Post-sorption of Cd, Pb, and Zn onto peat, compost, and biochar: Short-term effects of ecotoxicity and bioaccessibility

Abstract

Contamination by potentially toxic metals and metalloids (PTMs) has become a significant health and environmental issue worldwide. Sorption has emerged as one of the most prominent strategies for remediating both soil and water contamination. New sorbents are being developed to provide economically viable and environmentally sound alternatives, in alignment with the principles of the Sustainable Development Goals. This research aimed to assess the potential effects on human health and environmental toxicity following the sorption of cadmium (Cd), lead (Pb), and zinc (Zn) using peat, compost, and biochar as sorbents. The peat was collected in Brazil, a country with a tropical climate, while the compost and biochar were produced from the organic fraction of municipal solid waste (OFMSW). In terms of bioaccessibility, the results showed the following order: compost < biochar < peat for Pb, and compost < peat < biochar for Cd and Zn. There was a significant growth inhibition for Eruca sativa and Zea mays exposed to increasing concentrations of PTMs treated with peat and compost. The presence of contaminants played a decisive role on immobilization of neonates of Ceriodaphnia silvestrii after treatments with compost and, especially, peat. However, the biochar addition rate caused a significant influence on the outcomes of ecotoxicity across all tested species. Although the samples treated with biochar exhibited lower residual concentrations of PTMs than those treated with compost and peat, the inherent toxicity of biochar might be attributed to the material itself. The exposure to residual PTM concentrations post-desorption caused ecotoxic effects on tested species, emphasizing the need to assess PTM desorption potential. Peat, compost, and biochar are promising alternatives for the sorption of PTMs, but the addition rates must be properly adjusted to avoid the occurrence of undesirable ecotoxicological effects. This research offers valuable insights for sustainable environmental management and protection by thoroughly investigating the impacts of different sorbents and contaminants on aquatic and terrestrial ecosystems.