A railroad tank car is derailed and ruptured. It discharges 380 m^3 of the mixture of ammonia (NH3) and ammonium ions (NH4+) into the Mud lake drain. As shown in figure below, the drain flows into Mud lake which has a liquid volume of 40, 000 m^3. The water in the creek has a low rate of 0.1 m^3/s, a velocity of 0.1 m/s. Assume that the spill is short and fast enough to be treated as the one-time injection (a pulse) of the discharge into the lake, that the lake behaves as a flow balanced CSTR, and that the discharge is nonreactive. The figure depicts a single stream flowing into a lake, and then flowing out the other side of the lake. Estimate the time it will take to flush 99% of the discharge from the lake.

The figure depicts a single stream flowing into a lake, and then flowing out the other side of the lake.

(1) Estimate the time it will take to flush 99% of the discharge from the lake.

(2)Immediately after the spill, the lake, completely mixed, has a pH of 8 and the total molar concentration of nitrogen species (NH3 and NH4+) is 7.1×10-4 mol/L. what is the percentage of aqueous NH3 in the lake?

(3) If we stop the entry of the fresh water from the creek, which means there will be no water coming in or out of the lake. However, due to the transfer or evaporation of NH3 from the lake into the atmosphere, we expect a decrease in contaminant concentrations. We know the Henry's constant (KH) is 57 mol/(L·atm) and the partial pressure of NH3 in the atmosphere is 5.0×10-10am. The lake eventually reached the pH of 10. Determine the removal rate (%) of ammonia/ammonium ion contamination due to the evaporation.