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

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

Dec 04, 2022 38 likes •409 views

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

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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

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SLIDE 2

Cooperative Study:

  • U.S. GEOLOGICAL

SURVEY

  • TAHOE REGIONAL

PLANNING AGENCY

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FUNDING SOURCES:

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SLIDE 3

TRPA In-Kind Contribution:

Boat Crew & staff

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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

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Historical Sampling & Findings:

Carbureted 2-Stroke Engines were banned in 1999 – this has greatly decreased gasoline compounds in Lake Tahoe

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Pre/Post 2-Stroke Ban:

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Lake Tahoe Organics Sampling:

Lake Tahoe

 1999-2003  2005-07  2009-11

Other Lakes:

1997-98

Streams:

  • 1998
  • 2002-03

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SLIDE 8

Increased to 20 sites-some in areas of potential buoy fields & piers

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Monitoring Re-established again & part of Shorezone Water-Quality Monitoring Program

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  • 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

  • r need refinement.

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SLIDE 10

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

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SLIDE 11

Sites:

2009 & 2010:

  • VOC
  • SPMD &

VOC

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Sample periods: 2009

  • No. Time period - Boat Usage - Sample Type
  • 1. Post Memorial Day Light VOC
  • 2. Pre 4th of July Medium VOC + SPMD
  • 3. Post 4th 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

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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 4th of July Medium VOC + SPMD
  • 5. Post 4th 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

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SLIDE 14

Sites: 2011

  • VOC only

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Sample periods: 2011

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

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Methods: Clean VOC Sampler & Load

with 4 vials:

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Methods: VOC Sampler lowered in Lake to

3 meters, until full

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Methods: VOC Sample vials removed,

acidified & sent via FEDX to USGS NWQL

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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)

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Results:

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10 20 30 40 50 60 70 80 90 100 Benzene Toluene Ethyl Benzne Xylene Percentage

Lake Tahoe BTEX Percent Detections, 2010

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0.1 0.2 0.3 0.4 0.5 0.6

Toluene concentration, ug/L

Lake Tahoe Toluene concentrations, May-Oct, 2010

5/3/2010 Toluene (ug/L) 5/28/2010 Toluene (ug/L) 6/1/2010 Toluene (ug/L)

7/1/2010 Toluene (ug/L) 7/6/2010 Toluene (ug/L) 8/2/2010 Toluene (ug/L) 8/18/2010 Toluene (ug/L) 9/9/2010 Toluene (ug/L) 10/11/2010 Toluene (ug/L)

North

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Lake Tahoe Toluene concentrations by site, 2009-11

Site Toluene concentration, ug/L

0.0 0.1 0.2 0.3 0.4 0.5

South East Mid North

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Lake Tahoe Toluene concentration by area, 2009-11

Area

South East Mid Lake North West

Toluene concentration, ug/L

0.0 0.1 0.2 0.3 0.4 0.5

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0.02 0.04 0.06 0.08 0.1 0.12 0.14

Toluene concentration, ug/L

Lake Tahoe Median Toluene Concentration by Period, 2010

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Lake Tahoe Toluene by Sample Season, 2009-11

Sample Season

May Memorial Day 4th of July August Labor Day October

Toluene concentration, ug/L

0.0 0.1 0.2 0.3 0.4 0.5

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0.5 1 1.5 2 2.5

Toluene, ug/L

Lake Tahoe Emerald Bay Toluene concentrations, 1998-2011

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0.000 0.200 0.400 0.600 0.800 1.000 1.200 1.400 1.600 1.800 2.000

Toluene concentration, ug/L

Lake Tahoe -Emerald Bay Annual Median Toluene concentrations , 1998-2011

Long-term median

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0.5 1 1.5 2 2.5 3 3.5 4 4.5

MTBE, ug/L

Lake Tahoe-Emerald Bay MTBE concentrations, 1998-2011

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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.

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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 4th of July &

August sample periods

 Lower detections in May &

October sample periods

 Trends continue downward since

1999

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PAHs passively sampled using SPMDs - deployed & secured for ~30 days

SPMD: 3 Polyethylene Layflat Films With Lipid Triolein layer

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10 20 30 40 50 60 70

Emerald Bay Diver's Buoy Kiva Beach Tahoe Keys- East Channel Zephyr Cove Dollar Point Tahoe City Chambers Landing Sugar Pine Point

Percent Detections Site

Lake Tahoe Percent PAH Detections by Sampling Site, 2009

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SLIDE 34

500 1000 1500 2000 2500 3000 3500 4000

Emerald Bay Kiva Beach Tahoe Keys Marina East Zephyr Cove Dollar Point Tahoe City Chambers Sugar Pine Pt

PAH, nanograms per ampoule Site

Lake Tahoe Results for Key PAH constituents, Fluoranthene and Pyrene, by site, 2009

Fluoranthene Pyrene LT 2012

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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;

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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

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SLIDE 37

Any Questions?

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