Collaborative Research: Do CFCs and SF6 behave as reactive (sorbing) tracers in low carbon content sedimentary aquifers? This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5). Intellectual Merit: CFCs and SF6 are environmental tracers used to date recent groundwater (up to ~50 years). Because these compounds are relatively soluble, the current paradigm expects conservative (no sorption or degradation) transport of these compounds in aerobic, low carbon content (foc) aquifers. We posit that CFCs and SF6 act as reactive (sorbing) tracers in many low foc sedimentary aquifers ? in particular those that contain thermally altered carbonaceous matter (TACM). TACM examples include char, coal and kerogen. TACM occurs commonly in sediments deposited since the Devonian. Our preliminary experiments demonstrate that CFC sorption is sufficient to significantly retard CFC transport in low foc aquifers. This project will provide the first systematic assessment of the impact of different forms of TACM on CFC and SF6 sorption. The experiments will be completed for selected low foc sediments over an unprecedented concentration range of ~9 orders of magnitude. CM will be fractionated, quantified and classified using established methods. The isotherm models and parameters deduced will be used to evaluate the conditions in which significant retardation of these solutes are expected in low foc aquifers. Broader Impacts: The proposed project will provide support for a new collaboration between Drs. Allen-King and Sheldon, faculty members at neighboring and complementary SUNY institutions: Geneseo, a primarily undergraduate institution, and Buffalo, a PhD granting institution. This project will enhance educational opportunities through direct support of four undergraduate students and one PhD student. It will provide opportunities to develop connections through student exchanges between the institutions. The PIs will invite applications from qualified students with particular attention to soliciting participation from members of underrepresented groups. Benefit to society from this project will come through improved understanding of the reactive transport of moderately hydrophobic chemicals in groundwater and improved groundwater age estimates. This project will support economic stimulus through providing well paid positions for research students and valuable training that will enhance their technical contributions as they enter the workforce.
