Copper toxicity in soils amended with copper containing fungicides

Abstract

The long-term application of copper containing pesticides can cause a significant accumulation of Cu in soils. In order to assess the potential toxic effects of these increased Cu concentrations, a comprehensive comparison of Cu toxicity in a set of soils with high Cu concentrations due to the application of Cu pesticides and corresponding reference soils was performed. Soils with a long history of application of Cu containing fungicides were sampled at 11 vineyards across Europe including an uncontaminated control soil outside each vineyard. Standard ecotoxicity tests for plant yield, root length, nitrification and invertebrates (Enchythraeus albidus) reproduction were performed on each soil of both the vineyard gradient and the corresponding control soil spiked with CuCl2. For all vineyard gradients, the increased Cu concentration (maximum 349 - 689 mg Cu/kg) did not decrease the response of any test compared to the corresponding control soils. Spiking these control soils with CuCl2 however resulted in clear dose-response curves and toxicity data for these freshly spiked control soils are in the range of toxicity data for these endpoints reported in the European Voluntary Risk Assessment Report (VRAR) on Cu and its compounds. Soil limits (Predicted No Effect Concentration, PNEC) calculated according to this VRAR are a factor 2.2 to 5.7 below the Cu concentrations observed in the sampled vineyard soils and therefore seem to be over-protective for soils contaminated with Cu due to the long term use of Cu containing pesticides. It is assumed that long-term accumulation of Cu in soils due to the annual application of small amounts of Cu, as is the case for Cu plant protection products, may result in stronger attenuation of Cu availability with time and hence a lower toxicity of Cu in soils compared to the default assumptions in the VRAR on the effect of ageing on toxicity (as reflected in the so-called leaching-ageing factor). Therefore, a larger scenario-specific leaching/ageing factor is proposed for the effects assessment of Cu in soils affected by long-term application of Cu containing pesticides.status: accepte