Copper toxicity to Folsomia candida in different soils: a comparison between nano and conventional formulations

Environmental context Nanotechnology has great potential for managing agricultural plant disease. This study compares effects of various nano and conventional copper formulations on Collembola Folsomia candida, a model arthropod often used to test soil pollutants. Although toxicity varied between formulations, with a nanopesticide showing one of the highest toxicities, the differences were mainly due to the active copper compound rather than its nano formulation. Abstract Nanotechnology has recently become a major asset in agricultural practices owing to the improvement and provision of solutions for plant disease management, especially in the form of nanopesticides. These products are considered as one of the main direct sources of nanomaterials in terrestrial ecosystems, and for that reason, it is essential to understand and evaluate their behaviour and toxicity in the environment. In addition, the panoply of similar compounds makes it difficult to accurately evaluate if different formulations may induce different effects on non-target organisms. We aim to compare the toxicity and bioavailability of different copper formulations (nano and non-nano) applied to the soil using the model organism Folsomia candida. Reproduction tests were performed in two different soils (Lufa 2.1 and 2.2) with two equilibrium times after spiking (0 and 48 h). Depending on the copper form present in the formulation, the half maximal effective concentration (EC50) values of the non-nano pesticides varied from 274 mg Cu kg−1 in Champion® to 3030 mg Cu kg−1 in Cupravit® in Lufa 2.2 and 48 h equilibrium. The nano formulation displayed one of the highest toxicities to collembolans, with an EC50 of 156 mg Cu kg−1. Regarding the soil type, a higher toxicity in Lufa 2.1 was observed probably related to the soil characteristics, namely lower pH and lower organic content, which increase the metal solubility and consequently the bioavailability. The only exception was the nanopesticide Kocide 3000®, whose toxicity was higher in Lufa 2.2. This study emphasises the importance of understanding the links between metal bioavailability and toxicity to support the more robust environmental risk assessment of different Cu fungicide formulations.