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. 

With the Ohio River Basin covering over 204,000 square miles and being 981 miles long, it contains a wide range of lithologies. The basin has a broad area of carbonate rocks that allows us to assess Freshwater Reservoir Effects. Also, there is a wide range in slope, land use, soils, and other factors that may also influence alkalinity. 

Data Extraction

USGS water quality samples were used to find alkalinity, discharge, and specific conductance values for sites within the Ohio River Basin that were also located within limestone-dominated regions.

Graphing

Initial research involved graphing each individual stream within the Ohio River Basin to determine a relationship between alkalinity, specific conductance, and stream discharge. Data was then used to assess monthly variation in alkalinity and specific conductance values. Monthly water chemistry values were averaged and graphed with the inclusion of one sigma standard deviation. Specific conductance and alkalinity values for individual streams were graphed to examine the reliability of using specific conductance in place of alkalinity.

Using GIS

ArcGISPro was used to create two maps: One displays the relationship of alkalinity and discharge values with the other showing the relationship of specific conductance and discharge values. Both maps show study sites within limestone-dominated regions of the Ohio River Basin.

Data about selected streams in ascending order below

Results indicate that there is spatial variation in alkalinity values found within the Ohio River Basin. Although the presence of carbonate lithology in the watershed is likely the primary cause of high alkalinity values, other factors are also important. Stream hydrology was also found to play a role in the alkalinity and specific conductance values. Graphs above display alkalinity and specific conductance for streams with different discharge volumes. All of the selected graphs display a negative relationship between alkalinity and discharge as well as between specific conductance and discharge. When comparing the smallest (lowest discharge stream) to the largest (highest discharge stream), Clifty Creek was seen to have higher R-squared and mean values, likely due to the greater role of base flow to stream discharge. 

USGS data will be used to analyze possible causes for the spatial variance in alkalinity and specific conductance values in Indiana.

The relationship between alkalinity and discharge will be explored to determine the influence of discharge and stream size on alkalinity values.

Aquatic mollusk samples will be collected for radiocarbon dating from watersheds of different sizes within the Ohio River Basin to determine if freshwater reservoir effects correlate with stream alkalinity and specific conductance values.

Career and Self Development 

Undergraduate attended conferences to discuss research as well as collaborate with USGS employee. 

Leadership 

Undergraduate was responsible for leading research and relaying information of progress during weekly lab meetings. 

Critical Thinking 

Decision-making and use of previously learned knowledge was applied to explanations of spatial variations in values. 

Technology

Microsoft Excel and ArcGISPro were utilized in research analysis, allowing for exploration of new software. 

Thank you to the Undergraduate Summer Scholars program for funding research during the summer of 2024. 

Citations:

Rech, J. A., Tenison, C. N., Baldasare, A., & Currie, B. S. (2023). Radiocarbon Dating and Freshwater

        Reservoir Effects of Aquatic Mollusks Within Fluvial Channel Deposits in the Midwestern

        United States. Radiocarbon, 65(5), 1098–1117.doi:10.1017/RDC.2023.93

Map Citations:

Horton, J.D., 2017, The State Geologic Map Compilation (SGMC) geodatabase of the conterminous United States (ver. 1.1, August 2017): U.S. Geological Survey data release, Retrieved from https://doi.org/10.5066/F7WH2N65.

National Weather Service, (1999). U.S. States and Territories, [Shapefile}]. National Weather Service. Retrieved from https://www.weather.gov/gis/USStates

U.S. Geological Survey, (2023). NHD Rivers, Streams, Canals, etc, [Shapefile]. National Hydrologic Dataset. Retrieved from https://www.indianamap.org/datasets/INMap::nhd-rivers-streams-canals-etc/about

U.S. Geological Survey. Water Quality Samples for USA: Sample Data, [Excel]. U.S. Geological Survey. Retrieved from https://nwis.waterdata.usgs.gov/nwis/qwdata