A lake contains 2 x 105 m3 of water and is fed by a river with a feed rate of 9 x 104 m3/year. Evaporation across the surface takes away 1 x 104 m3/year. The lake feeds into the downstream stretch of the river at 8 x 104 m3/year. The upstream river is polluted with mercury at a concentration of 6.0 gm/L (i.e. 1 L has 6 gm mercury and 994 gm of water). Only water evaporates from the lake surface. Assuming steady state, continuous flow:
a. Draw the flowchart for this system.
b. Calculate the concentration of mercury in the downstream river.