Schatting van de bijdrage van achtergronduitspoeling aan de emissie van metalen van bodem naar oppervlaktewater : aanvulling op WENR-rapport 3139

Leaching from soil contributes significantly to the total load of heavy metals in Dutch surface waters. In 2022 the model used to quantify the emission caused by leaching from soil to surface waters was revised and extended to be used for 13 metals and arsenic. This model however was not used to discriminate between leaching of metals from natural origin and those that have entered the soil as a result of anthropogenic activities. In this report we therefore describe a recently developed method that enables us to discriminate between naturally present metals in soil versus those from anthropogenic activities. Used measured data from approx. 350 samples from the Geochemical Soil Atlas from the Netherlands a model and based on soil properties (pH, Fe- and Al-oxide, P) the model is able to calculate the distribution of metals of natural origin versus metals added to soil due to anthropogenic activities. This distribution is used to calculate the contribution of what is called background leaching and leaching of metals from anthropogenic origin; both for the topsoil (0 – 30 cm) and the subsoil at a depth equal to 1 m below the average lowest groundwater level (GLG -1m). Data are presented in ton/year at national level and at regional level based on concentration in the percolating water from both the 0-30 layer and at a depth equal to 1 meter below the mean lowest groundwater level solution (GLG -1m).