Influence of the soil water content and heavy metals/metalloid on woody plant’s aboveground biomass

Abstract

Toxic elements causing soil pollution and degradation are able to enter the substance cycle of ecosystem. Woody plants often act as critical objects for accumulating toxicants with their subsequent removal from the cycle of substances for a long period. Understanding the conditions of soil water saturation is essential for hydrological processes, and therefore influences this parameter in soil on the transfer of toxicants to vegetation too. The objective of this study was therefore to determine whether soil water saturation relate with heavy metals/metalloid accumulation in soils and whether it is possible to describe the relationship between accumulated toxic elements in soils and woody plants. The was conducted at 21 locations in the Freiberg region, Germany, where soil contamination with toxic metals is increasingly becoming problematic.The content of metals in the soil, leaves and branches were measured by ICP-MS. The relationship between soil saturation and accumulated heavy metals/ metalloid levels in the soil and the aboveground biomass of plants was analyzed. The maximum concentration of the studied toxic elements reached 7.36 mg kg-1 in the soil for Cd (Freiberg city forest), 618.1 for Pb (Freiberg Davidschaft vicinity), and 23276 for As (Davidschaft). The ability of woody plants Populus tremulae and Salix caprea to accumulate heavy metals/metalloid (Cd, Pb, and As) in aboveground biomass was studied under the condition of their growth in areas with increased content of these elements in the substrates.  The ability of the studied plants to absorb heavy metals/metalloid was determined based on the bioaccumulation coefficient. The accumulation of metal elements occurs more intensively in the assimilation part of plant biomass as compared to the wood of tree branches. The study demonstrates a more significant accumulation of toxic elements in  Salix caprea trees' aboveground biomass than Populus tremulae. The level of Cd accumulation in the biomass of Salix caprea defines this species as a potential hyperaccumulator of this element, allowing the strategies to be adjusted for the phytoremediation purposes of disturbed landscapes.