The worms ability to decontaminate soils polluted with heavy metals is not generally known and worms have not been used for this purpose in Australia.
In 1975 a Welsh researcher named Ireland, conducted trials on polluted mining sites in Wales He extracted lead (Pb), zinc (Zn) and Calcium (Ca) from the soil, from worm castings produced from that soil, and from the worms which produced the castings; The castings contained less Pb, Zn and Ca than the original contaminated soil, but the worms contained considerably more - twelve times more in the ease of the Lead,
As the levels of zinc and calcium are higher in the castings than in the soil, Ireland concluded that the presence of worms in heavily contaminated soil could increase the amount of these minerals available to plants, The lead, however, was less in the castings than in the soil, and was being progressively transferred from the soils into the worms where it was retained. If the worms were then removed from the soil, the lead would be removed with them
In 1976, two other researchers, Martin and Coughtree, recorded cadmium (Cd) concentrations of 38 and 29 parts per million respectively in soil on two sites. Worms extracted from these soils were found lo have in both cases a concentration of 143.7 parts per million. Despite the difference in concentrations of the cadmium in the soul, the worms had absorbed an identical amount into their bodies and this suggests that some worms will absorb poisonous heavy metals until their presence becomes life threatening, at which lime they are able to stop. However, much more research needs to be done on this subject.
I a not suggesting that we can use worms to recover heavy metals for recycling. Nor is it safe to assume that all or any worms can absorb heavy metals without harm. In research, some species have demonstrated an ability to absorb specific metals far more readily than others. It may be that a specific type of worm should be used to remove lead, another for cadmium, another for chromium and so on. In practice, if worms were to be used to decontaminate soil, the worm population would need to be changed at intervals by removing the adults which could perhaps then be incinerated. The time to do this would be decided by analysing a sample of the worms, This is a specific area of research that warrants further investigation. These are just a few examples of ways in which worms can be used to clean up or prevent pollution, There are many other uses for worms and if just one were adopted, even on a small scale, the demand for worms would skyrocket.
