AN AUTOMATED SAMPLING SYSTEM FOR LARGE SOIL COLUMN TRANSPORT STUDIES

An automated column effluent sampling system for large unsaturated soi l columns was constructed and evaluated The automated collection syste m consist of a programmable three-solenoid valve system that maintains a constant matric potential at the bottom of the soil column and peri odically switches column effluent from a waste receptacle to a samplin g vial. We compared the automated system to a traditional vacuum chamb er-fraction collector system that continuously sampled all column effl uent. Comparisons were made by measuring (H2O)-H-3 breakthrough curves (BTCs) generated by the two collection systems using the same intact soil columns. No significant differences were observed in (H2O)-H-3 BT Cs between collection systems. These results indicate that the automat ed collection system is effective for large column transport studies a nd provides additional advantages by maintaining effluent resolution ( sample volume), yet reduces sample size (numbers) and labor required f or sample collection.