An automated sampling system for large soil column transport studies

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