Effects of Emission Adjustments on Peak Ground-Level Ozone Concentration in Southeast Texas

Jerry Lin, Thomas Ho, Hsing-wei Chu, Heng Yang, Santosh Chandru, Nagesh

Krishnarajanagar, Paul Chiou, and Jack R. Hopper

Lamar University2003 CMAQ Users’ Workshop

October 28, 2003

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Motivation Air quality in southeast Texas metroplex

among the worst in the nation Ongoing debates on the contribution to

air quality problems from various emission sources

To investigate the impact of emission adjustments on peak ground-level ozone levels in Houston-Galveston and Beaumont-Port Arthur airshed

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Models & Inputs

Emission Inventory: NEI99 Final Version 2 pasted with Texas EI by Texas Commission on Environmental Quality.

Meteorological Fields: TexAQS 2000 MM5 meteorology (TCEQ/TAMU) – August 22 to September 2, 2000.

Emission Model: SMOKE 1.5 with MIMS spatial surrogate for gridded emission processing.

Chemical Mechanism: SAPRC99 mechanism. Chemical Transport Model: CMAQ June 2002 Release on

Linux platform. Data Analysis & Visualization: PAVE and Matlab with

netCDF/statistics toolboxes.

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Domain and Approach 87 87 Lambert Conformal

grids. 12-km grid resolution. Period: August 22-26, 2000. Texas point source VOC

scaled up for base case simulation.

Modeled O3 levels compared to field observations made by TCEQ.

Sensitivity simulations based on same input meteorology but varied emission adjustments.

Beaumont

Galveston

Houston

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Base-case Simulation (8/25/2000)

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Statistics for Data Analysis

M e a n b i a s ( M B ) ),(),(mod txatxa obs

M e a n n o r m a l i z e d b i a s ( M N B ) )),(

),(),(( mod

txa

txatxa

obs

obs

M e a n f r a c t i o n a l b i a s ( M F B ) )),(),((5.0

),(),(

mod

mod

txatxa

txatxa

obs

obs

M e a n a b s o l u t e g r o s s e r r o r ( M A G E ) ),(),(mod txatxa obs

M e a n n o r m a l i z e d g r o s s e r r o r ( M N G E ) )),(

),(),(( mod

txa

txatxa

obs

obs

U n p a i r e d p e a k p r e d i c t i o n a c c u r a c y ( U P A ) max

maxmaxmod

),(

),(),(

txa

txatxa

obs

obs

C o r r e l a t i o n c o e f f i c i e n t ( R ) 5.02

5.02

modmod

modmod

)),(()),((

)),(()),((

obsobs

obsobs

atxaatxa

atxaatxa

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Base-case Verification

Parameters Houston-Galveston

Beaumont-Port Arthur

Mean bias (MB), ppbv -2.72 4.08

Mean normalized bias (MNB), % DNC* DNC*

Mean fractional bias (MFB), % - 9.36 14.8

Mean absolute gross error (MAGE), ppbv 10.8 9.07

Mean normalized gross error (MNGE), % DNC* DNC*

Unpaired peak prediction accuracy (UPA), % 1.01 6.45

Correlation coefficient (R) 0.894 0.897

*: DNC – did not calculate due to zero ozone concentration in observation.

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Scatter Plots – August 25, 2000

Houston-Galveston Beaumont-Port Arthur

17 monitoring stations 4 monitoring stations

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Sensitivity Cases

Case No. Emission Adjustment

1 Remove Texas point source VOCs

2 Remove Texas mobile source VOCs

3 Remove Texas area and non-road source VOCs

4 Remove Texas point source NOx

5 Remove Texas mobile source NOx

6 Remove Texas area and non-road source NOx

7 Remove biogenic source VOCs and NOx for entire domain

8 Remove Texas mobile source CO

9 Reduce 50% of anthropogenic VOCs and NOx for entire domain

10 Reduce 50% of anthropogenic NOx for entire domain

11 Reduce 50% of anthropogenic VOCs for entire domain

12 Remove anthropogenic VOCs and NOx in non-Texas region

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Impact on Peak O3

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Ozone Difference for Cases 1 & 4

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Ozone Difference for Cases 5 & 6

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Ozone Difference for Cases 7 & 12

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Summary Removing point source emissions (VOC or NOX)

leads to the greatest reduction in peak O3 concentration.

The impact of point source emissions on O3 concentration only affect a small urban area for a relatively short period of time.

Removing area, mobile or biogenic source emission (VOC or NOx) causes O3 reduction in a larger area. However, the magnitude of reduction is less than that of point sources.

Transport from adjacent states may contribute significantly to the BPA O3 levels.

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Acknowledgement Texas Commission on

Environmental Quality (Work Order #48561-03)

Texas Air Research Center Prof. Daewon Byun at University of

Houston Alison Eyth at Carolina

Environmental Program