The effects of dissolved organic matter and pH on sampling rates for polar organic chemical integrative samplers (POCIS)

A smartphone-based supramolecular biosensor for portable and rapid detection of buprofezin in real food samples

Buprofezin (BUP) is an insect growth regulator widely used in agriculture to control hemipteran pests, particularly the melon aphid, Aphis gossypii, due to its efficiency and low toxicity. Although approved by the Chinese government, its maximum residue limit (MRL) in food is strictly regulated, and conventional techniques for detecting BUP have several limitations. Our study reports successful BUP detection using a supramolecular fluorescent probe DP@ALB, constructed with chalcone-based fluorescent dye DP and albumin as the host. The probe offers advantages such as low cost, visual signal output with high fluorescence color variation, rapid response, and high sensitivity. Additionally, portable test strips enable convenient on-site BUP detection and simplifying field monitoring of spiked real samples. The study achieves precise qualitative and quantitative BUP analysis in grape fruit, groundwater, and soil with satisfactory recoveries. Further, the biological applicability of sensor for the in vitro detection of BUP in L929 living cells was demonstrated. This research breakthrough overcomes the limitations of traditional analytical methods, offering an efficient and reliable approach for food and environmental monitoring and pesticide residue detection.

Utility of a modified o-DGT passive sampler for measurement of bisphenol analogues in freshwater and coastal waters

Bisphenol analogues (BPs) are commonly found in riverine and coastal waters. However, the lack of a reliable and robust passive sampling method has hindered our ability to monitor these compounds in aquatic systems. The study developed a novel organic-diffusive gradients in thin film (o-DGT) sampler based on stainless steel mesh membrane, polyacrylamide diffusive gel, and hydrophilic-lipophilic balance (HLB) binding gel. This innovative design tackled issues of filter membrane sorption in traditional o-DGT devices and potential gel damage in membrane-less o-DGT devices, showing promising application prospects. The mass accumulation of 15 target BPs was linear over 10 days in both freshwater (r2 ≥ 0.92) and seawater (r2 ≥ 0.94), with no saturation observed. The diffusion coefficients (D) through polyacrylamide diffusive gels ranged from 4.04 × 10-6 to 5.77 × 10-6 cm2 s-1 in freshwater and from 1.74 × 10-6 to 4.69 × 10-6 cm2 s-1 in seawater for the target BPs (except for bisphenol PH) at 22 °C. The D values of the target BPs in seawater were lower than those in freshwater due to the high salinity in seawater (35 ‰). The o-DGT samplers demonstrated good integrity in field applications. The total concentrations of the eight detected BPs ranged from 9.2 to 323 ng L-1, which was consistent with the measurements obtained by grab sampling. Among all BPs, bisphenol S, bisphenol F, and bisphenol A were consistently detected at all sites using both sampling methods. The concentrations of some novel BPs in coastal water measured by grab sampling were comparable to those measured in rivers, suggesting the need to strengthen pollution control of BPs in coastal areas. These results indicate that the o-DGT passive sampling method developed in the present study can be effectively used for monitoring BPs in freshwater and coastal environments.

Wastewater and seawater monitoring in Antarctica: Passive sampling as a powerful strategy to evaluate emerging pollution

The Ross Sea, among the least human-impacted marine environments worldwide, recently became the first marine protected area in Antarctica. To assess the impact of the Italian research station Mario Zucchelli (MZS) on the surrounding waters, passive sampling - as well as spot sampling for comparison - took place in the effluent of the wastewater treatment plant (WWTP) and the receiving surface marine waters. Polar Organic Chemical Integrative Samplers (POCIS) were deployed for six consecutive 2-week periods from November to February in a reservoir collecting the wastewater effluent. Passive samplers were also deployed at shallow depth offshore from the wastewater effluent outlet from MZS for two separate 3-week periods (November 2021 and January 2022). Grab water samples were collected alongside each POCIS deployment, for comparison with passive sampling results. POCIS, used for the first time in Antarctica, demonstrated to be advantageous to estimate time-averaged concentrations in waters and the results were comparable to those obtained by repeated spot samplings. Among the 23 studied ECs - including drugs, UV-filters, perfluorinated substances, caffeine - 15 were detected in both grab and passive sampling in the WWTP effluent and followed similar concentration profiles in both types of sampling. High concentrations of caffeine, naproxen and ketoprofen in the dozens of μg L-1 were detected. Other compounds, including drugs and several UV filters, were detected down to sub- μg L-1 concentrations. In marine waters close to the effluent output, only traces of a drug (4.8 ng L-1) and two UV filters (up to 0.04 μg L-1) were quantified.

Prediction of the accumulation behavior of pesticides in PDMS-coated stir bars used as passive samplers in freshwaters

Passive samplers accumulate organic contaminants at rates that depend on in-field exposure conditions such as freshwater flow velocity, water temperature and water quality. Time-weighted average concentrations can be determined by using a correction process such as the performance reference compound (PRC) method. This study presented a new approach to predict the accumulation behavior of pesticides in polydimethylsiloxane-coated stir bars under different exposure conditions and assign a specific PRC to each pesticide for quantitative purposes. We used an experimental design with eight simultaneous accumulation kinetics of 13 pesticides and elimination kinetics of three PRC candidates run in a flow-through system to determine the effects of flow velocity, water temperature and dissolved organic matter on the kinetic constants. We identified the parameters that had a significant effect on the accumulation of each pesticide and assigned a PRC candidate to each pesticide. We then used a discriminant function analysis to find the parameters that had a significant effect on accumulation of the 13 pesticides via their physical-chemical properties and to predict through a stochastic approach the parameters for seven other pesticides. This approach provides a better framework for identifying a PRC than conventional methods to determine unbiased concentrations in future monitoring efforts.

A passive sampler for synchronously measuring inorganic and organic pollutants in sediment porewater: Configuration and field application

In situ measurement of multiple pollutants coexisting in sediment porewater is an essential step in comprehensively assessing the bioavailability and risk of pollutants, but to date, this needs to be better developed. In this study, a passive sampler, consisting of an "I-shaped" supporting frame and inorganic/organic sampling units, incorporating equilibrium dialysis theory and kinetic/equilibrium sorption principle, was developed for the synchronous measurement of inorganic (e.g., phosphorus and metal(loid)s) and organic pollutants (e.g., parent and substituted PAHs). The equilibrium time and sampling rates were explored in laboratory tests to support in situ application. Profiles of pollutants in porewater within a vertical resolution of centimeters, i.e., 1 cm and 2 cm for inorganic and organic pollutants, respectively, were obtained by field deployment of the sampler for further estimation of diffusive fluxes across the sediment-water interface. The results suggested that the role of sediments for a specific pollutant may change (e.g., from "sink" to "source") during the sampling time. This study demonstrated the feasibility of synchronous measurement of inorganic and organic pollutants in sediment porewater by the passive sampler. In addition, it provided new insight for further investigation into the combined pollution effects of various pollutants in sediments.

Application of passive sampling device for exploring the occurrence, distribution, and risk of pharmaceuticals and pesticides in surface water

Pharmaceuticals and pesticides are compounds of high concern in surface waters around the world. However, few studies have used passive sampling methods to screen and detect these compounds in natural waters. In this study, a self-developed passive sampler was employed to measure pharmaceuticals and pesticides in the rivers of Nanjing, China. A total of 41 pharmaceuticals and 11 pesticides were detected, among which antibiotic and insecticide were the predominant classes, respectively. Valproic acid, caffeine and triclosan from the pharmaceuticals, and isoprocarb and imidacloprid from the pesticides were found frequently with high concentrations. At most sampling sites, the concentration ratios of caffeine versus carbamazepine exceeded 10, and even above 50, indicating relatively poor efficiency of wastewater treatment, or possibly the direct discharge of raw sewage, or other unknown source of pollution. It was found that the concentrations and ecological risks in the northern area of Yangtze River were higher than those in the southern area of Yangtze River, implying that economic development and population density were not the main contributors to the discovered pollution. The total concentration of pharmaceuticals and pesticides in Qinhuai River increased gradually with the direction of water flow, demonstrating the success of water diversion project in flushing and scouring pollutants.

Compatibility of polar organic chemical integrative sampler (POCIS) with compound specific isotope analysis (CSIA) of substituted chlorobenzenes

Compound specific isotope analysis (CSIA) is a powerful technique to demonstrate in situ degradation of traditional groundwater contaminants when concentrations are typically in the mg/L range. Currently, an efficient preconcentration method is lacking to expand CSIA to low aqueous concentration environmental samples. Specially for the H- and N-CSIA of heteroatom-bearing non-traditional compounds, the CSIA analytical detection limits are significantly higher than that of the C-CSIA. This work demonstrates the compatibility of polar organic chemical integrative sampler (POCIS) with C-, H-, and N-CSIA using four nitro- and amino-substituted chlorobenzenes that are common industrial feedstocks for numerous applications and are commonly detected in the environment at mg/L to μg/L range. Using lab experiments, we showed isotopic equilibrium in POCIS was achieved after 30 days with either a negligible (<0.5 ‰) or a constant shift for C (<1 ‰) and N (<2 ‰). Similar negligible (<5 ‰) or constant shift (<20 ‰) was evident for H isotope except for 3,4-dichloroaniline. The method quantification limits for the combined sorbent and membrane of one POCIS were comparable to that of the solid phase extraction (SPE) using 10 L water. Next, we demonstrated the field applicability of POCIS for C- and N-CSIA after a 60-day deployment in a pilot constructed wetland by showing <1 ‰ difference between the δ13C and δ15N obtained from POCIS and SPE. Finally, we evaluated whether the biofilm development on POCIS membrane could affect the isotope signature of the sampled compounds during field deployment. Although a diverse microbial community was identified on the membrane after a 60-day deployment, we did not observe significant isotope fractionation. This was likely due to either slower diffusion in the biofilm or microbial degradation of the sampled compounds. This work demonstrates the potential of using POCIS-CSIA as a simple, fast, and sensitive method for low-concentration contaminants, such as pesticides, pharmaceuticals, and flame-retardants.

Examining the applicability of polar organic chemical integrative sampler for long-term monitoring of groundwater contamination caused by currently used pesticides

The possibilities of expanding a groundwater quality monitoring scheme by passive sampling using polar organic chemical integrative sampler (POCIS) comprising HLB sorbent as the receiving phase were explored. Passive sampling and grab sampling were carried out simultaneously in the regions with vulnerable groundwater resources in Slovakia, between 2013 and 2021. For 27 pesticides and degradation products detected both in POCIS and the grab samples, in situ sampling rates were calculated and statistically evaluated. The limited effectiveness of the receiving phase in POCIS for sampling polar or ionized compounds was confirmed through a comparison of the medians of compound-specific sampling rates. For the majority of the monitored compounds the median sampling rates varied between 0.01 and 0.035 L/day. In some cases, the actual in situ values could be confirmed by parallel exposure of POCIS and silicone rubber sheet employed to obtain a benchmark for maximum attainable sampling rate. Sampling site and sampling period appear to have also some influence on the sampling rates, which was attributed in part to the groundwater velocity varying in both space and time. The influence of physico-chemical parameters (temperature, pH, electrolytic conductivity) remains mostly questionable due to the naturally limited ranges of recorded values over the entire duration of the study. Concentrations of pollutants in POCIS could be used for predicting time weighed average concentrations in water, provided the sampling rates were known and relatively constant. Generally, the compound-specific sampling rate cannot be considered constant due to a combination of naturally varying environmental factors that influence the actual in situ sampling rate. The relative standard deviation of concentration data from POCIS exposed in triplicates varied between approx. 5 %-50 %. Utilizing exploratory data analysis approach and tools enabled us to obtain a relatively complex picture of the situation and progress regarding pesticide pollution of groundwater in the monitored areas.

Implications of polar organic chemical integrative sampler for high membrane sorption and suitability of polyethersulfone as a single-phase sampler

Polar organic chemical integrative sampler (POCIS) contains sorbent, which is typically enclosed between two polyethersulfones (PES) membranes. A significant PES uptake is reported for many contaminants, yet, aqueous concentration is mainly correlated with the sorbent uptake using first-order kinetics. Under high PES sorption, the first-order kinetics often provide erroneous sampling rate for the sorbent phase due to increased membrane resistance. This work evaluated the uptake of four high PES sorbing chemicals, i.e., three Cl- and CH₃-substituted nitrobenzenes and one chlorinated aniline using POCIS and the potential of a single-phase PES sampler using laboratory experiments. POCIS calibration results demonstrated that both sorbent and membrane had similar affinity for the target compounds. A rapid PES sorption occurred in the earlier days (<7 days) followed by a gradual increase in the PES phase concentration (equilibrium not achieved after 60 days). Especially, the membrane was the primary sink for 3,4-dichloroaniline and 3,4-dichloronitrobenzene for up to 14 and 31 days, respectively. On the other hand, the single-phase PES sampler showed similar mass uptake as POCIS and reached equilibrium within 19 days under static condition, indicating its potential suitability in the equilibrium regime. PES-water partition coefficient of the target compounds was between 1.2 and 6.5 L/g. Finally, we present a poly-parameter linear-free energy relationship (pp-LFER) using published data to predict the PES-water partition coefficients. The pp-LFER models showed moderate predictability as indicated by R²_adj values between 0.7 and 0.9 for both internal and external data set consisting of a wide range of hydrophobic and hydrophilic compounds (-0.1 ≤ logK_OW ≤ 7.4). The proposed pp-LFER model can be used to screen high PES-sorbing chemicals to increase the reliability and accuracy of aqueous concentration prediction from POCIS sampling and to select the most appropriate sampling approach for new compounds.

A Review on Polyethersulfone Membranes in Polar Organic Chemical Integrative Samplers: Preparation, Characterization and Innovation

The membranes in polar organic chemical integrative samplers (POCIS) enclose the receiving sorbent and protect it from coming into direct contact with the environmental matrix. They have a crucial role in extending the kinetic regime of contaminant uptake, by slowing down their diffusion between the water phase and the receiving phase. The drive to improve passive sampling requires membranes with better design and enhanced performances. In this review, the preparation of standard polyethersulfone (PES) membranes for POCIS is presented, as well as methods to evaluate their composition, morphology, structure, and performance. Generally, only supplier-related morphological and structural data are provided, such as membrane type, thickness, surface area, and pore diameter. The issues related to the use of PES membranes in POCIS applications are exposed. Finally, alternative membranes to PES in POCIS are also discussed, although no better membrane has yet been developed. This review highlights the urge for more membrane characterization details and a better comprehension of the mechanisms which underlay their behavior and performance, to improve membrane selection and optimize passive sampler development.

Carbon nanotube-passive samplers as novel tools for sampling and determining micropollutants in the aquatic environment

Passive sampling is an interesting and cost-effective strategy for the quantification of micropollutants in the aquatic environment. When combined especially with a sensitive analytical method such as liquid chromatography coupled with triple quadrupole mass spectrometry (LC-MS/MS), the use of passive sampling devices (PSDs) enables long-term and reliable determination of a wide range of chemicals. In this study, carbon nanotubes (CNTs) were used as an innovative sorbent in POCIS-like samplers (Polar Organic Chemical Integrative Sampler). The developed CNTs-PSDs were calibrated by the flow-through method and the obtained sampling rates (R_s) of analytes were compared with the previously obtained R_s values using the semi-static method. Subsequently, passive samplers were placed in the Baltic Sea, the Nogat River, and the Sztumskie Pole Lake in order to sample and concentrate 28 chemical compounds belonging to the group of contaminants of emerging concern (CECs). For the first time, the effectiveness of the use of CNTs-PSDs in the field was proven by the quantification of carbamazepine, diclofenac, p-nitrophenol, bisphenol A, 3,5-dichlorophenol, 17-β-estradiol, 17-α-ethinylestradiol and metoprolol in the tested surface waters. The obtained time-weighted average (TWA) concentrations of analytes ranged from 0.22 ± 0.12 ng/L (for metoprolol in the Nogat River) to 32.1 ± 2.4 ng/L (for bisphenol A in the Sztumskie Pole Lake). More importantly, CNTs-PSDs determined a greater amount of micropollutants than grab sampling and solid-phase extraction (SPE), which proves the advantage of passive sampling over grab sampling, especially when monitoring contaminants in the aquatic environment at low concentration levels.

Monitoring of Environmental Contaminants in Mixed-Use Watersheds Combining Targeted and Nontargeted Analysis with Passive Sampling

Understanding the environmental fate, transport, and occurrence of pesticides and pharmaceuticals in aquatic environments is of utmost concern to regulators. Traditionally, monitoring of environmental contaminants in surface water has consisted of liquid chromatography-tandem mass spectrometry analyses for a set of targeted compounds in discrete samples. These targeted approaches are limited by the fact that they only provide information on compounds within a target list present at the time and location of sampling. To address these limitations, there has been considerable interest in suspect screening and nontargeted analysis (NTA), which allow for the detection of all ionizable compounds in the sample with the added benefit of data archiving for retrospective mining. Even though NTA can detect a large number of contaminants, discrete samples only provide a snapshot perspective of the chemical disposition of an aquatic environment at the time of sampling, potentially missing episodic events. We evaluated two types of passive chemical samplers for nontargeted analysis in mixed-use watersheds. Nontargeted data were processed using MS-DIAL to screen against our in-house library and public databases of more than 1300 compounds. The data showed that polar organic chemicals integrative samplers (POCIS) were able to capture the largest number of analytes with better reproducibility than organic compound-diffusive gradients in thin film (o-DGT), resulting from the greater amount of binding sorbent. We also showed that NTA combined with passive sampling gives a more representative picture of the contaminants present at a given site and enhances the ability to identify the nature of point and nonpoint pollution sources and ecotoxicological impacts. Environ Toxicol Chem 2022;41:1131-1143. © 2021 Her Majesty the Queen in Right of Canada Environmental Toxicology and Chemistry © 2021 SETAC. Reproduced with the permission of the Minister of Agriculture and Agri-Food Canada.

Distinct uptake and accumulation profiles of triclosan in youdonger (Brassica campestris subsp. Chinensis var. communis) under two planting systems: Evidence from 14C tracing techniques

Triclosan is a widely used biocide against microorganisms and is ubiquitously distributed in the environment. Triclosan can be accumulated into plants from soil and hydroponic media. However, little information is currently available on the comparative fate of triclosan in plants under soil and hydroponics cultivation conditions and factors governing uptake. Therefore, this study was designed to comparatively elucidate the uptake mechanism of ¹⁴C-triclosan in youdonger (Brassica campestris subsp. Chinensis var. communis) grown under different soils and hydroponics and clarify dominant uptake factors. Results showed that 77.2% of ¹⁴C were accumulated in youdonger grown in a hydroponic system, while only 1.24%-2.33% were accumulated in the two soil-planting systems. In addition, the bioconcentration factor (BCF) of ¹⁴C-triclosan in soil-plant systems was approximately 400-fold smaller than that in the hydroponics. In the soil-planting system, a strong linear correlation was found between concentrations of triclosan in soil pore water and youdonger plant (R² > 0.85, p < 0.01) at different incubation times. Therefore, triclosan in pore water might be a good indicator to estimate its accumulation in plants and is significantly affected by soil pH, clay, and organic matter contents. The estimated average dietary intakes of triclosan for youdonger grown in hydroponic and soil-planting systems were estimated to be 1.31 ng day^-1 kg^-1 and 0.05-0.12 ng day^-1 kg^-1, respectively, much lower than the acceptable dietary intakes of triclosan (83 μg day^-1 kg^-1), indicating no significant human health risks from youdonger consumption. This study provided insights into uptake routes of triclosan into youdonger plants from both soil and hydroponic systems, bioavailability of triclosan in different soils, and further assessment of human exposure to triclosan from youdonger.

Passive sampling of chlorophenols in water and soils using diffusive gradients in thin films based on β-cyclodextrin polymers

Chlorophenols (CPs) have been listed as priority control pollutants because of their high toxicity and wide range. An In-situ monitoring technique using diffusive gradients in thin films based on porous β-cyclodextrin polymers as binding materials (CDP-DGT), was established to monitor four typical CPs, namely, 4-Chlorophenol (4-CP), 2,4-Dichlorophenol (2,4-DCP), 2,4,5-Trichlorophenol (2,4,5-TCP), 2,4,6-Trichlorophenol (2,4,6-TCP) in water and soils. The performance of CDP-DGT are stable under the conditions of pH 3.5-9.3, ionic strength 0.001-0.500 mol L^-1 and dissolved organic matter concentration 0-20 mol L^-1. The adsorption capacities of CDP-DGT for 4-CP, 2,4-DCP, 2,4,5-TCP, 2,4,6-TCP were 57.80 μg cm^-2, 98.82 μg cm^-2, 95.69 μg cm^-2 and 98.91 μg cm^-2, respectively. The time-average weighted concentrations of four CPs determined by CDP-DGT at Sanjiangkou wharf (Yangtze river, China) were consistent with the results of grab sampling, indicating the feasibility of CDP-DGT application in actual water. In addition, the distribution of CPs in the red soil of Kunming and paddy soil of Yixing were also studied by CDP-DGT, and the desorption kinetics in the two soils were analyzed with the DIFS model. The higher the soil organic matter content is, the more CPs are distributed in the soil solid phase. CPs in both soils can be partially resupplied to soil solution from the soil solid phase and the higher the partition coefficient for labile CPs is, the stronger the supplement capacity is.

Unravelling the role of membrane pore size in polar organic chemical integrative samplers (POCIS) to broaden the polarity range of sampled analytes

Polar organic chemical integrative samplers (POCIS) are widely used in their standard configuration for sampling contaminants in water bodies. A wider polyethersulfone (PES) membrane pore size was employed in POCIS exposed in a static calibration experiment to investigate the uptake of 21 emerging contaminants ranging from hydrophilic (perfluoroalkyl compounds, xanthines, an artificial sweetener) to more hydrophobic compounds (pharmaceuticals, oestrogens, UV filters). Compared to standard POCIS with 0.1-µm pore size PES membranes, the POCIS with 5-µm pore size PES membranes did not increase sampling rates for compounds of relatively low and mid-hydrophobicity. However, the uptake of more hydrophobic and anionic compounds, which either poorly diffuse through or are retained within the standard 0.1-µm PES membrane, showed a marked increase. This led to the first ever recorded sampling rates for triclosan (0.249 L day^-1) and two UV filters (0.075-0.123 L day^-1). Based on these results, more attention should be placed on the choice of the appropriate membrane for each POCIS application. The most suitable configuration depends on the studied compound physico-chemical characteristics-such as the polarity and the compound membrane-to-sorbent partitioning coefficient-but also on the site conditions (deployment time, fouling, flow variations, et.).

Multisite Calibration of a Microporous Polyethylene Tube Passive Sampler for Quantifying Drugs in Wastewater

Passive sampling approaches to monitor licit and illicit drugs of concern in wastewater shows promise as a supplementary sampling technique to grab sampling when conventional composite autosampling may not be possible. Recent studies have assessed the applicability of passive sampling at a single wastewater treatment plant (WWTP). However, it remains unknown whether a single-site calibration can be applied to other WWTPs. This study evaluated the in situ calibration of microporous polyethylene tube passive samplers (MPTs) against simultaneously collected composite samples for 22 different WWTPs. Samples were analyzed for methylamphetamine, amphetamine, hydroxycotinine, cotinine, benzoylecgonine, 3,4-methylenedioxymethamphetamine, and noroxycodone. Estimated rates of chemical uptake (sampling rates) were calculated using the mass accumulated in the samplers, the concentration measured in composite samples, and the duration of deployment. The estimated sampling rates were consistent between WWTPs (>90% within a factor of two) and ranged from 5 mL day^-1 (amphetamine) to 9 mL day^-1 (noroxycodone). The samplers were effective at estimating analyte concentrations, with 77% of results having a normalized difference to 24 h composite samples of below 30%. Our study suggests that MPT passive samplers provide a tool for the spatiotemporal monitoring of drug use where automated integrative sampling techniques may not be feasible.

A Simple Teabag Equilibrium Passive Sampler using hydrophilic divinylbenzene sorbent for contaminants of emerging concern in the marine environment

A promising concept for sampling contaminants of emerging concern (CECs) using a home-made Simple Teabag Equilibrium Passive Sampler (STEPS) containing hydrophilic divinylbenzene (h-DVB) sorbent is presented and evaluated for application in estuarine systems. The uptake of a multi-class mixture of CECs with a broad polarity range (Log P ranging from -0.1 to 9.9) was investigated in static exposure batch experiments. Sampling rates (R_s) and equilibrium partitioning coefficients (K_sw) were determined for up to 74 CECs. Fast uptake (R_s = 0.3-12 L d^-1) was noticed and the STEPS attained equilibrium partitioning after 1 to 2 weeks of exposure, with Log K_sw ranging from 4.1 to 6.5 L kg^-1. Field application of this novel h-DVB containing STEPS, followed by ultra-high performance liquid chromatography coupled to high-resolution Orbitrap mass spectrometry, revealed the presence of up to 40 steroidal hormones, (alkyl)phenols, phthalates, pharmaceuticals, personal care products, and pesticides in the Belgian Part of the North Sea. The measured trace concentrations (from 0.003 ng L^-1 to 1.9 μg L^-1) and good precision (average RSD < 30%, n = 3) demonstrate the STEPS as fit-for-purpose for micropollutant analysis in the marine environment.

Evaluation of Illicit Drug Consumption by Wastewater Analysis Using Polar Organic Chemical Integrative Sampler as a Monitoring Tool

Illicit drug abuse is a worldwide social and health problem, and monitoring illicit drug use is of paramount importance in the context of public policies. It is already known that relevant epidemiologic information can be obtained from the analysis of urban residual waters. This approach, named wastewater-based epidemiology (WBE), is based on the measurement of specific markers, resulting from human biotransformation of the target drugs, as indicators of the consumption of the compounds by the population served by the wastewater treatment installation under investigation. Drug consumption estimation based on WBE requires sewage sampling strategies that express the concentrations along the whole time period of time. To this end, the most common approach is the use of automatic composite samplers. However, this active sampling procedure is costly, especially for long-term studies and in limited-resources settings. An alternative, cost-effective, sampling strategy is the use of passive samplers, like the polar organic chemical integrative sampler (POCIS). POCIS sampling has already been applied to the estimation of exposure to pharmaceuticals, pesticides, and some drugs of abuse, and some studies evaluated the comparative performances of POCIS and automatic composite samplers. In this context, this manuscript aims to review the most important biomarkers of drugs of abuse consumption in wastewater, the fundamentals of POCIS sampling in WBE, the previous application of POCIS for WBE of drugs of abuse, and to discuss the advantages and disadvantages of POCIS sampling, in comparison with other strategies used in WBE. POCIS sampling is an effective strategy to obtain a representative overview of biomarker concentrations in sewage over time, with a small number of analyzed samples, increased detection limits, with lower costs than active sampling. Just a few studies applied POCIS sampling for WBE of drugs of abuse, but the available data support the use of POCIS as a valuable tool for the long-term monitoring of the consumption of certain drugs within a defined population, particularly in limited-resources settings.

Limitations of Integrative Passive Samplers as a Tool for the Quantification of Pharmaceuticals in the Environment - A Critical Review with the Latest Innovations

This review starts with a presentation of the theory of kinetic uptake by passive sampling (PS), which is traditionally used to distinguish between integrative and equilibrium samplers. Demonstrated limitations of this model for the passive sampling of pharmaceuticals from water were presented. Most notably, the contribution of the protective membrane in the resistance to mass transfer of lipophilic analytes and the well documented effect of external parameters on sampling rates contributed to the greatest uncertainty in PS application. The diffusion gradient in thin layer (DGT) technique seems to reduce the effect of external parameters (e.g., flow rate) to some degree. The laboratory-determined integrative uptake periods over defined sampler deployments was compared, and the discrepancy found suggests that the most popular Polar Organic Chemical Integrative Sampler (POCIS) could in some cases utilized as an equilibrium sampler. This assertion is supported by own calculations for three pharmaceuticals with extremely different lipophilic characters. Finally, the reasons performance reference compounds (PRCs) are not recommended for the reduction in uncertainty of the TWAC found by adsorptive samplers were presented. It was concluded that techniques of passive sampling of pharmaceuticals need a new uptake model to fit the current situation.

Impact of environmental factors on the sampling rate of β-blockers and sulfonamides from water by a carbon nanotube-passive sampler

Passive techniques are a constantly evolving approach to the long-term monitoring of micropollutants, including pharmaceuticals, in the aquatic environment. This paper presents, for the first time, the calibration results of a new CNTs-PSDs (carbon nanotubes used as a sorbent in passive sampling devices) with an examination of the effect of donor phase salinity, water pH and the concentration of dissolved humic acids (DHAs), using both ultrapure and environmental waters. Sampling rates (R_s) were determined for the developed kinetic samplers. It has been observed that the impact of the examined environmental factors on the R_s values strictly depends on the type of the analytes. In the case of β-blockers, the only environmental parameter affecting their uptake rate was the salinity of water. A certain relationship was noted, namely the higher the salt concentration in water, the lower the R_s values of β-blockers. In the case of sulfonamides, water salinity, water pH 7-9 and DHAs concentration decreased the uptake rate of these compounds by CNTs-PSDs. The determined R_s values differed in particular when the values obtained from the experiments carried out using ultrapure water and environmental waters were compared. The general conclusion is that the calibration of novel CNTs-PSDs should be carried out under physicochemical conditions of the aquatic phase that are similar to the environmental matrix.

Rapid direct analysis of river water and machine learning assisted suspect screening of emerging contaminants in passive sampler extracts

A novel and rapid approach to characterise the occurrence of contaminants of emerging concern (CECs) in river water is presented using multi-residue targeted analysis and machine learning-assisted in silico suspect screening of passive sampler extracts. Passive samplers (Chemcatcher®) configured with hydrophilic-lipophilic balanced (HLB) sorbents were deployed in the Central London region of the tidal River Thames (UK) catchment in winter and summer campaigns in 2018 and 2019. Extracts were analysed by; (a) a rapid 5.5 min direct injection targeted liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for 164 CECs and (b) a full-scan LC coupled to quadrupole time of flight mass spectrometry (QTOF-MS) method using data-independent acquisition over 15 min. From targeted analysis of grab water samples, a total of 33 pharmaceuticals, illicit drugs, drug metabolites, personal care products and pesticides (including several EU Watch-List chemicals) were identified, and mean concentrations determined at 40 ± 37 ng L^-1. For targeted analysis of passive sampler extracts, 65 unique compounds were detected with differences observed between summer and winter campaigns. For suspect screening, 59 additional compounds were shortlisted based on mass spectral database matching, followed by machine learning-assisted retention time prediction. Many of these included additional pharmaceuticals and pesticides, but also new metabolites and industrial chemicals. The novelty in this approach lies in the convenience of using passive samplers together with machine learning-assisted chemical analysis methods for rapid, time-integrated catchment monitoring of CECs.

In situ calibration of polar organic chemical integrative sampler (POCIS) for monitoring of pharmaceuticals in surface waters

POCIS is the most widely applied passive sampler of polar organic substances, because it was one of the first commercially available samplers for that purpose on the market, but also for its applicability for a wide range of substances and conditions. Its main weakness is the variability of sampling performance with exposure conditions. In our study we took a pragmatic approach and performed in situ calibration for a set of 76 pharmaceuticals and their metabolites in five sampling campaigns in surface water, covering various temperature and flow conditions. In individual campaigns, R_S were calculated for up to 47 compounds ranging from 0.01 to 0.63 L d^-1, with the overall median value of 0.10 L d^-1. No clear changes of R_S with water temperature or discharge could be found for any of the investigated substances. The absence of correlation of experimental R_S with physical-chemical properties in combination with the lack of mechanistic understanding of compound uptake to POCIS implies that practical estimation of aqueous concentrations from uptake in POCIS depends on compound-specific experimental calibration data. Performance of POCIS was compared with grab sampling of water in seven field campaigns comprising multiple sampling sites, where sampling by both methods was done in parallel. The comparison showed that for 25 of 36 tested compounds more than 50% of POCIS-derived aqueous concentrations did not differ from median of grab sampling values more than by a factor of 2. Further, for 30 of 36 compounds, more than 80% of POCIS data did not differ from grab sampling data more than by a factor of 5. When accepting this level of accuracy, in situ derived sampling rates are sufficiently robust for application of POCIS for identification of spatial and temporal contamination trends in surface waters.

Untargeted characterisation of dissolved organic matter contributions to rivers from anthropogenic point sources using direct-infusion and high-performance liquid chromatography/Orbitrap mass spectrometry

RATIONALE

Anthropogenic organic inputs to freshwaters can exert detrimental effects on aquatic ecosystems, raising growing concern for both environmental conservation and water security. Current regulation by the EU water framework directive (European Union, 2000/60/EC) relates to organic pollution by monitoring selected micropollutants; however, aquatic ecosystem responses require a comprehensive understanding of dissolved organic matter (DOM) composition. The introduction of high-resolution mass spectrometry (HRMS) is set to greatly increase our understanding of the composition of DOM of both natural and anthropogenic origin derived from diffuse and point sources.

METHODS

DOM was extracted from riverine and treated sewage effluent using solid-phase extraction (SPE) and analysed using dissolved organic carbon analysis, direct-infusion high-resolution mass spectrometry (DI-HRMS) and high-performance liquid chromatography (HPLC)/HRMS. The data obtained were analysed using univariate and multivariate statistics to demonstrate differences in background DOM, anthropogenic inputs and in-river mixing. Compound identifications were achieved based on MS2 spectra searched against on-line databases.

RESULTS

DI-HRMS spectra showed the highly complex nature of all DOM SPE extracts. Classification and visualisation of extracts containing many thousands of individual compounds were achieved using principal component analysis (PCA) and hierarchical cluster analysis. Kruskal-Wallis analyses highlighted significant discriminating ions originating from the sewage treatment works for more in-depth investigation by HPLC/HRMS. The generation of MS2 spectra in HPLC/HRMS provided the basis for identification of anthropogenic compounds including; pharmaceuticals, illicit drugs, metabolites and oligomers, although many thousands of compounds remain unidentified.

CONCLUSIONS

This new approach enables comprehensive analysis of DOM in extracts without any preconceived ideas of the compounds which may be present. This approach has the potential to be used as a high throughput, qualitative, screening method to determine if the composition of point sources differs from that of the receiving water bodies, providing a new approach to the identification of hitherto unrecognised organic contribution to water bodies.

Sampling Rate of Polar Organic Chemical Integrative Sampler (POCIS): Influence Factors and Calibration Methods

As a passive sampling device, the polar organic chemical integrative sampler (POCIS) has the characteristics of simple operation, safety, and reliability for assessing the occurrence and risk of persistent and emerging trace organic pollutants. The POCIS, allowing for the determination of time-weighted average (TWA) concentration of polar organic chemicals, exhibits good application prospects in aquatic environments. Before deploying the device in water, the sampling rate (Rs), which is a key parameter for characterizing pollutant enrichment, should be determined and calibrated accurately. However, the Rs values strongly depend on experimental hydrodynamic conditions. This paper provides an overview of the current situation of the POCIS for environmental monitoring of organic pollutants in an aquatic system. The principle and theory of the POCIS are outlined. In particular, the effect factors such as the ambient conditions, pollutant properties, and device features on the Rs are analyzed in detail from aspects of impact dependence and mechanisms. The calibration methods of the Rs under laboratory and in situ conditions are summarized. This review offers supplementary information on comprehensive understanding of mechanism and application of the POCIS. Nevertheless, the Rs were impacted by a combined effect of solute–sorbent–membrane–solution, and the influence extent of each variable was still unclear. On this basis, the ongoing challenges are proposed for the future application of the POCIS in the actual environment, for instance, the need for this device to be improved in terms of quantitative methods for more accurate measurement of the Rs.

Systematic Evaluation of Different Coating Chemistries Used in Thin-Film Microextraction

A systematic evaluation of eight different coatings made of solid phase extraction (SPE) and carbon-based sorbents immobilized with polyacrylonitrile in the thin-film microextraction (TFME) format using LC-MS/MS was described. The investigated coatings included graphene, graphene oxide, multi-walled carbon nanotubes (MWCNTs), carboxylated MWCNTs, as carbon-based coatings, and polystyrene-divinylbenzene (PS-DVB), octadecyl-silica particles (C18), hydrophilic-hydrophobic balance particles (HLB) and phenyl-boronic acid modified particles (PBA), as SPE-based coatings. A total of 24 compounds of diverse moieties and of a wide range of polarities (log P from -2.99 to 6.98) were selected as probes. The investigated coatings were characterized based on their extraction performance toward the selected probes at different pH values and at optimized desorption conditions. In the case of SPE-based coatings, PS-DVB and HLB exhibited a balanced extraction for compounds within a wide range of polarities, and C18 showed superior extraction recoveries for non-polar analytes. Carbon-based coatings showed high affinity for non-polar compounds given that their main driving force for extraction is hydrophobic interactions. Interestingly, among the studied carbon-based coatings, graphene oxide showed the best extraction capabilities toward polar compounds owing to its oxygen-containing groups. Overall, this work provided important insights about the extraction mechanisms and properties of the investigated coatings, facilitating the coating selection when developing new TFME applications.

Measuring the occurrence of antibiotics in surface water adjacent to cattle grazing areas using passive samplers

A wide variety of antibiotics and other pharmaceuticals are used in livestock production systems and residues passed to the environment, often unmetabolized, after use and excretion. Antibiotic residues may be transported from manure-treated soils via runoff and are also capable of reaching surface and groundwater systems through a variety of pathways. The occurrence and persistence of antibiotics in the environment is a concern due to the potential for ecological effects and proliferation of environmental antibiotic resistance in pathogenic organisms. In the present study, the occurrence and seasonal variation of 24 commonly-used veterinary antibiotics was evaluated in surface water adjacent to several livestock production systems using Polar Organic Chemical Integrative Samplers (POCIS). Uptake rates for all compounds, nine of which have not been previously reported, were measured in the laboratory to permit estimation of changes in the time-weighted average (TWA) antibiotic concentrations during exposure. The antibiotics detected in POCIS extracts included sulfadimethoxine, sulfamethoxazole, trimethoprim, sulfamerazine, sulfadiazine, lincomycin, erythromycin, erythromycin anhydro- and monensin. The maximum TWA concentration belonged to sulfadiazine (25 ng/L) in the August-September sampling period and coincided with the highest number of precipitation events. With the exception of monensin that showed an increase in concentration over the stream path, none of the detected antibiotics were prescribed to livestock at the facility. The detection of antibiotics not prescribed by the facility may be attributable to the environmental persistence of previously used antibiotics, transfer by wind from other nearby livestock production sites or industrial uses, and/or the natural production of some antibiotics.

Performance of the organic-diffusive gradients in thin-films passive sampler for measurement of target and suspect wastewater contaminants

Although passive sampling is widely accepted as an excellent tool for environmental monitoring, their integration with suspect or non-targeted screening by high-resolution mass spectrometry has been limited. This study describes the application of the organic-diffusive gradients in thin-films (o-DGT) passive sampler as a tool for accurate measurement of both targeted and suspect polar organic contaminants (primarily pharmaceuticals) in wastewater. First, performance of o-DGT was assessed alongside the polar organic chemical integrative sampler (POCIS) and active sampling at two wastewater treatment facilities using targeted analyses. Overall, water concentrations measured by o-DGT, POCIS, and 24-hr integrative active samples were in good agreement with each other. There were exceptions, including a systematic difference between o-DGT and POCIS at certain sites that we propose was a result of site-specific conditions and a difference in sampling rates between the two techniques. The second component of this work involved suspect screening of the o-DGT extracts using high-resolution, high mass accuracy quadrupole time-of-flight mass spectrometry (QTOF). Lamotrigine, venlafaxine, and des-methylvenlafaxine were three suspect compounds identified and selected as proof-of-concept case studies to determine the feasibility and accuracy of o-DGT for estimating water concentrations based upon predicted sampling rates using a previously validated o-DGT diffusion model. Semi-quantification of the suspect compounds was conducting using an average surrogate response factor based on the suite of compounds measured by the targeted analyses. This, combined with the modelled sampling rates provided time-weighted average wastewater concentrations of the identified suspects within a factor of 2 of the true value, confirmed by isotope dilution with mass labelled internal surrogates. To the knowledge of the authors, this work is the first to demonstrate the utility of the o-DGT passive sampler as a potential environmental screening tool that can be integrated into the rapidly advancing field of non-targeted high resolution mass spectrometry.

Estimating 42 pesticide sampling rates by POCIS and POCIS-MIP samplers for groundwater monitoring: a pilot-scale calibration

Pesticides occur in groundwater as a result of agricultural activity. Their monitoring under the Water Framework Directive is based on only a few spot-sampling measurements per year despite their temporal variability. Passive sampling, which was successfully tested in surface water to provide a more representative assessment of contamination, could be applied to groundwater for a better definition of its contamination. However, few reliable calibration data under low water flow are available. The objective of our study thus consisted in determining sampling rates by two types of passive samplers, a POCIS (polar organic chemical integrative sampler) for polar pesticides, and a POCIS-MIP sampler based on a receiving phase of molecular imprinted polymers, specific for AMPA and glyphosate under low flow conditions as exist in groundwater. To our knowledge, this is the first time that sampling rates (sampling rate represents the volume of water from which the analyte is quantitatively extracted by the sampler per unit time) are estimated for groundwater applications. Our calibrations took place in an experimental pilot filled with groundwater and with low water flow (a few metres per day). Pesticide uptake in POCIS showed good linearity, with up to 28 days before reaching equilibrium. Two types of accumulation in POCIS were noted (a linear pattern up to 28 days, and after a time lag of 7 to 14 days). Sampling rates for 38 compounds were calculated and compared with those available in the literature or obtained previously under laboratory conditions. The values obtained were lower by a factor 1 to 14 than those estimated under stirring conditions in the literature, whereas water flow velocity (m s^-1) differed by a factor of 2000 to 10,000.

Calibration and validation of a microporous polyethylene passive sampler for quantitative estimation of illicit drug and pharmaceutical and personal care product (PPCP) concentrations in wastewater influent

Wastewater-based epidemiology (WBE), the per capita normalised measurement of drugs, chemicals or metabolites in wastewater influent, relies on sampling and quantitative analysis to evaluate temporal and spatial trends of chemical consumption. Continuous, high-resolution, flow proportional composite sampling is optimal for accurate representations of chemical mass loads, but is rarely implemented, with conventional autosamplers providing relatively low frequency time or volume proportional samples. However, due to equipment or resource constraints at many wastewater treatment plants (WWTPs), even this may not be feasible. Passive sampling may provide an alternative sampling strategy. To investigate this, samplers comprising hollow, cylindrical Microporous Polyethylene Tubes (MPTs) containing polymeric sorbent phases of Strata-X and Strata-X in agarose were simultaneously deployed in a municipal WWTP influent stream. Samplers were extracted, analysed and evaluated for a range of illicit drugs and pharmaceuticals and personal care products (PPCPs) after 4, 7, 15, 21, and 29 day deployments. The MPT samplers were calibrated against 24-hour time proportional composite grab samples that were collected in parallel. Diffusion through the MPT governed uptake, reducing or eliminating the influence of external flow rates that may fluctuate unpredictably in a WWTP environment. Calibration data for six illicit drugs and fourteen PPCPs, including methamphetamine, benzoylecgonine, MDMA, codeine and carbamazepine, demonstrated linear accumulation in the samplers (R² ≥ 0.84). Derived sampling rates for these analytes ranged from 0.25 to 17 mL d^-1 for ibuprofen and verapamil, respectively. A validation study using this sampling rate data showed the MPT could effectively quantify concentrations (≥0.1 ng mL^-1) of a range of amphetamine-type stimulants, opioids and metabolites as well as nicotine, accounting for 95% of the variance in parallel composite grab sample concentrations of these compounds. The MPT sampler shows promise for providing essential monitoring data for WBE, informing future intervention and research strategies.

Salinity and pH as factors affecting the passive sampling and extraction of pharmaceuticals from water

Passive sampling is an attractive technique for the long-term monitoring of pharmaceuticals in the water environment. The reliability of the received results depends on the properly performed calibration, namely the determination of analyte sampling rates. This step can be the source of a systematic error, as the sampling rate values are dependent on the water donor phase parameters. This is especially important for pharmaceuticals, since their chemical characteristics and ionic form change with pH. In this study, the cross-effect of pH (3, 7, and 9) and salinity (0, 7, and 35 practical salinity unit, using artificial sea water) on the passive sampling of 21 pharmaceuticals (antiparasitics, beta-blockers, non-steroidal anti-inflammatory drugs, sulfonamides) was tested. The primarily determined parameter was the sampling rate. In addition, the extraction efficiency, partitioning coefficient, and the concentration of the analytes on the sorbent were calculated. Generally, for the non-steroidal anti-inflammatory drugs, beta-blockers, and antiparasitics, the change both in pH and salinity had a negligible impact on the mentioned experimental parameters. In contrast, the extraction of sulfonamides was impacted by both pH and salinity, while lipophilicity was not a decisive parameter.

Application of diffusive gradients in thin-films for in-situ monitoring of nitrochlorobenzene compounds in aquatic environments

Nitrochlorobenzene compounds (NCBs) are of key interest in environmental monitoring due to their high toxicity. To better understand the presence and fate of NCBs in aquatic environments, an in-situ sampling technique of diffusive gradients in thin films (DGT) based on hydrophilic-lipophilic-balanced (HLB) resin, combined with gas chromatography, was developed to measure four typical NCBs, e.g. meta-chloronitrobenzene (MNCB), para-chloronitrobenzene (PNCB), ortho-chloronitrobenzene (ONCB), and 2,4-dinitrochlorobenzene (CDNB). The diffusion coefficients of MNCB, PNCB, ONCB, and CDNB in agarose-based gel were firstly determined in diffusion cell experiments and ranged from 7.19 × 10^-6 to 7.49 × 10^-6 cm/s. The capacities of HLB-DGT for MNCB, PNCB, ONCB, and CDNB were higher than 114.65, 117.52, 117.72, and 37.58 μg/cm², respectively. The HLB-DGT performance on NCBs determination was demonstrated to be independent of natural fluctuations in pH (3-9), ionic strength (0.001-0.5 M), and dissolved organic matter concentrations (0-20 mg/L) and of deployment time (0-120 h). In the field application, the DGT-based method to measure NCBs not only proved to be accurate and effective, but also performed better than the grab sampling method under the variable conditions. This study demonstrates that the newly developed in-situ method based on DGT can provide an attractive alternative for the routine monitoring of NCBs in aquatic environments.

Development of a Passive Sampling Technique for Measuring Pesticides in Waters and Soils

It is essential to monitor pesticides in the environment to help ensure water and soil quality. The diffusive gradients in thin-films (DGT) technique can measure quantitative in situ labile (available) concentrations of chemicals in water, soil, and sediments. This study describes the systematic development of the DGT technique for nine current pesticides, selected to be representative of different classes with a wide range of properties, with two types of resins (HLB (hydrophilic-lipophilic-balanced) and XAD 18) as binding layer materials. The masses of pesticides accumulated by DGT devices were proportional to the deployment time and in inverse proportion to the thickness of the diffusive layer, in line with DGT theoretical predictions. DGT with both resin gels were tested in the laboratory for the effects of typical environmental factors on the DGT measurements. DGT performance was independent of the following: pH in the range of 4.7-8.2; dissolved organic matter concentrations <20 mg L^-1; and ionic strength from 0.01 to 0.25 M, although it was slightly affected at 0.5 M in some cases. This confirms DGT as a sampler suitable for controlled studies of environmental processes affecting pesticides. Field applications of DGT to measure pesticides in situ in waters and controlled laboratory measurements on five different soils (prepared at fixed soil/water ratios) demonstrated DGT is a suitable tool for environmental monitoring in waters and for investigating chemical processes in soils.

Limitation of flow effect on passive sampling accuracy using POCIS with the PRC approach or o-DGT: A pilot-scale evaluation for pharmaceutical compounds

Flow velocity is known to alter passive sampling accuracy. We investigated the POCIS (Polar Organic Chemical Integrative Sampler) with PRC (Performance Reference Compounds) approach and Diffusive Gradients in Thin Films samplers (o-DGT) to limit the effect of flow on the quantification accuracy of ten model pharmaceuticals compounds (0.16 ≤ log K_OW ≤ 4.51). POCIS and o-DGT samplers were exposed for seven days in controlled pilot-scale (hundreds of liters) experiments under quiescent or flowing (2 < V < 18 cm s^-1) conditions. Under flowing conditions, both POCIS-PRC and o-DGT efficiently limited the flow effect and led, in most cases, to biases within analytical uncertainty (20%). Under quiescent conditions, o-DGT performed accurately (bias < 30% for most compounds) whereas the PRC approach was unsuitable to improve upon the accuracy of POCIS (PRC was unable to desorb). Therefore, both approaches are helpful in limiting the effects of flow on accuracy, but only o-DGT is efficient in quiescent conditions. However, o-DGT currently suffers from poorer sensitivity compared to POCIS, but the future development of o-DGT devices with wider windows could overcome this limitation.

Field Evaluation and in Situ Stress Testing of the Organic-Diffusive Gradients in Thin-Films Passive Sampler

The organic-diffusive gradients in thin-films (o-DGT) technique has emerged as a promising aquatic passive sampler that addresses many of the challenges associated with current sampling tools used for measurement of polar organic contaminants. This study represents the first comprehensive field evaluation of the o-DGT in natural surface waters, across a wide suite of polar pharmaceuticals and pesticides. We explore the utility and limitations of o-DGT as a quantitative measurement tool compared to grab sampling and the polar organic chemical integrative sampler (POCIS) across four connected agricultural and wastewater-influenced freshwater systems spanning 600 km from the U.S. border to northern Manitoba, Canada. Overall, the suite of analytes detected with o-DGT and POCIS was similar. Concentrations in water estimated using o-DGT were greater than concentrations estimated from POCIS in 71 of 80 paired observations, and on average, the estimates from o-DGT were 2.3-fold greater than estimates from POCIS. Grab sample concentrations suggested that the systematic underestimation with POCIS were largely a result of sampling rate variation related to flow rate and boundary-layer effects, an issue reported consistently in the POCIS literature. These comprehensive measurements in an agriculturally influenced fast-flowing river, long-term sampling (>40 days) in a large dilute lake system, deployments in wastewaters, and under ice at near-freezing temperatures represent effective stress testing of o-DGT under representative and challenging conditions. Overall, its strong performance and improved accuracy over POCIS supports its use as a robust, quantitative, and sensitive measurement tool for polar organic chemicals in aquatic systems.

The application of molecularly imprinted polymers in passive sampling for selective sampling perfluorooctanesulfonic acid and perfluorooctanoic acid in water environment

Modeling and predicting of a novel polar organic chemical integrative sampler (POCIS) for sampling of perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) using molecularly imprinted polymers (MIPs) as receiving phase are presented in this study. Laboratory microcosm experiments were conducted to investigate the uptake kinetics, effects of flow velocity, pH, and dissolved organic matter (DOM), and also the selectivity of the POCIS. In this study, uptake study of PFOA and PFOS sampling on MIP-POCIS, over 14 days, was investigated. Laboratory calibrations of MIP-POCIS yielded sampling rate (R_s) values for PFOA and PFOS were 0.387 and 0.229 L/d, higher than POCIS using commercial sorbent WAX as receiving phase (0.133 and 0.141 L/d for PFOA and PFOS, respectively) in quiescent condition. The R_s values for PFOA and PFOS sampling on MIP-POCIS were increased to 0.591 and 0.281 L/d in stirred condition (0.01 m/s), and no significant increase occurred when the flow velocity was further increased. The R_s values were kept relatively high in the solution of which the pH was lower than the isoelectric point (IEP) of MIP-sorbent and decreased when the solution pH was extend the IEP value. Under the experimental conditions, DOM seemed to slightly facilitate the R_s values of PFOA and PFOS in MIP-POCIS. The results showed that the interaction between the target compounds and the receiving phase was fully integrated by the imprinting effects and also the electrostatic interaction. Finally, comparing the sampling rate of WAX-POCIS and the MIP-POCIS, the MIP-POCIS offers promising perspectives for selective sampling ability for PFOA and PFOS.

In situ measurement of perfluoroalkyl substances in aquatic systems using diffusive gradients in thin-films technique

To better understand the environmental impact of ubiquitous perfluoroalkyl substances (PFASs) in waters, reliable and robust measurement techniques are needed. As one of the most widely used passive sampling approaches, diffusive gradients in thin-films (DGT) is not only easy to handle but also provides time-weighted analyte concentrations. Based on DGT with XAD18 as a binding agent, we developed a new methodology to measure two frequently detected PFASs in surface waters and wastewaters, i.e. perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS). Their diffusion coefficients in the diffusive gel, measured using an independent diffusion cell, were 4.37 × 10^-6 and 5.08 × 10^-6 cm² s^-1 at 25 °C, respectively. DGT had a high capacity for PFOA and PFOS at 196 and 246 μg per gel disk, suggesting the DGT sampler was suitable for deployment of several weeks. Time-integrated concentrations of PFOA and PFOS in a natural lake and river, and a municipal wastewater treatment plant effluent using DGT samplers deployed in situ for 12-33 d were comparable to those measured by a solid-phase extraction method coupled with high-frequency grab sampling. This study demonstrates that DGT is an effective tool for in situ monitoring of PFASs in natural waters and wastewaters.

Concentrations, fluxes and field calibration of passive water samplers for pesticides and hazard-based risk assessment

Three passive sampler types including Chemcatcher® C₁₈, polar organic chemical integrative sampler-hydrophilic-lipophilic balance (POCIS-HLB) and silicone rubber (SR) based on polydimethylsiloxane (PDMS) were evaluated for 124 legacy and current used pesticides at two sampling locations in southern Sweden over a period of 6 weeks and compared to time-proportional composite active sampling. In addition, an in situ calibration was performed resulting in median in situ sampling rates (R_S, L day^-1) of 0.01 for Chemcatcher® C₁₈, 0.03 for POCIS-HLB, and 0.18 for SR, and median in situ passive sampler-water partition coefficients (log K_PW, L kg^-1) of 2.76 for Chemcatcher® C₁₈, 3.87 for POCIS-HLB, and 2.64 for SR. Deisopropylatrazine D₅ showed to be suitable as a performance reference compound (PRC) for SR. There was a good agreement between the pesticide concentrations using passive and active sampling. However, the three passive samplers detected 38 pesticides (including 9 priority substances from the EU Water Framework Directive (WFD) and 2 pyrethriods) which were not detected by the active sampler. The most frequently detected pesticides with a detection frequency of >90% for both sites were atrazine, 2,6-dichlorobenzamide, bentazone, chloridazon, isoproturon, and propiconazole. The annual average environmental quality standard (AA-EQS) for inland surface waters of the EU WFD and the risk quotient (RQ) of 1 was exceeded on a number of occasions indicating potential risk for the aquatic environment.

A novel active-passive sampling approach for measuring time-averaged concentrations of pollutants in water

Passive sampling with in situ devices offers several advantages over traditional sampling methods (i.e., discrete spot sampling), however, data interpretation from conventional passive samplers is hampered by difficulties in estimating the thickness of the diffusion layer at the sampler/medium interface (δ), often leading to inaccurate determinations of target analyte concentrations. In this study, the performance of a novel device combining active and passive sampling was investigated in the laboratory. The active-passive sampling (APS) device is comprised of a diffusion cell fitted with a pump and a flowmeter. Three receiving phases traditionally used in passive sampling devices (i.e., chelex resin, Oasis HLB, and silicone rubber), were incorporated in the diffusion cell and allowed the simultaneous accumulation of cationic metals, polar, and non-polar organic compounds, respectively. The flow within the diffusion cell was accurately controlled and monitored, and, combined with diffusion coefficients measurements, enabled the average δ to be estimated. Strong agreement between APS and time-averaged total concentrations measured in discrete water samples was found for most of the substances investigated. Accuracies for metals ranged between 87 and 116%, except Cu and Pb (∼50%), whilst accuracies between 64 and 101%, and 92 and 151% were achieved for polar and non-polar organic compounds, respectively. These results indicate that, via a well-defined in situ preconcentration step, the proposed APS approach shows promise for monitoring the concentration of a range of pollutants in water.

Effects of hydrodynamic conditions and temperature on polar organic chemical integrative sampling rates

The effects of changing hydrodynamic conditions and changing temperatures on polar organic chemical integrative sampler (POCIS) sampling rates (R_s ) were investigated for 12 crop protection chemicals. Exposure concentration was held constant in each laboratory experiment, and flow velocities were calculated from measured mass transfer coefficients of the water boundary layer near the surface of POCIS devices. At a given temperature R_s generally increased by a factor of 2 to 5 between a stagnant condition and higher flow velocities (6-21 cm/s), but R_s for most compounds was essentially constant between the higher flow velocities. When temperature was varied between 8 and 39 °C for a given flow condition, R_s increased linearly. In general, R_s increased by a factor of 2 to 4 and 2 to 8 over this temperature range under flow and stagnant conditions, respectively. An Arrhenius model was used to describe the dependence of POCIS sampling rates on temperature. Adjustments of R_s for temperature did not fully explain observed differences between time-weighted average concentrations of atrazine determined from POCIS and from composite water sampling in a field setting, suggesting that the effects of other competing factors still need to be evaluated. Environ Toxicol Chem 2018;37:2331-2339. © 2018 SETAC.

Relationship between geosorbent properties and field-based partition coefficients for pesticides in surface water and sediments of selected agrarian catchments: Implications for risk assessment

Studies on pesticide behavior, adsorption-likelihood, and bioavailability vis-a-vis geosorbent properties and seasons, are critical for understanding pesticide-fate and risks in pesticide-prone environments. We examined the relationship between geosorbent profiles of sediments (percentage sand, silt, clay, organic carbon content) across seasons and occurrence of pesticide residues in surface water and sediment of agricultural catchments at Owan, Ogbesse and Illushi communities of Edo State, Nigeria. Pesticide concentrations were measured monthly in samples of surface water and sediments across the selected sites for 18-months. Pesticide behavior and sorption-likelihoods were examined using partition coefficients K_d (sediment-water coefficient), K_oc (sediment-water coefficient normalized for organic carbon) and Log K_ow (octane-water coefficient); the relationship between K_d and K_oc was also examined. Results of the principal component analysis (PCA) indicated that pesticide levels in sediment and surface water were positively associated with the rainy season, total organic content (TOC), percentage silt and clay in sediment. Field-derived pesticide partition coefficients (K_d < 100 and log K_oc < 3) indicated that pesticide species were largely mobile and less likely to be retained in sediments by adsorption. As such, pesticides irrespective of solubility would end up in surface water, increasing risks for pelagic biota and humans sourcing river water for domestic use. Values of Log K_ow indicate that organochlorines including DDT, dieldrin, endrin and heptachlor epoxide portend significant bioaccumulation risks to humans and biota across sites. The relationship between K_d and K_oc for each site fitted into a quadratic model; it depicted a biphasic behavior of pesticide adsorption and desorption to sediments revealing that concentration of organic carbon across study sites was a limiting factor determining the extent of pesticide adsorption. This study demonstrates that understanding pesticide mobility using field-based partition coefficients could give a clearer picture of pesticide risks to biota and human populations.

Neonicotinoid pesticides in drinking water in agricultural regions of southern Ontario, Canada

Because of the persistence and solubility of neonicotinoid insecticides (NNIs), there is concern that these compounds may contaminate sources of drinking water. The objective of this project was to evaluate the distribution of NNIs in raw and treated drinking water from selected municipalities that draw their water from the lower Great Lakes in areas of southern Ontario, Canada where there is high intensity agriculture. Sites were monitored using Polar Organic Chemical Integrative Samplers (POCIS) and by collecting grab samples at six drinking water treatment plants. Thiamethoxam, clothianidin and imidacloprid were detected in both POCIS and grab samples of raw water. The frequency of detection of NNIs was much lower in treated drinking water, but some compounds were still detected at estimated concentrations in the low ng L^-1 range. Thiamethoxam was detected in one grab sample of raw drinking water at a mean concentration of 0.28 μg L^-1, which is above the guidelines for drinking water recommended in some jurisdictions, including the European Union directive on pesticide levels <0.1 μg L^-1 in water intended for human consumption. Further work is required to determine whether contamination of sources of drinking water with this class of insecticides is a global problem in agricultural regions.

Comparison of the sampling rates and partitioning behaviour of polar and non-polar contaminants in the polar organic chemical integrative sampler and a monophasic mixed polymer sampler for application as an equilibrium passive sampler

In this work, Oasis HLB® beads were embedded in a silicone matrix to make a single phase passive sampler with a higher affinity for polar and ionisable compounds than silicone alone. The applicability of this mixed polymer sampler (MPS) was investigated for 34 aquatic contaminants (log K_OW -0.03 to 6.26) in batch experiments. The influence of flow was investigated by comparing uptake under static and stirred conditions. The sampler characteristics of the MPS was assessed in terms of sampling rates (R_S) and sampler-water partition coefficients (K_SW), and these were compared to those of the polar organic chemical integrative sampler (POCIS) as a reference kinetic passive sampler. The MPS was characterized as an equilibrium sampler for both polar and non-polar compounds, with faster uptake rates and a shorter time to reach equilibrium than the POCIS. Water flow rate impacted sampling rates by up to a factor of 12 when comparing static and stirred conditions. In addition, the relative accumulation of compounds in the polyethersulfone (PES) membranes versus the inner Oasis HLB sorbent was compared for the POCIS, and ranged from <1% to 83% depending on the analyte properties. This is indicative of a potentially significant lag-phase for less polar compounds within POCIS. The findings of this study can be used to quantitatively describe the partitioning and kinetic behaviour of MPS and POCIS for a range of aquatic organic contaminants for application in field sampling.

Diffusive gradients in thin-films (DGT) for in situ sampling of selected endocrine disrupting chemicals (EDCs) in waters

A passive water sampler based on the diffusive gradients in thin-films (DGT) technique was developed and tested for 3 groups of endocrine disrupting chemicals (EDCs, including oestrogens, alkyl-phenols and bisphenols). Three different resins (hydrophilic-lipophilic-balanced (HLB), XAD18 and Strata-XL-A (SXLA)) were investigated for their suitability as the binding phase for DGT devices. Laboratory tests across a range of pH (3.5-9.5), ionic strength (0.001-0.5 M) and dissolved organic matter concentration (0-20 mg L^-1) showed HLB and XAD18-DGT devices were more stable compared to SXLA-DGT. HLB-DGT and XAD18-DGT accumulated test chemicals with time consistent with theoretical predictions, while SXLA-DGT accumulated reduced amounts of chemical. DGT performance was also compared in field deployments up to 28 days, alongside conventional active sampling at a wastewater treatment plant. Uptake was linear to the samplers over 18 days, and then began to plateau/decline, indicating the maximum deployment time in those conditions. Concentrations provided by the DGT samplers compared well with those provided by auto-samplers. DGT integrated concentrations over the deployment period in a way that grab-sampling cannot. The advantages of the DGT sampler over active sampling include: low cost, ease of simultaneous multi-site deployment, in situ analyte pre-concentration and reduction of matrix interferences compared with conventional methods. Compared to other passive sampler designs, DGT uptake is independent of flow rate and therefore allows direct derivation of field concentrations from measured compound diffusion coefficients. This passive DGT sampler therefore constitutes a viable and attractive alternative to conventional grab and active water sampling for routine monitoring of selected EDCs.

Grab and passive sampling applied to pesticide analysis in the São Lourenço river headwater in Campo Verde - MT, Brazil

In this study, the quality of surface water in the headwaters of São Lourenço River in Mato Grosso, Brazil, was evaluated in relation to contamination by pesticides. For this purpose, samples were collected between December 2015 and June 2016 by grab sampling and by passive sampling using an integrative polar organic compound sampler installed in the field during four 14-day cycles between March and June 2016. The analyses were performed by gas chromatography (CG/MS) and by liquid chromatography (UPLC-MS/MS). The results showed the detection of two pesticides (atrazine and pyraclostrobin) of the five analyzed by passive sampling and eight active principles among the 20 analyzed (malathion, diuron, carbofuran, carbendazim, trifluralin, imidacloprid, metolachlor, and acetamiprid) by grab sampling. The detection of 10 pesticides, even almost a decade after the beginning of a recovery process of the ciliary forest, confirms the headwaters' vulnerability to these contaminants and passive sampling proved to be an important tool in capturing small concentrations of pesticides constituting an interesting complement to grab sampling.