ANALYZING DISSOLVED CARBON IN SHALLOW GROUNDWATER

Interest in the global carbon cycle is at an all-time high due to efforts to fully understand the impact of humanity on our changing climate. Extensive work has been completed to document and quantify carbon in various terrestrial and marine sources and sinks. However, groundwater’s place in the carbon cycle has been surprisingly under-researched, considering that groundwater often serves as an important connection between many sources and sinks of carbon. Despite this important role, research has been primarily focused on hydrocarbon contaminants rather than naturally occurring dissolved carbon that would play a role in the global carbon cycle.

This study seeks to address the paucity of information regarding carbon within groundwater itself rather than contaminants or biota. The Brazos River Alluvium Aquifer, an unconfined shallow aquifer was chosen as the study area as its connectivity with the surface allows for relatively rapid recharge and demonstrates changes in carbon concentrations dependent on geography. Water samples were analyzed through field and lab methods for dissolved carbon concentrations (both organic and inorganic), carbon isotopes, nutrients (nitrates and phosphates), as well as basic water chemistry. Samples were collected using an existing network of privately owned wells and a recently acquired Geoprobe 6620 DT equipped with in situ water sampling hardware.

The gathered data are used to better understand the role and presence of carbon within this specific groundwater system. Understanding this system is the first step in understanding similar systems and will help inform research efforts into understanding deeper systems as well. Quantifying the sequestered carbon in ground water will help give a more complete picture of the naturally occurring carbon cycle and will help us to understand the role we have played in altering it.