Aquatic nanopollution: Ecotoxicological mechanisms, multilevel environmental interactions

The exponential advancement of nanotechnology has led to the pervasive dissemination of engineered nanomaterials (ENMs) and micro/nanoplastics (MNPs) across global aquatic ecosystems, from freshwater rivers and lakes to marine environments and wetlands. These emerging pollutants, characterized by unique physicochemical properties, pose profound and cascading ecological risks, threatening the integrity of food webs, biodiversity, and ecosystem services. Given the urgency of addressing this global challenge, a holistic and integrated understanding of nanopollutants’ environmental behaviors, transformation pathways, and toxicological impacts is indispensable for guiding effective risk management and conservation efforts. However, current research suffers from several critical gaps: inadequate insights into the synergistic toxicity of transformed ENMs (T-ENMs), product-released ENMs (PR-ENMs), and nano-mixtures (combinations of NMs with heavy metals, antibiotics, or organic pollutants); incomplete elucidation of interaction mechanisms between climate change factors (acidification, warming) and nanopollutants; and a lack of systematic integration of ecosystem-specific transmission patterns (e.g., freshwater vs. marine vs. wetland) that shape pollutant fate and bioavailability. This review aims to bridge these knowledge voids by synthesizing state-of-the-art research on aquatic nanopollution. Its core objectives are threefold: first, to systematically organize the five functionally distinct categories of aquatic nanopollutants (ENMs, MNPs, T-ENMs, PR-ENMs, and nano-mixtures) and clarify their diverse sources, environmental fates, and physicochemical transformations; second, to decode the multi-dimensional transformation mechanisms (physical aggregation, chemical oxidation/sulfidation/valence conversion, and biological ecocorona formation) that reshape nanopollutant bioavailability; and third, to reveal cross-trophic-level toxicity pathways (e.g., oxidative stress, ionic release, transgenerational transmission, and endocrine disruption) and quantify the dual regulatory effects of climate factors (e.g., acidification enhancing metal ion release, warming accelerating metabolic uptake) and ecosystem types (e.g., low salinity in freshwater promoting dissolved fractions, high organic matter in wetlands facilitating detrital transfer). Ultimately, this review seeks to construct a science-based risk assessment framework and targeted regulatory strategies for nanopollution control. This review establishes a holistic "physicochemical properties-transformation processes-toxic effects-ecological interactions" full-chain analytical framework and emphasizes the dual regulatory roles of climate change and ecosystem types, providing interdisciplinary theoretical support for the precise prevention and control of aquatic nanopollution.