Abstract :
It was established in Part 1 that potential impediments to movement of colloids through soil can be subdivided into straining and filtration, depending on whether a particle has a dimension similar to pores (leading to physical trapping) or much smaller. Information about size distributions of particles was also presented in Part 1. Owing to the dependence of colloid or particle capture processes on the relative size distributions of the particles and pores, information about pore sizes distributions has been derived here (Part 2) from hydrological equations. Various approaches to extending this mathematical treatment to indicate when particles would be trapped by necks or irregularities in the pore are also presented. Results suggest that protozoan microorganisms (such as Cryptosporidium and Giardia) are the only colloidal contaminants with sufficiently large diameter to have their movement restricted by physical straining in the soil pores when water drains from the soil under gravity, but if the soil is very wet (near to saturation) even these will move without restriction.
