Ecotoxicological Assessment of Leachates from Waste-Derived Alkali-Activated Cements using Zebrafish Embryos

Alkali-activated materials derived from industrial waste are promising alternatives to Portland cement for geotechnical applications. However, their environmental safety under realistic exposure conditions remains poorly understood, particularly due to the limitations of conventional chemical assessments, which may not capture early-stage curing effects, leaching behavior, and associated ecotoxicological risks. This study investigates whether conventional chemical assessment methods are sufficient to evaluate the environmental performance of such materials. An alkali-activated cement produced from photovoltaic module glass and hydrated oyster shell lime was evaluated through an integrated approach combining leaching tests and ecotoxicological assays. Leaching behavior was assessed at curing ages ranging from 7 to 91 days. Ecotoxicological effects were evaluated using extracts obtained from the alkaline cement after 7 days of curing, with zebrafish embryos under both acetic acid‑extracted and water-extracted conditions. Leaching tests showed a progressive reduction in several regulated metals; however, Ba, Cd, Cu, Ni, Pb, and Zn exceeded regulatory thresholds at specific curing ages. All mixtures produced highly alkaline leachates (pH > 13), and non-regulated elements (Ga, In, K, and Li) were also detected. Ecotoxicological assays revealed acute toxicity in acetic acid‑extracted leachates and sublethal effects in water- extracted leachates, including impaired hatching and reduced spontaneous movement. The results demonstrate that reductions in leached concentrations and compliance with conventional chemical criteria do not necessarily correspond to biological safety, highlighting the need to integrate ecotoxicological assays into environmental assessments of sustainable cementitious materials. Graphical Abstract