Depth function of manganese (Mn) concentration in soil solutions: Hydropedological translocation of trace elements in stratified soils

Abstract

Periglacial cover beds are an important trigger of slope-water paths in sloped terrain of the midlatitudes. Most hydropedological studies focus on the quantitative analysis about the interrelation between subsurface layering and runoff processes at the slope scale. In this research we emphasis on a qualitative environmental geochemical analysis of trace elements and dissolved organic carbon in a small forest hydrological study area in the central parts of the subdued mountains of Germany (Location: KrofdorferForst, +50° 41' 3.69", +8° 38' 38.87"). The main objective is to assess the effect of lithological discontinuities of stratified soils within the depth functions of trace elements concentration in soil solutions (soil water and its dissolved and mobile fraction in a vertical distribution). Lorz (2008) show that depth functions of manganese (Mn) are characterized by strong pedogenic dynamics, analysing a shortened sequential extraction of solid soil material. We investigated the hypothesis that lithological discontinuities act like aquicludes. Therefore we expect abrupt changes within the depth function of manganese as a result of such water-blocking effect (= geochemical barriers) as a consequence of mobilization under wet soil conditions. In a preliminary case study we sampled soil solutions from three different plots within a 400m-toposequence. We use in situ trench installed suction lysimeters with ceramic tips (Irrometer Soil Solution Access Tube) to extract soil water samples each 20 cm from top-(10 cm) to subsoil (110 cm). For geochemical element analysis we use an inductively coupled plasma mass spectrometry (ICP-MS). The results: A clear character of abrupt changes within the depth function could be illustrated for most of the plots. For example, at the upper slope plot a contrast of the depth function is from 1013 ppb mean concentration at 50 cm profile depth to 290 ppb mean concentration at 70 cm profile depth (17 month sampling period). To conclude, these results demonstrate that hydrochemical quality and translocation processes of soil solutions determining an interrelation between subsurface layering and run off processes-respectively could be seen as an environmental consequence of it.

How can we model subsurface stormflow at the catchment scale if we cannot measure it?

“…For instance, generation of SSF on low mountain ranges in middle Europe is strongly influenced by the widespread periglacial cover beds, which are a typical example for stratified soils (Hübner, Günther, Heller, Noell, & Kleber, 2016;Hübner, Heller, Günther, & Kleber, 2015;Kleber & Terhorst, 2013;Moldenhauer, Heller, Chifflard, Hübner, & Kleber, 2013). Although in soil science the Substrate-Oriented-Soil-Evolution-Model (Lorz, Heller, & Kleber, 2011) underlines the importance of stratified soils and lithological discontinuities as a key element controlling ecological processes, in hydrologic research, less attention has been paid to the stratification of soils as a major trigger of lateral water paths (e.g., Reinhardt-Imjela, Maerker, Schulte, & Kleber, 2018, Reiss & Chifflard, 2015, Zhang, Lin, & Doolittle, 2014. The existence of a non-linear and threshold-type response of SSF to precipitation (e.g., Ali et al, 2015;Graham, Woods, & McDonnell, 2010) adds to the challenge of both measuring and modelling this process.…”

An Opinion on Spring Habitats within the Earth’s Critical Zone in Headwater Regions

“…For example, runoff generation in low mountain ranges is strongly influenced by the lateral fluxes of soil water caused by periglacial cover beds [60,61]. Here, stratified soils not only generate a preferential lateral interflow, but the soil architecture in particular influences the geochemical transport of substances, e.g., the depth distribution of trace element concentrations depends on lithological discontinuities in soils [62][63][64]. Hydropedology also encompasses the important linkages and feedback mechanisms between soil development, water movement, and the response of ecosystems at different spatio-temporal scales [65].…”