Katie Larkin '22

Katie Larkin '22: Research with Keck Geology Consortium, Summer 2021

This summer, I was granted the opportunity to do research here in Rockbridge County as part of a Keck Geology Consortium Advanced Project. With Professors Hinkle and Lyon as leaders, myself and 8 other students from various colleges delved into a two-pronged project focused on water, soil, and sediment quality in the Shenandoah Valley. All of us participated in the fieldwork and data collection for the first two weeks, but we narrowed our scope during the next two in order to develop and refine our individual theses. This experience exposed me to real research (a rarity during COVID!), encouraged collaboration between like-minded students, and made for a truly great start to my work-filled upcoming months. We did a lot of stuff, so I've tried to summarize it all!

Professor Hinkle's 4 students focused on the presence of manganese in the Shenandoah Valley's springs and soils. Aqueous manganese has been linked to developmental delays, lowered IQ, and other health risks. Notably, Mn in a solid phase does not pose a similar health risk! High aqueous Mn values were observed in several Rockbridge County wells during a 2018 study. By collecting spring water samples and soil cores, we were, broadly, able to determine whether it is present in the Shenandoah Valley, and to what extent. We travelled to numerous sites and collected a multitude of samples, many of which are actively being processed using ICP-OES XRF, XRD, SEM, etc. In addition to collecting samples, we measured various field parameters (pH, temperature, dissolved oxygen, and specific conductivity) at each site.

Professor Lyon's 5 students, me included, worked on a series of dams in Rockbridge County. Our goal was to create a suite of geochemical, stratigraphic, and historical data based on the contents and properties of legacy sediments, or the sediments that collect behind active dams. Upon the dam's removal, these sediments can be incised and remobilized as local base level decreases. We created vertical legacy sediment profiles at each site by locating banks upstream of the dam structure and sampling them in intervals. Several dam sites were still active; for those sites we used a lake corer and a ‘claw' sampler to grab sediment cores and surface samples near the dams. These sediments are actively being processed for their heavy metal contents, TOC (total organic carbon), total nitrogen (TN), and respective isotopic values using the EA/IRMS. We hope to correlate results between transects and create an understanding of land use and anthropogenic activity for the region by identifying distinct stratigraphic sequences! In addition to the sediment, we collected and processed water samples from behind the dam structures in order to locate any stratifications (which is associated with aqueous manganese and iron). Our work was very hands-on and involved a lot of time spent in waders and/or canoes!

Between the two groups, we consistently worked on improving our lab notebook skills by learning how to translate our observations to concise notes, drawings, and figures. We spent long days collecting field data and processing it back in the W&L Geology Department's labs. That way, we became well-accustomed to the demands of a research career...field and lab work are both equally important and require lots of time and effort!

Following this enthralling 4-weeks in the field, I built on my research experience by collecting data for my own thesis. Professor Lyon and I built on the Chantal Iosso's 2020 thesis; her work examined channel changes immediately following the removal of the Jordan's Point Dam on the Maury River, and I repeated some of her work in order to determine long-term change in the channel. We recreated a series of 8 cross sections using a total station and GPS unit, enabling us to examine changes in channel geometry between 2019 and 2021. Using a gravelometer, we performed several channel bed grain size analyses in order to check for changes in competency and/or mobilization of material downstream. We also began processing sediment samples, both from Jordan's Point and from other sites. This work is ongoing and will continue during the year, but this summer allowed me to truly focus on building my research skillset. I feel that I have gained many useful and marketable abilities, all of which will serve me well as I transition from undergraduate to graduate studies.

Supported by the Keck Geology Consortium and the Edgar W. Spencer '53 Geology Field Research Fund