TRANSPORT OF MICROORGANISMS THROUGH SOIL

Microorganisms migrating into and through soil from sources on the lan d surface may cause a serious threat to both ground and surface waters . It has been estimated that microorganisms can migrate significant di stances in the field. Results from various studies suggested that pref erential flow through macropores, worm holes, cracks, and fractures is the main reason for such observations. However, a quantitative repres entation of this phenomenon has not been provided. Microorganisms migr ate through soil by advection and dispersion, while being subjected to effects of filtration, adsorption, desorption, growth, decay, sedimen tation and chemotaxis. Both laboratory and field investigations have c ontributed important information on bacterial movement in soils. Quali tative comparisons are generally transferable from laboratory to field situations. Quantitative agreement is much more difficult to establis h. Available mathematical modelling of microbial transport is limited in practical application because of the simplifying assumptions used i n its development.