In situ measurement of synthetic musks in wastewaters using diffusive gradients in thin film technique

Seasonal characteristics, source apportionment and ecological risk assessment of priority and emerging contaminants using passive samplers in the coastal water

The presence of priority and emerging contaminants in aquatic environments is a worldwide concern. This study utilized the diffusive gradients in thin-films (DGT) technique for in situ monitoring of polycyclic aromatic hydrocarbons (PAHs) and synthetic musks (SMs) in coastal waters over a year. DGT provided time-integrated and reliable pollutant measurements, outperforming grab sampling in terms of repeatability and stability. Seasonal and spatial variations in PAH and SM concentrations were observed, influenced by proximity to vehicle and maritime transport and tourist areas. Source apportionment using diagnostic ratios, positive matrix factorization, and principal component analysis indicated mixed pollutant origins. High ecological risks for certain PAHs emerged in the summer, highlighting significant seasonal threats. These findings provide critical insights for the long-term monitoring and management of PAHs and SMs, offering valuable regional data to support pollution mitigation efforts in the coastal water.

Diffusive gradients in thin-films (DGT) for in situ measurement of neonicotinoid insecticides (NNIs) in waters

Neonicotinoid insecticides (NNIs) are among the most widely-used insecticides, although their threat to non-target organisms has attracted attention in recent years. In this study, a diffusive gradient in thin-films (DGT) passive sampling technique was developed for in situ monitoring of time-weighted average (TWA) concentrations of NNIs in groundwater and wastewater. Systematic studies demonstrated that DGT with HLB as binding gels (HLB-DGT) is suitable for quantitative sampling of NNIs under a wide range of conditions, independent of pH (5-9.5), ionic strength (0.001-0.5 M) and dissolved organic matter (0-10 mg/L). The HLB-DGT performance was also independent of the typical groundwater ionic environments. The thicknesses of in-situ measured diffusive boundary layer were 0.35 and 0.25 mm in the groundwater and effluent, respectively. HLB-DGT can provide TWA concentrations over 14-18 days' deployment with linear uptake in both groundwater and wastewater. Concentrations and occurrence patterns of NNIs obtained by HLB-DGT were consistent with those measured from grab samples. The median TWA concentration of NNIs was 4.42 ng/L in water from the largest urban lake of China (the Tangxun Lake) in winter, with wastewater discharge being the main potential source. The reliability and stability of the HLB-DGT for measuring NNIs in the groundwater and surface water were confirmed and can be used to improve understanding of the occurrence and fate of NNIs in aquatic environment.

Development and application of diffusive gradients in thin-films for in-situ monitoring of 6PPD-Quinone in urban waters

The occurrence and risk of N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine-quinone (6PPD-Q), derived from the oxidation of the tire antidegradant 6PPD, has raised significant concern since it was found to cause acute mortality in coho salmon when exposed to urban runoff. Given the short half-life period and low solubility of 6PPD-Q, reliable in situ measurement techniques are required to accurately understand its occurrence and behaviour in aquatic environments. Here, using the diffusive gradients in thin-films (DGT) method with HLB as a binding agent, we developed a new methodology to measure 6PPD-Q in urban waters. 6PPD-Q was rapidly and strongly adsorbed on the HLB-binding gel and was efficiently extracted using organic solvents. The HLB-DGT accumulated 6PPD-Q linearly for >7 d and its performance was not significantly affected by pH (6.5-8.5), ionic strength (0.0001-0.5 M) or dissolved organic matter (0-20 mg L-1). Field evaluation of the DGT method demonstrated its effectiveness in urban runoff, detecting 6PPD-Q levels of 15.8-39.5 ng L-1 in rivers. In snowmelt, DGT detected 6PPD-Q levels of 210 ng L-1 which is two times higher than the value obtained by grab sampling. 6PPD-Q levels were much higher in snowmelt than those in rivers. This indicates that snowfall constitutes an important transport pathway for 6PPD-Q and that DGT effectively captured the fraction continuously released from dust particles in the snow samples. 6PPD-Q posed a substantial risk to migratory fish in urban waters, and its release from tire wear particles requires further investigation. This study is the first to develop a DGT-based method for 6PPD-Q determination in urban waters, and the method can ensure an accurate measurement of the release of 6PPD-Q to the environment, particularly in rainfall or snowmelt, important pathways for its entry into the aquatic environment.

Development and validation of an imprinted polymer based DGT for monitoring β-blocker drugs in wastewater surveillance

Wastewater surveillance is an effective and objective approach to monitor contaminant releases and drug usage in the catchment, the estimation requires accurate measurement. In this study, a novel diffusive gradients in thin-film (DGT) technique based on molecularly imprinted polymers (MIPs) for selective measurement of a class of widely prescribed cardiovascular drugs (β-blockers) in wastewater was developed. The synthesized MIPs showed strong affinity and selectivity for the target compounds. The MIP-DGT had large effective capacities, its performance was independent of a wide range of environmental conditions, including pH (4.58 - 8.89), ionic strength (0.01 - 0.5 M) and dissolved organic matter (< 20 mg L-1). Biofouling had little effect on the uptake of target compounds within 7 days. MIP-DGT devices were applied in a Chinese urban WWTP alongside an auto-sampler. Metoprolol concentrations detected were much higher than other β-blockers. Concentrations obtained using MIP-DGT were comparable to the 24 h composite samples using an autosampler. The estimated daily consumption calculated based on the data obtained with MIP-DGT implied that metoprolol and propranolol were the most popular β-blockers in the studied area. Overall, the results in this study demonstrate that the MIP-DGT is a cost-effective, reliable and efficient tool for in situ wastewater monitoring.

Development of diffusive gradients in thin-films technique for monitoring polycyclic aromatic hydrocarbons in coastal waters

Addressing the challenge of accurately monitoring polycyclic aromatic hydrocarbons (PAHs) in aquatic systems, this study employed diffusive gradients in thin-films (DGT) technique to achieve methods detection limits as low as 0.02 ng L-1 to 0.05 ng L-1 through in situ preconcentration and determination of time-integrated concentrations. The efficacy of the developed DGT samplers was validated under diverse environmental conditions, demonstrating independence from factors such as pH (5.03-9.01), dissolved organic matter (0-20 mg L-1), and ionic strength (0.0001-0.6 M). Notably, the introduction of a novel theoretical approach to calculate diffusion coefficients based on solvent-accessible volume tailored for PAHs significantly enhanced the method's applicability, particularly for organic pollutants with low solubility. Field deployments in coastal zones validated the DGT method against traditional grab sampling, with findings advocating a 4 to 7-day optimal deployment duration for balancing sensitivity and mitigating lag time effects. These results provide a sophisticated, efficient solution to the persistent challenge of monitoring hydrophobic organic pollutants in aquatic environments, broadening the scope and applicability of DGT in environmental science and providing a robust tool for researchers.

A critical review of distribution, toxicological effects, current analytical methods and future prospects of synthetic musks in aquatic environments

Synthetic musks (SMs) have gained widespread utilization in daily consumer products, leading to their widespread dissemination in aquatic environments through various pathways. Over the past few decades, the production of SMs has consistently risen, prompting significant concern over their potential adverse impacts on ecosystems and human health. Although several studies have focused on the development of analytical techniques for detecting SMs in biological samples and cosmetic products, a comprehensive evaluation of their global distribution in diverse aquatic media and biological matrices remains lacking. This review aims to provide an up-to-date overview of the occurrence of SMs in both aquatic and various biological matrices, investigating their worldwide distribution trends, assessing their ecological toxicity, and comparing different methodologies for processing and analysis of SMs. The findings underscore the prevalence of polycyclic musks as predominant SMs, with consumption of various products in different countries leading to contrasting distribution of contaminants. Furthermore, the migration of SMs from sediments to the water phase is investigated, indicating the role of solid-phase reservoirs. Incomplete degradation of SMs in the environment could contribute to their accumulation in aquatic systems, impacting the growth and oxidative stress of aquatic organisms, and having a possibility of genotoxicity to them. Human exposure data highlight substantial risks for vulnerable populations such as pregnant women and infants. Moreover, contemporary methods for SMs analysis are presented in this review, particularly focusing on advancements made in the last five years. Finally, research enhancement and critical questions regarding the analysis of SMs are provided, offering suggestions for future research endeavors.

Measurement of perfluoroalkyl substances in drinking water sources by DGT sampler with a novel fluorinated graphite binding gel

Extensive use of per- and polyfluoroalkyl substances (PFASs) has resulted in their widespread presence in natural waters. Concern for public health requires reliable measurement methods for determining their distribution and risks. Here, a sampling method based on diffusive gradients in thin films (DGT) was developed for measuring PFASs in drinking water sources. Fluorinated graphite (FG) particles were used to prepare the DGT binding gel for selective enrichment of trace PFASs in an aqueous environment. The FG-DGT method did not show sensitivity to relevant environmental parameters including pH (5.0-9.0), ionic strength (0.001-0.5 M), or DOM concentration (0-30 mg/L). The FG-DGT had enough capacity for deployment of up to four months. Six traditional and emerging PFASs including PFOS, PFOA, PFHpA, PFHxS, PFNA, and 6:2 FTSA at the ng/L level were detected in two major reservoirs serving as public drinking water sources by FG-DGT method coupled with liquid chromatography tandem mass spectrometry (LC-MS/MS). PFOA appeared at the highest observed concentrations in the drinking water sources. The research demonstrates that FG-DGT is an effective and efficient tool for monitoring PFASs in drinking water.

Development and application of diffusive gradients in thin films for in situ sampling of the organic UV filter 4-methylbenzylidene camphor (4-MBC) in waters

4-Methylbenzylidene camphor (4-MBC), a typical organic UV filter (OUVF) in personal care products, is considered to be a potential endocrine disruptor due to its estrogenic activity and bioaccumulation. Although 4-MBC residues have been extensively identified in aquatic waters, little is known about their occurrence, levels, and potential risk in coastal waters. This study developed a reliable sampling approach, based on diffusive gradients in thin films (DGT) with XAD-2 as the binding agent, for monitoring 4-MBC in coastal waters. The diffusion coefficients of 4-MBC in freshwater and artificial seawater were 3.65 × 10-6 cm2/s and 3.83 × 10-6 cm2/s, respectively. XAD-2 binding gel showed rapid adsorption to 4-MBC. The accumulated masses of 4-MBC in XAD-2 DGT increased linearly with deployed time for 7 days in freshwater and seawater, which agreed well with theoretical predictions. The sampling performance was independent of ionic strength (0.0001-0.5 M), pH (4.0-8.5), and dissolved organic matter (0-20 mg/L). Field deployment in the river estuary and bathing beach showed that DGT-measured 4-MBC concentrations were consistent in comparison with grab sampling. Environmental risk assessment showed that 4-MBC may pose a medium risk to aquatic organisms based on computed risk quotient (RQ) values. Sewage discharge is the main source of 4-MBC risk, while the residue in recreation beaches contributes more significantly in summer. The established DGT sampling is suitable for seasonal monitoring, source identification, and risk assessment of 4-MBC in coastal waters.

Development and applications of diffusive gradients in thin films for monitoring pharmaceuticals in surface waters

Pharmaceutical contaminants in surface water have raised significant concerns because of their potential ecological risks. In particular, coronavirus disease 2019 (COVID-19)-related pharmaceuticals can be released to surface water and reduce environmental water quality. Therefore, reliable and robust sampling tools are required for monitoring pharmaceuticals. In this study, passive sampling devices of diffusive gradients in thin films (DGTs) were developed for sampling 35 pharmaceuticals in surface waters. The results demonstrated that hydrophilic-lipophilic balance (HLB) was more suitable for DGT-based devices compared with XAD18 and XDA1 resins. For most pharmaceuticals, the performance of the HLB-DGT devices were independent of pH (5.0-9.0), ionic strength (0.001-0.5 M), and flow velocity (0-400 rpm). The HLB-DGT devices exhibited linear pharmaceutical accumulation for 7 days, and time-weighted average concentrations provided by the HLB-DGT were comparable to those measured by conventional grab sampling. Compared to previous studies, we extended DGT monitoring to include three antiviral drugs used for COVID-19 treatment, which may inspire further exploration on identifying the effects of COVID-19 on ecological and human health.

Validation and application of diffusive gradient in thin-film (DGT) equipped novel cyclodextrin polymer gels for monitoring endocrine disrupting chemicals (EDCs) and environmental risk assessment in the Taihu lake basin

Taihu Lake is the most important drinking water source of the major cities in the Yangtze River Delta. The pollution of endocrine disruptors (EDCs)in Taihu Lake has been increasing recently, the accurate determination is an important guide for predicting its health risks and developing appropriate controls. Monitoring organic pollutants in water using the diffusive gradient in thin film technique (DGT) has attracted much attention due to more accuracy and convenience than the grab sampling methods. In this study, a novel cyclodextrin polymer (CDP) synthesized by the simple and green method in water was taken as an adsorbent for the binding gel. Four endocrine-disrupting chemicals (EDCs), bisphenol A (BPA), 17α-ethinylestradiol (EE2), 17β-estradiol (E2), and estriol (E3), were taken as models to determine the diffusion coefficients (4.68 × 10^-6, 3.38 × 10^-6, 3.34 × 10^-6 and 4.31 × 10^-6 cm²/s) and to test the performance of DGT, such as adsorption capacity and deployment time (1-5 day). The assembled CDP-DGT was adopted to determine four EDCs in a simulated water environment (3-9 of pH, 0.001-0.5 M of ionic strength (IS), and dissolved organic matter (DOM) of 0-20 mg/L). The ability of CDP-DGT sampling was verified in the Jiuxiang River and was carried out for a large-scale field application of in situ sampling EDCs in Taihu Lake basin. The results show that the total EDCs concentration range and the estradiol equivalent concentrations (EEQ) in Taihu Lake and its main rivers are 2.78 ng/L to 11.08 ng/L and 2.62 ng/L to 10.91 ng/L, respectively. The risk quotients (RQs) of all sampling sites in the region were greater than 1, indicating that EDCs pose a serious threat to aquatic organisms in the area. Therefore, the monitoring of EDCs in the Taihu Lake basin should be further strengthened.

Development of diffusive gradients in thin film technique for seasonal monitoring of benzophenone-type UV filters in coastal waters

Benzophenone(BP)-type UV filters are continuously released into various aquatic environments via the effluent discharge of wastewater treatment plants (WWTPs) and recreational activities in coastal beaches. In this study, we developed a robust and reliable sampling approach, diffusive gradients in thin-films (DGT), for seasonal monitoring of six BP derivatives in coastal waters to investigate their occurrence and environmental risk. The binding capacities of both XAD-2 and HLB gels for test BPs were over 252 μg with no significant deterioration in marine environment, suggesting that theoretically, DGT is capable of sampling for at least 3 months effectively. The diffusion coefficients of BPs in freshwater and seawater were determined for the first time. The sampling performance showed no dependence on environmental conditions including pH (4.0-8.5), ionic strength (0.0001-0.5 M) and dissolved organic matter (0-20 mg L^-1). The developed DGT samplers were successfully applied in a river estuary linked to a WWTP and a bathing beach at different periods of one year. Results showed that the concentrations of BPs in the coastal waters were dependent on seasonal variation. The highest level in summer and the ecological risk should be considered based on the risk quotient values. These results demonstrated that the present DGT method is suitable for measuring, characterization, and risk assessment of BPs in freshwater and marine environment.

Effects of biofouling on the uptake of perfluorinated alkyl acids by organic-diffusive gradients in thin films passive samplers

While organic-diffusive gradients in thin films (o-DGT) passive samplers have been used to assess organic contaminants in water, the effects of biofouling on accurate analyte quantification by o-DGT are poorly understood. We evaluated the effects of biofouling on the uptake of six common perfluoroalkyl substances (PFAS) using a previously developed polyacrylamide-WAX (weak anion exchange) o-DGT without a filter membrane. Linear uptake (R² > 0.91) over 21 days was observed in fouled samplers. The measured sampling rates (R_s) and accumulated masses of PFAS in pre-fouled o-DGT were significantly lower (p < 0.05, 20-39% relative error) than in control-fouled samplers. However, compared to clean o-DGT (no biofouling), the R_s of most PFAS in control-fouled samplers (i.e., those with clean diffusive and binding gels initially) were not affected by biofouling. Under flowing (∼5.8 cm s^-1) and static conditions, the measured diffusive boundary layer (DBL) thicknesses for clean o-DGT were 0.016 and 0.082 cm, respectively, whereas the effective in situ biofilm thicknesses for fouled o-DGT were 0.018 and 0.14 cm, respectively. These results suggest that biofilm growth does not have significant effects on target PFAS sampling by o-DGT under typical flowing conditions (≥2 cm s^-1). However, rapid surface growth of biofilm on o-DGT deployed in quiescent waters over long periods of time may exacerbate the adverse effects of biofilms, necessitating the estimation of biofilm thickness in situ. This study provides new insights for evaluating the capability of o-DGT samplers when biofilm growth can be significant.

In situ monitoring of phthalate esters (PAEs) pollution and environmental risk assessment in Poyang Lake Basin by DGT Technology using cyclodextrin polymer as binding phase

Poyang Lake is the first freshwater lake in China, which is an important drinking water source. In recent years, industrial pollution has led to the increased phthalate acid esters (PAEs) in Poyang Lake. PAEs are a class of typical endocrine disruptors that can accumulate in organisms and interfere with their secretion systems. Thus, the accurate determination of PAEs in Poyang Lake is important for health risk prediction and the development of corresponding control means. Monitoring organic pollutants in water using the diffusive gradient in thin films technique (DGT) has attracted much attention due to more accuracy and convenience than the traditional methods. This study used an inexpensive amphiphilic cyclodextrin polymer (PBCD) as the sorbent for the binding gel. This new binding gel has an ultra-high specific surface area and excellent adsorption performance. Diffusion coefficients of the five PAEs were determined, and the performance of DGT such as adsorption capacity and deployment time (1-4 days) was tested using five PAEs as models. The assembled PBCD-DGT was used to examine the performance in a complex simulated water environment. The sampling capability of PBCD-DGT was verified in Yangshan Lake, and a large-scale field application was conducted in Poyang Lake basin. The results of 11 sampling points showed that the concentration ranges of dimethyl phthalate, diethyl phthalate, diallyl phthalate, dipropyl phthalate, and dibutyl phthalate were 434-2594 ng/L, 40-314 ng/L, 80-527 ng/L, 45-308 ng/L, and ND-182 ng/L, respectively. The health risk index (HI) and ecological risk quotient (RQ) values of PAEs in the Poyang Lake watershed were far below 1, indictating a lower health and ecological risk. Considering that PAEs are bioaccumulative and persistent, it is very necessary to continue to pay attention to its pollution status and health and ecological risk changes in Poyang Lake Basin in the future.

Tetrafluoroterephthalonitrile-crosslinked β-cyclodextrin polymer as a binding agent of diffusive gradients in thin-films for sampling endocrine disrupting chemicals in water

β-Cyclodextrin (β-CD) is an inexpensive and reproducible material derived from corn starch. It is possible that tetrafluoroterephthalonitrile-crosslinked β-cyclodextrin polymer (TFN-CD), a cheap but efficient adsorbent, could be a suitable binding agent for use in the passive sampling technique, diffusive gradients in thin-films (DGT). Herein, the TFN-CD binding gel was prepared and then evaluated as the binding phase of DGT to sample six endocrine disrupting chemicals (EDCs) in water. The TFN-CD dispersed uniformly in the binding gel due to its hydrophilicity. The quantitative recoveries (99.3%-106%) of EDCs from the TFN-CD binding gel could be conveniently achieved by ultrasonic extraction using 5 mL methanol for 10 min. Compared with the excellent HLB (hydrophilic-lipophilic-balanced resin) binding gel, the TFN-CD binding gel had comparable or even faster adsorption kinetics, although the equilibrium adsorption capacity was slightly lower. The effective adsorption capacities of TFN-CD-based DGT (TFN-CD-DGT) were roughly estimated to enable a 7-days deployment in EDC solution of 25.7-30.0 μg L^-1. Studies of influencing factors showed that the ionic strength (0-0.5 M), pH (3.73-9.13), dissolved organic matter (0-20 mg L^-1) and long-term storage (204 days) had negligible influence on the performance of TFN-CD-DGT. Finally, the TFN-CD-DGT was successfully used to record sudden increases in bulk concentrations during simulated discharge events in pond water. These results demonstrate that TFN-CD is a suitable binding agent for sampling of EDCs, and the low cost of TFN-CD could be conducive to the application of DGT in large-scale sampling.

Polydopamine-coated magnetic nanoparticles for the determination of nitro musks in environmental water samples by stir bar sorptive-dispersive microextraction

Magnetic-based microextraction approaches have gained popularity in recent years due to the magnetic properties of the extraction phases allowing to handle them easier and more efficiently. This work describes a magnetic-based analytical method for the determination of the family of nitro musks in environmental water samples. These compounds have been of great concern due to their environmental impacts and potential health effects. The method is based on stir bar sorptive-dispersive microextraction (SBSDME) as extraction approach, prior to thermal desorption coupled to gas chromatography-mass spectrometry analysis (TD-GC-MS). For this purpose, polydopamine-coated cobalt ferrite magnetic nanoparticles (CoFe₂O₄@PDA) were used as extraction material. The main parameters involved in the extraction procedure (i.e., sorbent amount, extraction time and ionic strength) as well as in the thermal desorption step (i.e., temperature and desorption time) were evaluated in order to obtain the highest sensitivity. Under the selected conditions, the method showed good linearity, limits of detection and quantification in the low ng L^-1 range, intra- and inter-day repeatability with RSD <15%, and high enrichment factors (178-640). Finally, the method was applied to four environmental water samples of different origin. Relative recovery values ranging from 91 to 120% highlighted that the matrices under consideration do not affect the extraction process. This work constitutes the first time in which nitro musks compounds were selectively extracted by taking advantage the high potential that magnetic-based microextraction techniques offer, specially SBSDME.