Submitted to: Communications in Soil Science and Plant Analysis
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 8, 2005
Publication Date: May 1, 2006
Repository URL: http://sand.nwisrl.ars.usda.gov/publist.shtml
Citation: Lentz, R.D. 2006. Automated system for collecting multiple sequential samples from soil water samplers under continuous vacuum. Communication in Soil Science and Plant Analysis. 37:1195-1203. Interpretive Summary: Leaching of soil nutrients, pesticides, and other organic solutes from agricultural soils into groundwater threatens human and environmental health. The dynamic character of soil solute chemical and transport processes is difficult to study. Such research requires that a series of individual solute samples be collected manually from tension lysimeters (soil water samplers that extract water under continuous vacuum). This timely, manual sample collection is labor intensive and expensive. A Sequential Tension Auto-Sampler was developed to automatically collect a series of sequential, discrete water samples from soil water percolation samplers, or similar devices, that withdraw water from unsaturated porous media. This apparatus will allow soil scientists and engineers from ARS, university, industry, and environmental consulting organizations to perform this sampling more conveniently and economically. Resulting research will provide better management guidelines for reducing soil nutrient and chemical drainage losses from agricultural soils.
Technical Abstract: 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 paper describes a sequential tension autosampler (STAS) that executes such sampling automatically. The STAS operates on 12 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.