Visualization of Flow Pathways in Degraded Peat Soils Using Titanium Dioxide

Abstract

Dye tracing is a valuable method for studying the flow patterns in soils. However, limited information is available on water flow and solute transport pathways in dark‐colored peat soils because the frequently used Brilliant Blue FCF dye does not visibly stain the soil. In this study, we were aiming at testing the suitability of TiO2 as a dye tracer for dark peat soils. The dye tracer experiments were conducted in differently degraded peat soils by applying a TiO2 suspension (average particle size 0.3 μm; 10 g L−1) in a pulse of 40 mm. A Br solution was additionally applied as a comparison to evaluate the suitability of TiO2. The TiO2 suspension clearly marked the flow and transport pathways. The distribution of TiO2 in the soil profile, as analyzed from 5‐ by 5‐cm grid cells, compared with the Br patterns. It was found that both tracers took the same preferential flow pathways, but the lateral spreading of Br was more pronounced, which was attributed to the limited access of TiO2 particles to the fine pore system. Both tracers showed a strong spatial correlation according to the cross‐semivariance analysis, confirming the suitability of TiO2 as a dye tracer in peat soils.