Review of emerging contaminants in green stormwater infrastructure: Antibiotic resistance genes, microplastics, tire wear particles, PFAS, and temperature

Synergistic oxidation and coagulation of raw water by novel Fe(II)/sulfite process: A comparative study with peroxydisulfate and peroxymonosulfate

Latest findings demonstrate that the oxidative Fe(II)/sulfite (Fe(II)/S(IV)) process can rapidly generate iron particles, holding potential for coagulation while simultaneously removing emerging contaminants. Herein, we first report the synergistic oxidation-coagulation treatment of RW by Fe(II)/S(IV) process, and compare with traditional Fe-based coagulation (FeSO4, Fe2(SO4)3), Fe(II)/PDS and Fe(II)/PMS processes. Results revealed that the Fe(II)/S(IV) process outperformed traditional Fe-based coagulants, Fe(II)/PDS and Fe(II)/PMS in removing turbidity, UV254, and DOC. For emerging contaminants removal from RW, Fe(II)/PMS showed the highest efficiency, followed by Fe(II)/PDS, while Fe(II)/S(IV) was slightly less effective, it still demonstrated a significant improvement (40 %∼65 %) over traditional coagulation processes. Moreover, the Fe(II)/S(IV) process is the most effective in reducing DBPs formation (56 %∼86 %). Although Fe(II)/PDS and Fe(II)/PMS also significantly reduce DBPs formation, their high oxidation potential at low pH generated toxic N-DBPs. Mechanistic analysis indicated that the Fe(II)/S(IV) process was most effective in removing humic substances and biopolymers. Its moderate oxidation preserved macromolecular structures, enhancing coagulation. And the hydrolysis of S(IV) generates OH⁻, promoting electrostatic neutralization and floc enlargement. Cost analysis revealed that the Fe(II)/S(IV) process is significantly more economical, with costs only 1/60 of Fe(II)/PMS. These results highlight the Fe(II)/S(IV) process as a promising and cost-effective approach to advanced water treatment.

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.

Occurrence, concentration and distribution of 50 organic contaminants in water and bottom sediment from urban streams affected by stormwater discharges

Stormwater runoff transports organic contaminants from urban areas to receiving water bodies, yet its contribution to these pollutants in the aquatic environment is still poorly understood. Additionally, contaminants behave differently in receiving waters, with some binding to particles and accumulating in sediments while others stay dissolved in the water. This study was carried out three Swedish urban streams receiving stormwater discharges through separate sewer systems, under dry and wet weather conditions. Stream water and bottom sediment samples were collected along an urbanization gradient, from rural upstream to urban downstream sections, and analyzed for 50 stormwater-related organic contaminants to assess the impact of stormwater on contaminant levels. Polycyclic aromatic hydrocarbons (PAHs) and phthalates were more prevalent in sediment samples, with concentrations increasing along the urbanization gradient, indicating contributions from urban areas and stormwater runoff. In contrast, organotin compounds and phenols showed no clear pattern indicating transport through stormwater runoff in the water phase. Per and polyfluoroalkyl substances (PFAS) behaved differently from other contaminant groups by exhibiting a clear contribution from stormwater runoff in both phases. Though carried out in streams passing through relatively small urban settings, the findings clearly demonstrate that stormwater discharges can impact receiving waters. Of the 50 analyzed contaminants, three exceeded toxicity-based limits in dry weather (DW), seven in wet weather (WW), and twenty in bottom sediments. In the water phase, under DW and WW conditions, the three contaminants with the highest exceedance of toxicity-based limits were Perfluorooctanesulfonic acid (PFOS), Tributyltin (TBT), and 4-nonylphenol (4-NP). In the sediment phase, 4‑tert-octylphenol (4-t-OP), Tributyltin (TBT), and di-2-ethylhexyl phthalate (DEHP) were the three compounds with the highest exceedance of toxicity-based limits. Compared to relatively hydrophilic contaminants (e.g., PFAS), hydrophobic organic contaminants, particularly those accumulating in sediments (e.g. phenols, phthalates), posed a greater risk to the aquatic environment with exceedance levels reaching up to 105 times the thresholds. These findings raise concerns about the long-term impact on aquatic environments and highlight the need for mitigation strategies, including regulatory or operational restrictions on the contaminant sources and implementation of stormwater treatment facilities.

Postprocessing methods based on minimum detectable amount and method blank for data reporting of particle count and refining estimation of matrix spike recovery in environmental microplastics analysis

Data handling that converts the raw data into a deliverable dataset is a necessary step in any analytical work. This procedure involves applying detection limits to shaping the raw data to form a deliverable dataset. The detection limit for microplastics analysis is the minimum detectable amount (MDA) that can be calculated from the particle counts of procedural blank samples following the rules of the Poisson distribution. Currently, there is a lack of adequate data reporting guidance encompassing the MDA for microplastics analysis. The goal of this study was to establish a robust protocol for processing count-based raw data using the particle counts of the MDA and the procedural blank. Utilizing the dataset of an interlaboratory comparison exercise, effectiveness of the protocol was elaborated to generate a deliverable dataset and to accurately define the matrix spiking recoveries. The guidance was applied to the raw data of all size fractions (1 - >500 μm), four individual size fractions (>500, 212-500, 20-212, 1-20 μm), and two morphologies (fiber and non-fiber). Six possible data reporting scenarios were identified, with the raw data ranging well above the MDA to below the critical value. One-third (12 of 34) of the raw data for all size fractions needed blank-MDA corrections. The mean values of the spiking recoveries decreased by up to 10 % after performing the data reporting guidance. Application of this suggested data reporting guidance may be beneficial for high quality data for microplastics analysis.

Size-dependent ecotoxicological impacts of tire wear particles on zebrafish physiology and gut microbiota: Implications for aquatic ecosystem health

The ecological impact of tire wear particles (TWP), a significant source of microplastics pollution, is increasingly concerning, especially given their potential effects on the health of aquatic ecosystems. This study investigates the size-dependent ecotoxicological responses of zebrafish (Danio rerio) to TWP exposure, focusing on physiological, metabolic, and microbial community impacts over a 15-day exposure period followed by a 15-day excretion period. Through integrated analysis of gut microbiome composition, liver transcriptomics, and host physiological markers, we found that smaller TWP particles (< 120 μm) induced oxidative stress, evidenced by increased SOD and MDA levels, and inhibited growth by reducing body mass and gut length. In contrast, larger TWP particles (250-380 μm) caused more substantial disruptions in lipid and xenobiotic metabolic pathways, as shown by significant downregulation of key metabolic genes (acads, cpt2_1, hadhaa), and alterations in the gut microbiome, including the enrichment of pathogenic genera, such as Enterococcus and Fusobacterium, while depleting beneficial microbes like Acinetobacter and Methyloversatilis. These microbiome shifts led to a more complex and potentially pathogenic gut microbiome. Notably, zebrafish displayed adaptive resilience during the excretion period, with significant recovery in body mass and microbial composition, emphasizing the adaptive capacity of aquatic organisms to pollutants. Our findings underscore the broader ecological risks posed by TWP, the pivotal role of gut microbiota in host resilience to pollutants, and the need for comprehensive management strategies addressing emerging contaminants in aquatic ecosystems.

Critical field evaluations of biochar-amended stormwater biofilters for PFAS and other organic micropollutant removals

Biochar is often promoted as an ideal amendment for stormwater biofilters; however, its effectiveness has rarely been tested under field conditions. This study evaluates the impact of biochar addition on the removal of organic micropollutants (OMPs) in field-scale biofilters operating under real-world conditions for the first time. The research comprised four vegetated biofilter facilities (3 - 5 years old), two without and two with 2.1 wt. % (10 vol. %) biochar amendment. Stormwater and filter material samples from various locations after four years of operation were analyzed for a wide range of common and emerging OMPs found in urban runoff. Unlike hydrophobic OMPs (hydrocarbons, polychlorinated biphenyls, and di(2-ethylhexyl) phthalate), the investigated biofilters demonstrated low, or inconsistent, removal of hydrophilic and slow-adsorbing OMPs like bisphenol A, monobutyltin, and per-fluoroalkyl substances (PFASs). Although the physiochemical properties of biochar were well-adapted to pollutant removal, biochar amendment did not significantly improve OMP removal when compared with the status quo. This can be attributed to several field conditions and suboptimal design interfering with the biochar's sorption capacity, namely, the large particle size (D50 ∼4 mm) and low quantity of biochar, high levels of competing agents (i.e., dissolved oxygen carbon (DOC) and cations), co-contaminants in stormwater, limited contact time, biochar pore blockage (e.g., by DOC molecules and sediments/minerals), diminished biochar surface porosity, and sometimes increased removal uncertainty due to low influent concentrations. Our findings demonstrated the complexities associated with applying biochar for stormwater treatment. Further research on biochar-specific biofilter designs is needed to optimize the sorption potential of this material under field conditions.

Development of a Nontargeted Algorithm for Per- and Polyfluoroalkyl Substances in the FT-ICR Mass Spectra of Complex Organic Mixtures

The unrivaled mass resolving power and subppm mass error enable the application of Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) for nontargeted screening of per- and polyfluoroalkyl substances (PFAS). Few automated FT-ICR MS methods exist for nontargeted analysis of PFAS in solutions containing other dissolved organic matter. In this study, isotopic pattern analysis and dynamic homologous series inspection were complementarily employed in the FTMSDeu algorithm to simultaneously assign chemical formulas for PFAS and other organic molecules, with an overall assignment accuracy of 91.2% for 1,802 unique PFAS formulas and their 11,634 isotopic formulas. The negative effects of fluorine-related isobaric isotopes with sub-mDa mass differences on formula assignment for PFAS and natural organic matter were addressed by an empirical F/(H + X) rule and the adoption of a threshold for the isotopic formula number plus the homologous series number. There were 203 unique PFAS formulas containing one novel PFAS formula, C9H6O4S1I1F11, identified in a fluoropolymer industry-impacted river water sample using our algorithm for analyzing FT-ICR MS spectra. Overall, the results of this study highlighted the great potential of the updated FTMSDeu algorithm for nontargeted and high-throughput chemical assignment for the FT-ICR MS spectra of complex mixtures containing PFAS and dissolved organic matter from real environmental samples.

Managed aquifer recharge as a potential pathway of contaminants of emerging concern into groundwater systems - A systematic review

Groundwater is an often-overlooked resource, while its declining quantity and quality is of global concern. To protect and ensure stable quantity and quality of groundwater systems used as drinking water supplies, a common method is to artificially recharge these groundwater supplies with surface water, a process called managed aquifer recharge (MAR), that has been used globally for decades. However, surface waters used for MAR often contain elevated concentrations of anthropogenic chemicals of emerging concern (CECs), such as plastics, pesticides, pharmaceuticals and personal care products (PPCPs), or per- and polyfluoroalkyl substances (PFAS). When infiltrating this surface water, MAR can thus act as a shortcut for CECs into groundwater systems and eventually drinking water supplies. Especially PFAS are an example of very persistent contaminants showing atypical transport patterns during MAR and thus posing a risk for ground- and drinking water contamination. This systematic review addresses the transport process of CECs through MAR systems by looking at (1) common CEC concentrations in surface waters, (2) factors affecting CEC transport and possible retention during MAR, such as sorption and other physio-chemical mechanisms of CECs, biological and chemical decomposition, or hydrogeological properties of the MAR system, and (3) key contaminants leaching through the MAR systems as well as possible treatment options to improve the retention of CECs during MAR. Since we are facing increasing needs for high quality drinking water, lower CEC drinking water guidelines as well as an increasing number of identified CECs in surface waters, we conclude with a series of recommendations and future research directions to address these issues. Those include the need for regular monitoring programs specifically addressing CECs and especially not yet regulated, (very) persistent and (very) mobile contaminants, such as PFAS, as well as redesigned MAR systems to ensure stable ground- and drinking water quantity and quality.

Occurrence, Concentration, and Distribution of 35 PFASs and Their Precursors Retained in 20 Stormwater Biofilters

Current knowledge about the fate and transport behaviors of per- and polyfluoroalkyl substances (PFASs) in urban stormwater biofilter facilities is very limited. C5-14,16 perfluoroalkyl carboxylic acids [perfluorinated carboxylic acids (PFCAs)], C4,8,10 perfluoroalkanesulfonic acids (PFSAs), methyl-perfluorooctane sulfonamide acetic acid (MeFOSAA, a PFSA precursor), and unknown C6-8 PFCA and perfluorooctanesulfonic acid precursors were frequently found in bioretention media and forebay sediments at Σ35PFAS concentrations of <0.03-19 and 0.064-16 μg/kg-DW, respectively. Unknown C6-8 PFCA precursor concentrations were up to ten times higher than the corresponding PFCAs, especially at forebays and biofilters' top layer. No significant trend could be attributed to PFAS and precursor concentrations versus depth of filter media, though PFAS concentrations were 2-3 times higher in the upper layers on average (significant difference between the upper (0-5 cm) and deepest (35-50 cm) layer). PFASs had a similar spatial concentration distribution in each filter media (no clear difference between short- and long-chain PFASs). Commercial land use and organic matter were important factors explaining the concentration variations among the biofilters and between the sampling depths, respectively. Given the comparable PFAS accumulations in deeper and superficial layers and possible increased mobility after precursor biotransformation, designing shallow-depth, nonamended sand biofilters or maintaining only the top layer may be insufficient for stormwater PFAS management.

Removal and fate of microplastics in permeable pavements: An experimental layer-by-layer analysis

The increasing prevalence of microplastics (MP) in urban environments has raised concerns over their negative effects on ecosystems and human health. Stormwater runoff, and road dust and sediment, act as major vectors of these pollutants into natural water bodies. Sustainable urban drainage systems, such as permeable pavements, are considered as potential tools to retain particulate pollutants. This research evaluates at laboratory scale the efficiency of permeable interlocking concrete pavements (PICP) and porous concrete pavements (PCP) for controlling microplastics, including tire wear particles (TWP) which constitute a large fraction of microplastics in urban environments, simulating surface pollution accumulation and Mediterranean rainfall conditions. Microplastic levels in road dust and sediments and stormwater runoff inputs were 4762 ± 974 MP/kg (dry weight) and 23.90 ± 17.40 MP/L. In infiltrated effluents, microplastic levels ranged from 2.20 ± 0.61 to 5.17 ± 1.05 MP/L; while tire wear particle levels ranged between 0.28 ± 0.28 and 3.30 ± 0.89 TWP/L. Distribution of microplastics within the layers of PICP and PCP were also studied and quantified. Microplastics tend to accumulate on the pavements surface and in geotextile layers, allowing microplastic retention efficiencies from 89 % to 99.6 %. Small sized (< 0.1 mm) fragment shaped microplastics are the most common in effluent samples. The results indicate that permeable pavements are a powerful tool to capture microplastics and tire wear particles, especially by surface and geotextile layers. The study aims to shed light on the complex mobilisation mechanisms of microplastics, providing valuable insights for addressing the growing environmental concern of microplastic pollution in urban areas.

Unearthing Earth's secrets: Exploring the environmental legacy of contaminants in soil, water, and sediments

The Earth's history is documented in human civilizations, soil layers, river movement, and quiet sediments throughout millennia. This investigation explores the significant legacy of environmental toxins in these key planet components. Understanding how ancient activity shaped the terrain is crucial as mankind faces environmental issues. This interdisciplinary study uses environmental science, archaeology, and geology to uncover Earth's mysteries. It illuminates the dynamic processes that have built our globe by studying pollutants and soil, water, and sediments. This research follows human actions, both intentional and unintentional, from ancient civilizations through contemporary industrialization and their far-reaching effects. Environmental destiny examines how contaminants affect ecosystems and human health. This study of past contamination helps solve modern problems including pollution cleanup, sustainable land management, and water conservation. This review studies reminds us that our previous activities still affect the ecosystem in a society facing rapid urbanisation and industrialization. It emphasises the importance of environmental stewardship and provides a framework for making educated choices to reduce toxins in soil, water, and sediments. Discovery of Earth's secrets is not only a historical curiosity; it's a necessary step towards a sustainable and peaceful cohabitation with our home planet.

Deciphering the Role of the Gut Microbiota in Exposure to Emerging Contaminants and Diabetes: A Review

Emerging pollutants, a category of compounds currently not regulated or inadequately regulated by law, have recently become a focal point of research due to their potential toxic effects on human health. The gut microbiota plays a pivotal role in human health; it is particularly susceptible to disruption and alteration upon exposure to a range of toxic environmental chemicals, including emerging contaminants. The disturbance of the gut microbiome caused by environmental pollutants may represent a mechanism through which environmental chemicals exert their toxic effects, a mechanism that is garnering increasing attention. However, the discussion on the toxic link between emerging pollutants and glucose metabolism remains insufficiently explored. This review aims to establish a connection between emerging pollutants and glucose metabolism through the gut microbiota, delving into the toxic impacts of these pollutants on glucose metabolism and the potential role played by the gut microbiota.

Emerging Contaminants: An Emerging Risk Factor for Diabetes Mellitus

Emerging contaminants have been increasingly recognized as critical determinants in global public health outcomes. However, the intricate relationship between these contaminants and glucose metabolism remains to be fully elucidated. The paucity of comprehensive clinical data, coupled with the need for in-depth mechanistic investigations, underscores the urgency to decipher the precise molecular and cellular pathways through which these contaminants potentially mediate the initiation and progression of diabetes mellitus. A profound understanding of the epidemiological impact of these emerging contaminants, as well as the elucidation of the underlying mechanistic pathways, is indispensable for the formulation of evidence-based policy and preventive interventions. This review systematically aggregates contemporary findings from epidemiological investigations and delves into the mechanistic correlates that tether exposure to emerging contaminants, including endocrine disruptors, perfluorinated compounds, microplastics, and antibiotics, to glycemic dysregulation. A nuanced exploration is undertaken focusing on potential dietary sources and the consequential role of the gut microbiome in their toxic effects. This review endeavors to provide a foundational reference for future investigations into the complex interplay between emerging contaminants and diabetes mellitus.