Date of Award

Spring 2-21-2018

Degree Type

Dissertation

Degree Name

PhD Molecular Bioscience

Department

Biology

Advisor

Carolyn S. Bentivegna, Ph.D.

Committee Member

Angela Klaus, Ph.D.

Committee Member

Jane L. Ko, Ph.D.

Committee Member

Heping Zhou, Ph.D.

Committee Member

David Sabatino, Ph.D.

Keywords

tributyl tetradecyl phosphonium chloride, sodium chloride, hydraulic fracturing, mitochondria, Chironomus riparius, red (cool) laser.

Abstract

Tributyl tetradecyl phosphonium chloride (TTPC) is a biocide utilized in the hydraulic fracturing process to extract oil and natural gas from deep underground. This study used 4th instar Chironomus riparius to investigate the toxicity of TTPC, NaCl, and TTPC+NaCl. Our results show that the 24 h LC50s for TTPC, NaCl, and TTPC+NaCl were 0.57 mg/L, >10,000 mg/L, and 0.32 mg/L, respectively, while the 48 h LC50s for the same treatments were 0.48 mg/L, 9808 mg/L, and 0.22 mg/L, respectively. Additionally, TTPC’s mechanism of action was investigated by measuring the levels of adenosine triphosphate (ATP), superoxide dismutase (SOD), and lipid hydroperoxides (LPO) as indicators of compromised viability. Red (cool) laser light, which stimulates cytochrome c activity and enhances ATP production, was utilized for a first time in macroinvertebrates to test the mitochondrial function. TTPC treatment resulted in significant increases in ATP levels, SOD activity, and levels of LPO. Additionally, there was a failure in the stimulation of ATP production in response to red laser exposure. Furthermore, TTPC+NaCl treatment resulted in significant increases in SOD activity, ATP, and LPO levels. These results showed increasing toxicity as a synergistic effect with the combined TTPC+NaCl treatment. However, results for NaCl alone showed no change in ATP levels but increased in SOD and LPO levels. These results indicated that radical oxygen species caused mitochondrial dysfunction by damaging the membrane. Adding NaCl to TTPC showed to increase the toxicity of TTPC, which enhanced the damage to mitochondrial membrane, even though the SOD activity was not detected. The toxicity of TTPC to macroinvertebrates was addressed for the first time with calculation of LC50. This shows that hydraulic fracturing fluids entering freshwater ecosystems could put aquatic organisms at risk.

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