OPAL Metals Survey – the results

Alongside the OPAL water survey, we ran a national experiment to assess the metal content of pond and lake sediments. The metals survey has now closed, but you can find out more about what we discovered.

How did you help?

We asked you to join in the OPAL Metals Survey and help us learn more about metal contamination by collecting a small mud sample from your local pond and sending it to the OPAL Water team at UCL, where we measured the element concentrations using X-ray fluorescence spectroscopy (XRF).

These results have shown which water bodies are affected by metal contamination and will feed into maps of metal distribution produced by the British Geological Survey and into research on aquatic contamination.

Thank you to everyone who took part. This experiment has been novel in combining public participation and environmental contaminant research.

What did we find out?

Your results show that in many ponds and lakes there are considerable amounts of metals in the sediments, which could affect organisms that live in the water. The national pattern reflects historical industrial activity, the background geology of the area and current activity in the atmosphere and catchment area. At a local level there are often many reasons why some lakes and ponds have higher concentrations than others.

Can you find your lake or pond?

Explore the interactive maps below which show the concentrations of the metals found in the mud you sent in. The colours of the dots show high, medium and low sediment concentrations of six metals. The blue dots are sites where there was not enough sample to be analysed. The high / medium values show a metal concentration at which harmful biological effects are likely to be observed. At the medium / low thresholds, harmful effects are rarely seen.


  Pb (lead) Zn (zinc) Cu (copper) Ni (nickel) Cd (cadmium) Hg (mercury)
   µg g-¹  µg g-¹  µg g-¹   µg g-¹   µg g-¹   ng g-¹
High > 91 > 315 > 197 > 36 > 3.5 > 485
Medium 35 - 91 123 - 315 35 - 197 18 - 36 0.6 - 3.5 175 - 485
Low  < 35  < 123 < 35  < 18   < 0.6 < 175 


(The metal concentrations are measured in micrograms per gram of sediment (µg g-¹), equal to one millionth of a gram. However, mercury in sediments is usually found at lower concentrations so the unit used is a nanogram (ng g-¹) – one billionth of a gram.)


Pb – lead

Zn – zinc















Cu – copper

Ni – nickel















Cd – cadmium

Hg – mercury