Does the aging behavior of microplastics affect the process of denitrification by the difference of copper ion adsorption?

Microplastics removal from stormwater runoff by bioretention cells: A review

Microplastics (MPs), as a new category of environmental pollutant, have been the hotspot of eco-friendly issues nowadays. Studies based on the aging process, the migration pattern of MPs in runoff rainwater, and the use of bioretention cells to remove MPs from runoff rainwater are beginning to attract widespread attention. This review analyses the migration patterns of MPs in rainwater runoff through their sources, structure and characteristics. The mechanism of removing MPs from runoff stormwater, the purification efficiency of different fillers and their influencing factors, and the accumulation, fate, and aging of MPs in bioretention cells are described. Furthermore, the hazards of MP accumulation on the performance of bioretention cells are summarised. Future directions for removing MPs in bioretention cells are proposed: (1) research on MPs smaller than 100 µm; (2) influence of MPs aging process on bioretention cells; (3) exploration of more effective fillers to enhance their removal efficiency; (4) research on synergistic removal mechanism of MPs and other pollution.

Aging behaviors intensify the impacts of microplastics on nitrate bioreduction-driven nitrogen cycling in freshwater sediments

Microplastics (MPs) inevitably undergo aging processes in natural environments; however, how aging behaviors influence the interactions between MPs exposures and nitrate bioreduction in freshwater sediments remains poorly understood. Here, we explored the distinct impacts of virgin and aged MPs (polystyrene (PS) and polylactic acid (PLA)) on nitrate bioreduction processes in lake sediments through a long-term microcosm experiment utilizing the 15N isotope tracing technique and molecular analysis. Compared to virgin MPs, aged PLA significantly increased the rates of denitrification, anaerobic ammonium oxidation (anammox), and dissimilatory nitrate reduction to ammonium (DNRA) (p < 0.05), facilitating sediment nitrogen loss, while aged PS only significantly improved the rates of DNRA by 272-297 % and contributed to nitrogen retention in sediments. Metagenomic sequencing demonstrated that a more significant enrichment of functional genes responsible for nitrate bioreduction pathways occurred with aged MPs exposures than with virgin MPs. By combining analyses of MPs aging traits and the key drivers of nitrate bioreduction, we revealed that aging behaviors directly regulated sediment nutrient status (e.g., DOC/NOx- ratio) and microbiological properties (from genes to bacteria), thereby further determining the activity of nitrate bioreduction. This work provides new insights into the impacts of aged MPs on sediment nitrate reduction and highlights the role of MPs aging in future assessments of long-term MPs pollution in freshwater ecosystems.

Impacts of environmentally persistent free radicals on the denitrification toxicity of photoaged tire wear particles in estuarine sediments

The widespread detection of tire wear particles (TWPs) in estuaries has raised concerns about their potential environmental hazards. However, knowledge of photoaging-induced environmentally persistent free radicals (EPFRs) formation on TWPs in estuarine environments and their impact on sediment denitrification remains limited. This study investigated the formation of EPFRs on TWP during photoaging in estuarine environments and evaluated their effects on sediment denitrification and nitrous oxide (N2O) accumulation. Sixty days of illumination increased EPFR concentration on TWPs by 373 %, with the generated EPFRs persisting in sediments for over 20 days. Exposure to pristine TWP (PTWP) reduced denitrification rates by 10.3 ± 5.6 % and increased N2O accumulation by 18.3 ± 4.5 %. Further exposure to photoaged TWP (ATWP) under 10-60 days of illumination expanded denitrification suppression and N2O accumulation to 28.1 ± 7.1-42.5 ± 6.6 % and 18.8 ± 4.3-31.7 ± 4.6 %, respectively. EPFRs exacerbated the accumulation of reactive nitrogen species in sediment and compromised the antioxidant systems. Structural equation modeling confirmed that EPFRs indirectly suppressed denitrification rates by directly impairing microbial processes involved in carbon metabolism and electron transfer. This study is the first to report that the formation of EPFRs enhances the negative effects of ATWP on the sediment's nitrogen cycle, offering valuable insights for assessing the ecological risks associated with TWP.

Microplastic-derived dissolved organic matter: Generation, characterization, and environmental behaviors

Microplastics (MPs) represent a substantial and emerging class of pollutants distributed widely in various environments, sparking growing concerns about their environmental impact. In environmental systems, dissolved organic matter (DOM) is crucial in shaping the physical, chemical, and biological processes of pollutants while significantly contributing to the global carbon budget. Recent findings have revealed that microplastic-derived dissolved organic matter (MP-DOM) constitutes approximately 10 % of the DOM present on the ocean surface, drawing considerable attention. Hence, this study's primary objective is to explore, the generation, characterization, and environmental behaviors of MP-DOM. The formation and characteristics of MP-DOM are profoundly influenced by leaching conditions and types of MPs. This review delves into the mechanisms of the generation of MP-DOM and provides an overview of a wide array of analytical techniques, including ultraviolet-visible (UV-Vis) spectroscopy, fluorescence spectroscopy, Fourier transform infrared spectroscopy (FTIR), and mass spectroscopy, used to assess the MP-DOM characteristics. Furthermore, this review investigates the environmental behaviors of MP-DOM, including its impacts on organisms, photochemical processes, the formation of disinfection by-products (DBPs), adsorption behavior, and its interaction with natural DOM. Finally, the review outlines research challenges, perspectives for future MP-DOM research, and the associated environmental implications.

Effects of micro-nano plastics on the environmental biogeochemical cycle of nitrogen: A comprehensive review

Micro-nano plastics (MNPs; size <5 mm), ubiquitous and emerging pollutants, accumulated in the natural environment through various sources, and are likely to interact with nutrients, thereby influencing their biogeochemical cycle. Increasing scientific evidences reveal that MNPs can affect nitrogen (N) cycle processes by affecting biotopes and organisms in the environmental matrix and MNPs biofilms, thus plays a crucial role in nitrous oxide (N2O) and ammonia (NH3) emission. Yet, the mechanism and key processes behind this have not been systematically reviewed in natural environments. In this review, we systematically summarize the effects of MNPs on N transformation in terrestrial, aquatic, and atmospheric ecosystems. The effects of MNPs properties on N content, composition, and function of the microbial community, enzyme activity, gene abundance and plant N uptake in different environmental conditions has been briefly discussed. The review highlights the significant potential of MNPs to alter the properties of the environmental matrix, microbes and plant or animal physiology, resulting in changes in N uptake and metabolic efficiency in plants, thereby inhibiting organic nitrogen (ON) formation and reducing N bioavailability, or altering NH3 emissions from animal sources. The faster the decomposition of plastics, the more intense the perturbation of MNPs to organisms in the natural ecosystem. Findings of this provide a more comprehensive analysis and research directions to the environmentalists, policy makers, water resources planners & managers, biologists, and biotechnologists to do integrate approaches to reach the practical engineering solutions which will further diminish the long-term ecological and climatic risks.

Underappreciated microplastic galaxy biases the filter-based quantification

Long-term environmental loading of microplastics (MPs) causes alarming exposure risks for a variety of species worldwide, considered a planetary threat to the well-being of ecosystems. Robust quantitative estimates of MP extents and featured diversity are the basis for comprehending their environmental implications precisely, and of these methods, membrane-based characterizations predominate with respect to MP inspections. However, though crucial to filter-based MP quantification, aggregation statuses of retained MPs on these substrates remain poorly understood, leaving us a "blind box" that exaggerates uncertainty in quantitive strategies of preselected areas without knowing overview loading structure. To clarify this uncertainty and estimate their impacts on MP counting, using MP imaging data assembled from peer-reviewed studies through a systematic review, here we analyze the particle-specific profiles of MPs retained on various substrates according to their centre of mass with a fast-random forests algorithm. We visualize the formation of distinct galaxy-like MP aggregation-similar to the solar system and Milky Way System comprised of countless stars-across the pristine and environmental samples by leveraging two spatial parameters developed in this study. This unique pattern greatly challenges the homogeneously or randomly distributed MP presumption adopted extensively for simplified membrane-based quantification purposes and selective ROI (region of interest) estimates for smaller-sized plastics down to the nano-range, as well as the compatibility theory using pristine MPs as the standard to quantify the presence of environmental MPs. Furthermore, our evaluation with exemplified numeration cases confirms these location-specific and area-dependent biases in many imaging analyses of a selective filter area, ascribed to the minimum possibility of reaching an ideal turnover point for the selective quantitive strategies. Consequently, disproportionate MP schemes on loading substrates yield great uncertainty in their quantification processing, highlighting the prompt need to include pattern-resolved calibration prior to quantification. Our findings substantially advance our understanding of the structure, behavior, and formation of these MP aggregating statuses on filtering substrates, addressing a fundamental question puzzling scientists as to why reproducible MP quantification is barely achievable even for subsamples. This study inspires the following studies to reconsider the impacts of aggregating patterns on the effective counting protocols and target-specific removal of retained MP aggregates through membrane separation techniques.