Researchers from Northeastern University (NU), Boston have demonstrated a way to effectively rid soil of contamination using laser beams.
According to the scientists, lasers pointed at the soil break down chemical structures of contaminants, converting them into less harmful substances.
Researchers were able to rid a test batch of porous silica soil of DDE– a product of the banned, carcinogen DDT that was used as a pesticide till the 1970s – using their laser decontamination method. The DDE glows under UV light, making it easy to detect, Science daily reports.
The team of researchers headed by professor Ming Su claimed that the soil got decontaminated after the laser treatment was performed on it as UV light did not show any fluorescence, the report added.
"There is no other method that can do it at such high efficiency," said Su.
According to Su, in due course of time, a truck carrying a laser system driving across swathes of land with the light delivered through fibre optic cables and a plough to loosen the soil could be a possibility.
So how does it work? According to the report, the laser light heats up the pollutant locally, reaching temperatures of thousands of degrees Celsius. And this, in turn, is enough to break down contaminants by fragmenting their chemical bonds. In this case, the lasers fragmented the DDE molecules into safe molecules like carbon dioxide and water.
Su says that this method should be, in principle, effective against all types of contamination, including metal ions. However, he added that his team would have to run tests on various other forms and types of contaminants as well. There is also a need to run careful analysis to ensure that the chemicals that are broken down as a result of the lasers are broken down sufficiently enough to pass standards, said the report.
The development assumes significance as all the traditional methods of soil decontamination, "are either costly, labour intensive, have low efficiency or take a long time."
Soil decontamination is a long and arduous process as it usually involves physically moving the soil to a decontamination plant and returning it. Soil will have to be then washed either with water or biological solvents. Although this method is effective, it leaves the treatment plant with contaminated water, which effectively means that the contamination has moved from one place to another, not necessarily gotten rid of. If solvents are used, the soil remains harmful to humans.
On-site decontamination can be done by using plants and microbes or through soil vapour extraction, but according to the report, both methods only work on certain types of soils or when dealing with low concentrations and specific contaminants.