# Calculate the geologic sink and source of As (arsenic) at the lake bottom.

A situation with an industrial input of arsenic directly into the lake at 10kg/Day. The lake volume is 1.2 x 10^8 m^3, and the average depth is 10m. The river velocities are measured as 100 L/min at both the inflow and outflow points. Water samples taken from the rivers show incoming arsenic is 0.02mg/L and the outgoing arsenic is 0.5 mg/L. From the sample, the sedimentation rate in in the lake is estimated to be 200g/m^2 per year.

Calculate the geologic sink and source of As (arsenic) at the lake bottom assuming steady state.

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#### Solution Preview

Because,

Volume (V) of the lake = 1.2*10^8 m^3

depth (d) of the lake = 10 m

Therefore, surface area or area of the bottom of the lake,

A = V/d = 1.2*10^8/10 = 1.2*10^7 m^2

The sedimentation rate in the lake (Rs) = 200 g/m^2/year

Hence,

The ...

#### Solution Summary

The incoming arsenic = the outgoing arsenic, So + Ri + Ra = Si + Ro.

So = Geological source of arsenic of the lake

Ri = Incoming rate of arsenic

Ra = Rate of arsenic added

Si = The geologic sink

Ro = Outgoing arsenic rate