Four Mile Creek is an important watershed in Southwestern Ohio, including floodplain deposits that have historically been used for agriculture. However, due to extensive anthropogenic use, it is difficult to determine pre-human geochemical norms. Organic carbon and nitrogen abundances are important for understanding the soil health overall, as well as providing important benchmarks for carbon sequestration. These geochemical datasets provide a unique advantage, as soil organic carbon reaches an accumulation equilibrium, wherein a soil will not accumulate more organic carbon past a certain threshold. This study examines historical organic carbon and nitrogen abundances along Four Mile Creek using time-calibrated samples to reconstruct historic organic carbon and nitrogen values in the area. Soils range in age from 50+- 20 years to upwards of 16,820 +- 1,010 years, which should provide enough range to pinpoint the time at which organic soil geochemistry equilibrium occurs. The timing of this equilibrium indicates how long soil will naturally recuperate lost organic elements, which is important for sustainable agriculture. The limits of the soil organic carbon equilibrium is vital for soil carbon sequestration efforts in order to provide reasonable sequestration estimates to combat climate change. Once these samples are processed, data will be combined with age calibration at-depth in order to construct an organic carbon/nitrogen age plot, which will allow for the accumulation equilibrium to be shown. This provides important context for understanding anthropogenic interference in soil development, along with potential maximums for soil carbon sequestration efforts. Additionally, it provides important measurements for the importance of sustainable agricultural practices.
Author(s): Samuel Kerr, Geology Major
Advisor(s): Jason Rech, Department of Geology & Environmental Earth Science
Abigale O’Connor, Department of Geology & Environmental Earth Science
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