Ecotoxicological effects of pre-salt and post-salt drilling cuttings waste on soil invertebrates and plants: Implications for terrestrial ecosystem risk and land management

This study assessed the ecotoxicological effects of drilling cuttings waste (DCW) generated from offshore oil exploration, focusing on samples derived from both pre-salt and post-salt geological layers. A multi-species approach was employed, including avoidance and reproduction tests with four soil invertebrates ( Proisotoma minuta , Folsomia candida , Enchytraeus crypticus , and Sinella curviseta ), and growth and germination tests with two plant species ( Lactuca sativa and Mimosa scabrella ). Species-specific sensitivity patterns were identified, with P. minuta showing the highest sensitivity to pre-salt DCW (EC50: 0.13%) and S. curviseta the greatest tolerance (EC50: 6.89%). Notably, E. crypticus exhibited higher tolerance to pre-salt than to post-salt residues, indicating that compositional differences influence ecotoxicity. In contrast, plant responses showed no significant effects on germination or biomass development at DCW concentrations up to 5%, suggesting lower susceptibility under short-term exposure. These findings underscore the importance of incorporating ecologically relevant species in ecotoxicity testing to encompass the full range of biological responses and potential risks associated with DCW application in terrestrial ecosystems. Furthermore, the absence of phytotoxicity under tested conditions supports the feasibility of controlled DCW reuse in land management strategies, such as soil restoration and formulation of organomineral fertilisers. However, long-term monitoring and site-specific evaluations are recommended to mitigate potential cumulative impacts.