Alexandra K. Richardson: A community-guided approach to monitoring contaminants of emerging concern in freshwater systems using passive samplers

Monitoring chemical contamination in rivers globally has identified over 630 unique contaminants using conventional analytical techniques, such as liquid chromatography (LC) or gas chromatography (GC) coupled to mass spectrometry (MS) for targeted compound lists2,3,4,5,6. The emergence of high-resolution accurate mass spectrometry (HRMS) in suspect screening and/or non-target modes can aid in the identification of unknowns7. The detection and identification of unknowns in a sample using analytical instruments represent the final step in the analysis pipeline. The initial steps of site selection and sample collection are often viewed as relatively straightforward processes, but can unexpectedly present logistical and practical challenges, especially when required at a large spatio-temporal scale.

To reliably capture the impact and magnitude of chemical pollution in water systems, one of the most important considerations is how, where, and when to take the sample for analysis. Grab sampling is a relatively straightforward sampling technique that is useful for capturing and monitoring short-term elevated contaminant exposures; however, this technique is laborious and logistically intensive when used to monitor chronic exposure at a high spatio-temporal scale. Alternative approaches to monitor chronic exposures include real-time sensing8, automated composite sampling9, and passive sampling. The location of a sample must be considered in the context of other samples collected from the same water system to identify sources of contamination (diffuse and/or point sources). As an example, discharges from wastewater treatment works or combined sewage overflow points (CSOs) are usually characterised by a significant increase in the number, type and concentration of specific contaminants of emerging concern (CECs) compared to other water samples collected from the river catchment during the same campaign10,11. Taking this information further, computational models have recently been used to apportion sources of chemicals using data collected through monitoring campaigns using grab water samples12. To maximise knowledge and identify new pollution sources, high spatio-temporal resolution water data need to be collected, analysed, and key sites identified for continued monitoring. This initial pilot work, which is undoubtedly necessary, can be costly and laborious. Utilising knowledge from local communities to identify the potential occurrence and sources of pollution, and to scale up monitoring capability can be invaluable. Engaging the local communities in scientific research also raises awareness of environmental issues, management challenges, how individuals contribute to the issue, and empowering them to develop strategies to minimise their impact13.

The term ‘citizen science’ is broadly used to define any public participation in scientific research and knowledge generation and has successfully been utilised in various water quality monitoring studies due to the larger spatial and temporal scales at which data can be collected14,15. In addition, citizen science is an important tool for engaging the public in scientific research16. To date, citizen science has predominantly been used to collect data on general water quality parameters such as physical (temperature and conductivity17), chemical (pH and nitrate/phosphate concentrations18), and biological (macroinvertebrate species characterisation19 and Escherichia coli counts20) conditions. These parameters are most frequently tested due to the ease of equipment use, low training requirements and the low cost of testing kits15. By comparison, traditional CEC monitoring using citizen science is generally under-represented in the scientific literature due to challenges with analyte stability and transporting large volumes of water samples (~ 1 L) from the collection site to the analytical laboratory for analysis21,22.

We recently developed a 3D-printed passive sampler device (3D-PSD) for the monitoring of CECs in river water23. Due to its small size, ease of use, and low cost, this device could potentially be utilised by citizen scientists in large numbers for river water monitoring programmes. Passive samplers have previously been used in published citizen science projects, mainly to measure air quality (e.g., nitrogen dioxide (NO2) in urban environments24,25, volatile organic compounds (VOCs) and polycyclic aromatic hydrocarbons (PAHs) in indoor environments25, and the occurrence of air-born Aspergillus fumigatus in the environment26), but have not been used as extensively to measure water quality.

The aim of this work was to collaborate with citizen scientists to monitor English freshwater rivers for CECs using 3D-PSDs. This was achieved through the following objectives: a) to identify and engage local river users in three English cities to take part in the study; b) to deliver training workshops to the citizen scientists to teach where and how to deploy, collect, and return the 3D-PSD; c) to analyse the returned 3D-PSDs for 164 CECs using a rapid targeted LC-MS/MS method; and d) present the findings to the citizen scientists and collect feedback about the project. Therefore, this work represents one of the first studies to trial a miniaturised passive sampler device for use by citizen scientists to measure CECs in freshwater

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