Sampling by the local Department of Environmental Quality (DEQ)

of the water in a small creek has revealed a steady concentration of a highly toxic chemical of 0.015 g/m³. At some distance upstream from the sampling point, the DEQ personnel have spotted a cylindrical concrete beam lying in the creek and it is suspected that the contaminating chemical has been leaching out of the beam into the water. The creek flows at a velocity of 0.2 m/s and its cross-section is 10 m². The concrete beam is 0.3 m in diameter and 1.8 m long. Assuming that the DEQ suspicion is correct, determine (a)

the rate of mass transfer of the chemical and

(b) the mass transfer flux of the chemical at the concrete–water interface.