Problems of solute transport involving sequential first-order decay reactions frequently occur in soil systems. Examples are the migration of radionuclides, in which the chain members form a first-order decay reaction, and the simultaneous movement of various interacting nitrogen species. The CHAIN computer code may be used to evaluate analytical solutions describing the simultaneous convective-dispersive transport of up to four species involved in such a consecutive chain reaction. Evaluation of the analytical solutions is not straightforward but requires, among other things, the calculation of complex complementary error functions. Application of CHAIN to problems of solute transport is illustrated in two examples, one dealing with radionuclide transport and one involving a nitrification decay chain.
M. Th. van Genuchten. 1985. Convective-dispersive transport of solutes involved in sequential first-order decay reactions. Computers and Geosciences. 1985. 11(2):129-147.