education, and Extension Service (CSREES) Water Quality Program.
Graduate Program: Environmental Science and Health
Graduation Date: August 2007

Title of Research Project: Fecal Contamination of Water from a Dog Park and Water Potential Changes Affecting Bacterial Survival

Key Findings of Research Project: Land use may result in runoff to surface waters, and with increased urbanization, the proportion of rainfall and
snowmelt occurring as runoff is increased by impervious surfaces. Fecal matter from companion animals may enter waterways and cause microbial contamination in drinking and recreational waters. This research included two studies, a field study at Lake Tahoe that examined the links between a heavily used dog exercise area and microbial water quality, and a laboratory study that looked at effects of evaporation on indicator organism populations losses through time. The 14 month field study measured fecal accumulation and distribution on land and E. coli levels in a creek passing through the site. This study utilized Inverse Distance Weighting to estimate fecal loading on site, and membrane filtration to test microbial water quality. Results showed localized loading with an estimated 45.4 kg dry mass accumulation over the study period. Results also showed lower E. coli levels downstream from the park than upstream, presumably due to an on-line sedimentation basin on the creek in the park. Based on results of the field study, a laboratory study examined survival of indicator organisms in feces, specifically the relationship of evaporation to microbial survival. Canine feces were used to make a standardized sterile matrix, which was inoculated with E. coli, ATCC strain 25922. An environmental chamber study examining fecal bacteria degradation in canine feces evaluated bacterial degradation rates at evaporation conditions of 0.08, 0.21, and 0.29 in/ day. With the data fitted to Chick’s law, estimates of decay coefficients corresponded to results of -.07, -.22 and -.23/ hr, respectively. High and medium rate studies were not statistically different from one another, but significantly different from the low rate study. Control studies showed that high temperatures add to bacterial degradation rates, and that E. coli survival in feces is mostly limited by water potential. We measured changing water potential with water content losses and created a moisture release curve for canine feces. The data corresponded to previous research stating that E. coli would not survive conditions below ~ -22.4 MPa water potential.

Current Position: Hydrologist, Public Works Sanitary Engineering Team, City of Reno, Reno, Nevada

Publications from Graduate Research:

  • “Water Potential Changes in Fecal Matter and E. coli Survival” Thesis Chapter 3, published in the Journal of American Microbiology, Spring 2008.
  • “Microbial Water Quality and Influences of Fecal Accumulation from a Dog Exercise Area” Thesis Chapter 2, TBP to the Journal of Environmental Health November, 2008.

Student Name: Leland Tarnay
Major Professor and Institutional Affiliation: Dr. Alan Gertler, Desert Research Institute
Graduate Program: Environmental Sciences and Health
Graduation Date: December 2001

Title of Research Project: Atmospheric Nitrogen Deposition to the Lake Tahoe Basin

Key Findings of Research Project: Sources of dry nitrogen deposition are likely local and direct wet and dry deposition to Lake Tahoe proper explains only a fraction of the amount thought to be causing Tahoe’s eutrophication. Watershed sources of nitrogen may be more important than previously thought.

Current Position: Air Resources Specialist, Yosemite National Park.

Selected publications from Graduate Research:
Gertler, A. W., B. A., M. Arbaugh, S. S. Cliff, J. K. Koracin, L. Tarnay, R. Alonso, and W. Fraczek (2006). Local Air Pollutants Threaten Lake Tahoe’s Clarity. California Agriculture 60 (2): 53-58.
Tarnay, L.W., D.W. Johnson, and A.W. Gertler (2005). Modeled inputs of atmospheric nitrogen to the Lake Tahoe Basin due to gaseous pollutant deposition. Journal of the Nevada Water Resources Association 2 (4): 41-57 http:// www.nvwra.org/docs/journal/jnwra_2_article4_tarney.pdf.
Tarnay, L.W., A.W. Gertler, and G.E. Taylor (2002). An Inferential Model for HNO3 Deposition to Semi-arid Coniferous Forests. Atmospheric Environment 36 (20), 3277-3287.
Tarnay, L.W., A.W. Gertler, and M. Luria (2001). Sources and Magnitudes of Nitrogen-containing Compounds Responsible for Deposition in the Lake Tahoe Basin, California-Nevada. Paper #395 AWMA 94th Annual Meeting & Exhibition, Orlando, FL, June 24-28.
Tarnay, L.W., A.W. Gertler, R.R. Blank, and G.E. Taylor Jr. (2001). Preliminary Measurements of Summer Nitric Acid and Ammonia Concentration in the Lake Tahoe Basin Airshed: Implications for Dry Deposition of Atmospheric Nitrogen. Environmental Pollution, 113(2): 145-153.