The partition or distribution coefficient Kd relates the amount of solute sorbed on the soil to the amount of chemical that is dissolved in the water. Kd is defined as the product of the organic carbon (foc) content and, organic carbon – water partition coefficient (Koc). The coefficient is a relative measure of the hydrophobic nature of the solute. This property is very important when evaluating the fate and transport of contaminants. Typical values of foc range from 0.01 to 0.06.
How to use it:
Check the radio box next to ‘Retardation’ to simulate the retardation of a solute due to biochemical processes or soil:water partitioning. By default, a retardation factor of 1 is used during simulation. Update the value in the text box next to ‘Retardation Factor’, or select the radio box next to ‘Partitioning Kd:’ to use a partitioning coefficient to simulate partitioning of a solute to the solid (sorbed) phase during transport. If a soil density (g/m3) is known, check the radio box next to ‘Soil Particle Density:’ and enter the known value in the provided text box.