Variation in the height to which tracer is moved by splash during natural summer rain in the UK

Abstract

The relative capacity of rain events to transport material between ground level and a given height can be compared using a splashmeter. This consists of a central pole carrying a sheet of strong absorbent paper, surrounded by a ring of small dishes containing cellulose-reactive ultraviolet fluorescent dye. After rain, the dye coverage on the paper gives a permanent record of the total dye moved to any zone above the reservoirs. Results were comparable when the dishes were 15–25 cm from the central axis, but became more variable at greater distances. Results from replicate splashmeters were concordant, and there appeared to be a linear relationship between the results obtained using an open dye surface and dishes filled with glass fibre. Splashmeters were exposed at Long Ashton near Bristol, from April to August, during the period 1985–1989. The relative amount of splash projected above a given height during an individual rain event had a Weibull (extreme-value) probability distribution. The parameters of this distribution varied systematically with height. This allows, for example, calculation of the extent to which healthy plant tissues at any given height were at risk from splash-dispersed disease propagules produced lower down in a crop.