Automated System for Collecting Multiple, Sequential Samples from Soil Water Percolation Samplers under Continuous Vacuum

Manually collecting a series of sequential, discrete water samples from soil water percolation samplers, or similar devices that withdraw water from unsaturated porous media under continuous vacuum, is a logistical challenge, though the resulting collection can provide valuable information on the dynamics present in both laboratory and field studies. This article describes a sequential tension autosampler (STAS) that executes such sampling automatically. The STAS operates on 12 volts direct current (VDC) and can be adapted for laboratory and field applications. A data logger was programmed to operate a series of solenoid valves, which direct soil water collected under tension to seven individual collection bottles. The number of sequential samples, sample period, start time, and between‐sample interval are specified by the user. The operator only need to attend the system periodically to transfer water samples to storage vials and program the next sampling sequence. In a laboratory study, the apparatus successfully collected samples overnight or over several days.