In this work we develop, via volume averaging, the macroscale transport equation for a reactive chemical species undergoing a heterogeneous reaction with first- order kinetics. We describe the closure problem required to predict (1) the effective macroscale reaction rate, and (2) the effective dispersion tensor from the microscale geometry, chemical, and physical properties of the media. The effective parameters are computed for a 3D simple unit cell. Particular attention is given to the influence of...