How usage of chemicals of emerging concern during the pandemic impacted the River Thames and its tributaries Melanie Egli 1 , Helena Rapp Wright 1 , FrédéricPiel 2 and LeonBarron 1 1 MRC Centre for Environment and Health, Environmental Research Group, United Kingdom 2 Department of Epidemiology and Biostatistics, School of Public Health, United Kingdom With 39 million tonnes of raw sewage entering the Thames every year due to illegal discharges and overflows caused by high rainfall, chemical contamination of this tidal river presents a challenge, not only for river ecology and human exposure, but also analytically [1,2]. Given the scale of the issue, sensitive and high-throughput methods are urgently needed, ideally which do not need time-consuming sample preparation. This high spatial resolution study investigated chemical contamination and environmental risk assessment of the River Thames and five of its tributaries across three years (2019 - 2021), covering pre-, mid-, and post-pandemic conditions. The aim was to more rapidly understand the sources of chemicals of emerging concern (CECs) and any risks they pose on the aquatic environment. Of particular interest were pharmaceuticals including analgesics, antibiotics, and antidepressants, but also other substances such as lifestyle chemicals and pesticides. To achieve this, water samples were collected from >350 locations covering ~60 km of the River Thames, and ~40 km of five tributaries (Rivers Brent, Grand Union Canal, Hogsmill, Lee and Wandle). Using rapid direct-injection liquid chromatography – mass spectrometry (LC-MS/MS), samples could be analysed quantitatively at the ng/L concentration level for 200 CECs in approximately 5.5 min [3,4]. The main River Thames showed a different CEC composition in comparison to the tributaries suggesting they all had unique ‘fingerprints’, and contamination sources despite their geographical proximity. Across the years, distinct differences in CEC occurrence were seen which might reflect a changing public health and consumption status in London following the COVID-19 pandemic. In this poster, a multivariate analysis approach to classify CEC-contaminated rivers based on concentrations and environmental risks from >80 detected compounds is presented. This represents the most comprehensive quantitative study of CECs in the River Thames to date. Our findings and workflow will contribute to potentially classifying changes in city-scale CEC consumption and/or exposure and will help to inform wastewater and environmental monitoring programmes in the future. References 1. Munro, K. et al. Evaluation of combined sewer overflow impacts on short-term pharmaceutical and illicit drug occurrence in a heavily urbanised tidal river catchment (London, UK), Sci. Total Environ. 2019. 657. 1099-1111. 2. Panorama. The River Pollution Scandal. BBC One . United Kingdom. April 12, 2021. 3. Egli, M. et al. Quantitative determination and environmental risk assessment of 102 chemicals of emerging concern in wastewater-impacted rivers using rapid direct-injection liquid chromatography-tandem mass spectrometry, Molecules . 2021. 26. 5431. 4. Ng, K.T. et al. High-throughput multi-residue quantification of contaminants of emerging concern in wastewaters enabled using direct injection liquid chromatography-tandem mass spectrometry, J. Hazard. Mater. 2020. 398. 122933.
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