A river segment can be idealized as two well$-$mixed pools joined by a plug$-$flow channel as sketched below. A seep from an old fuel tank maintains a contaminant concentration of $100\frac{g}{L}$ into the upstream pool. A tributary that is contaminant free joins the channel segment just above the second pool. The tributary water and channel water instantly mix. If the contaminant is subject to first$-$order degradation in this system with a kinetic constant of $\frac{0\mathrm{.}7}{?}$ day, calculate the steady$-$state contaminant concentration leaving the downstream pool. All volumes are constant. State all of your assumptions and communicate your work clearly.

$Q_{in}=10,000\frac{m^3}{d}ay$

$C_{in}=100\frac{g}{L}$

$Q_{\text{t}\text{r}\text{i}\text{b}}=1000\frac{m^3}{d}ay$

$V_1=1000m^3$

$C_{\text{t}\text{r}\text{i}\text{b}}=0\frac{g}{L}$

Stream Segment

Length $=600m$

Stream Segment

Area $=2m^2$