Jon Golla Researcher Feature on Critical Zone Hydrology

Photo credit: Laura Crossey

Introduction

My name is Jon Golla and I am a Ph.D. candidate in the Department of Geology at the University of Illinois at Urbana-Champaign. I study fluid-rock interactions in the Critical Zone. My current work combines metal(loid) stable isotopes (i.e., Li and Si) and reactive transport modeling to characterize the biogeochemical and transport pathways that constitute weathering exports in headwater hillslope catchments.

How did you end up in the field of Hydrology?

My interest in hydrology stems from my unfamiliarity with potable water as a resource growing up. I grew up in a small town in the Philippines called Baras, where tap water was safe enough to wash dishes or brush your teeth with but not suitable for consumption due to a lack of proper management of water resources and quality. This past experience conditioned me to believe that an undrinkable water supply was common. Unfortunately, I maintained this mentality as a teenager when my family and I immigrated to the United States. I would later spend the last two years of high school in Jakarta, Indonesia, where similar concerns about the municipal water supply in my hometown also persisted. Although it was a short period of time, my environment did not allow me to reflect upon and contest my preconceived notions of what tap water is and should be. When I returned to the United States to begin college, I slowly began to dispel this perception. Up until this point, I had never even thought about how a water resource could become impaired. This reflection led me to a deeper continuing curiosity in wanting to know what factors controlled water quality and chemistry.

What do you call yourself, mainly? Hydrologist? Biogeochemist? Ecohydrologist? Hydraulic engineer? Other?

The way I present my scientific background changes depending on who I am talking to. To those outside of hydrology, I generally introduce myself as a hydrologist. To hydrologists, I have introduced myself as an aqueous geochemist, a hydrogeochemist, and a reactive transport modeler. I once considered the label isotope hydrologist but realized it may be confusing since the isotope systems I study are not commonly used in hydrology but more so in Earth surface geochemistry.

Give us an elevator pitch of your last paper

My last publication is entitled ‘Subsurface weathering signatures in stream chemistry during an intense storm’, which can be fully accessed through this link (https://doi.org/10.1016/j.epsl.2022.117773). In this contribution, my co-authors and I demonstrate that stream lithium isotope ratios record continued subsurface routing of water and water-rock reactivity during an intense storm that was fed by an atmospheric river. We initially characterized the transport of the storm water delivered to the small headwater hillslope catchment. Novel measurements of rock moisture allowed us to show and track the subsurface infiltration of the water from the event, which is accompanied by an increase in water table elevation. However, the water isotope data show that the storm only reached the shallow vadose zone and indicates that the event water mixed with previously stored rock moisture and displaced stored water to groundwater. In conjunction with this observed subsurface infiltration, the continuation of subsurface reactivity is evidenced by temporal consistency of groundwater Sr and Li isotope ratios before and during the storm. Despite the intensity of the storm, event concentration-discharge patterns of rock-derived solutes appear to be an extrapolation of long-term behavior.

We employ lithium isotope ratios of streamflow to provide greater sensitivity to reactive transport processes that occur in the hillslope during the storm. The general increase in relative lithium concentrations and decrease in isotope ratios cannot be explained by mixing and thus transport processes alone. We apply and update a previously established reactive transport model to interpret these data, which are a result of the combined effects of a larger source area of lithium accessed by the stream and shorter subsurface residence times.  As the hillslope fills during the storm, an elevated water table accesses and mobilizes lithium from further upslope (i.e., thicker vadose zone) and groundwater flows faster, leading to delivery of less-reacted signatures to the stream. In other words, stream lithium isotope ratios reflect shifts in the balance between contributions from lithium solute source (vadose zone) and sink (saturated zone) areas as a result of transient hydrological perturbation.

Are there aspects of your work that allow you to be creative?

Yes, I consider making figures as a creative outlet of my research. Over the years, I’ve had a lot of fun finding my style for designing graphics. The way I present my figures now is a culmination of elements I’ve borrowed from other styles I’ve observed in papers and presentations. Figure design was my primary motivation for learning how to use a programming language and vector-image manipulation software because I wanted tools that allowed me to streamline the font, color schemes, and subtleties that defined my style. I try to carry these details over to my presentation material, which has led to an obsession in creating a LaTEX template for posters and talks (yet to be achieved…). In any case, I look to keep adjusting my style as I find (subjectively) more interesting and efficient ways of visualization.

Share a funny story from the field or the lab

As a master’s student in the Earth and Planetary Science department at the University of New Mexico, I conducted fieldwork in the Jemez Mountains and investigated natural trace metal input of the local geothermal system to the Jemez River. During one visit, I carried out a spatial survey of water quality parameters over a 50-km reach of the Jemez River. Along reaches of the river where a water sample was collected, I made measurements every 50 m and the best way to do so was to walk in the river. There came a point where being in the river was not preferable because the water was relatively deep. I emerged from the river and was glad to take a break until I realized a group of three dogs who appeared to be guarding private property were running towards me. It didn’t take me a while to realize I should also start running. I ran along the river bank for some time until I decided to jump back into the water. In the scientific presentations that featured the data from this field campaign, I would blame the dogs for the lack of spatial resolution in my data.

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