Overview of the Chemcatcher® for the passive sampling of various pollutants in aquatic environments Part A: Principles, calibration, preparation and analysis of the sampler

From capture to detection: A critical review of passive sampling techniques for pathogen surveillance in water and wastewater

Water quality, critical for human survival and well-being, necessitates rigorous control to mitigate contamination risks, particularly from pathogens amid expanding urbanization. Consequently, the necessity to maintain the microbiological safety of water supplies demands effective surveillance strategies, reliant on the collection of representative samples and precise measurement of contaminants. This review critically examines the advancements of passive sampling techniques for monitoring pathogens in various water systems, including wastewater, freshwater, and seawater. We explore the evolution from conventional materials to innovative adsorbents for pathogen capture and the shift from culture-based to molecular detection methods, underscoring the adaptation of this field to global health challenges. The comparison highlights passive sampling's efficacy over conventional techniques like grab sampling and its potential to overcome existing sampling challenges through the use of innovative materials such as granular activated carbon, thermoplastics, and polymer membranes. By critically evaluating the literature, this work identifies standardization gaps and proposes future research directions to augment passive sampling's efficiency, specificity, and utility in environmental and public health surveillance.

Breaking barriers in passive sampling: The potential of PTFE membranes in the monitoring of hydrophilic micropollutants

Passive samplers are key tools to sample hydrophilic micropollutants in water. Two main approaches address the influence of hydrodynamics: (1) determining site-specific sampling rate (RS) by characterizing kw, the mass transfer coefficient of the water-boundary layer (WBL), and (2) reducing WBL impact using a diffusive material to control the uptake. The first requires calibration data and the second has only been achieved using fragile diffusive material. This study assesses the transfer of hydrophilic contaminants through polytetrafluoroethylene (PTFE; 30 µm thick), a new membrane material with lower sorption than commonly used polyethersulfone (PES). Combined for the first time in a Chemcatcher-like configuration, we calibrated the modified samplers for 44 micropollutants to provide RS - kw relationships for in-situ RS determination (approach 1). Micropollutants accumulated over 2000 times more on the sorbent than on PTFE. PTFE-based RS (0.027 to 0.300 L day-1) were 2.5 higher than previously reported with PES. Membrane property measurements (porosity, tortuosity) indicated that accumulation is primarily controlled by the membrane. Extrapolation indicated that using thicker PTFE membranes (≥ 100 µm) would shift uptake control entirely to the membrane in river conditions (approach 2). This finding could enable RS prediction based on contaminants properties, thus representing a significant advancement in passive sampling.

Modelling passive sampling of hydrophilic compounds under time-variable aqueous concentrations

Passive sampling is a crucial method for evaluating concentrations of hydrophilic organic compounds in the aquatic environment, but it is insufficiently understood to what extent passive samplers capture the intermittent emissions that frequently occur for this group of compounds. In the present study, silicone sheets and styrene-divinyl benzene-reversed phase sulfonated extraction disks with and without a polyethersulfone membrane were exposed under semi-field conditions in a 31 m3 flume at three different flow velocities. Natural processes and spiking/dilution measures caused aqueous concentrations to vary strongly with time. The data were analyzed using two analytical models that account for these time-variable concentrations: a sampling rate model and a diffusion model. The diffusion model generally gave a better fit of the data than the sampling rate model, but the difference in residual errors was quite small (median errors of 19 vs. 25% for silicone and 22 vs. 25% for SDB-RPS samplers). The sampling rate model was therefore adequate enough to evaluate the time-integrative capabilities of the samplers. Sampler performance was best for SDB-RPS samplers with a polyethersulfone membrane, despite the occurrence of lag times for some compounds (0.1 to 0.4 days). Sampling rates for this design also spanned a narrower range (80 to 110 mL/day) than SDB-RPS samplers without a membrane (100 to 660 mL/day). The effect of biofouling was similar for all compounds and was consistent with a biofouling layer thickness of 150 µm.

Ongoing Laboratory Performance Study on Chemical Analysis of Hydrophobic and Hydrophilic Compounds in Three Aquatic Passive Samplers

The quality of chemical analysis is an important aspect of passive sampling-based environmental assessments. The present study reports on a proficiency testing program for the chemical analysis of hydrophobic organic compounds in silicone and low-density polyethylene (LDPE) passive samplers and hydrophilic compounds in polar organic chemical integrative samplers. The median between-laboratory coefficients of variation (CVs) of hydrophobic compound concentrations in the polymer phase were 33% (silicone) and 38% (LDPE), similar to the CVs obtained in four earlier rounds of this program. The median CV over all rounds was 32%. Much higher variabilities were observed for hydrophilic compound concentrations in the sorbent: 50% for the untransformed data and a factor of 1.6 after log transformation. Limiting the data to the best performing laboratories did not result in less variability. Data quality for hydrophilic compounds was only weakly related to the use of structurally identical internal standards and was unrelated to the choice of extraction solvent and extraction time. Standard deviations of the aqueous concentration estimates for hydrophobic compound sampling by the best performing laboratories were 0.21 log units for silicone and 0.27 log units for LDPE (factors of 1.6 to 1.9). The implications are that proficiency testing programs may give more realistic estimates of uncertainties in chemical analysis than within-laboratory quality control programs and that these high uncertainties should be taken into account in environmental assessments.

Application of diffusive gradient in thin films probes to monitor trace levels of labile methylmercury in freshwaters

This study aimed to optimize the methods for sampling and analyzing methylmercury (MeHg) concentrated within diffusive gradients in thin films (DGT) and its application to different water bodies. We explored the elution solution for MeHg, comprised of 1.13 mM thiourea and 0.1M HCl, optimizing its volume to 50 mL. In addition, we found that it is necessary to analyze the entire extraction solution after adjusting its pH, to ensure completion of the ethylation reaction. The DGT samplers were deployed in two distinct aquatic environments (i.e., Okjeong Lake and Nakdong River) for up to 6 weeks, and this study demonstrated to predict the time-weighted average concentration with a diffusion coefficient of 7.65 × 10-6 cm2 s-1 for MeHg in the diffusive gel. To assess the diffusive boundary layer (DBL) effects, the DGT samplers with different agarose diffusive gel thickness were deployed. The mass of MeHg accumulated in the DGT resin at a given time decreased with increasing diffusive gel thickness, because of creating longer diffusion pathways within thicker gels. The labile MeHg concentration estimated by the DGT in Okjeong Lake and Nakdong River are found in the range of 61-111 and 55-105 pg L-1, respectively, which were found to be similar to the grab sampling data. Additionally, this study evaluated depth-dependent MeHg in Okjeong Lake. The vertical profile results showed that the concentration of MeHg at the depth of 2.3 and 15.7 m are about 1.5 and 4.6 times of the DGT installed at 0.3 m of the surface layer, respectively, suggesting potential mercury methylation in deep waters. These findings have practical implications for predicting bioavailability, assessing risks, and formulating strategies for water body management and contamination remediation.

Pesticide occurrence in a subtropical estuary, Australia: Complementary sampling methods

Monitoring pesticide run-off in the aquatic environment is ecologically important. Effective methods are required to detect the wide range of possible pesticides that enter estuaries from the surrounding catchment. Here, we investigate the occurrence of pesticides in the Richmond River estuary, Australia, and compare the effectiveness of using oysters and Chemcatcher® passive sampling devices against composite water samples. Samples were collected from six sites during two sampling periods: from January to March 2020 (4 weekly composite water samples and oyster collections) and from February to March 2021 (8 twice weekly composite water samples and Chemcatcher® deployment). Samples were analysed for up to 174 pesticides. A total of 21 pesticides were detected across all sites using all methods. The number of pesticides and mixture of pesticides detected in the 2020 sampling was higher in oyster samples than in water samples. In 2021, Chemcatcher® samplers detected more pesticides than in water samples. Herbicides were the most common in all samples. Insecticides and most fungicides were detected only in oysters and Chemcatcher®. Overall, the use of three complementary sampling approaches demonstrated a high level of pesticide input into the Richmond River estuary, highlighting the usefulness of oysters as biomonitors for some pesticides.

Effect-based monitoring of two rivers under urban and agricultural influence reveals a range of biological activities in sediment and water extracts

Chemical contaminants, such as pesticides, pharmaceuticals and industrial compounds are ubiquitous in surface water and sediment in areas subject to human activity. While targeted chemical analysis is typically used for water and sediment quality monitoring, there is growing interest in applying effect-based methods with in vitro bioassays to capture the effects of all active contaminants in a sample. The current study evaluated the biological effects in surface water and sediment from two contrasting catchments in Aotearoa New Zealand, the highly urbanised Whau River catchment in Tāmaki Makaurau (Auckland) and the urban and mixed agricultural Koreti (New River) Estuary catchment. Two complementary passive sampling devices, Chemcatcher for polar chemicals and polyethylene (PED) for non-polar chemicals, were applied to capture a wide range of contaminants in water, while composite sediment samples were collected at each sampling site. Bioassays indicative of induction of xenobiotic metabolism, receptor-mediated effects, genotoxicity, cytotoxicity and apical effects were applied to the water and sediment extracts. Most sediment extracts induced moderate to strong estrogenic and aryl hydrocarbon (AhR) activity, along with moderate toxicity to bacteria. The water extracts showed similar patterns to the sediment extracts, but with lower activity. Generally, the polar Chemcatcher extracts showed greater estrogenic activity, photosynthesis inhibition and algal growth inhibition than the non-polar PED extracts, though the PED extracts showed greater AhR activity. The observed effects in the water extracts were compared to available ecological effect-based trigger values (EBT) to evaluate the potential risk. For the polar extracts, most sites in both catchments exceeded the EBT for estrogenicity, with many sites exceeding the EBTs for AhR activity and photosynthesis inhibition. Of the wide range of endpoints considered, estrogenic activity, AhR activity and herbicidal activity appear to be the primary risk drivers in both the Whau and Koreti Estuary catchments.

Innovative receiving phase for Chemcatcher® passive sampler for phosphorus in the water environment: Calibration of sampling rate by water temperature and pH

Passive sampling is a technique for monitoring orthophosphate (PO4-P) in the water environment. Compared with traditional grab sampling followed by PO4-P quantification, kinetic-type passive samplers such as Chemcatcher® express representative concentrations of PO4-P as time-weighted average concentrations (CTWA). They can also potentially evaluate much lower PO4-P concentrations, but the available receiving phases of Chemcatcher® used for PO4-P were extremely limited. We developed a new receiving phase, the PSfZS sheet, comprising a zirconium sulfate-surfactant micelle mesostructure and polysulfone matrix. We examined its performance in terms of PO4-P sorption characteristics, PO4-P selectivity, and PO4-P sampling rate (Rs). Its capacity was adequate (12.0 μg-P/cm2) and selectivity for PO4-P uptake was good. The Rs for PO4-P increased with increasing water temperature (8.1-29.1 °C) and decreasing pH (4.1-9.7) in a laboratory calibration, and ranged from 5.27 × 10-2 L/d to 1.66 × 10-1 L/d. We placed the samplers in a municipal wastewater treatment plant, a shallow eutrophic lake, and an oligotrophic caldera lake. The Rs in the deployment sites was calibrated by monitored water temperature and pH. The estimated CTWA of PO4-P in the municipal wastewater treatment plant was similar to the averaged concentration of soluble reactive phosphorus determined by multiple grab samplings. In the lake deployments, we found that the new sampler can quantify CTWA values of PO4-P below 10 μg/L, and thus it provides more technical monitoring options and contributes to the conservation and management of the water environment.

Effect of different levels of EDTA on phytoextraction of heavy metal and growth of Brassica juncea L

Heavy metal pollution of soil is a major concern due to its non-biodegradable nature, bioaccumulation, and persistence in the environment. To explore the probable function of EDTA in ameliorating heavy metal toxicity and achieve the sustainable development goal (SDG), Brassica juncea L. seedlings were treated with different concentrations of EDTA (0, 1.0, 2.0, 3.0, and 4.0 mM Kg-1) in heavy metal-polluted soil. Plant samples were collected 60 days after sowing; photosynthetic pigments, H2O2, monoaldehyde (MDA), antioxidant enzymes, and ascorbic acid content, as well as plant biomass, were estimated in plants. Soil and plant samples were also examined for the concentrations of Cd, Cr, Pb, and Hg. Moreover, values of the phytoremediation factor were utilized to assess the accumulation capacity of heavy metals by B. juncea under EDTA treatments. In the absence of EDTA, B. juncea seedlings accrued heavy metals in their roots and shoots in a concentration-dependent manner. However, the highest biomass of plants (roots and shoots) was recorded with the application of 2 mM kg-1 EDTA. Moreover, high levels (above 3 mM kg-1) of EDTA concentration have reduced the biomass of plants (roots and shoots), photosynthetic area, and chlorophyll content. The effect of EDTA levels on photosynthetic pigments (chlorophyll a and b) revealed that with an increment in EDTA concentration, accumulation of heavy metals was also increased in the plant, subsequently decreasing the chlorophyll a and b concentration in the plant. TLF was found to be in the order Pb> Hg> Zn> and >Ni, while TF was found to be in the order Hg>Zn>Ni>Pb, and the best dose was 3 mM kg-1 EDTA for Hg and 4 mM kg-1 for Pb, Ni, and Zn. Furthermore, hyperaccumulation of heavy metals enhanced the generation of hydrogen peroxide (H2O2), superoxide anions (O2•-), and lipid peroxidation. It also interrupts mechanisms of the antioxidant defense system. Furthermore, heavy metal stress reduced plant growth, biomass, and chlorophyll (chl) content. These findings suggest that the exogenous addition of EDTA to the heavy metal-treated seedlings increases the bioavailability of heavy metals for phytoextraction and decreases heavy metal-induced oxidative injuries by restricting heavy metal uptake and components of their antioxidant defense systems.

Determination of groundwater origins and vulnerability based on multi-tracer investigations: New contributions from passive sampling and suspect screening approach

Knowledge about groundwater origins and their interactions with surface water is fundamental to assess their vulnerability. In this context, hydrochemical and isotopic tracers are useful tools to investigate water origins and mixing. More recent studies examined the relevance of contaminants of emerging concern (CECs) as co-tracers to distinguish sources contributing to groundwater bodies. However, these studies focused on known and targeted CECs a priori selected regarding their origin and/or concentrations. This study aimed to improve these multi-tracer approaches using passive sampling and qualitative suspect screening by exploring a larger variety of historical and emerging concern contaminants in combination with hydrochemistry and water molecule isotopes. With this objective, an in-situ study was conducted in a drinking water catchment area located in an alluvial aquifer recharged by several water sources (both surface and groundwater sources). CECs determined by passive sampling and suspect screening allowed to provide in-depth chemical fingerprints of groundwater bodies by enabling the investigation of >2500 compounds with an increased analytical sensitivity. Obtained cocktails of CECs were discriminating enough to be used as chemical tracer in combination with hydrochemical and isotopic tracers. In addition, the occurrence and type of CECs contributed to a better understanding of groundwater-surface water interactions and highlighted short-time hydrological processes. Furthermore, the use of passive sampling with suspect screening analysis of CECs lead to a more realistic assessment and mapping of groundwater vulnerability.

Calibration of the Chemcatcher® passive sampler and derivation of generic sampling rates for a broad application in monitoring of surface waters

We determined sampling rates for 34 pesticides, five pesticide transformation products, and 34 pharmaceutical compounds with the Chemcatcher (CC) passive sampler in a laboratory-based continuous-flow system at 40 cm/s and ambient temperature. Three different sampling phases were used: styrene divinylbenzene disks (SDB-XC), styrene divinylbenzene reversed phase sulfonate disks (SDB-RPS), and hydrophilic lipophilic balance disks (HLB), in all cases covered with a diffusion-limiting polyethersulfone membrane. The measured sampling rates range from 0.007 L/d to 0.193 L/d for CC with SDB-XC (CC-XC), from 0.055 L/d to 0.796 L/d for CC with SDB-RPS (CC-RPS), and from 0.018 L/d to 0.073 L/d for CC equipped with HLB (CC-HLB). Comparison with sampling rates from literature enabled to derive generic sampling rates that can be used for compounds with unknown uptake kinetics such as transformations products and new compounds of interest. Field trial results demonstrate that the presently derived generic sampling rates are suitable for estimating time-weighted average concentrations within reasonable uncertainty limits. In this way, Chemcatcher passive sampling can be applied approximately to a broad range of solutes without the need for deriving compound-specific sampling rates, which enable compliance checks against environmental quality standards and further risk assessment.

An improved Chemcatcher-based method for the integrative passive sampling of 44 hydrophilic micropollutants in surface water - Part B: Field implementation and comparison with automated active sampling

Integrative passive sampling is particularly useful in the monitoring of hydrophilic contaminants in surface water, but the impact of hydrodynamics on contaminant uptake still needs to be better considered. In part A (Glanzmann et al., 2023), Chemcatcher-like hydrophilic samplers (i.e., SDB-RPS extraction disks covered by PES microporous membranes) were calibrated to determine the sampling rates R_S of 44 hydrophilic contaminants (pesticides, pharmaceuticals, industrial products) taking into account the hydrodynamic conditions. In this study, Chemcatcher-like passive sampling devices that allowed co-deploying hydrophilic samplers and performance reference compounds (PRC)-spiked silicone disks were tested in a Swiss river with intermediate water velocities (5-50 cm s^-1, 23 cm s^-1 on average) during 11 consecutive 14-day periods. The PRC dissipation from silicone disks - combined with the calibration data from part A - allowed to determine in-situ R_S that took into account hydrodynamic conditions. The obtained aqueous time-weighted average (TWA) concentrations were found to be robust with good concordance between duplicates (mean quotient of 1.16 between the duplicates). For most measurements (76 %), TWA concentrations showed no major difference (<factor 2) from concentrations obtained with automated sampling (14-day composite samples). This observation was also valid for TWA concentrations calculated with extrapolated R_S at infinite water velocity (R_S,MAX), revealing that the added value of using in-situ R_S compared to R_S,MAX is limited above intermediate water velocities (>20 cm s^-1). R_S from the literature (R_S,LIT) - obtained at water velocities between 8 and 37 cm s^-1 - were also shown to provide comparable TWA concentrations in the studied hydrodynamic conditions (average water velocity of 24 cm s^-1). The estimated errors due to the use of R_S,MAX or R_S,LIT rather than in-situ R_S are given as a function of the water velocity to determine in which conditions the developed method is required (or not) in monitoring programs.

Seasonal drivers and risks of aquatic pesticide pollution in drought and post-drought conditions in three Mediterranean watersheds

The Western Cape in South Africa has a Mediterranean climate, which has in part led to an abundance of agriculturally productive land supporting the wheat, deciduous fruit, wine, and citrus industries. South Africa is the leading pesticide user in Sub-Saharan Africa. There is limited data on the pesticide pollution of surface water over different seasons in low- and middle-income countries. We evaluated the seasonal drivers of aquatic pesticide pollution in three river catchments (Berg, Krom, and Hex Rivers) from July 2017 to June 2018 and April to July 2019, using 48 passive samplers. Our sampling followed the most severe drought (2015-2018) since recordings in 1960. Thus, our analyses focus on how drought and post-drought conditions may affect in-stream pesticide concentrations and loads. Samples were analyzed for 101 pesticide compounds using liquid chromatography - high-resolution mass spectrometry. Environmental Quality Standards (EQS) were used to assess the risks. We detected 60 pesticide compounds across the sampling periods. Our results indicate that all samples across all three catchments contained at least three pesticides and that the majority (83%) contained five or more pesticides. Approximately half the number of pesticides were detected after the drought in 2018. High concentration sums of pesticides (>1 μg/L) were detected over long time periods in the Hex River Valley (22 weeks) and in Piketberg (four weeks). Terbuthylazine, imidacloprid, and metsulfuron-methyl were detected in the highest concentrations, making up most of the detected mass, and were frequently above EQS. The occurrence of some pesticides in water generally correlated with their application and rainfall events. However, those of imidacloprid and terbuthylazine did not, suggesting that non-rainfall-driven transport processes are important drivers of aquatic pesticide pollution. The implementation of specific, scientifically sound, mitigation measures against aquatic pesticide pollution would require comprehensive pesticide application data as well as a targeted study identifying sources and transport processes for environmentally persistent pesticides.

Pesticides monitoring in surface water of a subsistence agricultural catchment in Uganda using passive samplers

Pesticides are intensely used in the agricultural sector worldwide including smallholder farming. Poor pesticide use practices in this agronomic setting are well documented and may impair the quality of water resources. However, empirical data on pesticide occurrence in water bodies of tropical smallholder agriculture is scarce. Many available data are focusing on apolar organochlorine compounds which are globally banned. We address this gap by studying the occurrence of a broad range of more modern pesticides in an agricultural watershed in Uganda. During 2.5 months of the rainy season in 2017, three passive sampler systems were deployed at five locations in River Mayanja to collect 14 days of composite samples. Grab samples were taken from drinking water resources. In these samples, 27 compounds out of 265 organic pesticides including 60 transformation products were detected. In the drinking water resources, we detected eight pesticides and two insecticide transformation products in low concentrations between 1 and 50 ng/L. Also, in the small streams and open fetch ponds, detected concentrations were generally low with a few exceptions for the herbicide 2,4-D and the fungicide carbendazim exceeding 1 ug/L. The widespread occurrence of chlorpyrifos posed the largest risk for macroinvertebrates. The extensive detection of this compound and its transformation product 3,4,5-trichloro-2-pyridinol was unexpected and called for a better understanding of the use and fate of this pesticide.

A miniaturized passive sampling-based workflow for monitoring chemicals of emerging concern in water

The miniaturization of a full workflow for identification and monitoring of contaminants of emerging concern (CECs) is presented. Firstly, successful development of a low-cost small 3D-printed passive sampler device (3D-PSD), based on a two-piece methacrylate housing that held up to five separate 9 mm disk sorbents, is discussed. Secondly, a highly sensitive liquid chromatography-tandem mass spectrometry (LC-MS/MS) method reduced the need for large scale in-laboratory apparatus, solvent, reagents and reference material quantities for in-laboratory passive sampler device (PSD) calibration and extraction. Using hydrophilic-lipophilic balanced sorbents, sampling rates (R_s) were determined after a low 50 ng L^-1 exposure over seven days for 39 pesticides, pharmaceuticals, drug metabolites and illicit drugs over the range 0.3 to 12.3 mL day^-1. The high sensitivity LC-MS/MS method enabled rapid analysis of river water using only 10 μL of directly injected sample filtrate to measure occurrence of 164 CECs and sources along 19 sites on the River Wandle, (London, UK). The new 3D-PSD was then field-tested over seven days at the site with the highest number and concentration of CECs, which was down-river from a wastewater treatment plant. Almost double the number of CECs were identified in 3D-PSD extracts across sites in comparison to water samples (80 versus 42 CECs, respectively). Time-weighted average CEC concentrations ranged from 8.2 to 845 ng L^-1, which were generally comparable to measured concentrations in grab samples. Lastly, high resolution mass spectrometry-based suspect screening of 3D-PSD extracts enabled 113 additional compounds to be tentatively identified via library matching, many of which are currently or are under consideration for the EU Watch List. This miniaturized workflow represents a new, cost-effective, and more practically efficient means to perform passive sampling chemical monitoring at a large scale. SYNOPSIS: Miniaturized, low cost, multi-disk passive samplers enabled more efficient multi-residue chemical contaminant characterization, potentially for large-scale monitoring programs.

Control of organic contaminants in groundwater by passive sampling and multivariate statistical analysis

Organic contaminants in groundwater are among the most challenging chemical compound contaminants today, particularly when it comes to understanding their occurrence, origin, and relations in groundwater, as well as the transport processes, fate, and environmental impacts involved. This paper presents the use of active carbon fibre (AFC) passive sampling and multivariate statistical processing of the results to predict the possible occurrence of organic compounds (OCs) in groundwater and to determine the origin of various anthropogenic activity. This study aims to deepen our knowledge on the control of OCs in groundwater by introducing a multi-analytical and multi-elemental holistic approach, using the Dravsko polje aquifer, the largest intergranular aquifer in Slovenia, as an example. The occurrence of OCs in groundwater was determined by means of ACFs and compared against the characteristics of the recharge area and the type of compounds detected. We combined hierarchical cluster analysis (HCA) and principal component analysis (PCA) to identify the relationship between different OCs in groundwater. The relationships between their occurrence, environmental setting and type of compound were determined using multiple linear regression (MLR). From the total of 343 organic compounds detected using passive sampling, 47 were included in further statistical analysis. MLR shows that the environmental setting is one of the most important factors affecting the different types of pollutants in groundwater. MLR models were calculated for different sources of pollution (agricultural, urban, and industrial) based on the environmental setting, land use, agglomeration, infrastructure networks, and hydrogeological characteristics of the aquifer. By means of HCA and PCA, we identified the relationships between different OCs in groundwater. As expected, the strongest correlations were found between primary compounds and their degradation products (e.g. atrazine and desethylatrazine) and compounds of similar use (e.g. atrazine and propazine, also desethylatrazine and propazine, atrazine and simazine). Some of them were also found to have a similar molecular structure (e.g. palmitic and stearic acid, 5-methoxygramine and 5-methoxytryptamine). The use of the same substances in different environments (agricultural/urban) makes them markers of both (different) origins. Therefore, it is particularly important to determine the combination of markers of different origin using multivariate statistical methods, especially in the case of mixed land use. This study identifies the main factors influencing the distribution of groundwater OCs and thus contributes to a more comprehensive understanding of the vulnerability of shallow groundwater to surface-derived contamination in similar environments.

The study of polar emerging contaminants in seawater by passive sampling: A review

Emerging Contaminants (ECs) in marine waters include different classes of compounds, such as pharmaceuticals and personal care products, showing "emerging concern" related to the environment and human health. Their measurement in seawater is challenging mainly due to the low concentration levels and the possible matrix interferences. Mass spectrometry combined with chromatographic techniques represents the method of choice to study seawater ECs, due to its sensitivity and versatility. Nevertheless, these instrumental techniques have to be preceded by suitable sample collection and pre-treatment: passive sampling represents a powerful approach in this regard. The present review compiles the existing occurrence studies on passive sampling coupled to mass spectrometry for the monitoring of polar ECs in seawater and discusses the availability of calibration data that enabled quantitative estimations. A vast majority of the published studies carried out during the last two decades describe the use of integrative samplers, while applications of equilibrium samplers represent approximately 10%. The polar Chemcatcher was the first applied to marine waters, while the more sensitive Polar Organic Chemical Integrative Sampler rapidly became the most widely employed passive sampler. The organic Diffusive Gradients in Thin film technology is a recently introduced and promising device, due to its more reliable sampling rates. The best passive sampler selection for the monitoring of ECs in the marine environment as well as future research and development needs in this area are further discussed. On the instrumental side, combining passive sampling with high resolution mass spectrometry to better assess polar ECs is strongly advocated, despite the current challenges associated.

Synthesis of an Organotin Specific Molecularly Imprinted Polymer for Organotin Passive Sampling in Seawater

Environmental contaminations can sometimes be difficult to measure, particularly in complex matrices such as seawater. This is the case of organotin compounds (OSn) such as the monobutyltin (MBT), dibutyltin (DBT), and tributyltin (TBT), whose range of polarity is wide. These compounds, mostly coming from antifouling paints used on ship shell, can be found in water and sediments where they are stable and can persist for years. Passive sampling is gaining in interest to offer solutions to monitor these kinds of compounds even in low concentrations. However, due to the diversity of pollutants present in the environment nowadays, it is important to propose solutions that allow a specific sampling. This work aims to highlight the usability of molecularly imprinted polymers (MIPs) in passive sampling for the monitoring of OSn. MIPs were synthetized using three synthesis ways (bulk, suspension, and mini-emulsion processes) and kinetics were realized in order to estimate the retention of OSn by the solid MIP phase. Results highlighted a good retention of OSn with mean retention kinetic constants near 10−5, 10−6 and 10−7 L·ng·s−1 for DBT, TBT and MBT respectively. The synthesis mode showed no impact on retention kinetics, therefore, bulk synthesis is recommended because of its simplicity. If the elimination of OSn from MIPs is to be optimized, the retention of OSn on MIPs has been demonstrated, and is very promising for their use in specific passive samplers.

Determining the Mass Transfer Coefficient of the Water Boundary Layer at the Surface of Aquatic Integrative Passive Samplers

Passive sampling devices (PSDs) offer key benefits for monitoring chemical water quality, but the uptake process of PSDs for hydrophilic compounds still needs to be better understood. Determining mass transfer coefficients of the water boundary layer (k_w) during calibration experiments and in situ monitoring would contribute toward achieving this; it allows for combining calibration data obtained at different temperature and hydrodynamic conditions and facilitate the translation of laboratory-derived calibration data to field exposure. This study compared two k_w measurement methods applied to extraction disk housings (Chemcatcher), namely, alabaster dissolution and dissipation of performance reference compounds (PRCs) from silicone. Alabaster- and PRC-based k_w were measured at four flow velocities (5-40 cm s^-1) and two temperatures (11 and 20 °C) in a channel system. Data were compared using a relationship based on Sherwood, Reynolds, and Schmidt numbers. Good agreement was observed between data obtained at both temperatures, and for the two methods. Data were well explained by a model for mass transfer to a flat plate under laminar flow. It was slightly adapted to provide a semi-empirical model accounting for the effects of housing design on hydrodynamics. The use of PRC-spiked silicone to obtain in situ integrative k_w for Chemcatcher-type PSDs is also discussed.

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.

Passive Sampling with Active Carbon Fibres in the Determination of Organic Pollutants in Groundwater

Legislation addressing the quality of groundwater and increasing concerns over public health calls for the development of analytical methods that can produce accurate and precise results at the ppt level. Passive sampling has been recognised as a helpful tool in identifying various organic pollutants in groundwater, even when their presence had not yet been identified through conventional groundwater quality monitoring. The article presents an analytical method involving a simple and cost-effective passive sampling device using Zorflex® activated carbon fibres (ACFs) for the qualitative monitoring of a broad range of organic pollutants in water in a single run. The applicability of the method developed was tested in three hydrogeological studies. In the first case, we present a non-targeted qualitative screening and a list of 892 different contaminants detected in the groundwater in Slovenia. In the second case, we discuss the presence and origin of organic compounds in the groundwater from a pilot area of the urban aquifer, Ljubljansko polje. The third case presents a comparison of results between passive and grab sampling. Passive sampling with ACFs confirmed the presence of a pollutant, even when it had not been previously detected through a quantitative method.

Technical design and optimisation of polymer inclusion membranes (PIMs) for sample pre-treatment and passive sampling - A review

This review reports on the increasing interest in technical designs, calibration, and application of PIM-based devices in sample pre-treatment and passive sampling in environmental water monitoring from 2010 to 2021. With regards to passive sampling, devices are calibrated in a laboratory setup using either a dip-in or flow-through approach before environmental application. In sample preparation, the device set-ups can be offline, online or in a continuous flow separation device connected to a flow injection analysis system. The PIMs have also demonstrated potential in both these offline and online separations; however, there is still a draw-back of low diffusion coefficients obtained in these PIM set-ups. Electro-driven membrane (EME) extraction has demonstrated better performance as well as improved analyte flux. Critical in electro-driven membrane extraction is applying correct voltage that may not compromise the PIM performance due to leaching of components to the aqueous solutions. Further, besides different PIM configurations and designs being developed, PIM based extractions are central to PIM components (base polymer, carrier and plasticizer). As such, recent studies have also focused on improving PIM stability by investigating use of various PIM components, incorporating nano additives into the PIM composition, and investigating novel green PIM synthetic routes. All these aspects are covered in this review. Further, some recent studies that have demonstrated the ability to eliminate effects of flow patterns and membrane biofouling in PIM based applications are also included.

Passive Sampler Exchange Kinetics in Large and Small Water Volumes Under Mixed Rate Control by Sorbent and Water Boundary Layer

Exchange kinetics of organic compounds between passive samplers and water can be partly or completely controlled by transport in the sorbent. In such cases diffusion models are needed. A model is discussed that is based on a series of cosines (space) and exponentials (time). The model applies to mixed rate control by sorbent and water boundary layer under conditions of fixed aqueous concentrations (open systems, infinite water volumes, in situ sampling) and fixed amounts (closed systems, finite water volumes, ex situ sampling). Details on the implementation of the model in computational software and spreadsheet programs are discussed, including numerical accuracy. Key parameters are Biot number (ratio of internal/external transfer resistance) and sorbent/water phase ratio. Small Biot numbers are always indicative of rate control by the water boundary layer, but for large Biot numbers this may still be the case over short time scales. Application to environmental monitoring of nonpolar compounds showed that diffusion models are rarely needed for sampling with commonly used single-phase polymers. For determining sorption coefficients in batch incubations, the model demonstrated a profound effect of sorbent/water phase ratio on time to equilibrium. Application of the model to sampling of polar organic compounds by extraction disks with or without a membrane showed that moderate to major sorbent-controlled kinetics is likely to occur. This implies that the use of sampling rate models for such samplers needs to be reconsidered. Environ Toxicol Chem 2021;40:1241-1254. © 2021 SETAC.

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.

Passive sampler phases for pesticides: evaluation of AttractSPE™ SDB-RPS and HLB versus Empore™ SDB-RPS

In this study, three different passive sampling receiving phases were evaluated, with a main focus on the comparability of established styrene-divinylbenzene reversed phase sulfonated (SDB-RPS) sampling phase from Empore™ (E-RPS) and novel AttractSPE™ (A-RPS). Furthermore, AttractSPE™ hydrophilic-lipophilic balance (HLB) disks were tested. To support sampling phase selection for ongoing monitoring needs, it is important to have information on the characteristics of alternative phases. Three sets of passive samplers (days 1-7, days 8-14, and days 1-14) were exposed to a continuously exchanged mixture of creek and rainwater in a stream channel system under controlled conditions. The system was spiked with nine pesticides in two peak scenarios, with log K_OW values ranging from approx. - 1 to 5. Three analytes were continuously spiked at a low concentration. All three sampling phases turned out to be suitable for the chosen analytes, and, in general, uptake rates were similar for all three materials, particularly for SDB-RPS phases. Exceptions concerned bentazon, where E-RPS sampled less than 20% compared with the other phases, and nicosulfuron, where HLB sampled noticeably more than both SDB-RPS phases. All three phases will work for environmental monitoring. They are very similar, but differences indicate one cannot just use literature calibration data and transfer these from one SDB phase to another, though for most compounds, it may work fine.

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.

First study of passive sampling to monitor short-chain chlorinated paraffins in water: Comparing capabilities of Chemcatcher® and silicone rubber samplers

Short-chain chlorinated paraffins (SCCPs) are high-volume chemicals raising concerns because of their classification as priority hazardous substances by the European Water Framework Directive (WFD) and their recent inclusion in the persistent organic pollutants' (POPs) list by the Stockholm convention. As this group cover up to 5000 isomers, their measurement is still challenging. Hence the SCCPs occurrence in the environment is poorly documented in comparison with other POPs, especially in matrices where they are present at ultratrace levels such as waters. In the two-past decades, passive sampling has been increasingly used as it overcomes some major drawbacks associated to the conventional grab sampling. This study constitutes the first work aiming to examine the passive sampling's applicability for the monitoring of such complex analytes' mixtures in waters. Optimization and calibration of two proven passive samplers, namely silicone rubbers and Chemcatcher®, were performed through batch and laboratory pilot experiments. Despite the thousands of molecules present in the SCCPs mixture, the resulting global kinetic uptakes fitted well with the theorical model, for both samplers. Sampling rates of 8.0 L d^-1 for silicone rubbers and 0.53 L d^-1 for Chemcatcher® were found, and logK_sw determined for silicone rubbers equaled 4.24 to 4.95. These values are in complete agreement with published data for other HOCs. A field trial carried out in marine coastal environments provided further evidence to demonstrate the applicability of the passive samplers to measure CPs amounts in water bodies. All these results unveil that passive sampling using silicone rubbers or Chemcatcher® can be a relevant approach to track traces of such complex mixtures in water.

A year-long passive sampling of phenolic endocrine disrupting chemicals in the East River, South China

The occurrence of endocrine disrupting chemicals (EDCs) in the aquatic environment is a global concern. In this study, we employed two different passive samplers Diffusive Gradients in Thin-films (DGT) and Chemcatcher for in situ measurement of 8 phenolic EDCs in the East River of the Pearl River system over one-year. These data were assessed alongside results from traditional grab sampling. Six chemicals (4tOP, 4NP, BPA, E1, EE2 and DES) were regularly detected in the water samples, of which the three phenols (i.e. 4tOP, 4NP and BPA) were in all samples and at high concentrations (0.4-1040 ng/L for 4tOP, 2.6-58500 ng/L for NP and 11.4-123300 ng/L for BPA). Fewer target chemicals were detected in both passive samplers, with only 4tOP, 4NP and BPA found in most samplers; E1 and DES were occasionally measurable above detection limits. The higher (by about a factor of 2-3) measurements provided by DGT compared to Chemcatcher could be attributed to the effect of the diffusive boundary layer on Chemcatcher uptake or the strong adsorption of target chemicals on the Chemcatcher PES filter. The temporal trends of EDC monthly loadings indicated that they were from different sources and that WWTPs were not effective in EDC removal and/or there was still some untreated wastewater discharged into the rivers.

Detection of pharmaceuticals in wastewater effluents-a comparison of the performance of Chemcatcher® and polar organic compound integrative sampler

Chemcatcher^® and POCIS passive sampling devices are widely used for monitoring polar organic pollutants in water. Chemcatcher^® uses a bound Horizon Atlantic™ HLB-L sorbent disk as receiving phase, whilst the POCIS uses the same material in the form of loose powder. Both devices (n = 3) were deployed for 21 days in the final effluent at three wastewater treatment plants in South Wales, UK. Following deployment, sampler extracts were analysed using liquid chromatography time-of-flight mass spectrometry. Compounds were identified using an in-house database of pharmaceuticals using a metabolomics workflow. Sixty-eight compounds were identified in all samplers. For the POCIS, substantial losses of sorbent (11-51%) were found during deployment and subsequent laboratory analysis, necessitating the use of a recovery factor. Percentage relative standard deviations varied (with 10 compounds exceeding 30% in both samplers) between individual compounds and between samplers deployed at the three sites. The relative performance of the two devices was evaluated using the mass of analyte sequestered, measured as an integrated peak area. The ratio of the uptake of the pharmaceuticals for the POCIS versus Chemcatcher^® was lower (1.84x) than would be expected on the basis of the ratio of active sampling areas (3.01x) of the two devices. The lower than predicted uptake may be attributable to the loose sorbent material moving inside the POCIS when deployed in the field in the vertical plane. In order to overcome this, it is recommended to deploy the POCIS horizontally inside the deployment cage.

Development of quantitative structure-property relationship model for predicting the field sampling rate (Rs) of Chemcatcher passive sampler

Passive sampling technology has been considered as a promising tool to measure the concentration of environmental contaminants. With this technology, sampling rate (R_s) is an important parameter. However, as experimental methods employed to obtain the R_s value of a given compound were time-consuming, laborious, and expensive. A cost-effective method for deriving R_s is urgent. In addition, considering the great dependence of R_s value on water matrix properties, the laboratory measured R_s may not be a good alternative for field R_s. Thus, obtaining the field R_s is very necessary. In this study, a multiparameter quantitative structure-property relationship (QSPR) model was constructed for predicting the field R_s of 91 polar to semi-polar organic compounds. The determination coefficient (R²_Train), leave-one-out cross-validated coefficient (Q²_LOO), bootstrap coefficient (Q²_BOOT), and root mean square error (RMSE_Train) of the training set were 0.772, 0.706, 0.769, and 0.230, respectively, while the external validation coefficient (Q²_EXT) and RMSE_EXT of the validation set were 0.641 and 0.253, respectively. According to the acceptable criteria (Q² > 0.600, R² > 0.700), the model had good robustness, goodness-of-fit, and predictive performances. Therefore, we could use the model to fill the data gap for substances within the applicability domain on their missing R_s value.

Influence of some physicochemical parameters on the passive sampling of copper (II) from aqueous medium using a polymer inclusion membrane device

Recently polymer inclusion membranes (PIMs) have been proposed as materials for passive sampling, nonetheless a theoretical base to describe the mass transfer process through those materials, under such conditions of monitoring, has not been elucidated. Under the assumption that: (i) the transport of the metal ion occurs at steady state conditions, (ii) the concentration gradients are linear, and (iii) the kinetics of the chemical reactions in the extraction process on the membrane are elemental; an equation for the passive sampling of copper (II) using a PIM system containing Kelex-100 as carrier is derived. The prediction capacity of this sampler under different conditions of temperature, metal concentration, flow velocity, ionic strength and pH is analyzed as well. Among the dependencies of the PIM on the physicochemical conditions, effects of concentration, temperature and flow velocity tend to increment copper (II) flux across the membrane, being the parameter temperature the one with the most pronounced effect at T ≥ 30 °C. Ionic strength had no great effect on passive sampler response, however the sampler is dependent on the acidity of the medium. The comparable metal ion concentrations estimated from the PIM sampler to those obtained by direct measurements of the sampling medium suggest that PIMs can be robust materials when used as passive sampler devices.

Development of biofilm collectors as passive samplers in sewerage systems-a novel wastewater monitoring method

In this study, a novel wastewater sampling method based on biofilm collection on a multi-armed polyethylene strips (so called "Octopus") is proposed. The implementation of this method is a step forward to prevent illegal industrial discharges into sewerage systems and receiving water bodies. Prior applications of biofilm collection were performed in Bielefeld, Germany, in 1994. The success of the method encouraged other municipalities to apply this method for monitoring indirect discharges into sewerage systems. Municipality of Konya, Turkey, started to use the method in 2013. Continuous monitoring has been performed for the determination of regulated heavy metals: chromium (Cr), copper (Cu), zinc (Zn), nickel (Ni), lead (Pb), mercury (Hg) and cadmium (Cd). Unauthorized discharges of Cr, Zn and Ni were identified in Konya by performing sewerage slime tests through biofilm analyses. 2686 mg/kg d.m. Cr, 3949 mg/kg d.m. Zn and 3300 mg/kg d.m. Ni were highest values determined for biofilm samples taken from monitoring sites. In this paper, the principles of the method will be introduced, and findings from the wastewater of Konya City will be given in comparison with findings from Bielefeld, Germany. Conducted results reveal high (and likely illegal) heavy metal discharges into the sewerage system in Konya. The continuous monitoring of sewerage systems with biofilm collectors is an effective and efficient method for point source control of wastewater pollutants.

Polyethersulfone as suitable passive sampler for waterborne hydrophobic organic compounds - Laboratory calibration and field test in the Sosiani river, Kenya

We report the application of polyethersulfone (PES) membrane as a cost-saving and less labour-intensive single-phase passive sampler for waterborne hydrophobic organic compounds (HOCs) like organochlorine pesticides (OCPs), polychlorinated biphenyls (PCBs), polyaromatic hydrocarbons (PAHs). The uptake kinetics of 31 HOCs from water to porous polyethersulfone (PES) membranes and their partitioning behaviour were investigated in laboratory studies. Sampling rates (R_s) of HOCs with PES were determined in a range from 1.15 to 12.9 L/d. The uptake of test chemicals and the elimination of analogous (pre-loaded) performance reference compounds (PRCs) showed anisotropy, both under laboratory and field conditions, implying that PRCs are not suitable for determining in situ sampling rates with PES. The PES-water partition coefficients (K_pw) are, on average, ten times higher than the related K_ow. A Linear Solvation Energy Relationship for modelling the measured log K_pw with PES under inclusion of all available published data yields a poor fit in comparison to what is usually obtained with homogeneous polymers like polydimethylsiloxane or low-density polyethylene. At least a strong linear relationship was found between log R_s and log K_pw for the narrow log K_ow range of HOCs investigated in this work which can be used for interpolation to other HOCs in this range. The PES membranes were also tested in a field trial in a tropical river against the well-established silicone rubber (SR) sheets. With laboratory-based R_s for PES generated under field-relevant temperature and water flow velocity it was possible to obtain time-weighted average concentrations in the lower ng/L range which are comparable (within a factor of two) with those derived from accumulated amounts in SR sheets (using in situ sampling rates).

Temporal variation of pesticide mixtures in rivers of three agricultural watersheds during a major drought in the Western Cape, South Africa

South Africa is the leading pesticide user in Sub-Saharan Africa. However, little is known about the occurrence of pesticide mixtures in surface water and potential environmental risks in Africa. This study investigated the occurrence of pesticides mixtures in three watersheds during a drought year in South Africa. The study was conducted in the Krom River, Berg River and Hex River watersheds within larger agriculture systems in the Western Cape. Pesticide spray records were collected from 38 farms. A total of 21 passive water samplers (styrenedivinylbenzene disks (SDB)) were deployed, each for two weeks per month, over seven sampling rounds during the main pesticide application period between July 2017 and January 2018. Samples were analyzed for 248 pesticide compounds using LC-HR-MS/MS. Pesticide occurrence was analyzed for temporal agreement with pesticide spraying events (Cohen's κ) and correlation with rainfall patterns and river discharge (Pearson correlation (r _p )). Pesticide time-weighted average concentrations were estimated and compared to environmental quality standards (EQS). According to the farm spray records, 96 different pesticides were sprayed during the sampling period and differed considerably between the three study areas, seasons and crops grown. In total, 53 compounds were detected in river water. We detected 39% of compounds from the spraying records and demonstrated close temporal correlations of seasonal patterns for 11 pesticide compounds between reported on spraying records and observations in the streams (κ = 0.90). However, 23 detected pesticides were not found on spray records, many of them being herbicides. Most of the estimated two-week average pesticide concentrations were below 40 ng/L. The insecticides imidacloprid, thiacloprid, chlorpyrifos and acetamiprid and the herbicide terbuthylazine exceeded at least once their EQS 58-fold (EQS 13 ng/L), 12-fold (EQS 10 ng/L), 9-fold (EQS 0.46 ng/L), 5-fold (EQS 24 ng/L) and 3-fold (EQS 220 ng/L), respectively. Our study substantially widens the view on pesticide pollution in surface water compared to previous studies in Sub-Saharan Africa by targeting more than 200 pesticides using passive sampling systems. This broad assessment revealed the presence of 53 compounds, some of them in high concentrations, indicating possible adverse effects on biota and the quality of the ecosystem. Whether the observed concentration levels in the year 2017 were exceptional due to the lowest ever recorded rainfall and river discharge needs to be tested with additional data to better understand how pesticide pollution levels manifest under average rainfall and river discharge conditions.

Hydrophilic Divinylbenzene for Equilibrium Sorption of Emerging Organic Contaminants in Aquatic Matrices

Hydrophilic divinylbenzene (DVB) (Bakerbond) has surfaced as a promising sorbent for active sampling of analytes from aqueous matrices over a very broad polarity range. Given this, hydrophilic DVB may likewise offer potential for passive sampling, if sorbent/water partitioning coefficients (K_sw) were to be available. In this work, static exposure batch experiments were performed to quantitatively study the equilibrium sorption of 131 environmentally relevant organic contaminants (P values ranging from -1.30 to 9.85) on hydrophilic DVB. The superior affinity of hydrophilic DVB, as compared to Oasis HLB, for compounds with a broad polarity range was confirmed by functional Fourier-transform infrared spectroscopy and Raman characterization, demonstrating the presence of carboxyl moieties. Concentration effects were studied by increasing compound concentrations in mixture experiments and resulted in the steroidal endocrine disrupting compounds in higher K_sw, while lower K_sw were obtained for the (alkyl)phenols, personal care products, pesticides, pharmaceuticals, and phthalates. Nevertheless, K_sw remained constant in the said design for equilibrium water concentrations at environmentally relevant seawater levels. An independent analysis of thermodynamic parameters (change in enthalpy, entropy, and Gibbs free energy) revealed the nature of the main partitioning processes. While polar (log P < 4) compounds were mainly served by physisorption, nonpolar (log P > 4) compounds also exhibited binding by multiple hydrogen bonding. In conclusion, this research facilitates the future application of hydrophilic DVB for active as well as passive sampling in the analysis of organic contaminants for monitoring purposes and for toxicity testing.

Monitoring of explosive residues in lake-bottom water using Polar Organic Chemical Integrative Sampler (POCIS) and chemcatcher: determination of transfer kinetics through Polyethersulfone (PES) membrane is crucial

Between 1920 and 1967, approximatively 8200 tons of ammunition waste were dumped into some Swiss lakes. This study is part of the extensive historical and technical investigations performed since 1995 by Swiss authorities to provide a risk assessment. It aims to assess whether explosive monitoring by passive sampling is feasible in lake-bottom waters. Polar organic chemical integrative sampler (POCIS) and Chemcatcher were first calibrated in a channel system supplied with continuously refreshed lake water spiked with two nitroamines (HMX and RDX), one nitrate ester (PETN), and six nitroaromatics (including TNT). Exposure parameters were kept as close as possible to the ones expected at the bottom of two affected lakes. Sixteen POCIS and Chemcatcher were simultaneously deployed in the channel system and removed in duplicates at 8 different intervals over 21 days. Sorbents and polyethersulfone (PES) membranes were separately extracted and analyzed by UPLC-MS/MS. When possible, a three-compartment model was used to describe the uptake of compounds from water, over the PES membrane into the sorbent. Uptake of target compounds by sorbents was shown not to approach equilibrium during 21 days. However, nitroaromatics strongly accumulated in PES, thus delaying the transfer of these compounds to sorbents (lag-phase up to 9 days). Whereas sampling rate (R_S) of nitroamines were in the range of 0.06-0.14 L day^-1, R_S of nitroaromatics were up to 10 times lower. As nitroaromatic accumulation in PES was integrative over 21 days, PES was used as receiving phase for these compounds. The samplers were then deployed at lake bottoms. To ensure that exposure conditions were similar between calibration and field experiments, low-density polyethylene strips spiked with performance reference compounds were co-deployed in both experiments and dissipation data were compared. Integrative concentrations of explosives measured in the lakes confirmed results obtained by previous studies based on grab sampling.

Simultaneous passive sampling of hydrophilic and hydrophobic emerging organic contaminants in water

Passive sampling techniques have been considered robust tools for monitoring freely dissolved concentrations of contaminants in aquatic systems. However, few passive samplers are currently available for the simultaneous sampling of both hydrophilic and hydrophobic chemicals. In this study, we developed a novel passive sampler (a hydrophilic-lipophilic balance sorbent-embedded cellulose acetate membrane (HECAM)) for estimating the time-weighted average (TWA) concentrations of both hydrophilic and hydrophobic organic contaminants in water. In our laboratorial controlled dynamic experiments, the accumulation results of thirty-seven target chemicals (including organophosphorus flame retardants, phenols, estrogens, organophosphorus pesticides, and triazine herbicides) with a wide polarity range (1.44 < log K_ow < 9.49) in the HECAM followed first-order kinetics well, and the passive sampling parameters were estimated successfully. The estimated sampling rates for the target chemicals in the HECAM ranged from 0.14 to 6.90 L d^-1 in the laboratory experiment, and the log K_sw (equilibrium partition coefficient between the sampler and water) values ranged from 2.75 to 6.00. The HECAM exhibited high sampling rate for moderately hydrophilic and moderately hydrophobic chemicals. The field validation study in an urban river resulted in the detection of four target chemicals (tris(chloroisopropyl)phosphate, tris(1,3-dichloroisopropyl)phosphate, prometryn, and 4-tert-octylphenol) by the HECAM at estimated TWA concentrations of 10.9-179.5 ng L^-1, which were in agreement with the measured levels found in traditional grab samples by solid-phase extraction. In summary, both the laboratory tests and field deployment showed practicable results for the HECAM passive sampling, which suggests that it is an efficient approach for simultaneous monitoring of hydrophilic and hydrophobic organic contaminants in water.

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.

Use of passive sampling and high resolution mass spectrometry using a suspect screening approach to characterise emerging pollutants in contaminated groundwater and runoff

Groundwater systems are being increasingly used to provide potable and other water supplies. Due to human activities, a range of organic pollutants is often detected in groundwater. One source of groundwater contamination is via stormwater infiltration basins, however, there is little information on the types of compounds present in these collection systems and their influence on the underlying groundwater. We developed an analytical strategy based on the use of passive sampling combined with liquid chromatography/high resolution quadrupole-time-of-flight mass spectrometry for screening for the presence of pesticide and pharmaceutical compounds in groundwater and stormwater runoff. Empore™ disk-based passive samplers (SDB-RPS and SDB-XC sorbents) were exposed, using for the first time a new specially designed deployment rig, for 10 days during a rainfall event in five different stormwater infiltration systems around Lyon, France. Stormwater runoff and groundwater (via a well, upstream and downstream of each basin) was sampled. Exposed Empore™ disks were solvent extracted (acetone and methanol) and the extracts analysed using a specific suspect compound screening workflow. High resolution mass spectrometry coupled with a suspect screening approach was found to be a useful tool as it allows a more comprehensive analysis than with targeted screening whilst being less time consuming than non-targeted screening. Using this analytical approach, 101 suspect compounds were tentatively identified, with 40 of this set being subsequently confirmed. The chemicals detected included fungicides, herbicides, insecticides, indicators of human activity, antibiotics, antiepileptics, antihypertensive and non-steroidal anti-inflammatory drugs as well as their metabolites. Polar pesticides were mainly detected in groundwater and pharmaceuticals were more frequently found in runoff. In terms of detection frequency of the pollutants, groundwater impacted by infiltration was found not to be significantly more contaminated than non-impacted groundwater.

An improved design of a passive sampler for polar organic compounds based on diffusion in agarose hydrogel

Passive samplers based on diffusive gradients in thin hydrogel films (DGT) were recently modified for sampling of polar organic compounds in water. However, since the sampling rates of the commonly used DGT design with the surface area of 3.1 cm² are low, we propose to increase them by applying a two-sided design with a larger sampling surface area of 22.7 cm². The sampler design consists of two sorptive hydrogel disks compressed between two diffusive hydrogel disk layers strengthened by nylon netting and held together by two stainless steel rings. Sorbent/water distribution coefficients (K_SW) were determined, and the sampler was calibrated for monitoring 11 perfluoroalkyl substances and 12 pharmaceuticals and personal care products in water at laboratory conditions using a closed system with artificial flow generated by submersible pumps. A field performance test was conducted at five locations in the Morava River basin in Czech Republic. The median value of laboratory-derived sampling rates was 43 mL day^-1 with extreme values of 2 mL day^-1 and 90 mL day^-1 for perfluorotridecanoic and perfluoroheptanoic acids, respectively. The log K_SW values of tested compounds ranged from 3.18 to 5.47 L kg^-1, and the estimated halftime to attain sampler-water equilibrium ranged from 2 days to more than 28 days, which is the maximum recommended exposure period, considering potential issues with the stability of hydrogel. The sampler can be used for assessment of spatial trends as well as estimation of aqueous concentration of investigated polar compounds.

Rapid assessment of heavy metal pollution using ion-exchange resin sachets and micro-XRF core-scanning

Conventional pollution monitoring strategies for heavy metals are often costly and unpractical. Innovative sampling and analytical approaches are therefore needed to efficiently monitor large areas. This study presents a novel, simple, fast, and inexpensive method to monitor heavy metal pollution that uses cation-exchange resin sachets and the micro-XRF core-scanning technique (XRF-CS). The resin passive samplers act as concentrators of cationic species and can be readily deployed spatially and temporally to record pollution signals. The large number of analytical tasks are then overcome by the fast and non-destructive XRF-CS to precisely assess elemental concentrations. Quantifying element loading involves direct comparison with a set of identically prepared and scanned resin reference standards containing Ca, Ti, Cr, Mn, Ni, Cu, Zn, Pb. The results show that within the test range (from 0-1000 s mg kg^-1), the calibration lines have excellent regressions (R² ≥ 0.97), even at the shortest exposure time (1 s). A pilot field survey of a suspected polluted area in central Taiwan, where 30 resin sachets had been deployed, identified a pollution hot spot in a rapid and economical manner. Therefore, this approach has the potential to become a valuable tool in environmental monitoring and forensics.

Mechanistic Model Describing the Uptake of Chemicals by Aquatic Integrative Samplers: Comparison to Data and Implications for Improved Sampler Configurations

Aquatic integrative passive samplers are used to determine aqueous concentrations of polar organic pollutants, yet their uptake mechanisms are poorly understood. We introduce a one-dimensional model to simulate uptake by a passive sampler, Chemcatcher. The model considers the uptake as molecular diffusion through a series consisting of the aqueous boundary layer (ABL), the membrane filter (MF), and the sorbent disk with concurrent sorption by matrix of the MF and the disk. Uptake profiles of ∼20 polar chemicals measured over a week and a month were accurately modeled. Characteristic behaviors such as lag phases, linear and curved uptake, and equilibrating behavior were explained well by the model. As the model is mechanistically based, it was able to show the combined influences of the MF/water ( K_MF/w) and disk/water ( K_disk/w) partition coefficients, diffusion coefficients, and the ABL thickness on the sampling rates. On the basis of the model results, we offer three concrete recommendations for achieving the linear uptake needed for measuring time-weighted average concentrations: (i) use a MF that does not significantly sorb chemicals (e.g., log K_MF/w < 3) to avoid lag phases, (ii) use a sorbent with strong sorption properties (e.g., log K_disk/w > 6) for effective trapping of chemicals on the disk top layer, and (iii) make the ABL and/or the MF thicker so that the diffusion toward the disk slows.

Wastewater recycling in Antarctica: Performance assessment of an advanced water treatment plant in removing trace organic chemicals

The Australian Antarctic Division (AAD) operates Australia's Davis Station in the Antarctic. In 2005, Davis Station's wastewater treatment plant failed and since then untreated, macerated effluent has been discharged to the ocean. The objectives of this study were to determine whether an advanced water treatment plant (AWTP) commissioned by the AAD and featuring a multi-barrier process involving ozonation, ceramic microfiltration, biologically activated carbon filtration, reverse osmosis, ultraviolet disinfection and chlorination was capable of producing potable water and a non-toxic brine concentrate that can be discharged with minimal environmental impact. The AWTP was tested using water from a municipal wastewater treatment plant in Tasmania, Australia. We used spot water and passive sampling combined with two multi-residue chromatographic-mass spectrometric methods and a range of recombinant receptor-reporter gene bioassays to screen trace organic chemicals (TrOCs), toxicity and receptor activity in the Feed water, in the environmental discharge (reject water), and product water from the AWTP for six months during 2014-15, and then again for three months in 2016. Across the two surveys we unambiguously detected 109 different TrOCs in the feed water, 39 chemicals in the reject water, and 34 chemicals in the product water. Sample toxicity and receptor activity in the feed water samples was almost totally removed in both testing periods, confirming that the vast majority of the receptor active TrOCs were removed by the treatment process. All the NDMA entering the AWTP in the feed and/or produced in the plant (typically < 50 ng/L), was retained into the reject water with no NDMA observed in the product water. In conclusion, the AWTP was working to design, and releases of TrOCs at the concentrations observed in this study would be unlikely cause adverse effects on populations of aquatic organisms in the receiving environment or users of the potable product water.

Calibration and application of the Chemcatcher® passive sampler for monitoring acidic herbicides in the River Exe, UK catchment

Acidic herbicides are used to control broad-leaved weeds. They are stable, water-soluble, and with low binding to soil are found frequently in surface waters, often at concentrations above the EU Drinking Water Directive limit of 0.10 μg L^-1. This presents a problem when such waters are abstracted for potable supplies. Understanding their sources, transport and fate in river catchments is important. We developed a new Chemcatcher^® passive sampler, comprising a 3M Empore™ anion-exchange disk overlaid with a polyethersulphone membrane, for monitoring acidic herbicides (2,4-D, dicamba, dichlorprop, fluroxypyr, MCPA, MCPB, mecoprop, tricolpyr). Sampler uptake rates (R_s = 0.044-0.113 L day^-1) were measured in the laboratory. Two field trials using the Chemcatcher^® were undertaken in the River Exe catchment, UK. Time-weighted average (TWA) concentrations of the herbicides obtained using the Chemcatcher^® were compared with concentrations measured in spot samples of water. The two techniques gave complimentary monitoring data, with the samplers being able to measure stochastic inputs of MCPA and mecoprop occurring in field trial 1. Chemcatcher^® detected a large input of MCPA not found by spot sampling during field trial 2. Devices also detected other pesticides and pharmaceuticals with acidic properties. Information obtained using the Chemcatcher^® can be used to develop improved risk assessments and catchment management plans and to assess the effectiveness of any mitigation and remediation strategies.