Hayle Estuary Reserve, which is a Site of Special Scientific Interest, is suffering from high levels of heavy metals caused by years of industrial mining which are contaminating plants and wildlife.

Arsenic, copper, tin and zinc are found in the mud at Hayle nature reserve and that is being described as bad news for wildfowl and wading birds in particular.

Now the Royal Society for the Protection of Birds (RSPB) is distributing about seven-and-a-half tonnes of cat litter into the estuary to absorb the metals after advice from the Camborne School of Mines.

The gravel-like cat litter contains the mineral calcium bentonite which will absorb the heavy metals and lock them away.

Flooded mines

The project, which started on Thursday and will take several days to complete, is costing about �8,000 with half of the money provided by English Nature.

Dave Flumm from the RSPB said: "About 29 mines used to be connected to the Hayle river, and the mines have all flooded out and the material settled in over time, hence the current problems."

The solution was suggested by experts from the Camborne School of Mines.

Professor Hylke Glass of the school said of the choice of material: "Of the various amendments tested, cat litter displayed a good absorption capacity for heavy metals.

"This was anticipated on account of the presence of clay-like substances, which are known to have a good capacity for absorbing heavy metals."