Accurate estimates of air-water gas exchange are fundamental to quantifying many biogeochemical processes, including aquatic metabolism and greenhouse gas emissions. Gas transfer velocity (k600, m d-1), which can also be expressed as the closely related depth-dependent gas exchange rate (K600, d-1), controls gas exchange and can be estimated via multiple approaches (e.g., tracer-gas experiments, diurnal DO timeseries, direct flux measurements), each of which have unique strengths and limitations. Here, the utility of a new approach using paired diurnal timeseries of dissolved oxygen (DO), pCO2, and pH is explored to estimate k600 in two large temperate rivers, the St. Joseph River, Indiana and Connecticut River, Connecticut. Estimating k600 from time-series of oxygen and carbon under a wider range of environmental conditions, including higher and lower alkalinities, seasons, winds, and ice, provides a broad scope to rigorously understand the physical and biogeochemical controls on gas transfer. Results from intensive observational campaigns will be shown and future research directions will be discussed.