For the first time, a science team has directly documented and extensively sampled a freshened water system beneath the ocean floor off the coast of New England in the USA. This major discovery comes from the initial analyses of sediment cores recovered during the , led by Co-Chief Scientists Professor Brandon Dugan (Colorado School of Mines, Golden, USA) and Professor Rebecca Robinson (Graduate School of Oceanography, University of Rhode Island, USA.

The 872 m of core, retrieved from deep below the sea floor, is now being opened, analysed and sampled by the science team, during almost a month of intensive, collaborative work. The expedition scientists are working side by side during January and February 2026 to uncover new insights into the formation, evolution and significance of this newly documented, sub-seabed, freshwater system.

Five BGS staff members are part of the operational team: Jeremy Everest, Margaret Stewart, Raushan Arnhardt (expedition project managers), Mary Mowat (database manager) and Bentje Brauns (hydrogeology). Their role is to coordinate and support the science team to process the core according to IODP³ standards and protocols.

The goal of this expedition went far beyond collecting sediment cores. Scientists also set out to sample the water stored within the sediments, including from sandy layers that act as aquifers and from clay layers known as aquitards that usually keep the water in place beneath the sea floor.

Although roughly 70 per cent of Earth surface is covered by water, significant volumes of water also move and are stored below ground. Many coastal communities depend on land-based aquifers for their freshwater supply. What fewer people realise is that, in many parts of the world, the aquifers continue offshore and contain zones of β€˜freshened’ water beneath the ocean floor. Scientists have known these offshore systems existed since 1976, but they have remained virtually unexplored until now. During the expedition, the science team successfully documented and sampled freshened water within a zone nearly 200 m thick below the sea floor.

We were excited to see that freshened water exists in multiple kinds of sediments – both marine and terrestrial. Freshened water in such different materials will help us understand the conditions that emplaced the water.

Prof Brandon Dugan, Colorado School of Mines, Golden, USA.

Further analyses, such as age models, conducted by the science team will help to find out where and especially when the water was placed here.

The cores contain sediment with a wide range of composition and ages. It was surprising to see sediment, not rocks, throughout the section. The sediment has not yet transformed into rock – I did not expect to see that and it will be an interesting component of our future work.

Prof Rebecca Robinson, Graduate School of Oceanography, University of Rhode Island, USA.

After a successful coring, sampling and downhole logging campaign last summer, the BGS team is incredibly excited to be supporting the science team to begin the scientific analysis the material collected. The cores have been safely held in their plastic liners since they were drilled out of the seabed and, at the Onshore Operation in Bremen, they are being opened and split, revealing the fresh split-core surfaces for the first time.

The BGS team are contributing to the detailed sampling and analysis of the cores that, when combined with the groundwater samples taken from the borehole, will improve our understanding of the development of the New England shelf and the freshened water reservoirs underlying it. It is such a satisfying moment, after years of effort to acquire the cores, to be rewarded with new data and insights in such an important and societally relevant subject.

David McInroy, marine geoscientist, BGS.

Shedding light on similar water aquifers around the world

The approach used during IODPΒ³-NSF Expedition 501 will not only deepen understanding of offshore freshened groundwater systems off the coast of New England, but will also shed light on similar hidden water aquifers around the world. Because many coastal regions rely on groundwater for their freshwater supply, the expedition initial findings are highly relevant to society. The research will also reveal how nutrients such as nitrogen cycle through continental shelf sediments and how these processes influence the abundance and diversity of microbes living in these environments.

These goals align closely with the 2050 Science Framework for Ocean Research Drilling – one of the foundations of the IODPΒ³ scientific programme. Ultimately, the expedition research will help to decipher how sediments and fluids cycle through the Earth system and improve our knowledge about sea level changes and freshwater flow beneath the seabed along our coastal shelves. β€œThe researchers will continue to work on and with the samples to decipher more – for example, to date the groundwater more accurately which is critical to advancing our knowledge,” adds Rebecca Robinson.

Background

The expedition is a joint collaboration between the International Ocean Drilling Programme (IODPΒ³) and the US National Science Foundation (NSF). The cores were retrieved during offshore operations between May and August 2025. For onshore operations the science team have met at the Bremen Core Repository, at MARUM – Center for Marine Environmental Sciences of the University of Bremen (Germany). β€œWe greatly appreciate being able to conduct this advanced research at MARUM, supported by its world-class laboratories, exceptional facilities, and dedicated staff,” adds Brandon Dugan

The cores will be archived and made accessible for further scientific research for the scientific community after a one year-moratorium period. All expedition data will be open access in the IODPΒ³ Mission Specific Platform (MSP) data portal in PANGAEA, and resulting outcomes will be published.

International approach

Forty science team members from 13 nations (Australia; China; France; Germany; India; Italy; Japan; the Netherlands; Portugal; Sweden; Switzerland; UK; USA) are taking part in this MSP expedition that consists of two phases: offshore and onshore operations. Offshore operations took place between May and early August 2025.

The expedition is conducted by the European Consortium for Ocean Research Drilling (ECORD) as part of IODPΒ³, funded by IODPΒ³ and the US National Science Foundation (NSF).

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Seventy-four days offshore, 718 cores and 871.83 m of total core from three locations: this is the successful outcome after the end of offshore operations of IODPΒ³-NSF Expedition 501: New England Shelf hydrogeology. The goal of the expedition was to take samples not only of sediment cores, but also of the water stored in both sandy aquifers and clayey aquitards beneath the ocean floor. Their existence has been known for decades but they remained virtually unexplored β€” until now.

The expedition is a joint collaboration between the International Ocean Drilling Programme (IODPΒ³) and the US National Science Foundation (NSF), with the expedition being managed and technically supported by the team at BGS.

We set out with lofty goals of understanding the origin and age of this offshore freshened groundwater system through sampling of sediment and water in a difficult drilling environment consisting of sand and mud. With great teamwork between the science team, the technical staff and the drilling crew, we managed to get great samples, including via multiple groundwater pumping tests.

Those tests were a critical to the expedition and a first for scientific ocean drilling. And we did it! Now we have the samples for the science team to really dive into the data and understand the system, which will be helpful for understanding other offshore freshened groundwater systems around the world.

Prof Brandon Dugan, expedition co-chief scientist.

The pump tests were challenging and required us to adapt our processes to get the best possible samples of the groundwater. In the end we pumped nearly 50 000 litres of water from nine distinct places, in terms of location and depth below the sea floor.

This is a huge success story for something so novel. For me in particular, as a geochemist and not a hydrogeologist, I am so appreciative to everyone that leant their expertise. The team of hydrogeologists from the 51ΑΤΖζ especially was outstanding.

Rebecca Robinson, expedition co-chief scientist.

During the expedition, the science team rotated on and off the Liftboat Robert, transported by helicopter or supply vessel. The entire science team will meet for the onshore operations at the Bremen Core Repository, at the Center for Marine Environmental Sciences at the University of Bremen (MARUM), in January and February 2026 to split, sample and analyse the sediment cores and water collected. The cores will be archived and made accessible for further scientific research for the scientific community after a one-year moratorium period. All the expedition data will eventually be open access in the IODPΒ³ MSP data portal in PANGAEA and resulting outcomes will be published.

I’m absolutely delighted for our BGS colleagues and the whole expedition team, who have delivered this outstanding and unique project for IODP³. The sediment cores, water samples and logging data they helped collect will now be analysed by the international science team to better understand the New England continental shelf and its freshened groundwater system, and I expect some groundbreaking results will emerge in the months and years ahead.

David McInroy, BGS project lead.

International approach

51ΑΤΖζ scientists are part of a science team with over 40 members from 13 nations (Australia, China, France, Germany, India, Italy, Japan, the Netherlands, Portugal, Sweden, Switzerland, the UK and the USA) that takes part in the expedition. The expedition itself consists of two phases: offshore and onshore operations. Offshore operations took place between May and early August 2025.

The expedition is conducted by the European Consortium for Ocean Research Drilling (ECORD) as part of the International Ocean Drilling Programme (IODPΒ³), funded by IODPΒ³ and the US National Science Foundation (NSF).

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Critical minerals are an increasingly essential part of modern society and a fundamental requirement of many technologies, including electronics, renewables and defence systems. As a result, global demand for technology-critical mineral resources is expected to quadruple by 2040.

In 2023, the UK and Canada unveiled a landmark agreement to cooperate on critical minerals. As part of this collaboration, UK Research and Innovation (51ΑΤΖζ) recently announced that five research partnerships will receive a share of the Β£1 million International Science Partnerships Fund. Collectively, these partnerships aim to reduce mining environmental footprint and enhance efficiency across critical mineral value chains.

51ΑΤΖζ scientists are actively involved in three of these partnerships:

• Exploration and Geomodels for Rare Earth Element Pegmatite Targets (EGRET)
• Metal Fertility and Transport in Volcanic-hosted Hydrothermal Systems
• Critical Minerals for Resilience and Sustainability (MINERS)

Exploration and Geomodels for Rare Earth Element Pegmatite Targets

EGRET is led by BGS economic geologist, Eimear Deady. Joining up with Canadian partners, the project is developing new geological models and exploration tools for rare earth element (REE) deposits in Saskatchewan, Canada. REEs are a crucial component for the magnets used in wind turbines and electric vehicles. The research will help diversify the REE supply chain and ensure high environmental standards.

We are delighted to have been awarded this grant, which allows us to work closely with our Canadian partners to improve our understanding of Saskatchewan REE-rich pegmatites. Our aim is to support the development of more diverse and resilient supply chains that can meet the rising demand for magnets, driven by green technologies.

Eimear Deady, EGRET project lead at BGS

Metal Fertility and Transport in Volcanic-hosted Hydrothermal Systems

This partnership is focused on the UK, Ireland, and Newfoundland and Labrador in Canada. Some regions are rich in volcanogenic massive sulfide deposits, which are sources of important metals such as copper, zinc and gold. The research aims to improve exploration and mining efficiency, furthering our understanding of the processes that create these deposits.

Critical Minerals for Resilience and Sustainability

Located in British Columbia, the MINERS project investigates how critical metals like tellurium, bismuth and the platinum group metals can be efficiently extracted as by-products from copper and gold deposits.

The MINERS project will explore the resilience and responsibility of UK/Canada critical minerals supply chains for lithium, nickel, cobalt and germanium, looking to develop the ways that stakeholders can improve environmental, social and governance performance and regulatory efficiency, and move towards a more circular economy.

Gavin Mudd, director of the BGS-led UK Critical Minerals Intelligence Centre

These research partnerships will protect national security interests by strengthening supply chains for critical minerals and reduce the environmental impact of mining.

β€˜UK/Canada sustainable critical minerals research partnerships’ is a .

In the 1960s, scientists were quite surprised when they looked at their data: it clearly showed that there was fresh or freshened water under the ocean floor. How did it get there? How long has it been there? Scientists have been trying to find answers to these questions since their intriguing discovery.

Starting in May 2025, an international team of scientists will embark on an expedition to take a closer look at and take samples from this freshened water stored beneath the ocean floor. Prof Karen Johannesson of University of Massachusetts Boston and Prof Brandon Dugan of Colorado School of Mines are the co-chief scientists of this international expedition. Samples will be collected using the lift boat L/B Robert, which departed from the port of Bridgeport, Connecticut, USA, on May 19.

Seventy per cent of the Earth’s surface is covered with water, but water also flows beneath its surface. Most coastal communities rely on traditional onshore aquifers for fresh water; however, in many locations worldwide, onshore aquifers may have an offshore component where freshened water exists under the ocean floor. Even though the existence of these waters has been known for decades, they remain virtually unexplored. This will change through the groundbreaking research to be completed during this expedition, which is a collaboration between the International Ocean Drilling Programme (IODPΒ³) and the US National Science Foundation (NSF). For the first time, scientists on IODPΒ³-NSF Expedition 501 ‘New England Shelf hydrogeology’ will take water and sediment samples from beneath the ocean on the New England Shelf with the intention of understanding this offshore aquifer system.

Aim: validate hypotheses about water origin

The key priority for researchers is to gain more knowledge about the origin of freshened groundwater in offshore aquifers so that they can confirm or dismiss existing hypotheses. For example, current hypotheses are that the water could have charged the aquifers at a time when sea level was 100 m lower than it is today, or perhaps it was generated under an ice sheet or pro-glacial lake during a glacial period such as existed approximately 450 000 and approximately 20 000 years ago.

We have anecdotal evidence of offshore freshened groundwater from samples and marine geophysical surveys. We have used this evidence to develop hypotheses on timing and mechanism of emplacement. It is exciting to use established scientific ocean drilling approaches with modern data analyses to provide direct tests of our hypotheses. Overall, this work offshore New England will help us better understand offshore freshened groundwater around the world.

Prof Brandon Dugan, hydrogeologist, Colorado School of Mines.

To date, we know very little about the dynamics of these shoreline-crossing groundwater systems and the age of the water in these systems, and even less about their influence on cycling of nutrients and trace elements and their isotopes.

Prof Karen Johannesson, environmental geochemist, University of Massachusetts Boston.

The expedition is managed and technically supported by the team at BGS. A special platform, the L/B Robert, equipped with a small drilling rig, will be used to access the sediments below the ocean floor at up to three locations on the New England Shelf offshore from the coast of Massachusetts, USA. The locations are in relatively shallow water and were identified through numerous preliminary geoscientific investigations. Sediment cores and water samples will be taken down to a maximum depth of 550 m below the ocean floor and will be examined by researchers from various disciplines drawn from across the international scientific community.

High societal relevance: to better understand aquifers around the world

The team believes that the data acquired will help to better understand the processes that lead to the emplacement of freshwater lenses in offshore coastal plain sediments and why this freshened water is present. The findings will be relevant for the hydrogeology of the New England Shelf and for multiple similar settings elsewhere around the world.

The research is essential for a better understanding of the biogeochemical and elemental cycles in the continental shelf environment and will support a focus on the protection and sustainable management of offshore freshwater systems.

Staff from BGS have critical roles in the expedition, including offshore operations management (Leonardo Barbosa; Graham Tulloch), offshore project management (Jeremy Everest; Margaret Stewart; Raushan Arnhardt), IT and data management (Mary Mowat; Alan Douglas; Julian Gray), and onshore project management and leadership (David McInroy). With the expedition extra focus on groundwater fieldwork, BGS is providing extra hydrogeology and geochemistry technical support (Chelsea Bambrick, Rachel Bell, Bentje Brauns, Jack Brickell, Rebecca N Chonchubhair, Antonio Ferreira, Alex Mulcahy, Kyle Walker-Verkuil).

The team is incredibly excited to be finally heading out to sea to begin field operations, after many years of planning with project partners. We hope to recover invaluable core material and groundwater samples to improve our understanding of the development of the New England Shelf and the freshened water reservoirs underlying it. Scientific ocean drilling is technically challenging, expensive and therefore infrequent, which makes it a privilege to be part of such a project. We have a reasonable idea of what to expect in our boreholes, but there always the chance of discovering something unexpected scientifically, and that what makes offshore fieldwork so exciting.

David McInroy, BGS project lead.

The expedition aims to find answers to the following questions:

• how old is the freshened groundwater and when was it emplaced?
• how much fresh water is there?
• how does the fresh water interact with sea water?
• what microbial communities are involved?
• what sources of carbon do microbes use?
• what is the general cycling of nutrients and energy in the shelf sediments?
• how might these fresh waters influence nutrient, carbon and metal concentrations in sea water?

International approach

Forty-one science team members from 13 nations (Australia, China, France, Germany, India, Italy, Japan, Netherlands, Portugal, Sweden, Switzerland, United Kingdom, USA) will take part in the expedition, which consists of two phases: offshore and onshore operations. Offshore operations will take place between May and early August 2025. The entire science team will meet for the onshore work at the Bremen Core Repository, at MARUM Center for Marine Environmental Sciences at the University of Bremen (Germany) in January 2026 to split, sample and analyse the sediment cores and interpret the data collected. The cores will be archived and made accessible for further scientific research for the scientific community after a one-year moratorium period following an onshore operations phase of the expedition. All expedition data will be open access and resulting outcomes published.

The expedition is conducted by the European Consortium for Ocean Research Drilling (ECORD) as part of the International Ocean Drilling Programme (IODPΒ³), funded by IODPΒ³ and NSF. IODPΒ³ is a publicly funded international marine research program supported by 16 countries, which explores Earth’s history and dynamics recorded in sea-floor sediments and rocks and monitors subsea-floor environments. Through multiple platforms β€” a feature unique to IODPΒ³ β€” scientists sample the deep biosphere and subsea-floor ocean, environmental change, processes and effects, and solid-Earth cycles and dynamics.

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The two-month long International Ocean Discovery Programme (IODP) Expedition 389: Hawai’ian drowned reefs, managed by a team from BGS, aimed to get a better understanding of sea-level changes by recovering samples of fossilised coral reefs. A total of 29 scientists from across the world participated in the expedition, with 10 scientists on board the MMA Valour, which set sail from Honolulu, Hawai’i, on 31 August 2023.

A total of 426m of core was recovered from below the seabed at water depths from 130 to 1240m. The core has now been opened, analysed and sampled by the scientific team, following almost a month of intensive work at the University of Bremen during February 2024.

The next phase of the research will involve scientists using cutting-edge methods in their laboratories to extract information about sea level and climate change from these tremendously important, high-resolution archives. The ability to look back at Earth history will provide valuable insights into the mechanisms that cause climate change, including abrupt events, and the impact of these changes on reef growth and health.

We are extremely proud to have coordinated this expedition with our UK and international partners, and to have successfully recovered high-resolution records of sea level and environmental changes over the last few hundred thousand years. Our team is now supporting the international science party to initially analyse the cores and create foundational datasets to support research on this important topic for many years to come.

David McInroy, BGS Marine Geoscientist.

About the expedition

The expedition is conducted by the (ECORD) as part of the (IODP). IODP is a publicly funded, international marine research programme, supported by 21 countries, which explores Earth’s history and dynamics recorded in seabed sediments and rocks, and monitors sub-seabed environments. Through multiple platforms β€” a feature unique to IODP β€” scientists sample the deep biosphere and sub-seabed ocean to study environmental change, processes and effects, and solid-Earth cycles and dynamics.

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A two-month expedition, running from 31 August 2023 to 31 October 2023 and managed by a team from BGS, has set sail from Hawai’i. The aim of the expedition is to better understand sea level and climate sea change by recovering and researching ancient fossilised coral reefs.

There is a series of twelve fossil coral reefs off the coast of Hawai’i that may reveal the history of sea level change in the region and beyond. The International Ocean Discovery Program (IODP) will sample these fossil coral reefs, giving scientists the first opportunity to investigate such high-resolution sea level, climate and reef response records from the past half a million years.

The international team will sample the ancient reefs at water depths up to 1155 m to study how sea level and climate have changed, how coral reefs respond to these changes, and the links between global sea-level changes and global climate change. The high-resolution records will also provide a framework for evaluating the effects of climate change originating from human activity.

A total of 29 scientists from across the world will participate in the expedition, with 10 scientists onboard the MMA Valour, which set sail from Honolulu on 31 August 2023.

Previous mission-specific platform expeditions around Tahiti () and the Great Barrier Reef () currently provide us with a record of past conditions over the past 30000 years, but the Hawai’i expedition will greatly extend this over the past 500000 years.

Due to the rapid subsidence of the island, Hawai’i is a perfect location for us to conduct this research, becausechanges in sea level and global climate are preserved in a greatly expanded and near-continuous fossil coral record covering the last half a million years.

It should also help us to reconstruct sea-level change at a much higher resolution than previously possible, as well as investigating the volcanic evolution of Hawai’i itself.

Dr Hannah Grant, BGS Marine Geoscientist and expedition project manager

Hannah is joined on board by two other BGS staff members, Graham Tulloch (operations manager) and Mary Mowat (data manager). Initial analysis of the recovered coral cores will begin on the ship and continue at the onshore science party, which will take place in February 2024 in Bremen, Germany.

Expedition organisation

The expedition is organised by the ECORD Science Operator (ESO) under instruction from the European Consortium for Ocean Research Drilling (ECORD) as part of IODP. IODP is an international marine research collaboration that explores Earth history and dynamics using oceangoing research platforms to recover data recorded in sea-floor sediments and rocks, and to monitor subsea-floor environments.

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Human activity has led to excess phosphorus concentrations and the continued over-enrichment of coastal and fresh waters across the United States. Alongside colleagues from Union College in New York and Lancaster University, BGS scientists are researching the biogeochemical cycling (how specific chemicals cycle through the biological and geological components of the Earth) of .

What is eutrophication?

Eutrophication is the process by which water becomes progressively enriched with minerals and nutrients, for example phosphorus and nitrogen. It can affect both coastal and fresh waters and can be caused by excess phosphorus entering the water system. Natural eutrophication is a very slow process, but it can occur much more rapidly when pollution accumulates from human sources such as sewage and fertilisers. Eutrophication can cause harmful algal blooms, leading to oxygen depletion in the water and damage to local ecosystems.

Previous and new research

This new research follows on from studies initially undertaken in the UK in 2016 (Gooddy et al., 2015; Ascott et al., 2016) that looked at mains water leakage and the associated inputs of phosphate that this causes. However, these studies only considered mains water leakage: the new study employs an innovative way of determining previously unaccounted-for phosphorus sources at a much bigger scale. It estimates, for the first time, the amount of phosphorus that enters the environment from the US public water supply.

Phosphorus in US public water supplies

Public water systems across the United States widely dose water with phosphate (PO₄) to control the corrosion of lead and copper within water distribution networks. When pipes leak or people water their lawns, this phosphate enters the environment and can find its way into rivers and groundwater. About 5 to 17 per cent of this phosphate-dosed water leaks out of water mains, whilst 5 to 21 per cent is used outdoors. In some parts of the US, the amount of phosphorus entering the environment from the water supply exceeds that coming from point sources like wastewater treatment plants, or from agriculture and fertilisers.

Developing a more effective phosphorus management policy requires a comprehensive understanding of phosphorus sources and routes into the environment, which are known as fluxes. These fluxes should be considered in relation to other sources of phosphorus in the aquatic environment (Gooddy et al., 2017) and can inform localised phosphorus management practices.

Future work

The next step is to look at carbon cycling and greenhouse gas emissions from water use in the US. A sister study, which was published by the same authors in 2022, looked at how water supply processes are responsible for significant nitrogen fluxes (Flint et al., 2022).

Researchers and funding

51ΑΤΖζ is the lead on this research with PhD candidate Elizabeth Flint supervised by Dr Matthew Ascott and Prof Daren Gooddy. There has also been input to the work from Dr Mason Stahl from Union College, NY, USA and Dr Ben Surridge at Lancaster University, UK.

This work has been funded through ENVISION DTP with supervisor support provided through the BGS BUFI programme and National Capability funding through Groundwater Processes.

Further reading

References

The problem

Human activities such as inefficient nitrogen fertiliser application have led to excess nitrogen concentrations and the continued degradation of coastal and fresh water around the globe (Figure 1). The effects of human activity on the nitrogen cycle are particularly strong across the United States of America, with the production of nitrogen-based fertiliser a major cause of the nutrient pollution that persists across the country. Although the associated environmental degradation is thought to cost the country billions of dollars a year and reducing human-derived nitrogen inputs is vital for restoring a functioning ecosystem, efforts such as those introduced by the have often resulted in slower than anticipated water-quality improvements. Correctly identifying and estimating all processes that can act as sources or sinks of nitrogen is thought to be an important step in reducing inputs.

The science

The USA has one of the largest freshwater abstraction volumes per capita in the world, with major uses for fresh water including irrigation, thermoelectric power, and public water supply. For this project, we used publicly available datasets on countrywide withdrawal volumes and nitrate (NO₃) concentrations for both surface water and groundwater. We found that freshwater abstraction will temporarily retain any associated NO₃ in the abstracted water from the aquatic environment.

We estimated the abstraction NO₃ flux for the contiguous United States to be 417 kilotons of nitrate nitrogen per year (kt NO₃-N yr^-1) and found large disparities between county-level abstraction flux estimates (Figure 2). We assessed the significance of the national-level abstraction NO₃ flux estimate in the context of pre-existing US nitrogen budgets through comparison to other nitrogen budget components and found our estimate to be equivalent to 57 per cent of total denitrification estimates.

The results

Our research indicates that freshwater abstraction can act as a significant temporary retention mechanism, meaning that it temporarily delays the delivery of nitrogen from the land to the oceans, hence it should be considered when developing nitrogen budgets.

When considering this mechanism, it worth noting that leaking US water mains cause an average of 16 per cent of the water initially entering the distribution network to be lost the environment. We used publicly available data to estimate the release of NO₃ to the environment in association with this leakage at around 7 kt NO₃-N yr^-1 (across the contiguous United States). Although this estimate is insignificant to national-level nitrogen cycling, county-level fluxes vary greatly (Figure 3), with the magnitude of the flux having a positive correlation with urbanisation.

The localised significance of leakage-derived NO₃ is highlighted by the exceedance of these fluxes over agricultural fertiliser nitrogen inputs across some counties (Figure 4) and suggests that these fluxes should be incorporated alongside abstraction NO₃ fluxes within nutrient budgets and considered when developing nutrient-management strategies. Future work should aim to further resolve these fluxes, both across the United States and around the world.

My PhD research

As part of my PhD thesis, I recently published a paper on investigating the effects of freshwater abstractions and mains water supply leakage upon nitrogen cycling across the United States (Flint et al., 2022).

My ongoing research will investigate the potential for both mains water leakage and the use of phosphate-dosed water outdoors at domestic residences to act as sources of phosphorus across the United States. I will also be investigating the potential for the stable oxygen isotope composition of phosphate to identify phosphate-dosed drinking water as a source of phosphorus within the environment and to assess the processes affecting phosphate-dosed drinking water within water and waste-water networks.

Author

Elizabeth Flint (ORCID 0000-0002-5781-2523)

With thanks to my supervisors Matthew Ascott, Daren Gooddy, Ben Surridge and Mason Stahl.