Methylmercury (MeHg) is a bioaccumulative neurotoxin, dangerous to human health even at trace levels. In inundated soils, MeHg is formed from inorganic mercury by mercury-methylating microorganisms; a process termed methylation. Demethylation, by contrast, converts MeHg into less-dangerous inorganic mercury, and also occurs via microbial activity throughout the aquatic soil profile. Rice grains can be contaminated with MeHg when grown in soils where methylation rates are high; human exposure to MeHg is thus a serious public health concern in places where rice cultivation, high rates of consumption, and soil mercury (Hg) contamination overlap. Our research aims to better understand the soil conditions that favor demethylation over methylation – this information can then be used to reduce rice grain contamination through agricultural practices or rice breeding programs. Specifically, our research focuses on the role of oxygenation and carbon root exudates on the net MeHg accumulation throughout the soil profile. Rice plants grow in flooded, oxygen-free (anoxic) soils, but their roots can leak oxygen (making the rice rhizosphere oxygenated in varying degrees), as well as carbon root exudates. Our project simulated both fully oxic and transiently-oxic (transition) zones, with two different levels of root exudates; we use isotopic tracers to assess respective methylation and demethylation rates in all four treatments in both the vegetated (rhizosphere) and non-vegetated (bulk) soil. Carbon root exudates have been collected from hydroponically-grown rice variety M-206, and can be applied to different soil zones via tubules. Oxygenation of the soil can be measured with mm-scale optode imagery, which allows delicate testing of various oxygen-introduction designs. My role in this interdisciplinary project has been to develop, scale-up, automate, and verify the accuracy and dependability of root-oxygenation and root-exudate introduction systems to be used in upcoming experiments.