Seasonal Analysis and Source Seasonal Analysis and Source Apportionment of Hourly Apportionment of Hourly

Volatile Organic Compound Volatile Organic Compound Data In the Corpus Christi Data In the Corpus Christi

Urban AirshedUrban AirshedAuthors: Robert CastroAuthors: Robert Castro11 and Kuruvilla John and Kuruvilla John22

1.1. Department of Environmental Engineering, Texas A&M University– Department of Environmental Engineering, Texas A&M University– KingsvilleKingsville

2.2. Professor and Interim Dean, Frank H. Dotterweich College of Engineering, Professor and Interim Dean, Frank H. Dotterweich College of Engineering, Texas A&M University-KingsvilleTexas A&M University-Kingsville

ObjectivesObjectives

Perform source receptor analysisPerform source receptor analysis Identify VOC source profilesIdentify VOC source profiles Quantify VOC source contributions Quantify VOC source contributions

Seasonal Trends of VOCs in the Corpus Seasonal Trends of VOCs in the Corpus Christi areaChristi area

Relate changes in the source contributions Relate changes in the source contributions to Seasonal trendsto Seasonal trends

Study AreaStudy Area

Data SetData Set

Study Period 2006-2007Study Period 2006-2007 1-hr average samples collected 24 hrs a 1-hr average samples collected 24 hrs a

day 7 days a week.day 7 days a week. Analyzed 46 VOCsAnalyzed 46 VOCs Analyzed onsite using Auto-GC with FID Analyzed onsite using Auto-GC with FID

following the EPA Compendium Method following the EPA Compendium Method TO-14.TO-14.55

5. U.S. Environmental Protection Agency Center for Environmental Research Information Office of Research and Development Compendium Method TO-14 Determination of Volatile Organic Compounds (VOC)s in Air Collected in specially Prepared Canisters and Analyzed by Gas Chromatography/Mass Spectrometry (GC/MS) ; EPA/625/R-

96/010b; United States Environmental Protection Agency: January, 1999.

Source Receptor ModelingSource Receptor Modeling

X is the measurement matrixX is the measurement matrix G is the source contribution matrixG is the source contribution matrix F is the source profile matrix F is the source profile matrix E is the residual errorE is the residual error There can be an infinite number of There can be an infinite number of

solutions in solving for G and Fsolutions in solving for G and F Source receptor models differ in the Source receptor models differ in the

techniques which the solution is techniques which the solution is constrained and error is minimized.constrained and error is minimized.

[X]= [G][F]+[E]

Positive Matrix Factorization (PMF) Positive Matrix Factorization (PMF) ModelModel33

The PMF solution is determined by minimizing The PMF solution is determined by minimizing the weighted sum of squares (Q).the weighted sum of squares (Q).

is the uncertainty determined by the user.is the uncertainty determined by the user. The PMF model solves for the profiles and the The PMF model solves for the profiles and the

contribution simultaneously using a modified contribution simultaneously using a modified alternating least squares method. alternating least squares method. 44

3. Paatero, P.; Tapper, U., Positive Matrix Factorization: a Non-negative Factor Model With Optimal Utilization of Error Estimates of Data Values. Environmetrics 1994, 5, 111-126.

4. Hopke, P. K. A Guide to Positive Matrix Factorization; Clarkson University, Department of Chemical Engineering: Potsdam, New York.

Natural Gas SourceNatural Gas Source

Isob

utan

e

Pro

pane

N-B

utan

e

Eth

ane

Fugitive Gasoline SourceFugitive Gasoline Source

Isop

enta

ne

n-B

utan

e

n-P

enta

ne

Vehicle Exhaust SourceVehicle Exhaust Source

Isop

enta

ne

Tol

uene

M&

P-X

ylen

e

Ben

zene

Catalytic Reforming SourceCatalytic Reforming Source

Cyc

lohe

xane

Met

hylc

yclo

hexa

ne

Met

hylc

yclo

pent

ane

N-H

exan

e

Refinery Evaporative SourceRefinery Evaporative Source

Isop

enta

ne

n-B

utan

e

1-bu

tene

Tra

ns-2

-But

ene

Source ContributionsSource Contributions

Seasonal Analysis of VOC Species Seasonal Analysis of VOC Species at Solar Estates C633at Solar Estates C633

Seasonal Analysis of VOC Species Seasonal Analysis of VOC Species at Oak Park C634at Oak Park C634

Seasonal Analysis of the Source Seasonal Analysis of the Source Contribution at Solar Estates C633Contribution at Solar Estates C633

Seasonal Analysis of Source Seasonal Analysis of Source Contribution at Oak Park C634Contribution at Oak Park C634

Summary and ConclusionsSummary and Conclusions The concentrations of the select species and the The concentrations of the select species and the

contributions at the Solar Estates, and Oak Park sites contributions at the Solar Estates, and Oak Park sites had a trend of having high concentrations and had a trend of having high concentrations and contributions in the winter months and having low contributions in the winter months and having low concentrations and contributions in the winter months. concentrations and contributions in the winter months.

During the winter months the VOC concentrations are During the winter months the VOC concentrations are much higher at Oak Park in comparison to Solar Estatesmuch higher at Oak Park in comparison to Solar Estates

Generally, the species at the Solar Estates and Oak site Generally, the species at the Solar Estates and Oak site remain in proportion to each other through the 2005-remain in proportion to each other through the 2005-2006 seasons2006 seasons

It is most likely that this observation is due to the It is most likely that this observation is due to the lowering of the mixing height of the air shed during the lowering of the mixing height of the air shed during the colder winter months.colder winter months.

Summary and Co conclusions Summary and Co conclusions ContinuedContinued

Both sites were impacted by natural gas, fugitive Both sites were impacted by natural gas, fugitive gasoline, and vehicle exhaust sources.gasoline, and vehicle exhaust sources.

Unique to the Solar Estates site is the catalytic Unique to the Solar Estates site is the catalytic reforming source reforming source

Unique to the Oak Park site is the refinery Unique to the Oak Park site is the refinery evaporative source.evaporative source.

At both the Solar Estates and Oak Park sites, At both the Solar Estates and Oak Park sites, the natural gas and fugitive gasoline sources the natural gas and fugitive gasoline sources had the highest contributions. At both the Solar had the highest contributions. At both the Solar Estates and Oak Park sites the vehicle exhaust Estates and Oak Park sites the vehicle exhaust source had the lowest contribution.source had the lowest contribution.

AcknowledgmentsAcknowledgments This project is supported by the National This project is supported by the National

Science Foundation funded (Science Foundation funded (CREST – CREST – RESSACARESSACA) Center for Research Excellence in ) Center for Research Excellence in Science and Technology – Research on Science and Technology – Research on Environmental Sustainability of Semi-Arid Environmental Sustainability of Semi-Arid Coastal Areas under Cooperative Agreement Coastal Areas under Cooperative Agreement No. HRD-0734850. No. HRD-0734850.

The authors would also like to thank the City of The authors would also like to thank the City of Corpus Christi and the University of Texas at Corpus Christi and the University of Texas at Austin Center for Energy and Environmental Austin Center for Energy and Environmental ResourcesResources for their support and information for their support and information provided for this research work.provided for this research work.

Thank YouThank You

Questions?Questions?