Zinc in topsoils

Zinc (Zn) plays a crucial role in various biological processes and is subsequently an essential micronutrient for living beings. Zinc can also be toxic when present in excess . As a result, too low or too high soil Zn concentrations negatively affect soil functions and may harm animal and human health.

The total zinc concentrations in soils depend on climate and soil properties (e.g. texture and pH), land use, the presence of natural deposits and anthropogenic activities. This map shows the total zinc concentrations in topsoils of all land cover types in the EU, and was created using the LUCAS topsoil 2009/2012 survey data with random forest modeling. Looking at the spatial distribution of topsoil Zn concentrations, the first and utmost important observation was the difference between North and Southern Europe, with predominantly higher concentrations in Southern Europe.

We identified topsoil clay content as the most important predictor for Zn concentrations, with higher concentrations in soils with higher clay content. As such, natural soil properties related to parent material were most important for the Zn distribution in Europe. This difference in parent material and soil texture explained the considerable difference in Zn levels between North and Southern Europe. In addition, soils with relatively low and high pH values (i.e. Calcisols and Podzols) were identified as regions with relatively low Zn levels.

Based on our analyses,we identified two possible natural and anthropogenic drivers for high Zn levels in soils. One was the natural mineral deposits and anthropogenic mining activities. Samples close to these locations (i.e. 10 km) had the highest Zn concentrations, often above 167 mg kg−1, representing only 1% of all LUCAS soil samples. In addition, we found that soils under grassland contribute primarily to the soils with the highest Zn concentrations. This could be due to additional Zn inputs by manure, which contains elevated Zn levels due to Zn additives given to livestock.

Based on our results, Northern European countries and, for example, the calcareous soils in Spain, may therefore impose challenges related to micronutrient deficiencies.

Reference: Van Eynde, E., Fendrich, A. N., Ballabio, C., & Panagos, P. 2023. Spatial assessment of topsoil zinc concentrations in Europe. Science of The Total Environment, 892, 164512.

Data: https://esdac.jrc.ec.europa.eu/content/zn-concentrations-eu-topsoils

The Zn concentration (mg kg⁻¹) in European topsoils as predicted by the quantile regression forest. The resolution of this map is 250 m by 250 m.

The ordered importance of the covariates in the random forest model for Zn concentrations in European topsoils. The importance is only shown for the 16 most important covariates (i.e. excluding parent material and land cover). The x-axis shows the variable importance based on the variance reduction at each split when the particular variable is used.