Back in my Nov. 4, 2011 posting where I reviewed the third episode in a limited series on nanotechnology, broadcast as a Nature of Things television science programme on  Canadian Broadcasting Corporation stations, I noted Dr. Dennis O’Carroll’s soil remediation work in southern Ontario.

There’s more news about professor O’Carroll, currently visiting Australia, in a June 4, 2012 news item on Nanowerk,

“Toxic contamination of soils is an historical problem,” says Dr Denis O’Carroll, a visiting academic at the University of New South Wales (UNSW) Water Research Lab. “Until the 1970s, people wrongly believed that if we put these toxins into the ground they would simply disappear – that the subsurface would act as a natural filtration unit.”

“The possibility of this waste polluting the environment, and potentially contaminating groundwater sources and remaining there for decades was ignored,” he says.

Far from magically disappearing, chemical contaminants from spilled gas and solvents, when not directly polluting surface waters, seep down into the earth, travelling through microscopic soil cracks, where they accumulate and can eventually reach the groundwater table.

Traditional clean-up methods have focussed on pumping out the contaminated water or flushing out toxins with a specially designed cleansing solution, but these are limited by difficulties in accurately pinpointing and accessing locations where contamination has occurred, says O’Carroll.

His approach is to tackle toxic contaminants with nanotechnology. O’Carroll, who is visiting UNSW from the University of Western Ontario in Canada, has been trialling an innovative new groundwater clean-up technology using metal nanoparticles 500 to 5,000 times narrower than a human hair.

There are more details about O’Carroll’s specific innovations in this field in the June 4, 2012 news item. As well, I published, in its entirety (and with permission), an excellent description of nanotechnology-enabled soil remediation by Joe Martin, a graduate student at the University of Michigan, in my March 30, 2012 posting. Here’s a tidbit from Joe’s article,

… The use of iron oxides to adsorb and immobilize metals and arsenic is not a new concept, but nano-particles offer new advantages. When I wrote “adsorb”, I was not making a spelling error; adsorption is a process by which particles adhere to the surface of another material, but do not penetrate into the interior. This makes surface area, not volume, the important characteristic. Nano-particles provide the maximum surface area-to-weight ratio, maximizing the adsorptive surfaces onto which these elements can attach. These adsorptive processes a very effective at binding and immobilizing metals and arsenic, but they do not allow for the removal of the toxic components. This may be less-than-ideal, but in places like Bangladesh, where arsenic contamination of groundwater poses major health risks, it may be just short of a miracle.

There’s an extensive list with links to further reading and videos on the topic of nanotechnology and site remediation at the end of the March 30, 2012 posting.