During this campaign, we collected groundwater samples for DNA and RNA extraction as well as geochemical analysis. Rotary drilling was performed to a depth of 45 meters in the subsurface redox transition zone in Van Phuc. We also collected sediment samples for comprehensive omics analyses and initiated in situ incubation experiments to enrich microorganisms capable of iron reduction and anaerobic methane oxidation. We’re thrilled to process these valuable samples in the lab and uncover new mechanisms driving arsenic mobilization from this work!