Quantification and risk assessment of polar organic contaminants in two chalk streams in Hampshire, UK using the Chemcatcher passive sampler.

Freshwater systems are facing a number of pressures due to the inputs of polar organic contaminants from a range of sources including agriculture, domestic and industry. The River Itchen and River Test are two sensitive chalk streams in Southern England that are experiencing a decline in invertebrate communities. We used Chemcatcher passive samplers to measure time-weighted average concentrations (14 days) of polar pollutants at nine sites on the River Itchen and eight sites on the River Test over a 12-month period. Sampler extracts were analysed using a targeted LC/MS method. In total, 121 plant protection products and pharmaceutical and personal care products were quantified (range of log Kow from - 1.5 to 7). Concentrations (sub ng L-1 to >500 ng L-1) in both rivers showed spatial and temporal variations. A greater number of compounds and higher concentrations were found in the River Test. The chemical profile was dominated by inputs from wastewater treatment plants and legacy plant protection products. On the River Itchen, high concentrations (∼100 ng L-1) of caffeine were observed directly downstream of a fish farm. Using the NORMAN database, the predicted no effect concentration (PNEC) freshwater values were exceeded by only five contaminants (2-hydroxy-terbuthylazine, alprazolam, azithromycin, diclofenac and imidacloprid). In addition, venlafaxine was detected above its EU Watch List concentration. These exceedances were mainly downstream of direct inputs from treatment plants. These compounds are known to have ecotoxicological effects on a range of aquatic biota including macroinvertebrates. Of concern is the ubiquitous presence of the ectoparasiticide imidacloprid, highlighting the need to control its use. The impact of the cocktail of pollutants found in this study on the long-term effects on chalk stream ecosystems remains unknown and needs further investigation.

Robotic beyond total mesorectal excision (TME) for locally advanced or recurrent rectal cancer: a systematic review protocol.

INTRODUCTION: The surgical treatment for locally advanced or recurrent rectal cancer requires oncological clearance with a pelvic exenteration or a beyond total mesorectal excision (TME). The aim of this systematic review is to explore the safety and feasibility of robotic surgery in locally advanced and recurrent rectal cancer by evaluating perioperative outcomes, oncological clearance rates, and survival and recurrence rates postrobotic beyond TME surgery. METHODS: The systematic review will include studies published until the end of December 2023. The MEDLINE, EMBASE and Scopus databases will be searched. The screening process, study selection, data extraction, quality assessment and analysis will be performed by two independent reviewers. Discrepancies will be resolved by consensus with a third independent reviewer. The risk of bias will be assessed with validated scores. The primary outcomes will be oncological clearance, overall and disease-free survival, and local and systemic recurrence rates post robotic or robot-assisted beyond TME surgery for locally advanced or recurrent rectal cancer. Secondary outcomes will include perioperative outcomes. ETHICS AND DISSEMINATION: No ethical approval is required for this systematic review as no individual patient cases are studied requiring access to individual medical records. The results of the systematic review will be disseminated with conference presentations and peer-reviewed paper publications. PROSPERO REGISTRATION OF THE STUDY: CRD42023408098.

Monitoring of polar organic compounds in fresh waters using the Chemcatcher passive sampler.

The monitoring of polar organic pollutants in surface water is now undertaken to fulfil a number of legislative requirements. Passive sampling is being frequently used for this purpose and includes the commercially available Chemcatcher device. This protocol is based on knowledge that has been acquired over the past ten years in the use of the Chemcatcher for monitoring a wide range of polar organic compounds in freshwater. It provides detailed procedures and guidelines of how to prepare the sampler in the laboratory, deploy and retrieve the device in the field (including water and sampling site measurements) and subsequent sample processing in the laboratory up to instrumental analysis. By end users adopting this standardized, systematic protocol it will help to ensure the reproducibility of their monitoring data.•Robust and detailed procedure for the sampling of polar pollutants in surface waters using the Chemcatcher passive sampler•A low cost, novel and versatile apparatus for deploying the Chemcatcher at riverine sites•Practical tips based on extensive experience of using the Chemcatcher are provided for end-users.

Occurrence of organic pollutants in the River Itchen and River Test-two chalk streams in Southern England, UK.

The River Itchen and River Test, two chalk streams in Southern England, are sites of special scientific interest. These ecosystems face a number of environmental pressures from anthropogenic inputs of organic pollutants. Hence, we investigated the occurrence of these chemicals within the two catchments. Spot water samples (1 L) were collected at nineteen sites along the catchment on two occasions (March and June 2019). Samples were extracted (HLB-L sorbent disks) and analysed using high-resolution liquid chromatography-quadrupole-time-of-flight mass spectrometry and gas chromatography-mass spectrometry. Compounds were identified against commercially available databases. Using this approach, we found 115 pharmaceutical and personal care products, 81 plant protection products and 35 industrial chemicals. This complex mixture of pollutants covered a range of physico-chemical properties and included priority substances in the EU Water Framework Directive or currently on the third Watch List. Both rivers had similar chemical profiles for both months. Herbicides and fungicides were dominant in the spring, whereas insecticides occurred more frequently in the summer. Point discharges from wastewater treatment plants were the main source of pharmaceutical and personal care products. Agricultural activities were the main contributor to the presence of plant protection products. The impact of these organic chemicals on the ecology, particularly on macroinvertebrate biodiversity, is unknown and warrants further investigation. Our suspect screening approach could guide future toxicological investigations to assess the environmental impacts of these diverse chemicals.

Pesticide fate during drinking water treatment determined through passive sampling combined with suspect screening and multivariate statistical analysis.

Emerging contaminants such as polar pesticides pose a potential risk to human health due to their presence in drinking water. However, their occurrence and fate in drinking water treatment plants is poorly understood. In this study we use passive sampling coupled to suspect screening and multivariate analysis to describe pesticide fate throughout the treatment stream of an operational drinking water treatment plant. ChemcatcherÒ passive sampling devices were deployed at sites (n = 6) positioned at all stages of the treatment stream during consecutive deployments (n = 20) over a twelve-month period. Sample extracts (n = 120) were analysed using high-resolution liquid chromatography-quadrupole-time-of-flight mass spectrometry and compounds identified against a commercially available database. A total of 58 pesticides and transformation products from different classes were detected. Statistical analysis of the qualitative screening data was performed to identify clusters of pesticides with similar fate during ozonation, granular activated carbon (GAC) filtration, and chlorination. The performance of each treatment process was investigated. Adsorption to GAC media was found to account for the greatest proportion of pesticide attenuation (average removal of 70% based on detection frequency), however, operational performance varied for certain pesticides during periods of episodic and sustained pollution. GAC breakthrough occurred for 21 compounds detected in the GAC filtrate. Eleven pesticides were found to occur in potable water following treatment. We developed a management plan containing controls, triggers, and responses, for five pesticides and a metabolite (atrazine, atrazine desethyl, DEET, dichlorobenzamide, metazachlor, and propyzamide) prioritised based on their current and future risk to treated water quality.

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 (Rs) 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.

Passive sampling with suspect screening of polar pesticides and multivariate analysis in river catchments: Informing environmental risk assessments and designing future monitoring programmes.

Pollution of surface water by polar pesticides is a major environmental risk, particularly in river catchments where potable water supplies are abstracted. In these cases, there is a need to understand pesticide sources, occurrence and fate. Hence, we developed a novel strategy to improve water quality management at the catchment scale using passive sampling coupled to suspect screening and multivariate analysis. Chemcatcher® passive sampling devices were deployed (14 days) over a 12 month period at eight sites (including a water supply works abstraction site) in the Western Rother, a river catchment in South East England. Sample extracts (n = 197) were analysed using high-resolution liquid chromatography-quadrupole-time-of-flight mass spectrometry and compounds identified against a commercially available database. A total of 128 pesticides from different classes were found. Statistical analysis of the qualitative screening data was used to identify clusters of pesticides with similar spatiotemporal pollution patterns. This enabled pesticide sources and fate to be identified. At the water supply works abstraction site, spot sampling and passive sampling were found to be complementary, however, the passive sampling method in conjunction with suspect screening detected 50 pesticides missed by spot sampling combined with targeted analysis. Geospatial data describing pesticide application rates was found to be poorly correlated to their detection frequency using the Chemcatcher®. Our analysis prioritised 61 pesticides for inclusion in a future water quality risk assessment at the abstraction site. It was also possible to design a seasonal monitoring programme to effectively characterise the spatiotemporal pesticide profiles within the catchment. A work flow of how to incorporate passive sampling coupled to suspect screening into existing regulatory monitoring is proposed. Our novel approach will enable water quality managers to target the mitigation (non-engineered actions) of pesticide pollution within the catchment and hence, to better inform drinking water treatment processes and save on operational costs.

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

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

Applications for Passive Sampling of Hydrophobic Organic Contaminants in Water-A Review.

We comprehensively review the current state-of-the-art of environmental monitoring for hydrophobic organic contaminants in aqueous matrices using passive sampling devices. Principles of the theory of passive sampling are presented. Strategies for passive sampler design and operation, limitations in performance and data quality-assurance and quality-control are reviewed. Advances in applications of available passive sampling devices are extensively critiqued. Future trends and current challenges facing practitioners and barriers to further adoption of the devices are discussed.

Use of Chemcatcher® passive sampler with high-resolution mass spectrometry and multi-variate analysis for targeted screening of emerging pesticides in water.

Pesticides present at trace concentrations are a common cause of poor water quality. Their concentrations can change dynamically, due to the stochastic nature of pesticide pollution. Consequently, characterisation of pesticide residues that are intermittently present, poses significant monitoring and analytical challenges. Traditional approaches rely on quantitation of a limited number of pesticides present in a discrete water sample. Expanding the analytical suite and/or the frequency of sampling to meet these challenges is often impractical. Comprehensive methods are needed, with selectivity and sensitivity for the hundreds of pesticides potentially present, and temporal representativeness to ensure changing conditions are understood, in order to identify and prioritise risk. Recent analytical advances have enabled the targeted screening of hundreds of compounds in the same run, and automated work-flows can now reliably identify compounds through the comparison of retention time and accurate mass with spectral libraries. Screening generates large qualitative data sets, therefore, there is a need for improved monitoring methods and data interpretation strategies to reduce the need for repetition, and increase the quality of information for end-users. Passive sampling is an in situ time integrative technique, increasingly used for monitoring pesticides in water. Here, we describe a method using the Chemcatcher® passive sampler, coupled to targeted screening using liquid chromatography-quadrupole-time-of-flight mass spectrometry, and a commercially available library. Statistical analysis was performed using Agilent Mass Profiler Professional software. Water sampling took place over one year, at three riverine sites in the south of England, UK. Statistical interpretation of time integrative data from passive sampling could distinguish regular and episodic pesticide inputs, and detected compounds neglected by routine monitoring methods. One hundred and eleven pesticides were identified including legacy and current use compounds with diverse origins and uses. Spatial and temporal trends were identified enabling prioritisation of seasonal monitoring at each site. This approach maximises the utility of qualitative assessment and may help water quality managers to rationalise pesticide fate in future, providing significant additional insight without the need to increase the scope and cost of monitoring.

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.

Using high-frequency phosphorus monitoring for water quality management: a case study of the upper River Itchen, UK.

Increased concentrations of phosphorus (P) in riverine systems lead to eutrophication and can contribute to other environmental effects. Chalk rivers are known to be particularly sensitive to elevated P levels. We used high-frequency (daily) automatic water sampling at five distinct locations in the upper River Itchen (Hampshire, UK) between May 2016 and June 2017 to identify the main P species (including filterable reactive phosphorus, total filterable phosphorus, total phosphorus and total particulate phosphorus) present and how these varied temporally. Our filterable reactive phosphorus (considered the biologically available fraction) data were compared with the available Environment Agency total reactive phosphorus (TRP) values over the same sampling period. Over the trial, the profiles of the P fractions were complex; the major fraction was total particulate phosphorus with the mean percentage value ranging between 69 and 82% of the total P present. Sources were likely to be attributable to wash off from agricultural activities. At all sites, the FRP and Environment Agency TRP mean concentrations over the study were comparable. However, there were a number of extended time periods (1 to 2 weeks) where the mean FRP concentration (e.g. 0.62 mg L-1) exceeded the existing regulatory values (giving a poor ecological status) for this type of river. Often, these exceedances were missed by the limited regulatory monitoring procedures undertaken by the Environment Agency. There is evidence that these spikes of elevated concentrations of P may have a biological impact on benthic invertebrate (e.g. blue-winged olive mayfly) communities that exist in these ecologically sensitive chalk streams. Further research is required to assess the ecological impact of P and how this might have implications for the development of future environmental regulations.

Calibration and field application of an innovative passive sampler for monitoring groundwater quality.

This study describes the development of a novel Empore™ disk-based passive sampler specially adapted to groundwater monitoring. The sampler was calibrated in the laboratory using conditions that corresponded to groundwater (i.e. matrix medium, water temperature, flow rate and water flow across the disks). The retention and elution performance for sixteen semi-polar and polar pollutants on the Empore™ disk (47 mm diameter, SDB-XC) was evaluated. Recoveries were ~80% for the majority of compounds. Sampler uptake kinetics were measured over fourteen days at three concentrations (10, 100 and 500 ng L-1) and the sampling rate (RS) calculated for four compounds. There was no influence of concentration of the test analyte on the uptake profile; with mean RS varying between 0.018 ±â€¯0.007 L day-1 and 0.047 ±â€¯0.001 L day-1. Passive samplers were deployed in twelve characterized groundwater wells near Lyon (France). Atrazine, atrazine-desethyl and diuron were the main pollutants found with a maximum time-weighted concentration of 61 ±â€¯3, 62 ±â€¯24 and 127 ±â€¯49 ng L-1 respectively.

Use of the Chemcatcher® passive sampler and time-of-flight mass spectrometry to screen for emerging pollutants in rivers in Gauteng Province of South Africa.

Many rivers in urbanised catchments in South Africa are polluted by raw sewage and effluent to an extent that their ecological function has been severely impaired. The Hennops and Jukskei Rivers lying in the Hartbeespoort Dam catchment are two of the worst impacted rivers in South Africa and are in need of rehabilitation. Passive sampling (Chemcatcher® with a HLB receiving phase) together with high-resolution tandem mass spectrometry-targeted screening was used to provide high sensitivity and selectivity for the identification of a wide range of emerging pollutants in these urban waters. Over 200 compounds, including pesticides, pharmaceuticals and personal care products, drugs of abuse and their metabolites were identified. Many substances (~ 180) being detected for the first time in surface water in South Africa. General medicines and psychotropic drugs were the two most frequently detected groups in the catchment. These accounted for 49% of the emerging pollutants found. Of the general medicines, antihypertensive agents, beta-blocking and cardiac drugs were the most abundant (28%) classes detected. The Hennops site, downstream of a dysfunctional wastewater treatment plant, was the most polluted with 123 substances detected. From the compounds detected, peak intensity-based prioritisation was used to identify the five most abundant pollutants, being in the order caffeine > lopinavir > sulfamethoxazole > cotinine > trimethoprim. This work provides the largest available high-quality dataset of emerging pollutants detected in South African urban waters. The data generated in this study provides a solid foundation for subsequent work to further characterise (suspect screening) and quantify (target analysis) these substances.

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.

Comparison of different monitoring methods for the measurement of metaldehyde in surface waters.

Metaldehyde is recognised as an emerging contaminant. It is a powerful molluscicide and is the active compound in many types of slug pellets used for the protection of crops. The application of pellets to land generally takes place between August and December when slugs thrive. Due to its high use and physico-chemical properties, metaldehyde can be present in the aquatic environment at concentrations above the EU Drinking Water Directive limit of 100 ng L-1 for a single pesticide. Such high concentrations are problematic when these waters are used in the production of drinking water. Being able to effectively monitor this pollutant of concern is important. We compared four different monitoring techniques (spot and automated bottle sampling, on-line gas chromatography/mass spectrometry (GC/MS) and passive sampling) to estimate the concentration of metaldehyde. Trials were undertaken in the Mimmshall Brook catchment (Hertfordshire, UK) and in a feed in a drinking water treatment plant for differing periods between 17th October and 31st December 2017. This period coincided with the agricultural application of metaldehyde. Overall, there was a good agreement between the concentrations measured by the four techniques, each providing complementary information. The highest resolution data was obtained using the on-line GC/MS. During the study, there was a large exceedance (500 ng L-1) of metaldehyde that entered the treatment plant; but this was not related to rainfall in the area. Each monitoring method had its own advantages and disadvantages for monitoring investigations, particularly in terms of cost and turn-a-round time of data.

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.

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 (Rs = 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.

Calibration and field evaluation of the Chemcatcher® passive sampler for monitoring metaldehyde in surface water.

Metaldehyde is a potent molluscicide. It is the active ingredient in most slug pellets used for crop protection. This polar compound is considered an emerging pollutant. Due to its environmental mobility, metaldehyde is frequently detected at impacted riverine sites, often at concentrations above the EU Drinking Water Directive limit of 0.1µgL-1 for an individual pesticide. This presents a problem when such waters are abstracted for use in the production of potable water supplies, as this chemical is difficult to remove using conventional treatment processes. Understanding the sources, transport and fate of this pollutant in river catchments is therefore important. We developed a new variant of the Chemcatcher® passive sampler for monitoring metaldehyde comprising a Horizon Atlantic™ HLB-L disk as the receiving phase overlaid with a polyethersulphone membrane. The sampler uptake rate (Rs) was measured in semi-static laboratory (Rs = 15.7mLday-1) and in-field (Rs = 17.8mLday-1) calibration experiments. Uptake of metaldehyde was linear over a two-week period, with no measurable lag phase. Field trials (five consecutive 14day periods) using the Chemcatcher® were undertaken in eastern England at three riverine sites (4th September-12th November 2015) known to be impacted by the seasonal agricultural use of metaldehyde. Spot samples of water were collected regularly during the deployments, with concentrations of metaldehyde varying widely (~ 0.03-2.90µgL-1) and often exceeding the regulatory limit. Time weighted average concentrations obtained using the Chemcatcher® increased over the duration of the trial corresponding to increasing stochastic inputs of metaldehyde into the catchment. Monitoring data obtained from these devices gives complementary information to that obtained by the use of infrequent spot sampling procedures. This information can be used to develop risk assessments and catchment management plans and to assess the effectiveness of any mitigation and remediation strategies.

Development and evaluation of a new diffusive gradients in thin-films technique for measuring organotin compounds in coastal sediment pore water.

Organotins present a toxicological risk to biota in the aquatic environment. Understanding the behaviour of these compounds in sediment is challenging, with sophisticated analytical techniques required for their measurement. We investigated the use of silica-bound sorbents for diffusive gradients in thin-films (DGT) adsorption gels to pre-concentrate five organotins (monobutlytin (MBT), dibutyltin (DBT), tributyltin (TBT), diphenyltin (DPhT), triphenyltin (TPhT)) found frequently in coastal sediment. C8 sorbent showed optimum performance in uptake and recovery of organotins for pH and ionic strength ranges typical of coastal waters. Recoveries from adsorption gels deployed in filtered sea water were MBT = 123 ± 20%, DBT = 75 ± 12%, TBT = 81 ± 16%, DPhT = 72 ± 30%, TPhT = 58 ± 10% respectively. Devices were used to investigate DGT fluxes and pore water concentrations of organotins in coastal sediment collected from a contaminated site. DGT fluxes measured in sediment cores for the five organotins ranged between 4.3 × 10-8 and 1.6 ×10-5ngcm2s-1. The depletion of organotin species within pore waters at the interface with DGT devices was measured over a series of deployment times (2, 7, 14, 21 and 28 days) and provided estimates of the concentration of organotins in pore waters at Langstone Harbour, UK, prior to depletion by the DGT device and information on their spatial heterogeneity. The novel in situ DGT device developed can pre-concentrate organotins from pore waters in coastal sediment core samples and allows their detection at low environmental concentrations using conventional gas chromatographic/mass spectrometric instrumentation. Use of the DGT device overcomes many problems associated with the conventional pore water sampling of organotins. Our preliminary data suggests it has potential in the future to be a useful tool in investigating the environmental fate of these pollutants. The use of the C8 gel will also allow for the simultaneous sequestration of other semi- and non-polar analytes present in the pore water.