Mar 30, 2007
Are nanoparticles safe for soil?
Synthetic nanoparticles do not harm soil ecology, according to new experiments by researchers at Purdue University in the US. The result was obtained by adding fullerenes (or buckyballs) to samples of soil and observing any changes.
Although nanomaterials are starting to be widely used by industry, how these materials behave in the natural environment is still largely unknown. In the new experiments, Ron Turco and colleagues added both dry and water-based forms of fullerenes to soil samples and found that the nanoparticles did not change how the soil, or the micro-organisms, in it functioned.
"Fullerenes will be in the soil eventually, so it's good to know they aren't affecting soil micro-organisms," said Turco.
The tests studied how different concentrations of buckyballs affect soil micro-organisms. These included bacteria, which are responsible for breaking down organic material and producing compounds such as carbon dioxide. As Turco explained: "Bacteria in the soil are the basis of the food chain, so you don't want to change them because then you affect everything up the food chain – plants, animals, people."
Turco and colleagues suspended dry and wet buckyballs in their soil samples in levels of one part per million and 1000 parts per million respectively. The researchers then monitored the size and composition of the bacterial community, as well as it how it functioned, over a period of six months. They found that carbon dioxide levels in the soil (soil respiration) were not affected. According to the team, if buckyballs were toxic, then affecting bacterial activity would reduce the amount of carbon dioxide produced.
"We thought we would see something negative in the soil due to the effects of fullerenes, especially at 1000 parts per million," said Turco. "Lo and behold, much to our pleasure and surprise, our data shows no adverse effects on the soil microbiology."
The results disagree with previous work that showed that buckyballs were toxic to microbes. However, Turco says that although these studies warrant further investigation they were performed in purified cultures. "You can't look at the effects of manufactured nanoparticles in isolation. You have to put them in a natural environment where other things are reacting with the nanoparticles," he stated.
The team now plans to look at the affect of other types of nanoparticle on soil. "Clearly, each manufactured nanomaterial is different so we do need to develop a better knowledge of each on a case-by-case basis," explained Turco.
The researchers will publish their work in Environmental Science and Technology.