Question $8$

Beijing can be approximated as a square with an area of $16,800k{m}^2.$ The upwind concentration of $P{M}_{2\mathrm{.}5}$ is $20\frac{g}{m^3},$ and the observed concentration is $671\frac{g}{m^3}.$ Assume that the mixing depth is $400m.$ If the wind speed is $2\frac{m}{s}$ directed at one edge of the square, estimate the PMs emission rate$-$in$-$Beijing in $k\frac{g}{s}.$ You may assume that the system is at steady$-$state and that all $P{M}_{2\mathrm{.}5}$ is of primary origin in the wintertime.