Animal wastewater lagoons nearby concentrated animal feeding operations (CAFOs) represent the latest tendency in global animal farming, severely impacting the magnitude of greenhouse gas emissions, including nitrous oxide (N(2)O). We hypothesized that lagoon wastewater could be supersaturated with N(2)O as part of incomplete microbial nitrification/denitrification processes, thereby regulating the N(2)O partitioning in the gaseous phase. The objectives of this study were: (i) to investigate the magnitude of dissolved N(2)O concentrations in the lagoon; and (ii) to determine the extent to which supersaturation of N(2)O occurs in wastewater lagoons. Dissolved N(2)O concentrations in the wastewater samples were high, ranging from 0.4 to 40.5 microg N(2)O mL(-1). Calculated dissolved N(2)O concentrations from the experimentally measured partition coefficients were much greater than those typically expected in aquatic systems (< approximately 0.6 microg N(2)O mL(-1)). Knowledge of the factors controlling the magnitude of N(2)O supersaturation could potentially bridge mass balance differences between in situ measurements and global N(2)O models.