ABSTRACT
This chapter describes the kinetics of open systems, with emphasis on the two main kinds of open reactors: plug-flow and completely mixed systems. It also describes applications of reactor principles to biogeochemical processes in aquatic systems and simple mass-balance models are presented for nutrients, organic contaminants, and alkalinity in lakes. Aquatic chemists often use equilibrium models for aquatic environments, but natural waters are open systems that exchange matter and energy with their external environment. Engineered systems like wastewater treatment plants usually are operated as continuous-flow open systems. The chapter illustrates the concepts of flow-through reactors are extended to multicompartment systems, and the use of matrix methods to model their behavior. Compared with other loss and transport processes, rates of sorption and desorption to and from suspended matter are often thought to be rapid. The treatment of tracer kinetics for compartment systems is only a brief introduction to a complicated subject.
