Mentor(s): Jason Rech, Ph.D.

Aquatic mollusk shells found in fluvial deposits can be radiocarbon dated to reconstruct climatic and environmental change. Unfortunately, aquatic mollusk shells can suffer from 14C reservoir effects if there are carbonate rocks in the watershed. Radiocarbon reservoir effects in streams in Ohio have been found to be as much as 1,300 years. In an effort to understand potential radiocarbon reservoir effects in streams in the midwestern US, this study examined alkalinity and specific conductance in streams within the Ohio River Basin. Data provided by USGS for the Ohio River Basin was used to examine relationships between discharge, alkalinity, and specific conductance for 65 site locations. ArcGIS was then used to examine spatial variability and relationships across the river basin. High alkalinity values (>300mg/L) were found in the lower midwestern states with carbonate platform rocks such as Indiana and Ohio and suggest that radiocarbon reservoir effect may be in the range of 1,500-2,000 years in some watersheds. Surprisingly, alkalinity values were much lower in streams within carbonate watersheds such as the Appalachian Mountains in Tennessee. Results also indicate that streams with lower discharge are more likely to have higher alkalinity values and therefore greater radiocarbon reservoir effects. Future work will determine how the presence of limestone in a watershed may be quantified using stream chemistry. Implications from this study will help in reconstructing a more accurate depiction of climate and environmental change through the use of 14C dating aquatic mollusks.

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