Monitoring Herbicide Concentrations and Loads during a Flood Event: A Comparison of Grab Sampling with Passive Sampling

Evaluation of the DGT passive samplers for integrating fluctuating concentrations of pharmaceuticals in surface water

Diffusive gradients in thin films (DGTs) have been well-documented for the measurement of a broad range of organic pollutants in surface water. However, the performance has been challenged by the inherent periodic concentration fluctuations for most organic pollutants. Therefore, there is an urgent need to assess the true time-weighted average (TWA) concentration based on fluctuating concentration profiles. The study aimed to evaluate the responsiveness of DGT and accuracy of TWA concentrations, considering various concentration fluctuating scenarios of 20 pharmaceuticals in surface water. The reliability and accuracy of the TWA concentrations measured by the DGT were assessed by comparison with the sum of cumulative mass of DGT exposed at different stages over the deployment period. The results showed that peak concentration duration (1-5 days), peak concentration fluctuation intensity (6-20 times), and occurrence time of peak concentration fluctuation (early, middle, and late stages) have minimal effect on DGT's response to most target pharmaceutical concentration fluctuations (0.8 < CDGT/CTWA < 1.2). While the downward-bent accumulations of a few pharmaceuticals on DGT occur as the sampling time increases, which could be accounted for by capacity effects during a long-time sampling period. Additionally, the DGT device had good sampling performance in recording short fluctuating concentrations from a pulse event returning to background concentrations with variable intensity and duration. This study revealed a satisfactory capacity for the evaluation of the TWA concentration of pharmaceuticals integrated over the period of different pulse deployment for DGT, suggesting that this passive sampler is ideally suited as a monitoring tool for field application. This study represents the first trial for evaluating DGT sampling performance for pharmaceuticals with multiple concentration fluctuating scenarios over time, which would be valuable for assessing the pollution status in future monitoring campaign.

Development of a novel DGT passive sampler for measuring polycyclic aromatic hydrocarbons in aquatic systems

Polycyclic aromatic hydrocarbons (PAHs) are priority pollutants and need to be measured reliably in waters and other media, to understand their sources, fate, behaviour and to meet regulatory monitoring requirements. Conventional water sampling requires large water volumes, time-consuming pre-concentration and clean-up and is prone to analyte loss or contamination. Here, for the first time, we developed and validated a novel diffusive gradients in thin-films (DGT) passive sampler for PAHs. Based on the well-known DGT principles, the sampler pre-concentrates PAHs with typical deployment times of days/weeks, with minimal sample handling. For the first time, DGT holding devices made of metal and suitable for sampling hydrophobic organic compounds were designed and tested. They minimize sorption and sampling lag times. Following tests on different binding layer resins, a MIP-DGT was preferred - the first time applying MIP for PAHs. It samples PAHs independent of pH (3.9 -8.1), ionic strength (0.01 -0.5 M) and dissolved organic matter < 20 mg L-1, making it suitable for applications across a wide range of environments. Field trials in river water and wastewater demonstrated that DGT is a convenient and reliable tool for monitoring labile PAHs, readily achieving quantitative detection of environmental levels (sub-ng and ng/L range) when coupled with conventional GC-MS or HPLC. ENVIRONMENTAL IMPLICATIONS: PAHs are carcinogenic and genotoxic compounds. They are environmentally ubiquitous and must be monitored in waters and other media. This study successfully developed a new DGT passive sampler for reliable in situ time-integrated measurements of PAHs in waters at the ng/L level. This is the first time to use passive samplers for accurate measurements of hydrophobic organic contaminants in aquatic systems without calibration, a big step forward in monitoring PAHs. The application of this new sampler will enhance our understanding of the sources, fate, behavior and ecotoxicology of PAHs, enabling improved environmental risk assessment and management of these compounds.

Determination of organic contaminants in L'Albufera Natural Park using microporous polyethylene tube passive samplers: An environmental risk assessment

L'Albufera Natural Park (Valencia, Spain) is a protected wetland of international significance that provides critical habitats to endemic and threatened bird and plant species. This study aims to use multiple cross-validation techniques to generate an accurate estimation of the environmental risk of organic contaminants (OCs) in an internationally important coastal wetland, to identify compounds of concern and their potential sources and risk factors. Microporous polyethylene tube (MPT) passive samplers were deployed at 12 locations across L'Albufera Natural Park with concurrent grab samples collected. A subset of MPT samplers were also analysed by an additional laboratory in Australia to widen the range of contaminants and assess interlaboratory reproducibility of results. Forty-three pesticides, 20 pharmaceuticals and personal care products (PPCPs), 20 per-and polyfluoroalkyl substances (PFAS) and 4 organophosphorus flame retardants (OPFRs) were detected in the MPT samplers. The fungicides tebuconazole and difenoconazole were detected at the highest concentrations in passive samplers (maximum concentrations, 153 ng sampler-1 and 106 ng sampler-1, respectively). Several other pesticides were detected in all locations (mean concentrations >1 ng sampler-1). The compounds fenamiphos, propyzamide, difenoconazole, propiconazole, metsulfuron methyl, sodium bis (perfluorohexyl) phosphinate (6:6 PFPiA), 6:2 fluorotelomer sulfonamide alkylbetaine (6:2 FTAB), 6:2 fluorotelomersulfonate (6:2 FTS), citalopram desmethyl and citalopram were reported in the wetland for the first time. Spatial distribution analysis revealed higher pesticide concentrations in the North of L'Albufera. A risk quotient (RQ) analysis showed that ibuprofen is of concern in the area. Overall, the MPT sampling approach is promising as a risk assessment tool for better understanding the transport and fate of OCs in protected areas.

Organic diffusive gradients in thin films (o-DGT) for determining environmental behaviors of antibiotics: A review

Antibiotics are recognized as effective medicine that has been extensively used in human and veterinary. Since the rate of releasing into the environment is stronger than the rate of elimination, antibiotics are regarded as persistent or "pseudo-persistent" organic compounds that result in the development of microbial antibiotic resistance. Therefore, assessment for their ecological risks to the environment are essential. Diffusive gradients in thin films for organic compounds (o-DGT) have been adapted to investigate the environmental behaviors of antibiotics. Currently, more than 20 compounds have been tested by o-DGT in waters and soil environments. In this review, we explained the theoretical reason that o-DGT is feasible to determine the labile fraction of antibiotics in different environmental media. The most used agarose diffusive gel, and various binding agents such as resin, porous carbon and nano-scale materials have been compared to optimize the sampling of antibiotics by o-DGT. Results of deploying o-DGT devices in waters and soils from previous studies were discussed to understand the bioavailability and dynamic transport of antibiotics. Also, we provided the feasibility analysis of using o-DGT in sediments for antibiotics measurements, which is required to be carried out in future studies. To have a deep view on the development of o-DGT, its technical limitations and viable improvements were summarized in this study for further applications on antibiotics research.

Calibration of a microporous polyethylene tube passive sampler for polar organic compounds in wastewater effluent

Water resources are vulnerable to contamination from polar organic compounds (POCs) originating from sources such as wastewater effluent. Two configurations of a microporous polyethylene tube (MPT) passive sampler were investigated for the time-integrative detection and quantification of POCs in effluent. One configuration contained the polymeric reversed phase sorbent Strata-X (SX) and the other Strata-X suspended in agarose gel (SX-Gel). These were deployed for up to 29 days and analysed for forty-nine POCs including pesticides, pharmaceuticals and personal care products (PPCPs) together with illicit drugs. Complementary composite samples were collected on days 6, 12, 20 and 26 representing the previous 24 h. Thirty-eight contaminants were detected in composite samples and MPT extracts, with MPT sampling rates (R_s) for 11 pesticides and 9 PPCPs/drugs ranging from 0.81 to 10.32 mL d^-1 in SX and 1.35-32.83 mL d^-1 in SX-Gel. Half-times to equilibrium of contaminants with the SX and SX-Gel equipped samplers ranged from two days to >29 days. MPT (SX) samplers were also deployed at 10 wastewater treatment effluent discharge sites across Australia for 7 days (again with complementary composite samples), to validate the sampler performance under varying conditions. Extracts from these MPTs detected 48 contaminants in comparison with 46 in composite samples, with concentrations ranging from 0.1 to 138 ng mL^-1. An advantage of the MPT was preconcentration of contaminants, resulting in extract levels often markedly above instrument analytical detection limits. The validation study demonstrated a high correlation between accumulated contaminant mass in the MPTs and wastewater concentrations from composite samples (r² > 0.70, where concentrations in composite samples were > 3× LOD). The MPT sampler shows promise as a sensitive tool for detecting POCs at trace levels in wastewater effluent and also quantifying these levels if temporal concentration variations are not significant.

Catchment sourcing urban pesticide pollution using constructed wetlands in Melbourne, Australia

A survey of 111 urban constructed stormwater wetlands (median watershed area = 86.8 ha) was conducted to identify the major pesticides present and to determine their major catchment sources (residential, industrial, commercial, sporting ovals) and associations with catchment imperviousness. Melbourne, Australia, has separate stormwater and sewerage systems and these wetlands are designed to treat urban stormwater. To maximise the pesticides that could be detected, three types of passive samplers (POCIS, Chemcatcher® SDB-XC and Chemcatcher® C18) were deployed, along with collection of fine sediments. A total of 231 pesticides were screened using these methods. Pesticides that were detected in >5 % of wetlands were checked to determine their registered use in urban areas using an Australian government database (PubCris). Twenty-five pesticides were detected in >5 % of wetlands: 4 pesticides were associated with non-urban land uses (agriculture and forests), another 4 pesticides had no known registered use in urban areas and 17 were associated with urban areas. The pesticides associated with urban areas were the herbicides simazine, diuron, metolachlor, bromacil, propyzamide and paclobutrazol, the fungicides tebuconazole, propiconazole, metalaxyl, trifloxystrobin, iprodione and carbendazim and the insecticides fipronil, bifenthrin, chlorantraniliprole, thiamethoxam and permethrin. Atrazine was also detected in 59 % of wetlands but has not been registered for urban uses in Australia since 2010. It's presence in Melbourne may be due to legacy issues or aerial transportation from rural areas where it's still widely used in crop cultivation. Generally, the major urban catchment source of pesticides is from residential areas (particularly fipronil and simazine), most likely in wood preservatives, paints and from weed or insect control. Many of these widely used pesticides were correlated with increased catchment imperviousness. Some pesticides (bromacil and imidacloprid) were correlated with commercial premises and chlorantraniliprole was correlated with the presence of sporting ovals in the catchment. No pesticides were specifically correlated with industrial areas. The use of passive samplers and fine sediments, in conjunction with detailed land use mapping of stormwater wetland catchments is very effective and efficient in monitoring and sourcing pesticide contamination in urban environments.

Multivariate Tiered Approach To Highlight the Link between Large-Scale Integrated Pesticide Concentrations from Polar Organic Chemical Integrative Samplers and Watershed Land Uses

This paper presents a multi-step methodology to identify relationships between integrative pesticide quantifications and land uses on a given watershed of the Adour-Garonne Basin (Southwestern France). In fact, a large amount of pesticide concentration data was collected from 51 sites located in the Adour-Garonne Basin for a 1 year monitoring period in 2016. The sampling devices used here were polar organic chemical integrative samplers (POCIS), which provided time-weighted average concentration estimates. For each study site, its associated watershed and land cover distribution were determined using Corine Land Cover 2012 (CLC 2012) and Geographic Information System (GIS). The large-scale data were analyzed using multivariate statistical analyses, such as hierarchical cluster analysis (HCA) and principal component analysis (PCA). HCA grouped the 51 sites into five clusters with similar primary land uses. Next, the integrated pesticide concentration and land use distribution data sets were analyzed in a PCA. The key variables responsible for discriminating the sample sites showed distribution patterns consistent with specific land uses. To confirm these observations, pesticide fingerprints from sites with contrasting land uses were compared using a waffle method. The overall multivariate approach allowed for the identification of contamination sources related to their likely initial use, at the watershed level, that could be useful for preventing or containing pesticide pollution beyond simply acting on areas at risk.

Evaluation of Chemcatcher® passive samplers for pesticide monitoring using high-frequency catchment scale data

Passive samplers (PS) have been proposed as an enhanced water quality monitoring solution in rivers, but their performance against high-frequency data over the longer term has not been widely explored. This study compared the performance of Chemcatcher® passive sampling (PS) devices with high-frequency sampling (HFS: 7-hourly to daily) in two dynamic rivers over 16 months. The evaluation was based on the acid herbicides MCPA (2-methyl-4-chlorophenoxyacetic acid), mecoprop-P, fluroxypyr and triclopyr. The impact of river discharge parameters on Chemcatcher® device performance was also explored. Mixed effects modelling showed that time-weighted mean concentration (TWMC) and flow-weighted mean concentration (FWMC) values obtained by the HFS approach were both significantly higher (p < 0.001) than TWMC values determined from PS regardless of river or pesticide. Modelling also showed that TWMC_PS values were more similar to TWMC_HFS than FWMC_HFS values. However, further testing revealed that MCPA TWMC values from HFS and PS were not significantly different (p > 0.05). There was little indication that river flow parameters altered PS performance-some minor effects were not significant or consistent. Despite this, the PS recovery of very low concentrations indicated that Chemcatcher® devices may be used to evaluate the presence/absence and magnitude of acid herbicides in hydrologically dynamic rivers in synoptic type surveys where space and time coverage is required. However, a period of calibration of the devices in each river would be necessary if they were intended to provide a quantitative review of pesticide concentration as compared with HFS approaches.

Combining Passive Sampling with Suspect and Nontarget Screening to Characterize Organic Micropollutants in Streams Draining Mixed-Use Watersheds

Organic micropollutants (OMPs) represent an anthropogenic stressor on stream ecosystems. In this work, we combined passive sampling with suspect and nontarget screening enabled by liquid chromatography-high-resolution mass spectrometry to characterize complex mixtures of OMPs in streams draining mixed-use watersheds. Suspect screening identified 122 unique OMPs for target quantification in polar organic chemical integrative samplers (POCIS) and grab samples collected from 20 stream sites in upstate New York over two sampling seasons. Hierarchical clustering established the co-occurrence profiles of OMPs in connection with watershed attributes indicative of anthropogenic influences. Nontarget screening leveraging the time-integrative nature of POCIS and the cross-site variability in watershed attributes prioritized and confirmed 11 additional compounds that were ubiquitously present in monitored streams. Field sampling rates for 37 OMPs that simultaneously occurred in POCIS and grab samples spanned the range of 0.02 to 0.22 L/d with a median value of 0.07 L/d. Comparative analyses of the daily average loads, cumulative exposure-activity ratios, and multi-substance potentially affected fractions supported the feasibility of complementing grab sampling with POCIS for OMP load estimation and screening-level risk assessments. Overall, this work demonstrated a multi-watershed sampling and screening approach that can be adapted to assess OMP contamination in streams across landscapes.

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

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

Polar organic chemical integrative samplers as an effective tool for chemical monitoring of surface waters - Results from one-year monitoring in France

In an effort to support European Union Water Framework Directive goals, we have set up a national demonstrator project to identify the advantages and limitations of passive samplers for regulatory monitoring of polar contaminants in surface waters. Here we carried out successive 14 day-deployments of polar organic chemical integrative samplers (POCIS) for one year at three sites. In parallel, we used the passive sampler deployment/retrieval operations to collect spot water samples for comparative analysis. We observed that frequency of quantification was significantly higher in POCIS than spot samples for 29 contaminants, similar for 15, and lower for one, because POCIS lowered the limits of quantification for most contaminants (median value factor of 11). We built a database of sampling rates (Rs) according to quality indices to convert concentrations in POCIS to concentrations in water (23 contaminants with a high-quality median Rs value, 20 with an approximate Rs and two with no usable Rs). Several phenomena were observed over one-year monitoring period. For example, after a flood episode, dilution phenomenon in rivers is correctly observed by using POCIS sampling whereas significant concentration increased due to soil leaching is observed with both passive and spot sampling. Cases of episodic contamination that were missed by spot sampling were observed with POCIS as it was able to capture contamination of short duration but sufficient intensity. Contamination by pharmaceuticals was found to come from wastewater treatment plant discharges and showed relatively little variation over the course of the year in both POCIS and spot samples. POCIS enables more reliable annual monitoring of pesticide and pharmaceutical contamination than spot sampling. Furthermore, POCIS also improves the environmental quality standards based assessment of chemical status and on annual average concentrations compared to spot sampling. This study demonstrates the value and practicability of POCIS-based chemical monitoring for use in regulatory control networks.

Lab-scale investigation of the ability of Polar Organic Chemical Integrative Sampler to catch short pesticide contamination peaks

In this lab-scale study, the POCIS capacity to integrate short contamination peaks of variable intensity and duration was evaluated. POCIS were immersed for 14 days in tanks filled with tap water and spiked at different concentrations with 12 pesticides of various polarities (log K_ow = 1.1-4.7) and classes (herbicides, fungicides, and insecticides). Concentrations were kept relatively constant at 1 μg L^-1 and 5 μg L^-1, respectively, in two "background" exposure tanks. Three contamination peaks of increasing intensity and decreasing duration were simulated (10 μg L^-1 for 24 h, 40 μg L^-1 for 6 h, and 60 μg L^-1 for 1 h). This lab-scale study demonstrated that ten moderately polar compounds (2 < log K_ow < 4) showed a linear uptake, as observed in previous studies, while a non-linear model fits the data of the two most polar pesticides (log K_ow < 2). Depending on chemical polarity, some compounds exhibited a "burst effect" or "lag effect" during the first 3 days of exposure. After 14 days of exposure, contamination peaks appeared integrated for seven compounds, showing the ability of POCIS to catch very short pollution events and to provide acceptable time-weighted average concentration estimates under laboratory-controlled conditions.

Symbiotic microalgae do not increase susceptibility of zooxanthellate medusae (Cassiopea xamachana) to herbicides

Herbicides are among the most detected pesticides in coastal environments. Herbicides may impact non-target organisms, but invertebrates that have a symbiotic relationship with microalgae (zooxanthellae) may be particularly susceptible. How zooxanthellae influence the response of organisms to herbicides, however, remains untested. We exposed zooxanthellate and azooxanthellate Cassiopea xamachana medusae to environmentally relevant concentrations of the herbicide atrazine (0 µg L ^- 1, 7 µg L ^- 1 and 27 µg L ^- 1) for 20 days. We hypothesised that atrazine would have adverse effects on the size, rate of bell contractions and, respiration of medusae, but that effects would be more severe in zooxanthellate than azooxanthellate medusae. We also predicted that photosynthetic efficiency, chlorophyll a (Chla) content and zooxanthellae density would decrease in zooxanthellate medusae exposed to atrazine. Both zooxanthellate and azooxanthellate medusae shrank, yet the size-specific respiration rates were not constant during the experiment. Photosynthetic efficiency of zooxanthellate medusae significantly decreased at 7 and 27 µgL^-1 atrazine, but atrazine did not affect the Chla content or zooxanthellae density. Our results showed that even though atrazine inhibited photosynthesis, zooxanthellae were not expelled from the host. We conclude that the presence of zooxanthellae did not increase the susceptibility of C. xamachana medusae to atrazine.

Distribution of organochlorine pesticide pollution in water, sediment, mollusk, and fish at Saguling Dam, West Java, Indonesia

This study aims to determine the distribution of organochlorine pesticide pollution in water, sediments, mollusks, and fish at Saguling Dam as baseline data of organochlorine pollution. Samples were obtained from 12 locations, with 9 and 3 sampling points inside and outside the dam, respectively. Measurement of organochlorine residues was carried out using methods of extraction, purification, evaporation, and gas chromatography. Results showed the presence of several types of organochlorine compounds, namely, lindane, aldrin, dieldrin, heptachlor, dichlorodiphenyltrichloroethane (DDT), and endosulfan. Aldrin was dominant in water (2-37 μg/L) and sediments (2-1438 μg/L), while DDT and heptachlor were dominant organochlorine compounds in mollusks (13-2758 µg/L) and fish (11-104 μg/L), respectively. Sediments demonstrated higher organochlorine concentrations than water, mollusk, and fish. The distribution of organochlorine was affected by land use around the Citarum watershed and pollutant input from tributaries.

Using a multi-dimensional approach for catchment scale herbicide pollution assessments

Worldwide herbicide use in agriculture, whilst safeguarding yields also presents water quality issues. Controlling factors in agricultural catchments include both static and dynamic parameters. The present study investigated the occurrence of herbicides in streams and groundwater in two meso-scale catchments with contrasting flow controls and agricultural landuse (grassland and arable land). Using a multi-dimensional approach, streams were monitored from November 2018 to November 2019 using Chemcatcher® passive sampling devices and groundwater was sampled in 95 private drinking water wells. The concentrations of herbicides were larger in the stream of the Grassland catchment (8.9-472.6 ng L^-1) dominated by poorly drained soils than in the Arable catchment (0.9-169.1 ng L^-1) dominated by well-drained soils. Incidental losses of herbicides during time of application and low flows in summer caused concentrations of MCPA, Fluroxypyr, Trichlorpyr, Clopyralid and Mecoprop to exceeded the European Union (EU) drinking water standard due to a lack of dilution. Herbicides were present in the stream throughout the year and the total mass load was higher in winter flows, suggesting a persistence of primary chemical residues in soil and sub-surface environments and restricted degradation. Losses of herbicides to the streams were source limited and influenced by hydrological conditions. Herbicides were detected in 38% of surveyed drinking water wells. While most areas had concentrations below the EU drinking water standard some areas with well-drained soils in the Grassland catchment, had concentrations exceeding recommendations. Individual wells had concentrations of Clopyralid (619 ng L^-1) and Trichlorpyr (650 ng L^-1). Despite the study areas not usually associated with herbicide pollution, and annual mass loads being comparatively low, many herbicides were present in both surface and groundwater, sometimes above the recommendations for drinking water. This whole catchment assessment provides a basis to develop collaborative measures to mitigate pollution of water by herbicides.

Monitoring of ammonia in marine waters using a passive sampler with biofouling resistance and neural network-based calibration

A biofouling resistant passive sampler for ammonia, where the semi-permeable barrier is a microporous hydrophobic gas-diffusion membrane, has been developed for the first time and successfully applied to determine the time-weighted average concentration of ammonia in estuarine and coastal waters for 7 days. Strategies to control biofouling of the membrane were investigated by covering it with either a copper mesh or a silver nanoparticle functionalised cotton mesh, with the former approach showing better performance. The effects of temperature, pH and salinity on the accumulation of ammonia in the newly developed passive sampler were studied and the first two parameters were found to influence it significantly. A universal calibration model for the passive sampler was developed using the Group Method Data Handling algorithm based on seawater samples spiked with known concentrations of total ammonia under conditions ranging from 10 to 30 °C, pH 7.8 to 8.2 and salinity 20 to 35. The newly developed passive sampler is affordable, user-friendly, reusable, sensitive, and can be used to detect concentrations lower than the recently proposed guideline value of 160 μg total NH₃-N L^-1, for a 99% species protection level, with the lowest concentration measured at 17 nM molecular NH₃ (i.e., 8 μg total NH₃-N L^-1 at pH 8.0 and 20 °C). It was deployed at four field sites in the coastal waters of Nerm (Port Phillip Bay), Victoria, Australia. Good agreement was found between molecular ammonia concentrations obtained with passive and discrete grab sampling methods (relative difference, - 12% to - 19%).

Toxicity of the herbicides diuron, propazine, tebuthiuron, and haloxyfop to the diatom Chaetoceros muelleri

Conventional photosystem II (PSII) herbicides applied in agriculture can pose significant environmental risks to aquatic environments. In response to the frequent detection of these herbicides in the Great Barrier Reef (GBR) catchment area, transitions towards 'alternative' herbicides are now widely supported. However, water quality guideline values (WQGVs) for alternative herbicides are lacking and their potential ecological impacts on tropical marine species are generally unknown. To improve our understanding of the risks posed by some of these alternative herbicides on marine species under tropical conditions, we tested the effects of four herbicides on the widely distributed diatom Chaetoceros muelleri. The PSII herbicides diuron, propazine, and tebuthiuron induced substantial reductions in both 24 h effective quantum yields (ΔF/Fm') and 3-day specific growth rates (SGR). The effect concentrations, which reduced ΔF/Fm' by 50% (EC50), ranged from 4.25 µg L-1 diuron to 48.6 µg L-1 propazine, while the EC50s for SGR were on average threefold higher, ranging from 12.4 µg L-1 diuron to 187 µg L-1 tebuthiuron. Our results clearly demonstrated that inhibition of ΔF/Fm' in PSII is directly linked to reduced growth (R2 = 0.95) in this species, further supporting application of ΔF/Fm' inhibition as a valid bioindicator of ecological relevance for PSII herbicides that could contribute to deriving future WQGVs. In contrast, SGR and ΔF/Fm' of C. muelleri were nonresponsive to the non-PSII herbicide haloxyfop at the highest concentration tested (4570 µg L-1), suggesting haloxyfop does not pose a risk to C. muelleri. The toxicity thresholds (e.g. no effect concentrations; NECs) identified in this study will contribute to the derivation of high-reliability marine WQGVs for some alternative herbicides detected in GBR waters and support future assessments of the cumulative risks of complex herbicide mixtures commonly detected in coastal waters.

Pervasive Pesticide Contamination of Wetlands in the Great Barrier Reef Catchment Area

Knowledge of the types and impacts of contaminants occurring in the freshwater wetlands of the Great Barrier Reef catchment area (GBRCA) is limited. The present study examined the presence and concentrations of pesticides occurring in 22 floodplain wetlands, situated in moderate to high-intensity land uses in the GBRCA. The dominant land use within 1 km of the wetlands was sugar cane for 12 wetlands, grazing for 6 wetlands, plantation forestry and conservation for 2 wetlands, and one with an equal mix of land uses. Fifty-nine pesticides and pesticide degradates were detected in the wetlands during 2 consecutive early wet seasons. These included 27 herbicides, 11 herbicide degradates, 11 insecticides, 8 fungicides, 1 nematicide, and 1 pesticide synergist. Each wetland sampled contained between 12 and 30 pesticides with an average of 21 pesticides detected per wetland sampling. Temporal differences existed in the number, types, and average concentrations of pesticides detected. No exceedances of Australian and New Zealand water guideline values were found during the first sampling season, while 10 wetlands had concentrations of at least 1 pesticide exceeding the guidelines during the following sampling season. For 1 wetland, concentrations of 4 pesticides were greater than the prescribed guideline values. Individually, the vast majority of aquatic species would be protected, but in some wetlands, diuron would affect 49% of species and atrazine up to 24% of species. Statistically significant correlations between the number of pesticides and the percentage of intensive land use, primarily sugar cane growing in a 1 km radius of the wetlands, were found. Integr Environ Assess Manag 2020;16:968-982. © 2020 SETAC.

Sampling rates for passive samplers exposed to a field-relevant peak of 42 organic pesticides

Pesticide concentrations in agricultural streams are often characterised by a low level of baseline exposure and episodic peak concentrations associated with heavy rainfall events. Traditional sampling methods such as grab sampling, which are still largely used in governmental monitoring, typically miss peak concentrations. Passive sampling represents a cost-efficient alternative but requires the additional determination of sampling rates to calculate time-weighted average (TWA) water concentrations from the accumulated pesticide mass in the sampler. To date, sampling rates have largely been determined in experiments with constant exposure, which does not necessarily reflect field situations. Using Empore styrene-divinylbenzene (SDB) passive sampler disks mounted in metal holders, we determined sampling rates for 42 organic pesticides, of which 27 sampling rates were lacking before. The SDB disks were in an artificial channel system exposed to a field-relevant pesticide peak. We used an open-source algorithm to estimate coefficients of equations for the accumulated pesticide mass in disks and to determine exposure time-dependent sampling rates. These sampling rates ranged from 0.02 to 0.98 L d^-1 and corresponded to those from previous studies determined with constant exposure. The prediction of sampling rates using compound properties was unreliable. Hence, experiments are required to determine reliable sampling rates. We discuss the use of passive sampling to estimate peak concentrations. Overall, our study provides sampling rates and computer code to determine these under peak exposure designs and suggests that passive sampling is suitable to estimate peak pesticide concentrations in field studies.

Groundwater sampling in karst terranes: passive sampling in comparison to event-driven sampling strategy

Karst aquifers are very easily contaminated because of the surficial features that commonly exist in karst terranes. Pollutant releases into sinkholes, sinking streams, and/or losing streams commonly result in concentrated solutes rapidly infiltrating and migrating through the subsurface to eventually discharge at downgradient springs unless intercepted by production wells, but slow percolation through soils also may result in serious contamination of karst aquifers. The unique features of karst terranes tend to cause significant problems in the interpretation of results obtained from water-quality grab samples of karst groundwater. To obtain more representative samples, event-driven sampling was proposed some decades ago, but event-driven sampling can be difficult and expensive to implement. In this paper, application of passive-sampling strategies is advocated as a means for effectively obtaining representative water-quality samples from karst aquifers. A passive-sampling methodology may be particularly useful for karst aquifers that may be found in complexly folded and faulted terranes. For example, a groundwater tracing investigation of a contaminated site in a karst terrane confirmed that several offsite springs and wells are connected to the contaminated site. Tracer recoveries suggested transport rates that were relatively slow for flow in a karstic aquifer (~0.02 m/s). Breakthrough curves were erratic and spiky. To obtain representative groundwater samples, a passive-sampling methodology is recommended.

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.

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.

Quantitative use of passive sampling data to derive a complete seasonal sequence of flood event loads: a case study for maize herbicides in Luxembourg

Pesticides are the class of compounds with the most dynamic behaviour in their surface water occurrence: their episodic release to surface waters is closely related to the date of application and the following weather conditions and poses substantial challenges to monitoring in order to yield accurate mass transfer figures. Moreover, pesticide use, dose and time of application are largely unknown catchment wide and pose an essential problem as to the realism and reliability of pesticide fate modelling as well as accurate farmer counselling. Spatially and temporally highly resolved monitoring establishing pesticide sources was logistically unthinkable until the advent of passive samplers which combine ease of deployment and continuous sampling. However, because research on passive sampler performance has been mainly driven by analytical precision issues, doubts were high as to whether passive samplers could yield accurate time weighted averages in the field, all the more so that the number of field validations is to this day very limited. Here we present a study that used a combination of spatially distributed passive- and autosamplers to capture the runoff dynamics of pesticides used for maize crops in a 82 km2 catchment in Luxembourg. We demonstrate that passive samplers are capable of accurately monitoring episodic emissions of pesticides through a longitudinal profile in a catchment, thus allowing the identification of pesticide source areas. Thanks to the time-proportional nature of the passive sampling it was furthermore possible to calculate event mean concentrations and loads which were behaving temporally according to the physico-chemical properties of the compounds and to the timing and extent of mobilising discharge.

Release of Munitions Constituents in Aquatic Environments Under Realistic Scenarios and Validation of Polar Organic Chemical Integrative Samplers for Monitoring

Munitions constituents (MC) may be released into aquatic environments as a result of underwater military munitions (UWMM) corrosion and breach. The present study investigated the release of 2,4,6-trinitrotoluene (TNT) and hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) from Composition B fragments under 2 realistic exposure scenarios in a large flume with flow set at 15 cm/s: the first represented the release of MC from fully exposed Composition B, and the second represented release through a small hole, simulating a breached munition. Release of MC through a small hole was approximately 10 times lower than from exposed Composition B, demonstrating the strong influence of exposure to flow on release. The rate of release of MC into the flume was similar to that previously reported in a related field experiment, but a similar mass loss resulted in MC concentration in the field >300 times lower, likely by the dilution effect of hydrodynamic transport. The present study corroborates previous findings of release of MC at UWMM sites resulting in concentrations below the toxicity threshold to most species. In the flume water, MC was quantified using frequent grab sampling and polar organic chemical integrative samplers (POCIS). For TNT, POCIS-estimated time-weighted average concentrations were up to 40% higher than those derived from grab samples, whereas for RDX differences were 6% or less, demonstrating that POCIS provide reliable temporal integration of changing environmental concentrations for common MC. Environ Toxicol Chem 2019;38:2383-2391. Published 2019 Wiley Periodicals Inc. on behalf of SETAC. This article is a US government work and, as such, is in the public domain in the United States of America.

Environmental health effects attributed to toxic and infectious agents following hurricanes, cyclones, flash floods and major hydrometeorological events

Extreme hydrometeorological events such as hurricanes and cyclones are increasing in frequency and intensity due to climate change and often associated with flash floods in coastal, urbanized and industrial areas. Preparedness and response measures need to concentrate on toxicological and infectious hazards, the potential impact on environmental health, and threat to human lives. The recognition of the danger of flood water after hurricanes is critical. Effective health management needs to consider the likelihood and specific risks of toxic agents present in waters contaminated by chemical spills, bio-toxins, waste, sewage, and water-borne pathogens. Despite significant progress in the ability to rapidly detect and test water for a wide range of chemicals and pathogens, there has been a lack of implementation to adapt toxicity measurements in the context of flash and hurricane-induced flooding. The aim of this review was to highlight the need to collect and analyze data on toxicity of flood waters to understand the risks and prepare vulnerable communities and first responders. It is proposed that new and routinely used technologies be employed during disaster response to rapidly assess toxicity and infectious disease threats, and subsequently take necessary remedial actions.

Transfer Pathways and Fluxes of Water-Soluble Pesticides in Various Compartments of the Agricultural Catchment of the Canche River (Northern France)

Five frequently used water-soluble pesticides (atrazine, diflufenican, metolachlor, pendimethalin, and ethofumesate) were monitored in surface water and groundwater of an agricultural catchment (Canche River) in Northern France for examining the edge-of-field pathways of substances and their characteristic time of transport. The study of surface water contamination was conducted in 2016 through two time scales: continuously over one year at a single location of the catchment and punctually during four seasons at 15 sampling locations along a longitudinal river profile. In addition, groundwater in winter and summer shows a generally low and relatively constant contamination level. Nevertheless, the outflow of pesticides from groundwater results in a background contamination of surface water. In addition to this, a contamination peak above the baseline level is observed in surface water subsequently to the period of substance application on the fields. Our results show that pesticides were essentially transported into the surface water by fast flow components (runoff water). Loss of pesticides during the contamination peak period and long-term monitoring were compared showing that the transport of substances within weeks after pesticides spreading dominates the annual flux of pesticides, except for atrazine which shows a constant background contamination pattern. Low frequency monitoring schemes provide only a partial picture of the contamination state and do not enable to evaluate the true contamination state of such rivers with regard to the fact that 3/4 of the annual load of pesticides are transported in the stream during only 2–3 months.

Expanding phytoremediation to the realms of known and unknown organic chemicals of concern

Recent advancements in analytical chemistry and data analyses via high-resolution mass spectrometry (HRMS) are evolving scientific understanding of the potential totality of organic chemical exposure and pollutant risk. This review addresses the importance of HRMS approaches, namely suspect screening and nontarget chemical analyses, to the realm of phytoremediation. These analytical approaches are not without caveats and constraints, but they provide an opportunity to understand in greater totality how plant-based technologies contribute, mitigate, and reduce organic chemical exposure across scales of experimental and system-level studies. These analytical tools can enlighten the complexity and efficacy of plant-contaminant system design and expand our understanding of biogenic and anthropogenic chemicals at work in phytoremediation systems. Advances in data analytics from biological sciences, such as metabolomics, are crucial to HRMS analysis. This review provides an overview of targeted, suspect screening, and nontarget HRMS approaches, summarizes the expanding knowledge of regulated and unregulated organic chemicals in the environment, addresses requisite HRMS instrumentation, analysis cost, uncertainty, and data processing techniques, and offers potential bridges of HRMS analyses to phytoremediation research and application.

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.

Calibration parameters for the passive sampling of organic UV filters by silicone; diffusion coefficients and silicone-water partition coefficients

In recent years, organic ultraviolet filters (UVFs) received considerable attention as a group of emerging contaminants, including in Australia where the use of UVFs is particularly relevant. Passive sampling using polymers has become widely used for routine monitoring of chemicals in the aquatic environment. Application of passive samplers for monitoring chemicals in the water relies on calibration data such as chemical's polymer-water partition coefficient (K_pw) and diffusion coefficients in the sampling material (D_p), for understanding uptake and kinetic limitations. In the present study, K_pw and D_p for nine UVFs were estimated. K_pw values were determined in different water - polymer partition experiments where (1) a given mass of chemicals was dosed into the water and (2) into the polymer. Diffusion coefficients were determined using the stacking method. The estimated log K_pw and log D_p ranged from 2.9 to 6.4 L kg^-1 and -11.1 to -10.5 m²s^-1, respectively. The sufficient high D_p allows application of kinetic models that only consider water boundary-controlled uptake for converting silicone sampler uptake into an aqueous phase concentration using the presented K_pw.

Combination of passive and grab sampling strategies improves the assessment of pesticide occurrence and contamination levels in a large-scale watershed

Fifty-one monitoring stations from the Water Framework Directive network (2000/60/CE) were selected in the Adour-Garonne basin (117,650 km², SW France). These stations were characterized by a diversity of land use, implying different water pesticide contamination profiles. In each, Polar Organic Chemical Integrative Sampler (POCIS) deployment (14 days) and grab water samples (1 per period) were performed 6 times in 2016 in order to obtain contamination levels (29 pesticides monitored). The large amount of data collected during this 1-year monitoring required specific graphical and map processing to compare the information provided by POCIS and grab samples. Graphical projections demonstrated that with POCIS the number of quantified pesticides and the quantification frequencies were higher than with grab samples. Additionally, projections showed that POCIS provided better temporal representativeness of monthly contamination levels. Indeed, the POCIS data showed seasonal trends which were directly linked with the use of each pesticide (application period) and the land use of each sampling site, that was not visible with the grab samples data. Map projections of the measured concentrations, using a common scale for the two sampling strategies, clearly showed the strengths of the POCIS deployment and the link between measured contamination levels, quantified pesticides and land use. Finally, this study shows that the combination of grab sample data (magnitude of contamination peaks) and POCIS data (average concentration over a given period) provided more complete and reliable knowledge of the contamination levels in the Basin than either method alone.

Passive samplers in sewers and rivers with highly fluctuating micropollutant concentrations - Better than we thought

Considerable pollutant loads can enter surface waters during rain events. Three factors challenge quantification of these pollutant fluxes using traditional sampling methods: (i) concentration fluctuations; (ii) unknown event duration; and (iii) placement, operation, and maintenance of equipment. Passive samplers offer the advantage of sampling in a continuous mode without power supply. However, variable uptake rates due to environmental factors and desorption in the case of fluctuating concentrations can affect the accuracy of time-weighted average (TWA) concentration estimates. While uncertainties related to environmental factors could be accounted for with additional effort, we can neither control nor quantify the concentration variability. We present measured and modelled concentration profiles at high temporal resolution and provide a systematic approach to assessing deviations from true TWA concentration due to fluctuating concentration profiles. We evaluate sampling of sewer overflows (0.3-14 h) with Chemcatcher and 1-week sampling in rivers. The uncertainty due to fluctuating concentrations is small, and other factors such as chemical analyses and sampler calibration have a similar or higher impact. The uncertainty due to fluctuations clearly increases with the sampling duration, particularly when exceeding the half-life of equilibrium. We conclude that passive sampling can also be used in wastewater systems with potentially high concentration variations.

A comparison of equilibrium and kinetic passive sampling for the monitoring of aquatic organic contaminants in German rivers

The performances of an equilibrium and a kinetic passive sampler for monitoring a range of organic contaminants (Log K_OW from -0.03 to 6.26) were evaluated in the effluent of a wastewater treatment plant, the receiving river Saar as well as the river Mosel in Germany. The polar organic chemical integrative sampler (POCIS) and a new mixed polymer sampler (MPS) were selected as kinetic and equilibrium passive samplers, respectively. Concentrations were described in terms of a time-weighted average concentration (C_TWA) from the POCIS measurements and as an equilibrium concentration from the MPS (C_Equil-MPS) and POCIS membrane (C_Equil-PES) analyses. Twenty-seven compounds could be detected, including eight priority substances of the EU Water Framework Directive. Both sampler types detected a similar range of compounds in the low ng/L to μg/L range, with a high proportion of pharmaceuticals being detected at all sampling sites. To account for uncertainty in the POCIS sampling rates, a range in C_TWA was estimated by applying low and high sampling rates. For the compounds that were detected in the POCIS this range was within a factor of 3.5. Interestingly, the MPS extracts showed lower ionisation artefacts than the POCIS extracts during the LC-MS/MS analysis. Finally, total water concentrations (C_Total) were estimated from the dissolved concentrations, literature organic carbon partition coefficients (K_OC) and the total organic carbon levels measured in the rivers. For the compounds in this study, negligible differences between C_Total and the passive sampler-derived dissolved concentrations were found with a maximum difference of 15% for diclofenac. Overall, this study demonstrated that the parallel application of kinetic and equilibrium passive samplers can improve the description of water quality.

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.

Selection of performance reference compound (PRC) for passive sampling of pharmaceutical residues in an effluent dominated river

A passive sampling device, a polar organic chemical integrative sampler (POCIS), was used to monitor 13 pharmaceuticals and 8 transformation products in upstream and downstream wastewater treatment plant effluent. A POCIS laboratory calibration study was performed to determine uptake behavior and the effect of water flow on the sampling rate. Most compounds showed a linear accumulation, and the sampling rate values ranged from 0.031 to 0.559 L/day. The developed POCIS samplers were used in field experiments in a wastewater-impacted river. Using the calculated sampling rates, the time-weighted average concentration values were measured by three different approaches: (1) laboratory calibration sampling rates (2) performance reference compound (PRC) correction sampling rates and (3) field calibration sampling rates. Nine deuterated compounds (acetaminophen-d₃, antipyrine-d₃, sulfamethoxazole-d₄, carbamazepine-d₁₀, diclofenac acid-d₄, clofibric acid-d₄, bezafibrate-d₆, ibuprofen-d₃ and naproxen-d₃) were studied as PRCs. Antipyrine-d₃ was successfully tested as a PRC for sulfamethoxazole, ibuprofen, 2-hydroxy ibuprofen, diclofenac acid, 4-hydroxydiclofenac acid, carbamazepin, carbamazepin 10,11-epoxide, sulfadiazine, 1-naphthol, antipyrine, naproxen and 4-chlorobenzoic acid. Finally, the POCIS was used to monitor target compounds in river water and measure their attenuation. For most compounds, the POCIS attenuation results were not significantly different from those of the spot samples, which demonstrated that a POCIS with a PRC correction can determine the attenuation of organic micropollutants in rivers.

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.

Measuring metaldehyde in surface waters in the UK using two monitoring approaches

Metaldehyde is a molluscicide and the active ingredient in formulated slug pellets used for the protection of crops. Due to its mobility in the environment it is frequently found in river catchments, often at concentrations exceeding the EU Drinking Water Directive limit of 100 ng L-1 for a single pesticide. This presents a major problem for water companies in the UK where such waters are abstracted for production of potable drinking water supplies. Therefore, it is important to understand the sources, transport and fate of this emerging pollutant of concern in the aquatic environment. We monitored metaldehyde in two contrasting river catchments (River Dee (8 sites) and River Thames (6 sites)) over a twelve month period that coincided with the agricultural application period of the molluscicide. Spot samples of water were collected typically weekly or fortnightly. Chemcatcher® passive samplers were deployed consecutively every two weeks. At the River Dee, there was little variability in the concentrations of metaldehyde (<10-110 ng L-1) measured in the spot samples of water. The Chemcatcher® gave similar time-weighted average concentrations which were higher following increased rain fall events. At the River Thames, concentrations of metaldehyde varied more widely (<9-4200 ng L-1) with several samples exceeding 100 ng L-1. Generally these concentrations were reflected in the time-weighted average concentrations obtained using the Chemcatcher®. Both monitoring techniques gave complementary data for identifying input sources, and in the development of catchment management plans and environmental remediation strategies.

Analyzing the uncertainty of diffusive gel-based passive samplers as tools for evaluating the averaged contamination of surface water by organic pollutants

Agarose gel-based passive samplers are nowadays one of the most effective sampling devices able to provide a quantitative evaluation of water contamination level for a broad range of organic contaminants. These devices show significant improvements in comparison to the previous passive samplers dedicated to hydrophilic compounds because they tend to reduce the effect of hydrodynamic flow conditions on the uptake rate of compounds and thus subsequently to improve their accuracy. However, albeit their effects minimized, hydrodynamic water flow and temperature are reported as variables likely to change the uptake rate of compounds that may lead to some inaccuracy if they are not adequately taken into account. This work aims to investigate the magnitude of effects of such uncorrected variables on the bias of the deduced water contamination level. The analysis of the error structure shows that the uncertainty on the diffusivity of contaminants in agarose gel and its dependency on temperature are the most inferring factors. At 8 °C, these factors are, respectively, responsible of 34 and 33% of the squared uncertainty on the final deduced contamination level. The overall uncertainty for a single exposed passive sampler is in the order of 39% and drops to 23% if threesamplers are co-exposed (at 8 °C). Despite this uncertainty, we present results for a set of pesticides and personal care products throughout a field monitoring conducted over a 4-month period, which show the potential of passive samplers to allow assessing the temporal trend of water contamination.

Pesticides in the rivers and streams of two river basins in northern Greece

The pollution caused by pesticides, and their ecotoxicological implications were investigated in water samples from the Strymonas and Nestos river basins (Northern Greece). Chlorpyrifos was the most frequently detected pesticide in both basins (42 and 37% in the Strymonas and Nestos basins, respectively), followed by fluometuron and terbuthylazine (25 and 12%, Strymonas), and bentazone and boscalid (24 and 10%, Nestos). The Annual Average and the Maximum Allowable Concentration of Environmental Quality Standards set in European Union Directives were exceeded in several cases by alphamethrin and chlorpyrifos. Risk Quotient assessment revealed significant ecological risk towards the aquatic organisms in over 20% of the water samples. Insecticides (mostly pyrethroids and organophosphosphates) contributed more in the ecotoxicological risk than herbicides and fungicides. The three main rivers in the current study (Strymonas, Aggitis, Nestos) exhibited similar sum of RQs indicating that aquatic life in all three of them was at the same risk level. However, the sums of RQs were higher in the various streams monitored than the three rivers.

Two sampling strategies for an overview of pesticide contamination in an agriculture-extensive headwater stream

Two headwaters located in southwest France were monitored for 3 and 2 years (Auvézère and Aixette watershed, respectively) with two sampling strategies: grab and passive sampling with polar organic chemical integrative sampler (POCIS). These watersheds are rural and characterized by agricultural areas with similar breeding practices, except that the Auvézère watershed contains apple production for agricultural diversification and the downstream portion of the Aixette watershed is in a peri-urban area. The agricultural activities of both are extensive, i.e., with limited supply of fertilizer and pesticides. The sampling strategies used here give specific information: grab samples for higher pesticide content and POCIS for contamination background noise and number of compounds found. Agricultural catchments in small headwater streams are characterized by a background noise of pesticide contamination in the range of 20-70 ng/L, but there may also be transient and high-peak pesticide contamination (2000-3000 ng/L) caused by rain events, poor use of pesticides, and/or the small size of the water body. This study demonstrates that between two specific runoff events, contamination was low; hence the importance of passive sampler use. While the peak pesticide concentrations seen here are a toxicity risk for aquatic life, the pesticide background noise of single compounds do not pose obvious acute nor chronic risks; however, this study did not consider the risk from synergistic "cocktail" effects. Proper tools and sampling strategies may link watershed activities (agricultural, non-agricultural) to pesticides detected in the water, and data from both grab and passive samples can contribute to discussions on environmental effects in headwaters, an area of great importance for biodiversity.

Carcinogenic and non-carcinogenic health risks of metal(oid)s in tap water from Ilam city, Iran

One of the most important pathways for exposure to metals is drinking water ingestion. Chronic or acute exposure to metals can endanger the health of the exposed population, and hence, estimation of human health risks is crucial. In the current study for the first time, the concentrations of Mercury (Hg), Arsenic (As), Zinc (Zn), Lead (Pb) and Cobalt (Co) in 120 collected tap water samples (2015, July-November) from Ilam city, Iran were investigated using flame atomic absorption spectrophotometer. Also, the metal-induced carcinogenic and non-carcinogenic risks for consumers exposed to tap drinking water were calculated. The average (range) concentrations of Hg, Zn, As, Pb and Co were defined as 0.40 ± 0.10 μg/L (ND-0.9 μg/L), 5014 ± 5707 μg/L (2900.00-5668.33 μg/L), 21.008 ± 2.876 μg/L (3.5-62 μg/L), 30.38 ± 5.56 μg/L (6-87 μg/L), and 11.34 ± 1.61 μg/L (0.1-50 μg/L), respectively. Average concentrations of all examined metals were significantly higher than WHO and national standard recommended limits. The ranking order of metals concentrations in the tap drinking water was Zn > Pb > As > Co > Hg. Except for Hg and Co, at least one age group consumers were at considerable non-carcinogenic risks induced by Zn, As and Pb [Target Hazard Quotient (THQ > 1)]. The rank order of age groups consumers based on THQ and Incremental lifetime cancer risk (ILCR) was <1 years >1-9 years > 20 + years > 10-19 years. The calculated ILCR for As in all age groups were higher than 10^-3 value. All age groups of consumers in Ilam city, especially infants (<1 years) and children (1-10 years), are at considerable non-carcinogenic and carcinogenesis risk.

Understanding the uncertainty of estimating herbicide and nutrient mass loads in a flood event with guidance on estimator selection

The aim of this study was to understand the uncertainty of estimating loads for observed herbicides and nutrients during a flood event and provide guidance on estimator selection. A high-resolution grab sampling campaign (258 samples over 100 h) was conducted during a flood event in a tropical waterway in Queensland, Australia. Ten herbicides and three nutrient compounds were detected at elevated concentrations. Each had a unique chemograph with differences in transport processes (e.g. dependence on flow, dilution processes and timing of concentration pulses). Resampling from the data set was used to assess uncertainty. Bias existed at lower sampling efforts but depended on estimator properties as sampling effort increased: the interpolation, ratio and regression estimators became unbiased. Large differences were observed in precision and the importance of sampling effort and estimator selection depended on the relationship between the chemograph and hydrograph. The variety of transport processes observed and the resultant variability in uncertainty suggest that useful load estimates can only be obtained with sufficient samples and appropriate estimator selection. We provide a rationale to show the latter can be guided across sampling periods by selecting an estimator where the sampling regime or the relationship between the chemograph and hydrograph meet its assumptions: interpolation becomes more correct as sampling effort increases and the ratio becomes more correct as the r² correlation between flux and flow increases (e.g. > 0.9); a stratified composite sampling approach, even with random samples, is a promising alternative.

Pharmaceuticals and pesticides archived on polar passive sampling devices can be stable for up to 6 years

In the present study, we report the freezer storage stability of pharmaceuticals and pesticides for the organic-diffusive gradients in thin-films (o-DGT) passive sampler and the polar organic chemical integrative sampler (POCIS). The average change on o-DGT after approximately 18 mo was 9 ± 9% across 30 compounds. For POCIS, the average change after approximately 6 yr was 14 ± 14% for the same compounds. Our data suggest that analytes stored on these samplers are stable and appropriate for archival purposes. Environ Toxicol Chem 2018;37:762-767. © 2017 SETAC.

Comparison of POCIS passive samplers vs. composite water sampling: A case study

The relevance of Polar Organic Chemical Integrative Samplers (POCIS) was evaluated for the assessment of concentrations of 46 pesticides and 19 pharmaceuticals in a small, peri-urban river with multi-origin inputs. Throughout the period of POCIS deployment, 24h-average water samples were collected automatically, and showed the rapid temporal evolution of concentrations of several micropollutants, as well as permitting the calculation of average concentrations in the water phase for comparison with those estimated from POCIS passive samplers. In the daily water samples, cyproconazol, epoxyconazol and imidacloprid showed high temporal variations with concentrations ranging from under the limit of detection up to several hundreds of ngL^-1. Erythromycin, cyprofloxacin and iopromide also increased rapidly up to tens of ngL^-1 within a few days. Conversely, atrazine, caffeine, diclofenac, and to a lesser extent carbamazepine and sucralose, were systematically present in the water samples and showed limited variation in concentrations. For most of the substances studied here, the passive samplers gave reliable average concentrations between the minimal and maximal daily concentrations during the time of deployment. For pesticides, a relatively good correlation was clearly established (R²=0.89) between the concentrations obtained by POCIS and those gained from average water samples. A slight underestimation of the concentration by POCIS can be attributed to inappropriate sampling rates extracted from the literature and for our system, and new values are proposed. Considering the all data set, 75% of the results indicate a relatively good agreement between the POCIS and the average water samples concentration (values of the ratio ranging between 0,33 and 3). Note further that this agreement between these concentrations remains valid considering different sampling rates extracted from the literature.