Quantification of raindrop kinetic energy for improved prediction of splash-dispersed pathogens

ABSTRACT An electronic sensor, based on a piezoelectric transducer, was tested in the laboratory using simulated raindrops, and in natural rainfall. Data were also collected for splash dispersal using tracer dyes in laboratory experiments and the Long Ashton splashmeter in field experiments. Droplets impacting on sensor produce sound waves that are detected by an omnidirectional microphone sealed within an acoustic chamber. An electrical charge, proportional to the sound wave, is produced by the microphone and is converted to a categorical scale and then stored to provide an accumulation of impacts over a specified period of time. Calibration of the sensor was done using single-droplet impacts of known mass and impacting velocity. A linear relationship was shown between the categorical scale and the kinetic energy of impacting droplets (adjusted r(2) = 0.99). The best relationship fitted between splash dispersal from dye cup, and kinetic energy was a second-order polynomial (adjusted r(2) > 0.99). Splash height, recorded by the Long Ashton splashmeter during 41 natural rainfall events, was correlated closely with sensor output (adjusted r(2) = 0.87). Our studies indicate that the sensor provides quantitative data which could be incorporated into disease management systems to provide estimates of inoculum dispersal gradients within crop canopies.