Recovery of trace elements in sediments from the alpine mountain stream affected by a severe flash flood in the Tatra Mountains

Abstract

Sediments in mountain streams are an essential component of aquatic ecosystems, providing nutrients and life space for many organisms. In this study, we focused on one alpine—mountain stream (in the Tatra Mountains, Slovakia) affected by a huge summer flash flood in 2018. We analyzed the content of trace elements (Hg, K, Ca, Ti, Cr, Mn, Fe, Zn, Rb, Sr, Zr, Mo, Ba and Pb) in sand-sized sediments, which were collected regularly in monthly intervals at five different sites determined by vegetation zones over a period of four years. Because we hypothesized that flash floods are one of the essential factor in long-term maintained of oligotrophic profile of mountain streams, we tried to find out if contents of trace elements in sediments from temporal aspect will increase after flood, and which season or part of the stream support recharge of trace elements in sediments. The results pointed to a main environmental factor (from PCA) which explains the gradual restoration of trace element accumulation in sediments after the flood. The seasonal pattern of this factor shows that the stream flow in spring and precipitation in autumn significantly influenced this increase. In addition, it was discovered that minerals present in granite probably support a higher enrichment of sediments with trace elements than minerals present in various Mesozoic sediments. This indicated that unstable bare land (rocks, debris and screes) and sparsely vegetated areas in higher elevations are crucial for the supply and release of trace elements to lowlands.