Ambient copper concentrations in agricultural and natural European soils: an overview

Copper concentrations in soil are affected by a large number of processes related to the natural spatial variability (geochemistry), the amount released, the spatial and temporal distributions of these releases, and the large number of transportation, complexation, and dissolution processes. The present study reports the generated country-specific and land use-specific environmental concentration distributions of ambient copper exposure levels in European soils that were used for the derivation of "reasonable worst-case" predicted environmental copper concentrations (RWC-ambient copper PEC) for three types of soil uses: Agricultural soils, forest soils, and undefined grassland soils. Only recent and high-quality monitoring data (Q1) that comply with a number of criteria (i.e., sampling strategy, land use, digestion method, and absence of point sources) were selected for this purpose. Data treatment procedures used in the present study were based on the methods and concepts laid down in the European Union Technical Guidance Document on Risk Assessment and in the "combined monitoring-based and modeling-based priority setting" procedure. The derived median RWC-ambient copper PEC for European agricultural soils is 31.1 mg/kg dry weight, with the lowest and highest RWC-ambient copper PEC found in Belgium (16.1 mg/kg dry wt) and northern Italy (57.5 mg/kg dry wt), respectively. The high value for Italian soils probably is related to the (recent) volcanic origin of these soils. Similarly, RWC-ambient copper PECs were derived for forest soils and undefined grassland soils (24.4 and 35.3 mg/kg, respectively). Observed differences between the diifferent soil uses could be related to various parameters and processes that determine the copper levels in soil (e.g., soil type associated with specitic soil uses, addition of fertilizers and pesticides, and presence of cattle).