Assessment of Semi-Volatile Organic Compounds Present in the Texas Colorado River and the San Saba Confluence

Elisabeth Davidson1 , Cameron Armstrong2 , Dr. Arthur Low21South West Texas Junior College (Uvalde, TX) 2Tarleton State University (Stephenville, TX)

Objective

• Acquire an understanding of the anthropogenic nature of the Texas Colorado River and how the San Saba watershed contributes

• Determine the presence of pesticides and herbicides in order to understand the involvement of semi-volatile organic compounds(SVOCs) and their contribution to the ecotoxicology of the Texas Colorado River

• Discover the concentration of the present SVOCs

• Determine if the present pesticides and herbicides are at an alarming level

Introduction to the Texas Colorado River

The Texas Colorado River is one of the most influential rivers in Texas as it serves both as a major water source for farming irrigation and provides sustainable water supply to many Texas Cities.

The San Saba, an important Colorado River watershed, is hypothesized to be a primary entry sit for pesticides, herbicides that contribute to the ecotoxicology of the Colorado River.

Acknowledgements• Cameron Armstrong for his partnership throughout the

research endeavor

• Dr. Low for his guidance and for always creating an educational environment

• Dr. Lamar Johanson for graciously allowing samples to be taken on his property and giving special access to the waterfront making sampling accessible

• Mrs. Joree Burnett for her assistance in the field

• NSF Research experience for undergraduates (RUE) for providing the funds for our research (Award #1658984)

• Tarleton State University for this research opportunity

SourcesMunch, J. W., et al. (2012). Method 525.3 Determination of

Semivolatile Organic Chemicals in Drinking Water by Solid Phase Extraction and Capillary Column Gas Chromatography/Mass Spectrometry (GC/MS) (Vol. 1.0). Cincinnati, Ohio: National Exposure Research Laboratory Office of Research and Development U.S. Environmental Protection Agency.

Technical fact sheet-Dinitrotoluene(DNT);United States Environmental Protection Agency Technical Fact Sheet for DNT: Washington, DC November 2017.

US Environmental Protection Agency.1989(Jan). Health Advisory Summary:Trifluarlin. US EPA, Washington, DC.

Figure 1. Google map of collection site. Thismap shows where samples were retrieved incorrelation with the San Saba confluence

Methodology

• Filtered each liter with an A/C Glass Fiber 1µm 47mm

• Ran each liter through solid phase extraction (SPE) column. Conditioned column with ethyl acetate equipped with an Oasis HLB 6 cc Vac Cartridge, 200 mg sorbent per Cartridge, 30 µm Particle Size, at 10mL a minute

• Compounds were eluted from the column using two organic solvents

• 5mL Ethyl Acetate• 5mL Dichloromethane

• Concentrated by evaporation in a hot water bath under nitrogen gas resulting in a 1mL sample diluted to 1.5mL in GC vial

• 1 µL injection of the sample was injected into a Shimadzu GC-2010 gas chromatograph(GC) with a SH-Rxi-5Sil MS column in splitless injection mode. Injection temperature was 270˚C. Oven temperature was 70˚C followed by a ramp of 10˚ C per minute until 200˚ C then ramped by 7˚C per minute until 320˚C and held for 3 minutes. Data acquisition began at 7 minutes

• Analytes were separated and identified by comparing the retention times to that of the standard and calibration curve

Results

ConclusionBased on concentrations of both 2,6-DNT and Trifluralin present in samples taken before and after the San Saba confluence, it can be concluded that the San Saba has less influence than that of the Colorado River concerning overall concentration of SVOCs.

Because sampling was conducted shortly after the Fourth of July, it is theorized that fireworks may have contributed to the heightened concentration of 2,6-DNT.

2,6-DNT and Trifluralin levels were not determined to be at an alarming concentration. Acute toxicological effects are not a concern, however, chronic toxicology is an issue that requires further study to understand the full toxicological effect.

Table 1. Sample compound concentration in ppb (parts per billion)

16.61

9.264

1.4622.009

2.488

4.382

8.183

2.619

1.315 0.9811.663 1.898

0.00

2.00

4.00

6.00

8.00

10.00

12.00

14.00

16.00

18.00

2,6-­‐DNT Trifluralin Hexazinone Tebuconazole Fenarimol Fluridone

Concentration/ppb

Contaminant   Compound

Pre-­‐Confluence

Post-­‐Confluence

Compound/Run 2.1 2.2 2.3 2.6 2.7 2.82,6-DNT 20.678 27.056 2.106 23.063 0.923 0.564Trifluralin 5.214 21.245 1.332 5.759 1.166 0.933Hexazinone 0.870 -0.320 3.836 -0.018 2.232 1.730Tebuconazole 1.575 0.615 1.380 0.650 1.934 0.359Fenarimol 3.960 0.996 2.508 1.523 2.663 0.804Fluridone 0.792 1.461 10.893 1.523 1.923 2.247

Figure 3. Comparison between pre and post San Sabaconfluence concentration

Figure 4. Chromatograph Run 2-6, Colorado River after the San Saba Confluence

Figure 5. DNT calibration curve

Figure 2. Chromatograph of RESTEK EPA Method 525.3 ONP Calibrant Standard

DiscussionThe resulting compound concentrations present in the Colorado River are very minimal with 2,6-DNT and Trifluralin having the highest concentration of the six compounds present.

2,6-DNT is a compound used in herbicides as well as explosive production.

Triflualin is a commonly used pesticide.

The resulting concentration values were surprisingly higher before the confluence rather than after, contrary to the hypothesis.

2,6-DNT is classified as a class B2 (Probable human) carcinogen.

Trifluralin concentration levels exceed that of the lifetime health advisory(LHA) level of 5 ppb for drinking water.

6: 2,6-DNT 15: Trifluralin 41: Hexazinone42: Tebuconazole 43: Fenarimol . 44: Flouridone