Detecting Pollutants Using Vibrations : Laser Doppler Vibrometry as a Non-Invasive Soil Organism Health Monitoring Method

Abstract: Due to a lack of in-situ methods capable of detecting sub-lethal effects of pollutants on soil organisms, many polluted environments are not identified prior to pollution-induced changes in the soil fauna. Therefore, there is a need to develop new non-invasive methods to measure the health of soil organisms. This study aimed to assess to what extent surface borne vibrations can inform about ant health effects from exposure to sublethal doses of a pesticide (imidacloprid). Twelve ant colonies were set up with artificial nests and fed a glucose and imidacloprid solution (0.01 mg/L, 0.1 mg/L, 1 mg/L and 10 mg/L imidacloprid). After two days, five random ants were placed in an arena where the vibrations were recorded in five one-minute blocks using a Laser Doppler Vibrometer (LDV). No significant difference was found in activity per minute between the different concentrations, although there was a measurable increase in mortality between the concentrations from the second day of exposure to the fifth. Even so, the LDV may still be a viable method, as it clearly recorded vibrations caused by ant movement. If more ants were recorded for longer periods, and more replicates were used, it seems likely the method would have been sensitive enough to detect the effect of the studied pesticide. With an improved experiment design, using the LDV for this purpose may be possible, and the current lack of such a method necessitates further research on the subject.