PARAMETERIZING THE EQUILIBRIUM DISTRIBUTION OF CHEMICALS BETWEEN THE DISSOLVED, SOLID PARTICULATE MATTER, AND COLLOIDAL MATTER COMPARTMENTS IN AQUEOUS SYSTEMS

The manner in which a chemical material partitions among the dissolved (D), particulate (P), and colloidal (C) phases affects both its chemical and physical behavior in the aquatic environment. The fractions of the chemical that are present in each of these three phases will be determined by the values of two simple parameters, K(p)S(p)/alpha(w) and K(c)S(c)/alpha(w). The variables K(p) and K(c) are the particle/water and colloid/water partition constants (mL/g), respectively, S(p) and S(c) are the volume concentrations of particulate arid colloidal material (mg/L), respectively, and alpha(w) is the fractional volume of the system that is aqueous. This parameterization allows a rapid overview of how partitioning (1) changes as a function of chemical partitioning properties and water type, (2) affects apparent partition constants (i.e., K(p)app values) computed between the particulate phase and the remainder of the system, and (3) causes K(p)app values to become independent of chemical properties at high values of K(c)S(c)/alpha(w).