Map traces UK's elemental signature
A 40-year quest to map Britain's geochemistry was celebrated on Tuesday.
Stream water and sediment samples were taken on the Isle of Wight to analyse the chemical elements that are present.
The results will be added to the more than 500,000 other samples gathered from across the UK by the British Geological Survey's G-BASE project.
G-BASE began as an effort to look for gold and copper deposits, but has since evolved into a giant database to help monitor environmental change.
"When it began, in Scotland, the thought was about finding new mineral deposits, but over time it has really become something more to do with environmental baselines," said BGS executive director Prof John Ludden.
"For example, we can now tell where the arsenic is, or where the radon gas is. This is not as a result of pollution; it's to do with the different rock types at different locations. But all these baselines now allow us to tell if changes occur," he told BBC News.
Data from the Isle of Wight completes the project, and Prof Ludden was on-hand to help gather the ceremonial sample.
BGS staff and hundreds of volunteers have done similar work at 110,000 sites across Britain.
It involves capturing a small volume of water from a stream, scooping up some sediment from the bed, and taking some nearby soil plugs. Subsequent analysis in the laboratory will detail the precise chemistry of the samples.
G-BASE now has geochemical data across the UK land surface at an average spacing of one sample for every 1-2 sq km.
The project has helped identify new features of British geology. It also helped find the world class Foss Barites (barium sulphate deposits), which are used in drilling muds to prevent blowouts during oil and gas exploration.
In addition, G-BASE has become a useful tool for understanding the relationship between the landscape and the health of livestock, by revealing the mix of essential elements at different grazing locations.
"We now have this remarkable knowledge of the composition of the UK land surface," said BGS's Dr Jo Wragg.
"It's a unique and robust benchmark for measuring environmental change. Its uses range from telling us about potential mineral resources to helping inform polices and management of contaminated land."
Jonathan.Amos-INTERNET@bbc.co.uk and follow me on Twitter: @BBCAmos