Sources of Atmospheric Pollutants Leading to Declining ...
Transcript of Sources of Atmospheric Pollutants Leading to Declining ...
Sources of Atmospheric Pollutants Leading to Declining Water Clarity in aHigh Altitude LakeAlan Gertler Jülide Kahyaoğlu-KoračinDesert Research Institute, Reno, NV
Leland TarnayU.S. National Park Service, Washington, DC
AcknowledgementsDesert Research Institute:
John LewisHebrew University:
Menachem LuriaUniversity of California, Davis
Geoffrey SchladowCalifornia Air Resources Board
Paul AllenVernon Hughes
Funding:Nevada NSF- EPSCoRNSF Advanced Computing in Environmental Sciences (ACES)DRI – Center for Watersheds and Environmental Sustainability
Presentation Overview
MotivationMonitoring Results
MethodologyFlux estimatesIn basin vs. out of basin sources
Modeling ResultsBack trajectory analysesMeteorological and dispersion simulations
Nature of the Problem
Since 1968, lake clarity has been decreasing at 0.25 m/yr.Possible causes of this include hydrologic and atmospheric input of:
Nitrogen (N)Phosphorous (P)Sediment
Sources of Nitrogen
Surface Runoff10%
Stream Loading20%
Groundwater Discharge
15%
Atmospheric Deposition
55%
Sources of Phosphorous
Surface Runoff35%
Stream Loading29%
Groundwater Discharge
9%
Atmospheric Deposition
27%
Monitoring Objectives
Measure ambient concentrations of N pollutants at sites located around the LTB.Perform measurements during periods when dry deposition is expected to dominate.Couple the ambient data with available air quality and meteorological data to provide an estimate of the contributions from in-basin and out-of-basin sources.
Lake Tahoe - Location
Prevailing Westerlies
Lake Tahoe - Location Reno
Central ValleyS. Lake Tahoe
NASA Photo
Lake Tahoe
Sampling Locations
Thunderbird LodgeThunderbird LodgeEcho SummitEcho Summit
BlissBlissBarkerBarker
South Lake TahoeSouth Lake Tahoe
(View from above Incline Village, at the north end of the Lake Tahoe Basin)
Methods: Measuring Pollutant Concentrations
HNO3NH3NH4NO3
Methods: Integrating Bigleaf with a GIS
Estimated Flux
Nitrogen species Lower limit(106 g)
Upper limit(106 g)
Estimate(106 g)
HNO3 26.7 33.7 30.2
NH3 2.9 22.1 14.6
NH4NO3 0.1 4.9 4.6
TOTAL 29.7 60.8 49.4
Comparison With Other Studies
In Basin vs. Out of Basin?
Spatial distributionsInter-site correlationsDevelopment of isoplethsAir mass age
2000 Results – HNO3
0
5
10
15
20
25
30
35
40
45
7/26 8/2 8/10 8/16 8/22 8/28 9/3 9/9 9/15
Date
HN
O3
(nm
ol/m
3)
BARKECHO BLISSOLATBRDBACKGROUND
Most sites similar, with So Lake higher → Regional + local source
2000 Results – NH3
0
20
40
60
80
100
120
140
7/26 8/2 8/10 8/16 8/22 8/28 9/3 9/9 9/15
Date
NH
3 (n
mol
/m3)
BARKECHOBLISSOLATBRDBACKGROUND
Major differences → Local source
2000 Results – All Sites
HNO3 (nmol m-3)
NH3 (nmol m-3)
24 hr median (± 1 S.E.) 14 (1.2) 14 (3.9) Day median (± 1 S.E.) 17 (1.8) 20 (5.0) Night median (± 1 S.E.) 13 (1.2) 10 (6.2) Background 5, 6 6.6-7.1 0.0-40 Stat. Sig. day/night difference (p = 0.05)? yes no
HNO3 – Inter-site Correlations
HNO3 South Lake
Tahoe Thunderbird
Lodge Echo
Summit Barker Pass
Bliss State Park
South Lake Tahoe 1 Thunderbird Lodge 0.65 1 Echo Summit 0.57 0.91 1 Barker Pass 0.72 0.87 0.88 1 Bliss State Park 0.70 0.84 0.85 0.90 1
NH3 – Inter-site Correlations
NH3 South Lake
Tahoe Thunderbird
Lodge Bliss State
Park Echo
Summit Barker Pass
South Lake Tahoe 1 Thunderbird Lodge -0.62 1 Bliss State Park -0.27 0.41 1 Echo Summit 0.01 0.41 0.61 1 Barker Pass -0.01 0.85 0.92 0.92 1
Spatial and Temporal HNO3Variation
Spatial and Temporal NH3Variation
Day Night
Air Mass Age
0.00
0.10
0.20
0.30
0.40
0.50
0.60
0.70
7/25
/00
8/1/
00
8/9/
00
8/15
/00
8/21
/00
8/27
/00
9/2/
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9/8/
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9/14
/00
Ave
rage
Date
HN
O3/
NO
x
Echo DayS. Lake DayEcho NTS. Lake NT
Summary Measurement Results
HNO3 accounts for 20% of direct Lake N deposition (wet and dry) and 50% or more of terrestrial N deposition (wet and dry).HNO3 is regional with a significant local component. The sources of NH3 are local.
Objectives of Modeling Component
To determine the characteristics of summertime transport of N to the Lake Tahoe Basin.To determine in-basin vs. out-of-basin sources of HNO3 using advanced atmospheric modeling systems.
Ensemble Analysis of Backward Air Mass Trajectories (day)
June-Sep/00 5 PM (24-hr)
P > 0.027, 25%P > 0.027, 25%0.015 < P < 0.027, 50%
0.0048 < P < 0.015, 75%
Modeling System (1)
MM5MM5
117x117x35117x117x3515 km15 km
193x169x35193x169x355 km5 km
73xx73x3573xx73x351.6 km1.6 km
• Two case studies coinciding with the field study by Tarnay (2001).
•Cases on August 22 and September 3, 2000.
•85 hours forecast for each simulation.
Modeling System (2)
CALMET/CALPUFF system using MM5 predicted fields as the first guess.Volume sources in California.72 hours simulation for each case.
50 100 150 200
50
100
150
200
250
Lake
Tah
oe
San Francisco
Sacramento
Point sourcesMeteorological sitesChemical sites
SOLA
ECHO
BLIS
TBLG
BARK
USCG
45 km
65 km
Emissions (1)
• Developed emissions estimates for the Tahoe basin: 7.3 NOx(tn/day).
•Data from 42 surface, 2 upper air, and 49 ozone stations.
Emissions (2)CALMETCALMET/CALPUFFCALPUFF250x265x8250x265x81 km1 km
SourcesSources
CALMET Predicted Winds: August 22
50 100 150 200X direction (km)
50
100
150
200
250
Y di
rect
ion
(km
)
50 100 150 200X direction (km)
50
100
150
200
250
Y di
rect
ion
(km
)
DayNight
•Regional background ~0.4 µg/m3
•Accounted for 81 to 98% of the observed HNO3
•Local sources responsible for 70% of the observations
HNO3 – Bytnerowicz et al.
Summary of Modeling ResultsThe amount of transported HNO3 was low (~0.4 µg/m3).
For the high concentration period, predicted concentrations accounted for 81% of the observations and local sources comprised approximately 70% of the predictions.
For the low concentration period, predicted concentrations accounted for 98% of the observations, and out- of-basin sources comprised approximately 70% of the predictions.
Summary and ConclusionsMeasurement Component:
HNO3 is the most important N species in terms of overall deposition.HNO3 is regional with a significant local component. The sources of NH3 are local.
Modeling Component:Backward trajectory analysis showed a transport potential from the California valley; however, the possibility of significant pollutant transport was weak. For the high concentration day, local sources dominated.
Bottom line: To reduce the atmospheric contribution of N to the lake, local sources must be controlled.
Something else to consider:Transport may be a significant source of N flux in remote watersheds.
Much Nicer Than Most of the Places I Work