Cross-border Transport of Fine Particulate Matter into Texas from Agricultural Burning

Presented at the2004 Models-3 Conference

Chapel Hill, NCOctober 18-20, 2004

Myoungwoo Kim,

Ieesuck Jung, and

Kuruvilla John

Department of Environmental and Civil Engineering

Texas A&M University – Kingsville

Kingsville, Texas 78363

Introduction • Corpus Christi, Texas is a major petrochemical center and its port is

the fifth busiest one in the United States in terms of annual tonnage. • Corpus Christi with a population of about 300,000 is the sixth largest

Consolidated Metropolitan Statistical Area (CMSA) in Texas.• It is currently in attainment of the NAAQS for all criteria pollutants.• However, the monitored air quality trend indicates that the city could

potentially be in danger of violating the annual average NAAQS for fine particulate matter in the near future.

• PM2.5 level of Corpus Christi area is influenced by atypical episodes affected by the long-range transport of continental haze and smoke events attributed to agricultural burns in Texas and beyond.

• Recent air pollution episodes such as the May 2-19, 2003 smoke event and the Sep 11-14, 2002 continental haze events significantly contributed to elevated levels of PM2.5.

• In this study, potential source contribution function (PSCF) and the UNMIX receptor model were used to obtain source apportionment details and to identify source-receptor relationship affecting the Corpus Christi urban area.

Annual PM2.5 levels in Corpus Christi, Texas

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The annual average concentration of the fine particles measured using TEOMs operated by TCEQ showed an increase of 10.6% between 2001 and 2002. The increase between 2002 and 2003 was approx. 17.3 %.

02468

1012

PM2.5 TEO M annual average (ug/m3)

2001 2002 2003

Year

PM2.5 Monitoring sites in South Texas

Sampling and Data

The study period: 2001-2003. Continuous PM2.5 data from TEOM located at the

CAMS04 site in Corpus Christi. FRM filter mass and fifty-three speciation elements

measured at CAMS199 by the Texas Commission on Environmental Quality (TCEQ) - once every six days.

The chemical speciation analysis: gravimetric, energy dispersive XRF, ion chromatography and thermal-optical methods.

As, Br, Cr, Cu, Fe, Pb, Mn, Mo, Ni, Sn, V, Si, S, Ta, K, K+, NH4

+, Na, Na+, EC, Non Volatile Nitrates (NvN),

OCX (Non Organic Carbonate Carbon) and OC.

South Texas PM2.5 level during smoke event

Corpus Christi

Laredo Mission Brownsville

1-hr max PM2.5 (mg/m3) 64 83 105 80

Source: TCEQ

Time Series Analysis

Pollution Rose for CAMS040

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May 2-19, 2003

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Corpus Christi CAMS04

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Mission CAMS43

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Brownsville, CAMS80

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DATA ANALYSIS METHODOLOGIES

Backward Trajectory Calculations

• NOAA’s Air Resources Laboratory developed and used HYSPLIT4 for air parcel trajectory computations.

• HYSPLIT4 trajectory model was used to effectively integrate winds in the transport layer over time, distance, and source regions.

• 2-day back trajectories were drawn using wind fields from datasets of:

- Eta Data Assimilation System (EDAS): 2003 - Model start height: 500 m, middle of mixed layer - Model start times: UTC hour of observed PM2.5 concentrations• The region covered by the trajectories was divided into

1583 grid cells of 11 latitude and longitude

Potential Source Contribution Function (PSCF)

• Hopke et al. developed and used the PSCF for air pollution source apportionment and source-receptor relationship studies.

• If a backward trajectory endpoint lies in the ijth cell, the air parcel assumes to collect PM emitted in the cell and transports along the trajectory to the monitoring site.

• PSCFij is the conditional probability that an air parcel that passed through the ijth cell has a high concentration upon arrival at the monitoring site

ijij

ij

mPSCF =

n

nij : total number of end points that fall in the ijth cell

mij : number of end points that exceeded the threshold criterion

(in this study, average concentration of PM was used for the threshold criterion)

Downweight Functions• Small values of nij produce high PSCF values with

high uncertainties.

• To minimize the artifacts, PSCF values were downweighted with weight function (W) when nij was less than the average nij.

)( ijnW

ijn43

435 ijn

52 ijn

2ijn

Average nij 43.2 1.0

Maximum nij 329 0.7

Standard Deviation

48.7

0.5

0.2

Potential Source Contribution Function (PSCF)

• PSCF describes the spatial distribution of probable geographical source locations.

• Grid cells which have high PSCF values are the potential source area whose emissions can contribute to the levels observed at the receptor (monitoring) site.

• For secondary pollutants, the high PSCF area may also include areas where secondary formation is enhanced.

Source Apportionment (UNMIX)

• R. C. Henry developed the multivariate receptor model, UNMIX, for source apportionment studies.

• The UNMIX model was applied to a set of air quality compositional data to identify the number, composition, and contribution of the various sources of air pollution.

• The data used in this study included concentrations of As, Fe, Si, S, K, NH4

+, Na+, OC, EC, Non Volatile Nitrates (NvN), OCX (Non Organic Carbonate Carbon), and SO4

• UNMIX was then applied to a set of PM2.5 and species data with and without data collected during the smoke events to identify unique source types associated with this event.

SUMMARY RESULTS

16

20

24

28

-110 -105 -100 -95 -90

48-hours Backward Trajectory Calculations

Corpus Christi

Analysis of the 2003 Agricultural Burning Season

May 2-19, 2003: Every spring, at the end of the tropical dry season, agricultural burning and wildfires produce large amounts of smoke in southeastern Mexico and Central America. The fires usually begin in March and by late May or early June the smoke production diminishes as the rainy season begins. The peak of the burning is usually in late April and early May. Persistent southeasterly winds carry the resulting smoke to Texas, most frequently in April and May.

Corpus Christi

MODIS source: University of Wisconsin (SSEC) and Texas Commission on Environmental Quality

Three-dimensional transport of PM2.5

• PSCF analysis was also applied to altitude and longitude to evaluate three-dimensional transport of the smoke event.

• Starting height of backward trajectory was 500m. • It was noted that air parcels arriving in the Corpus Christi area at the

500m level were transported from the source region and mixed within the PBL of approximately 1 km.

Corpus Christi

Source Apportionment (UNMIX)

Six-sources

sulfate44%

vehicles19%

soil11%

nitrate6%

seaspray10%

K10%

Species Source#1 Source#2 Source#3 Source#4 Source#5 Source#6

Total Mass 1.04441 0.56008 0.96753 0.97753 1.75667 4.16212As -0.00002 0.00012 0.00008 0.00002 0.00035 0Fe 0.052 -0.0008 -0.0044 0.00282 0.00778 0.00115Si 0.20325 -0.0047 -0.0061 0.0054 0.00086 0.00363S 0.02435 0.03672 0.206 -0.0677 0.06736 0.15983K 0.01573 0.00182 -0.0003 0.04502 -0.0006 0.00229

NH3 0.00459 0.20093 0.06021 -0.0792 0.07416 0.16061Na+ 0.02327 -0.0096 0.14937 0.0841 -0.0147 0.00186OC 0.08324 0.08326 0.22478 0.40437 0.55809 0.19364EC -0.011 0.01841 0.0323 0.00779 0.1284 0.01989

NvN 0.00519 0.41144 0.04622 0.00885 -0.0048 -0.0041OCX 0.02883 0.00225 0.18611 0.16274 0.20363 0.07204SO4 0.08194 0.11353 0.62681 -0.1563 0.15688 0.49786Na 0.0015 -0.0119 0.23667 0.01001 -0.004 -0.001

Source Identification Soil Nitrate Sea sprayPotassiumVehicles Sulfate

The six source model output revealed that crustal soil, nitrates, salt from sea spray, potassium, vehicular sources and sulfates were the major factors contributing to the total ambient PM2.5 mass in the

Corpus Christi urban airshed.

• The UNMIX model was run with and without the smoke episode data and the primary difference was noted in the apportionment of potassium (K) in the six-source model. K is a strong indicator of burning sources and is linked to agricultural burns in the region.

• Sulfate indicating industries accounted for 44% of the total variance.

Analysis of the Sept. 11-14, 2002 Haze Event

Sept. 11-14, 2002: Increasing levels of haze and high ozone began arriving in East and Central Texas. The haze and air pollution had accumulated for several days in a stagnant air mass centered near the junction of the lower Ohio River Valley and the middle Mississippi River Valley. A weak cool front then pushed the hazy air mass south-southwest into South Texas.

Corpus Christi

MODIS source: University of Wisconsin (SSEC) and Texas Commission on Environmental Quality

Summary Results • The PM2.5 level is influenced by long-range transport of

haze and smoke during episodes such as May 2-19, 2003. These events significantly elevated the annual PM2.5 levels observed in the Corpus Christi airshed.

• PSCF and UNMIX receptor models were applied to understand the source-receptor relationship and identify various source types affecting the urban area.

• PSCF analysis identified southern Mexico and Central America as possible source areas affecting the Corpus Christi area during the May 2-19, 2003 smoke event.

• UNMIX receptor modeling suggested that agricultural burning as one of the primary sources of PM during the smoke episode.

Acknowledgements

The authors are grateful to Texas Commission on Environmental Quality (TCEQ) – Austin Office for providing access to the air quality data and to the National Oceanic and Atmospheric Administration’s (NOAA) Air Resources Laboratory for the use of the HYSPLIT4 Model.

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1142 • Philip K. Hopke J. Chemometrics 2003, 17, 255-265.• Lin, C. J.; Cheng, M. D.; Schroeder, W.H. Atm. Env. 2001, 35, 1141-

1154.• Pollissar, A.V.; Hopke, P.K.; Paatero, P.; Kaufmann, Y.J.; Hall, D.K.;

Bodhaine, B.A.; Dutton, E.G.; Harris, J.M. Atm. Env. 1999, 33, 2441-2458.

• Draxler, R.R.; Hess, G.D. Description of the HYSPLIT4 Modeling System, NOAA Tech Memo: 1997; ERL ARL-224.

• Lucey, D.; Hakjiiski, L.; Hopke, P.K.; Scudlark, J.R.; Church, T. Atm. Env. 2001, 35, 3979-3986.

• Zeng, Y.; Hopke, P.K. Atm. Env. 1989, 23, 1499-1509.

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