Nitrogen isotopes in herbaria document historical nitrogen sewage pollution in the Mersey Estuary, England

Alldred, Freya C.; Gröcke, Darren R.; Jackson, Samuel E.; Reid, Geraldine

Abstract

A macroalgae (seaweed) herbarium nitrogen isotope (δ15N) record is produced for the River Mersey and Liverpool South Docks (England) between 1821 and 2018. A modern macroalgae δ15N record was also produced from September 2022. The herbaria δ15N record shows a stark difference from 1821 to the present. Lower δ15N in the early 1800s is attributed to agricultural and raw sewage pollution. From 1970 to the present the herbaria samples record very elevated δ15N values – peaking in 1978 at +31‰. The 1989 Water Act and privatisation of water companies in the UK had limited impact on the herbarium δ15N record but indicated a dominance of sewage nitrogen in the River Mersey. Macroalgae δ15N has become even more elevated since the last herbaria sample in 2013. The herbaria and modern data record some of the highest seaweed δ15N values (and therefore, sewage nitrogen pollution) recorded to date. This study highlights a novel use of herbaria macroalgae to document past changes in nitrogen pollution in estuarine environments. More poignantly it highlights that the River Mersey – Mersey Estuary is heavily polluted with sewage nitrogen and requires immediate action to resolve this environmental issue.

Citation

Alldred, F. C., Gröcke, D. R., Jackson, S. E., & Reid, G. (2024). Nitrogen isotopes in herbaria document historical nitrogen sewage pollution in the Mersey Estuary, England. Environmental Science: Advances, 3(5), 676-685. https://doi.org/10.1039/D4VA00015C

• Journal Article Type: Article
• Acceptance Date: Mar 8, 2024
• Online Publication Date: Apr 29, 2024
• Publication Date: May 1, 2024
• Deposit Date: Apr 29, 2024
• Publicly Available Date: Apr 29, 2024
• Journal: Environmental Science: Advances
• Print ISSN: 2754-7000
• Publisher: Royal Society of Chemistry
• Peer Reviewed: Peer Reviewed
• Volume: 3
• Issue: 5
• Pages: 676-685
• DOI: https://doi.org/10.1039/D4VA00015C
• Public URL: https://durham-repository.worktribe.com/output/2408178