Metals and PFAS in stormwater and surface runoff in a semi-arid Canadian city subject to large variations in temperature among seasons

Per-and polyfluoroalkyl (PFAS) eternal pollutants: Sources, environmental impacts and treatment processes

Per- and polyfluoroalkyl substances (PFAS) have become a growing environmental concern due to their tangible impacts on human health. However, due to the large number of PFAS compounds and the analytical difficulty to identify all of them, there are still some knowledge gaps not only on their impact on human health, but also on how to manage them and achieve their effective degradation. PFAS compounds originate from man-made chemicals that are resistant to degradation because of the presence of the strong carbon-fluorine bonds in their chemical structure. This review consists of two parts. In the first part, the environmental effects of fluorinated compound contamination in water are covered with the objective to highlight how their presence in the environment adversely impacts the human health. In the second part, the focus is put on the different techniques available for the degradation and/or separation of PFAS compounds in different types of waters. Examples of removal/treatment of PFAS present in either surface or ground water are presented.

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

Green stormwater infrastructure is a growing management approach to capturing, infiltrating, and treating runoff at the source. However, there are several emerging contaminants for which green stormwater infrastructure has not been explicitly designed to mitigate and for which removal mechanisms are not yet well defined. This is an issue, as there is a growing understanding of the impact of emerging contaminants on human and environmental health. This paper presents a review of five emerging contaminants - antibiotic resistance genes, microplastics, tire wear particles, PFAS, and temperature - and seeks to improve our understanding of how green stormwater infrastructure is impacted by and can be designed to mitigate these emerging contaminants. To do so, we present a review of the source and transport of these contaminants to green stormwater infrastructure, specific treatment mechanisms within green infrastructure, and design considerations of green stormwater infrastructure that could lead to their removal. In addition, common removal mechanisms across these contaminants and limitations of green infrastructure for contaminant mitigation are discussed. Finally, we present future research directions that can help to advance the use of green infrastructure as a first line of defense for downstream water bodies against emerging contaminants of concern.

Effect of heavy metal co-contaminants on the sorption of thirteen anionic per- and poly-fluoroalkyl substances (PFAS) in soils

Understanding the sorption behavior of per- and poly-fluoroalkyl substances (PFAS) in soils are essential for assessing their mobility and risk in the environment. Heavy metals often coexist with PFAS depending on the source and history of contamination. In this study, we investigated the effect of heavy metal co-contaminants (Pb2+, Cu2+ and Zn2+) on the sorption of 13 anionic PFAS with different perfluorocarbon chain length (C3-C9) in two soils with different properties. Results revealed that Pb2+, Cu2+ and Zn2+ had little effect on the sorption of most short-chain compounds, while the presence of these heavy metals enhanced the sorption of long-chain PFAS in two soils. The distribution coefficients (Kd) of several long-chain PFAS linearly increased with increasing concentrations of heavy metal, especially in the presence of Pb2+ (ΔKd/Δ [Pb2+] > 3 for PFOS and PFNA vs <1 for PFPeS and PFHxS). While several mechanisms may have contributed to the enhancement of sorption of PFAS, the heavy metals most likely contributed through enhanced hydrophobic interactions of PFAS by neutralizing the negative charge of adsorption surfaces in soils and thus making it more favorable for their partitioning onto the solid phase. Moreover, the increase in the concentrations of heavy metals led to a decrease in the pH of the system and promoted sorption of long-chain compounds, especially in soil with lower organic carbon content. Overall, this study provides evidence that the presence of co-existing heavy metal cations in soils can significantly enhance the sorption of long-chain PFAS onto soil, thereby potentially limiting their mobility in the environment.

New Perspective to Understand and Prioritize the Ecological Impacts of Organophosphate Esters and Transformation Products in Urban Stormwater and Sewage Effluents

Due to their prevalence in urban contaminated water, the driving factors of organophosphate esters (OPEs) need to be well examined, and their related ecological impacts should include that of their transformation products (TPs). Additionally, a robust framework needs to be developed to integrate multiple variables related to ecological impacts for improving the ecological health assessment. Therefore, OPEs and TPs in urban stormwater and wastewater in Hong Kong were analyzed to fill these gaps. The results revealed that the total concentrations of OPEs in stormwater were positively correlated with the area of transportation land. Individual TP concentrations and the mass ratios of individual TPs/OPEs were somewhat higher in sewage effluents than that in stormwater. OPEs generally showed relatively higher risk quotients than TPs; however, the total risk quotients increased by approximately 38% when TPs were factored in. Moreover, the molecular docking results suggested that the investigated TPs might cause similar endocrine disruption in marine organisms as their parent OPEs. This study employed the Toxicological-Priority-Index scheme to successfully integrate the ecological risks and endocrine-disrupting effects to refine the ecological health assessment of the exposure to OPEs and their TPs, which can better inform the authority on the prioritization for regulating these contaminants of emerging concern in urban built environments.

Quantification of the effects of conservation practices on surface runoff and soil erosion in croplands and their trade-off: A meta-analysis

Soil erosion coupled with high runoff poses a significant threat to the topsoil fertility, declining its productivity and raising major environmental and socio-economic issues such as land degradation, desertification, food scarcity, and hunger globally. Several conservation methods have been widely adopted in order to reduce runoff and protect the soil from erosion. The effectiveness of such conservation practices are controlled by many factors (i.e., climate, topography, soil properties, land use). To understand their efficiency and their trade-off, we conducted a meta-analysis by collecting 98 research articles within the time frame of 1981-2021, considering the most widespread soil and water conservation practices all over the world. The results exhibited that most of the conservation practices are useful in controlling soil erosion as compared to the runoff rate in which Hedgerow practice was found to be the most effective measure in controlling runoff rate (57 %) while no-tillage was proved to be the most efficient in reducing soil erosion (83 %). On the other hand, strip cropping showed a balanced runoff reduction efficiency (RRE) and soil erosion reduction efficiency (SERE), both reaching around 65 %, followed by hedgerow (59 % and 52 %) and mulching (51 % and 60 %). The results were restrained by varying climatic and physical scenarios. This study provides a systematic overview of the effectiveness of different runoff and soil erosion conservation practices and their controlling factors in a holistic way that can serve as the basis for the government and policymakers for the sustainable and rational implementation of such practices in the future.

Contaminant Exposure and Transport from Three Potential Reuse Waters within a Single Watershed

Global demand for safe and sustainable water supplies necessitates a better understanding of contaminant exposures in potential reuse waters. In this study, we compared exposures and load contributions to surface water from the discharge of three reuse waters (wastewater effluent, urban stormwater, and agricultural runoff). Results document substantial and varying organic-chemical contribution to surface water from effluent discharges (e.g., disinfection byproducts [DBP], prescription pharmaceuticals, industrial/household chemicals), urban stormwater (e.g., polycyclic aromatic hydrocarbons, pesticides, nonprescription pharmaceuticals), and agricultural runoff (e.g., pesticides). Excluding DBPs, episodic storm-event organic concentrations and loads from urban stormwater were comparable to and often exceeded those of daily wastewater-effluent discharges. We also assessed if wastewater-effluent irrigation to corn resulted in measurable effects on organic-chemical concentrations in rain-induced agricultural runoff and harvested feedstock. Overall, the target-organic load of 491 g from wastewater-effluent irrigation to the study corn field during the 2019 growing season did not produce substantial dissolved organic-contaminant contributions in subsequent rain-induced runoff events. Out of the 140 detected organics in source wastewater-effluent irrigation, only imidacloprid and estrone had concentrations that resulted in observable differences between rain-induced agricultural runoff from the effluent-irrigated and nonirrigated corn fields. Analyses of pharmaceuticals and per-/polyfluoroalkyl substances in at-harvest corn-plant samples detected two prescription antibiotics, norfloxacin and ciprofloxacin, at concentrations of 36 and 70 ng/g, respectively, in effluent-irrigated corn-plant samples; no contaminants were detected in noneffluent irrigated corn-plant samples.

The role of the sewer system in estimating urban emissions of chemicals of emerging concern

The use of chemicals by society has resulted in calls for more effective control of their emissions. Many of these chemicals are poorly characterized because of lacking data on their use, environmental fate and toxicity, as well as lacking detection techniques. These compounds are sometimes referred to as contaminants of emerging concern (CECs). Urban areas are an important source of CECs, where these are typically first collected in sewer systems and then discharged into the environment after being treated in a wastewater treatment plant. A combination of emission estimation techniques and environmental fate models can support the early identification and management of CEC-related environmental problems. However, scientific insight in the processes driving the fate of CECs in sewer systems is limited and scattered. Biotransformation, sorption and ion-trapping can decrease CEC loads, whereas enzymatic deconjugation of conjugated metabolites can increase CEC loads as metabolites are back-transformed into their parent respective compounds. These fate processes need to be considered when estimating CEC emissions. This literature review collates the fragmented knowledge and data on in-sewer fate of CECs to develop practical guidelines for water managers on how to deal with in-sewer fate of CECs and highlights future research needs. It was assessed to what extent empirical data is in-line with text-book knowledge and integrated sewer modelling approaches. Experimental half-lives (n = 277) of 96 organic CECs were collected from literature. The findings of this literature review can be used to support environmental modelling efforts and to optimize monitoring campaigns, including field studies in the context of wastewater-based epidemiology.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s11157-022-09638-9.

Concentration and distribution of metals, total fluorine, per- and poly-fluoroalkyl substances (PFAS) in vertical soil profiles in industrialized areas

The widespread usage of per- and poly-fluoroalkyl substances (PFAS) has caused great concern due to their potential toxicology to human and environmental health. However, there have been limited investigations on the vertical distribution of PFAS in fluorine (F) contaminated soils. In this study, the spatial and vertical distribution of metals, total F, and PFAS in the soil profiles were investigated at different areas in an industrial city. The higher F concentrations in the farmland soils with intensive agricultural activities suggested the impacts of soil tillage. The ΣPFAS concentrations ranged from 0.187 to 1.852 ng g^-1 in all soil samples, with PFOA as the dominant pollutant, which accounted for 17.2%-51.6% of the ΣPFAS in all samples. Highest level of PFAS was found in the shallow layer of the soil profiles. The long-chain PFAS such as PFUdA and PFTeDA tended to remain in the topsoil, while the short-chains (PFBA, PFPeA, and PFHxA) have migrated to depth of 100 cm in the vertical soil profile. The application of F-enriched phosphorus fertilizers and atmospheric deposition may be important sources of F and PFAS in soils in this area. Correlation analysis indicated that most of PFAS have similar common sources, and the significantly positive correlation between Zn and PFAS suggested they may share similar sources. This study highlights the need for further work to monitor the PFAS level in soil environments in industrialized areas, in addition to focusing on soil metal and F pollution.

Comparison of sub-lethal metabolic perturbations of select legacy and novel perfluorinated alkyl substances (PFAS) in Daphnia magna

Per- and polyfluoroalkyl substances (PFAS) are a class of pollutants of concern due to their ubiquitous presence, persistence, and toxicity in aquatic environments. Legacy PFAS pollutants such as perfluorooctanesulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) have been more widely studied in aquatic environments. However, replacement PFAS, such as ammonium perfluoro (2-methyl-3-oxahexanoate; GenX) are increasingly being detected with little known information surrounding their toxicity. Here, Daphnia magna, a model organism for freshwater ecotoxicology was used to compare the acute sub-lethal toxicity of PFOS, PFOA, GenX, and PFAS mixtures. Using liquid chromatography with tandem mass spectrometry (LC-MS/MS), the targeted polar metabolic profile extracted from single Daphnia was quantified to investigate perturbations in the exposure groups versus the unexposed organisms. Multivariate statistical analyses demonstrated significant non-monotonic separation in PFOA, GenX, and PFAS mixture exposures. Sub-lethal exposure to concentrations of PFOS did not lead to significant separation in multivariate analyses. Univariate statistics and pathway analyses were used to elucidate the mode of action of PFAS exposure. Exposure to all individual PFAS led to significant perturbations in many amino acids including cysteine, histidine, tryptophan, glycine, and serine. These perturbations are consistent with biochemical pathway disruptions in the pantothenate and Coenzyme A (CoA) biosynthesis, thiamine metabolism, histidine metabolism, and aminoacyl-tRNA biosynthesis pathways. Overall, the collected metabolomic data is consistent with disruptions in energy metabolism and protein synthesis as the primary mode of action of sub-lethal PFAS exposure. Secondary modes of action among individual pollutant exposures demonstrated that the structural properties (carboxylic acid vs. sulfonic acid group) may play a role in the metabolic perturbations observed. Sub-lethal exposure to PFAS mixtures highlighted a mixed response when compared to the individual pollutants (PFOS, PFOA, and GenX). Overall, this study emphasizes the niche capability of environmental metabolomics to differentiate secondary modes of action from metabolic perturbations in both single pollutant and pollutant mixtures within the same chemical class.

Urban stormwater runoff pollutant loadings: GIS land use classification vs. sample-based predictions

Cities are growing worldwide with an increase in stormwater quantity and decrease in quality, negatively impacting receiving water bodies. The characterization of stormwater is difficult given its high variability and the typically numerous outfalls to be monitored. However, loadings can be estimated via models and validated using actual outfall monitoring. This study determined stormwater pollutant loadings predicted using eight land-use classifications (i.e., a 'desktop' study) and via an outfall sampling regime (i.e., a 'monitoring' study) for seven stormwater catchment areas in Saskatoon, SK, Canada, where stormwater typically releases directly into the South Saskatchewan River. Pollutants considered were total suspended solids (TSS), chemical oxygen demand (COD), metals, and polycyclic aromatic hydrocarbons. Catchment areas were dominated by single-family residential (39%) and green areas (17%). The largest catchment area, Preston Crossing, was the major source of the predicted annual loadings, such as TSS at 550,000 kg and COD at 265,000 kg. For comparison, the sampled-based estimated loadings for TSS and COD were 362,700 kg and 652,700 kg, respectively. Differences between the average predicted and actual estimations ranged from 29 to 156% for the eight pollutants considered, with averages for the summed pollutants in each catchment area ranging from 48 to 130%. Overall, the assessment and monitoring of stormwater outfalls are needed for the determination of impacts of loadings on the environment and for the subsequent development and implementation of treatment technologies.

Assessment of stormwater discharge contamination and toxicity for a cold-climate urban landscape

BACKGROUND

Stormwater is water resulting from precipitation events and snowmelt running off the urban landscape, collecting in storm sewers, and typically being released into receiving water bodies through outfalls with minimal to no treatment. Despite a growing body of evidence observing its deleterious pollution impacts, stormwater management and treatment in cold climates remains limited, partly due to a lack of quality and loading data and modeling parameters. This study examines the quality of stormwater discharging during the summer season in a cold-climate, semi-arid Canadian city (Saskatoon, Saskatchewan).

RESULTS

Seven stormwater outfalls with mixed-land-use urban catchments > 100 km² were sampled for four summer (June-August 2019) storm events and analyzed for a suite of quality parameters, including total suspended solids (TSS), chemical oxygen demand (COD), dissolved organic carbon (DOC), metals, and targeted polyaromatic hydrocarbons (PAHs). In addition, assessment of stormwater toxicity was done using the two toxicity assays Raphidocelis subcapitata (algae) and Vibrio fischeri (bacteria). Notable single-event, single-outfall contaminant pulses included of arsenic (420 µg/L), cadmium (16.4 µg/L), zinc (924 µg/L), fluorene (4.95 µg/L), benzo[a]pyrene (0.949 µg/L), pyrene (0.934 µg/L), phenanthrene (1.39 µg/L), and anthracene (1.40 µg/L). The IC₅₀ in both R. subcapitata and V. fischeri was observed, if at all, above expected toxicity thresholds for individual contaminant species. Principal component analysis (PCA) showed no clear trends for individual sampling sites or sampling dates. In contrast, parameters were correlated with each other in groups including DOC, COD, TSS, and reduced algal toxicity; and total dissolved solids (TDS), sum of metals, and pH.

CONCLUSIONS

In general, stormwater characteristics were similar to those of previous studies, with a bulk of contamination carried by the first volume of runoff, influenced by a combination of rainfall depth, antecedent dry period, land use, and activity within the catchment. Roads, highways, and industrial areas contribute the bulk of estimated contaminant loadings. More intensive sampling strategies are necessary to contextualize stormwater data in the context of contaminant and runoff volume peaks.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1186/s12302-022-00619-x.

Traffic-derived contaminant loading in snow storage facilities during spring melt

Stormwater results from precipitation events and melting snow running off urban landscapes and typically being released into receiving water bodies with little to no treatment. Despite evidence of its deleterious impacts, snowmelt (SM) management and treatment are limited, partly due to a lack of quality and loading data. This study examines snowmelt quality during the spring for a cold climate, semi-arid Canadian city (Saskatoon, Saskatchewan). Four snow storage facilities receiving urban snow plowed from roads in mixed land use urban catchments (228 km²) were sampled including snow piles (five events) and SM (twelve events) runoff in 2019 and 2020. Samples were analyzed for pH, EC, TDS, TSS, COD, DOC, metals, chloride, PAHs, and Raphidocelis subcapitata and Vibrio fischeri toxicity. Notable event-specific TSS spikes occurred on April 13, 2019 (3,513 mg/L), and April 24, 2019 (3,838 mg/L), and TDS, chloride, and manganese on March 26, 2020 (15,000 mg/L, 5,800 mg/L, 574 mg/L), April 17, 2020 (5,200 mg/L, 2,600 mg/L, 882 mg/L), and April 23, 2020 (5,110 mg/L, 2,900 mg/L, 919 mg/L), though chloride remained elevated through May 1, 2020, samples (1,000 mg/L). Additionally, at two sites sampled April 13, 2019, pulses of aluminum (401 mg/L) and PAHs (pyrene, phenanthrene, anthracene; 71 µg/L, 317 µg/L, 182 µg/L) were detected. Concentrations of fluorene, benzo[a]pyrene, pyrene, phenanthrene, and anthracene in almost all SP samples exceeded national aquatic toxicity guideline thresholds, while 50% of SM samples exceeded guideline thresholds for benzo[a]pyrene and pyrene, and almost all exceeded the threshold for anthracene. Nevertheless, the EC₅₀ for R. subcapitata and V. fischeri was observed, if at all, above expected toxicity thresholds.

Phase partitioning, transport and sources of Benzotriazole Ultraviolet Stabilizers during a runoff event

Benzotriazole Ultraviolet Stabilizers (BT-UVs) are ubiquitous in the environment, given their wide use as additives in consumer products. Their bio-accumulative and toxic properties are increasingly being scrutinised, evinced by the recent proposition to add UV328 to the Stockholm Convention on Persistent Organic Pollutants. Here, we measured concentrations of six BT-UVs in the dissolved and particulate phases of stream water collected from an urban and rural stream during a runoff event. Under baseflow conditions, the less hydrophobic BT-UVs were present at low concentrations in the dissolved phase, while much higher loads of particulate BT-UVs occurred during stormflow, especially in the urban creek. Time-weighted average BT-UV concentrations were up to 4 times higher in the urban than in the rural creek. BT-UVs were found to be prevalent in water obtained from laundering textiles, which plausibly constitutes a major portion of domestic wastewater, and can serve as a BT-UV source to aquatic waterways. However, the observed dilution of a sewage tracer during the run-off event suggests that unregulated wastewater seepage is not responsible for the high BT-UV loads in storm water. High levels of UV328 and UV234 were detected in a select few plastic debris items collected from the urban watershed and in artificial turf grass, respectively. Whereas this may allow for the leaching of those BT-UVs into the creek, most plastic debris is more likely a sink than a source of BT-UVs. The observed input of particle-bound BT-UVs at the onset of the rain event indicates that most of the BT-UVs reach the creek with contaminated particles that had built up on surfaces during the antecedent dry period. UV328 was the dominant BT-UV in those particles. If such particle build-up occurs on road surfaces, it may suggest that the use of UV328 in automotive applications contributes to their presence in urban storm water.

Immobilization of TiO2 Nanoparticles in Cement for Improved Photocatalytic Reactivity and Treatment of Organic Pollutants

Non-point organic pollutants in stormwater are a growing problem in the urban environment which lack effective and efficient treatment technologies. Incorporation of conventional wastewater techniques within stormwater management practices could fundamentally change how stormwater quality is managed because contaminants can be degraded during stormwater transport or storage. This study investigated the photocatalytic reactivity of titanium dioxide functionalized with maleic anhydride (Ti-MAH) within cement pastes when compared to ordinary Portland cement. Preparation of Ti-MAH was performed by permanently bonding maleic anhydride to titanium in methanol, drying and powdering the residual material, and then inter-grinding the preparation with cement during mixing. When compared with OPC, the Ti-MAH cured cement paste is more reactive under a wider range of light wavelengths, possesses a higher band gap, sustains this heightened reactivity over multiple testing iterations, and treats organics effectively (>95% methylene blue removal). Amorphous silica within calcium-silica-hydrate, C-S-H, is theorized to bond to the powdered Ti-MAH during curing. Verification of silicon bonding to the titanium by way of MAH was demonstrated by FTIR spectra, SEM imagery, and XRD. Creating a sustainable and passive photocatalytic cement that precisely bonds silica to Ti-MAH is useful for organic contaminants in urban stormwater, but use can translate to other applications because Ti-MAH bonds readily with any amorphous silica such as glass materials, paints and coatings, optics, and LEDS, among many others.

Transcriptomic response of Gordonia sp. strain NB4-1Y when provided with 6:2 fluorotelomer sulfonamidoalkyl betaine or 6:2 fluorotelomer sulfonate as sole sulfur source

Abstract

Perfluoroalkyl and polyfluoroalkyl substances (PFAS) are environmental contaminants of concern. We previously described biodegradation of two PFAS that represent components and transformation products of aqueous film-forming foams (AFFF), 6:2 fluorotelomer sulfonamidoalkyl betaine (6:2 FTAB) and 6:2 fluorotelomer sulfonate (6:2 FTSA), by Gordonia sp. strain NB4-1Y. To identify genes involved in the breakdown of these compounds, the transcriptomic response of NB4-1Y was examined when grown on 6:2 FTAB, 6:2 FTSA, a non-fluorinated analog of 6:2 FTSA (1-octanesulfonate), or MgSO₄, as sole sulfur source. Differentially expressed genes were identified as those with ± 1.5 log₂-fold-differences (± 1.5 log₂FD) in transcript abundances in pairwise comparisons. Transcriptomes of cells grown on 6:2 FTAB and 6:2 FTSA were most similar (7.9% of genes expressed ± 1.5 log₂FD); however, several genes that were expressed in greater abundance in 6:2 FTAB treated cells compared to 6:2 FTSA treated cells were noted for their potential role in carbon–nitrogen bond cleavage in 6:2 FTAB. Responses to sulfur limitation were observed in 6:2 FTAB, 6:2 FTSA, and 1-octanesulfonate treatments, as 20 genes relating to global sulfate stress response were more highly expressed under these conditions compared to the MgSO₄ treatment. More highly expressed oxygenase genes in 6:2 FTAB, 6:2 FTSA, and 1-octanesulfonate treatments were found to code for proteins with lower percent sulfur-containing amino acids compared to both the total proteome and to oxygenases showing decreased expression. This work identifies genetic targets for further characterization and will inform studies aimed at evaluating the biodegradation potential of environmental samples through applied genomics.

Graphic Abstract

Electronic supplementary material

The online version of this article (10.1007/s10532-020-09917-8) contains supplementary material, which is available to authorized users.