THE PERCOLATION OF RAINWATER THROUGH SOIL DEMONSTRATED BY FLUORESCENT DYES

Summary Twelve fluorescent dyes were tested in the laboratory for their stability under conditions of alternate wetting and drying, and persistence of fluorescence in the presence of an acid soil. The strongly fluorescing Pyranine cone, was most suitable for tracing water percolating through soils. In the field this dye could be detected in the soil after several months and couldbe photographed in ultraviolet light. The greater percolation of water against tree trunks and lateral movement in the humus layer were demonstrated.