A system and method for controlling oxidation of sulfites in a slurry. The system includes a tank having an inlet for receiving a slurry used in wet flue gas desulfurization. The tank also includes an inlet for receiving a gas. The inlet for receiving the gas is configured so that at least a portion of the gas received in the tank is dispersed through at least a portion of the slurry received in the tank. A sensor is configured to measure a sulfite concentration S1 of the slurry received in the tank. In some embodiments, the sensor is a sulfite analyzer. In other embodiments, the sensor is a virtual analyzer. The system includes a controller. Software executing on the controller generates a signal indicative of an adjustment of a flow rate of gas into the tank based at least in part on the sulfite concentration S1.