Computer control for investigating water and chemical transport in a large isolated soil block

This paper describes the computer controlled data acquisition systems designed to obtain fine spatial and temporal resolution data of tracer in soil water within a large undisturbed soil block. Such information is desirable to help understand and model transport mechanisms in light of increasingly strict environmental pollution limits. The soil block was 5.4 × 3.4 × 1.2 m, instrumented in nine layers with time domain reflectometry (TDR) waveguides multiplexed using a PC; pressure transducer equipped tensiometers multiplexed using a datalogger and suction samplers connected to in situ flow-injection analysis systems controlled by a PC. A rainfall simulator capable of applying tracer to the block without altering the surface flux (which could range from 1 to 30 mm h −1) was controlled by a datalogger. Initial conditions when the soil block was subjected to a surface flux of 10 mm h −1 are presented along with an example of a chloride breakthrough curve to illustrate the nature of the data obtained from the soil block system. It is concluded that the integrated system described is a significant advance in working technology for field and plot scale tracer experiments because the spatial and temporal resolutions achieved are possible with a single person maintaining the system.