Mechanisms and influencing factors of wetlands in purifying new pollutants from water bodies

In modern society, the widespread use of pharmaceuticals, pesticides, and aquaculture-related compounds has significantly enhanced human well-being. However, their extensive application has also resulted in environmental contamination. These substances, now classified as new pollutants (NPs), are increasingly being detected in wetland ecosystems. Characterized by environmental persistence, bioaccumulation potential, and intrinsic toxicity, these pollutants are resistant to degradation. They exert multiple stresses on wetland ecosystems and pose long-term threats to human health, primarily through biomagnification along the food chain. Wetlands, as unique natural ecosystems, have the capacity to effectively remove NPs through a range of processes, including adsorption, filtration, sedimentation, photodegradation, hydrolysis, phytoremediation, and microbial degradation. However, wetland environments are highly complex, influenced by a combination of environmental conditions and the physicochemical properties of pollutants, leading to highly dynamic and intricate removal mechanisms. Despite growing interest, current research still lacks a systematic understanding of the transformation and degradation of these pollutants within complex wetland systems. In particular, the toxicological characteristics and ecological risks of many transformation products remain poorly characterized. First, the purification efficiency of pollutants and the dominant degradation pathways of NPs vary substantially under different environmental conditions, yet a comprehensive understanding of the transformation pathways of NPs in wetland systems is still limited. Second, the degradation of NPs often involves numerous intermediate metabolites and complex reaction pathways. Some of these transformation products may persist in the environment and bioaccumulate through the food chain, but their ecological impacts and toxicological risks remain largely unknown. Third, NPs may interact with other pollutants through co-adsorption, leading to combined pollution effects, further complicating risk assessment and management. Notably, the accumulation of antibiotics in wetlands may promote the development and dissemination of antibiotics resistance genes (ARGs), presenting additional challenges for the effective management of emerging pollutants. Building on the latest research advances, this review focuses on key NPs, including antibiotics, microplastics, and perfluoroalkyl and polyfluoroalkyl substances, and synthesizes the current research development on the purification of NPs in wetland systems. It summarizes the major research directions related to wetland-based purification of NPs and analyzes the underlying physical, chemical, and biological processes involved. These removal pathways are strongly influenced by environmental factors such as solar radiation, temperature, pH, and biological activity. Accordingly, this study systematically evaluates the key factors affecting NPs purification efficiency from two perspectives: environmental conditions and pollutant-specific properties. Finally, it outlines future research priorities to advance the mechanistic understanding and optimize the application of wetlands in NP remediations. By deepening the foundational knowledge of wetland purification processes and impact factors, this review provides a scientific basis for developing nature-based solutions to manage new pollutants and supports the conservation and sustainable management of wetland ecosystems. Future research should prioritize the following directions: (1) Advancing mechanistic understanding of the full life cycle, transformation pathways, and metabolite behavior of new pollutants; (2) Strengthening monitoring efforts to assess NP removal under varying environmental conditions and drivers; (3) Developing multi-media environmental models to simulate, predict, and evaluate the fate and ecological risks of NPs; and (4) Establishing integrated regulatory frameworks grounded in pollutant behavior and risk potential to support dynamic, life-cycle-based environmental management.