Two types of installation of <scp>3D</scp> ‐printed Zero Tension Lysimeter for soil leaching and Water Bucket Model validation

Cristina, Ariza‐Carricondo Struyf, Eric Roland, Marilyn Gielen, Bert Vincke, Caroline [UCL] Janssens, Ivan A.

Quantifying and analyzing leaching water is essential to understand water and nutrient cycles and the vertical transport of elements through soils. Zero Tension Lysimeters (ZTLs) have been widely used to capture the soil solution leaching by gravity. This study designed and evaluated a 3D-printed ZTL (ZTL3D) with specific characteristics and materials to quantitatively capture dissolved element fluxes. By 3D-printing the ZTLs, we were able to include specific 3D structures and precise details in the design allowing samplers installation from the surface rather than trenches, and thus avoiding the need for installation trenches to remain open. The ZTLs3D connect directly with the surface, do not depend on secondary collectors, can be installed at any depth and samplers are easily retractable when dismantling the field set up. The material used, Nylon 12, was tested for DOC release. The ZTL3D design was printed in two different external shapes while characteristics and internal design were identical. The difference in external shape was to study the effects of two contrasting types of installation: a cylindrical sampler for vertical installation (by soil coring from the surface) and a rectangular samplers for horizontal installation (from a pit or a trench wall). We installed them at different depths (2, 30 and 75 cm) in a forest soil and conducted rainfall simulation experiments. A Water Bucket Model (WBM), created to calculate the water drainage fluxes that the ZTLs3D should collect, reproduced very well the variation in soil water content measured by soil moisture sensors installed adjacent to the ZTLs3D at 16, 30, 50 and 75 cm depth. Drainage fluxes simulated by the WBM showed that the vertical installation performed better at collecting water at all depths than the horizontally installation, but overall the ZTLs3D failed to collect the simulated amounts of drainage water. Nonetheless, the ZTLs3D did collect leachate water, enabling their chemical analysis. Combining the concentrations in the water collected by the ZTLs3D with the modeled drainage fluxes does allow estimation of DOC- and elemental leaching rates. This article presents the novel design of these two types of ZTLs3D because future improvements may result in better performance, and discusses their (dis)agreement with the modelled WBM fluxes.