A computer-controlled system for exposing field crops to gaseous air pollutants

A system is described for exposing an area of about 400 m2 of a normally-managed field crop of winter wheat to controlled concentrations of sulphur dioxide. The gas is released from pipes at a rate which can be varied by a microcomputer which also controls the monitoring of SO2 concentrations. The SO2 release rate depends on measured concentration and on wind speed. The system was operated continuously for several months. Examples of the variability of concentrations in time and space are given to show that close control of a predetermined SO2 concentration can be maintained for long periods over a wide range of atmospheric conditions.