September 12, 2008
Scientists Say Earthworms Aid Soil Clean-Up
Researchers at Reading University have found that metal-munching earthworms can help plants to clean up contaminated soils.
The team noticed that subtle changes occurred in metals as worms ingested and excreted soil, making it easier for plants to take up potentially toxic metals from contaminated land.
The UK has many areas with contaminated soil due to previous industrial activities, including mines, engineering works and lead smelters.
Earthworms are ideal "soil detectives": their presence can act as a reliable indicator to the general health of the soil. They have evolved a mechanism that allows them to survive in soils contaminated with toxic metals including arsenic, lead, copper and zinc.
Mark Hodson from the University of Reading explained that earthworms produce metallothinein - a protein that is specifically designed to wrap around particular metals and keep them safe.
He added: "In broad terms, if an earthworm can cope with one type of metal, it can often cope with a suite of metals."
Diamond Light Source in Oxfordshire, the UK's newest synchrotron, was a key piece of equipment in the study.
Hodson said the X-ray technology there allowed scientists to examine metal samples that were "around 1,000 times smaller than a grain of salt".
The researchers noticed that properties of metals in the material excreted from earthworms were slightly different from those found in the rest of the soil.
Some plants can pull out toxic metals from the soil, incorporate them into their tissues, and then be harvested and removed.
Now this process may offer a sustainable and non-intrusive way to decontaminate land, although it can take a long time.
Earthworms make the metals more readily available to plants, speeding up the process and making it more efficient.
Hodson said the dream scenario is that the plants become so wonderfully efficient at extracting the metals that you can then take them off to a smelting plant.
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