& gasoline-derived compounds in Lake Tahoe, 2009-11 Timothy G. - PowerPoint PPT Presentation

Results of monitoring for gasoline & gasoline-derived compounds in Lake Tahoe, 2009-11 Timothy G. Rowe Hydrologist U.S. Geological Survey Nevada Water Science Center Carson City, NV U.S. Department of the Interior U.S. Geological Survey

FUNDING SOURCES: Cooperative Study : • U.S. GEOLOGICAL SURVEY • TAHOE REGIONAL PLANNING AGENCY LT 2012

TRPA In-Kind Contribution: Boat Crew & staff LT 2012

Outline :  Background  Historic Organics Sampling & significant Findings  Project Objectives  Compounds of Interest  Sampling & Sites  VOC Sampling Methods  VOC Results  PAH Sampling Methods  PAH Results  Plans LT 2012

Historical Sampling & Findings: Carbureted 2-Stroke Engines were banned in 1999 – this has greatly decreased gasoline compounds in Lake Tahoe LT 2012

Pre/Post 2-Stroke Ban : LT 2012

Lake Tahoe Organics Sampling : Lake Tahoe  1999-2003  2005-07 Streams :  1998  2009-11  2002-03 Other Lakes :  1997-98 LT 2012

Monitoring Re-established again & part of Shorezone Water-Quality Monitoring Program Increased to 20 sites-some in areas of potential buoy fields & piers LT 2012

1. Develop baseline conditions for gasoline-derived compounds, hydrocarbons (VOCs) and polycyclic aromatic hydrocarbons (PAHs) 2. Understand possible changes in water quality over time 3. Determine if possible mitigation measures are effective or need refinement. LT 2012

Hydrocarbons (VOCs): • Gasoline Components: BTEX- Benzene, Toluene, Ethylbenzene, & Xylene Note Toluene – used as surrogate • Gasoline Oxygenates: MTBE, ETBE, TAME, DIPE Polycyclic Aromatic Hydrocarbons (PAH’s):  Flouranthene  Pyrene  Naphthalene  others LT 2012

Sites: 2009 & 2010: -VOC -SPMD & VOC LT 2012

Sample periods: 2009 No. Time period - Boat Usage - Sample Type 1. Post Memorial Day Light VOC 2. Pre 4 th of July Medium VOC + SPMD 3. Post 4 th of July Heavy VOC 4. Early August Heavy VOC + SPMD 5. Mid-August Heavy VOC 6. Post Labor Day Heavy VOC 7. Early Fall Light VOC LT 2012

Sample periods: 2010 No. Time period - Boat Usage - Sample Type 1. Early May Light VOC + SPMD 2. Pre-Memorial Day Light VOC + SPMD 3. Memorial Day Light VOC 4. Pre 4 th of July Medium VOC + SPMD 5. Post 4 th of July Heavy VOC 6. Early August Heavy VOC + SPMD 7. Mid-August Heavy VOC 8. Post Labor Day Heavy VOC 9. Early Fall Light VOC + SPMD LT 2012

Sites: 2011 -VOC only LT 2012

Sample periods: 2011 No. Time period - Boat Usage - Sample Type 1. Pre Boating Light VOC 2. Post Memorial Day Light VOC 3. Post 4 th of July Heavy VOC 4. Mid-August Heavy VOC 5. Post Labor Day Heavy VOC 6. Early Fall Light VOC LT 2012

Methods: Clean VOC Sampler & Load with 4 vials : LT 2012

Methods : VOC Sampler lowered in Lake to 3 meters, until full LT 2012

Methods: VOC Sample vials removed, acidified & sent via FEDX to USGS NWQL LT 2012

Methods - QA/QC  Sampler/vials/equip sealed while engine on  Wait period after engine shut off  Wear new gloves every site  Rinse sampler after each sample & clean daily  Vary sampling order  Obtain 10% QA/QC samples:  Replicates every round – vary location  Source Water Blank (USGS NWQL)  Field and Sample Blanks (VOC grade) LT 2012

Results: LT 2012

Lake Tahoe BTEX Percent Detections, 2010 100 90 80 70 60 Percentage 50 40 30 20 10 0 Benzene Toluene Ethyl Benzne Xylene LT 2012

Lake Tahoe Toluene concentrations, May-Oct, 2010 0.6 5/3/2010 Toluene (ug/L) 5/28/2010 Toluene (ug/L) 6/1/2010 Toluene (ug/L) 0.5 7/1/2010 Toluene (ug/L) Toluene concentration, ug/L 7/6/2010 Toluene (ug/L) 0.4 8/2/2010 Toluene (ug/L) 8/18/2010 Toluene (ug/L) 9/9/2010 Toluene (ug/L) 0.3 10/11/2010 Toluene (ug/L) 0.2 North 0.1 0 LT 2012

Lake Tahoe Toluene concentrations by site, 2009-11 0.5 Toluene concentration, ug/L 0.4 0.3 0.2 0.1 0.0 South East Mid North Site

Lake Tahoe Toluene concentration by area, 2009-11 0.5 Toluene concentration, ug/L 0.4 0.3 0.2 0.1 0.0 South East Mid Lake North West Area

Lake Tahoe Median Toluene Concentration by Period, 2010 0.14 0.12 Toluene concentration, ug/L 0.1 0.08 0.06 0.04 0.02 0 LT 2012

Lake Tahoe Toluene by Sample Season, 2009-11 0.5 Toluene concentration, ug/L 0.4 0.3 0.2 0.1 0.0 October May Memorial Day 4th of July August Labor Day Sample Season

Lake Tahoe Emerald Bay Toluene concentrations, 1998-2011 2.5 2 1.5 Toluene, ug/L 1 0.5 0 LT 2012

Lake Tahoe -Emerald Bay Annual Median Toluene concentrations , 1998-2011 2.000 1.800 1.600 1.400 Toluene concentration, ug/L 1.200 1.000 0.800 0.600 0.400 0.200 Long-term median 0.000 LT 2012

Lake Tahoe-Emerald Bay MTBE concentrations, 1998-2011 4.5 4 3.5 3 MTBE, ug/L 2.5 2 1.5 1 0.5 0 LT 2012

VOC Results :  Detections were low for the most part.  VOC constituents detected : BTEX, MTBE, & acetone. BTEX were detected at all 20 sites  Toluene detected in 90% of the samples & ranged from <0.01 to 0.52 ug/L.  MTBE was detected in only 2 samples and ranged from 0.03 to 0.15 ug/L . LT 2012

VOC Results (cont):  South Sites had highest percentage (78%) of detections, maximum level of detections and highest medians.  Reference site; Mid-Lake; low  Higher detections in 4 th of July & August sample periods  Lower detections in May & October sample periods  Trends continue downward since 1999 LT 2012

PAHs passively sampled using SPMDs - deployed & secured for ~30 days SPMD: 3 Polyethylene Layflat Films With Lipid Triolein layer LT 2012

Lake Tahoe Percent PAH Detections by Sampling Site, 2009 70 60 50 Percent Detections 40 30 20 10 0 Emerald Bay Kiva Beach Tahoe Keys- Zephyr Cove Dollar Point Tahoe City Chambers Sugar Pine Diver's Buoy East Channel Landing Point Site LT 2012

Lake Tahoe Results for Key PAH constituents, Fluoranthene and Pyrene, by site, 2009 4000 Fluoranthene Pyrene 3500 PAH, nanograms per ampoule 3000 2500 2000 1500 1000 500 0 Emerald Bay Kiva Beach Tahoe Keys Zephyr Cove Dollar Point Tahoe City Chambers Sugar Pine Pt Marina East Site LT 2012

SPMD-PAH Results:  13 PAH’s detected at low levels – highest number of detections for, Acenaphthylene, Fluorene, Fluoranthene, Naphthalene, Phenanthrene & Pyrene  Highest percent detections were at Tahoe Keys & Emerald Bay  Fluoranthene & Pyrene were highest, in Tahoe Keys; LT 2012

Future Plans:  Sampling on hold for 2012 – due to budget constraints.  Hope to re-establish cooperative USGS-TRPA base-line data collection network in 2013 LT 2012

Any Questions? LT 2012