Field monitoring of solute and colloid mobility in a gneissic sub-catchment, South Australia

Collection of throughflow solutions and colloids from the vadose zone is difficult and commonly results in the collection of colloids and solutes unrepresentative of short-term temporal variations. This paper describes a technique for the simultaneous collection of both colloids and solutes. Modified capillary wick lysimeters were permanently installed in the vadose zone in an experimental subcatchment under native eucalyptus vegetation at Mount Crawford near Adelaide, South Australia. The mineralogy of colloids suspended in solutions collected from 3 separate lysimeters is presented. The mobility of colloids varies with landscape position, water availability and depth within the soil profile. The mineralogy of both the soil profiles and suspended colloids in throughflow is dominated by illite/mica and kaolin. For all but one site the amount of colloid mobilised is greatest for the A horizon. The average composition of solutions collected using the lysimeters are presented. After 1500 ml of solution had been transferred though the wicks, the wicks did not influence the passage of colloids or other soluble species.