PORTLAND, Ore. Nanotechnology's critics have hewn to speculation by Sun Microsystems co-founder Bill Joy that runaway nanobots could consume the planet's natural resources, and to studies suggesting that some nanoparticles, if allowed to accumulate in groundwater, could stunt plant growth. Now a scientist at Purdue University questions nanotechnology's threat in a study that claims to find certain manufactured nanoparticles have no negative effects on soil.
Ron Turco, a Purdue University soil and environmental microbiologist, will publish his findings in the April 15 issue of Environmental Science and Technology. Turco and colleagues claim that neither dry nor water-based forms of buckminsterfullerenescarbon nanoparticles containing only tens to hundreds of atoms called buckyballshave ill effects on soil or the microorganisms it contains.
Buckyballs are named after architect Buckminster Fuller, inventor of the geodesic dome (the nanoparticles evoke that structure's profile). They were first synthesized in a Rice University lab by Robert Curl, Harold Kroto and Richard Smalley in 1985, for which they were awarded the Nobel Prize in 1996. After the Rice University discovery, buckyballs were also discovered to occur in nature, for instance in a meteorite from Mars that landed in 1969. Prior to the Rice University discovery,"
Before that, only two forms of carbongraphite and diamondwere known. Today buckyballs, which are 100 to 1,000 times stronger than steel and have a hollow core that can be filled with chemicals, are mass-produced worldwide.
The nanoparticles Turco tested are already in use in coatings that make fabrics stainproof and sports equipment more durable, and as conduits for drugs and biological markers. In electronics, quantum dots use nanoparticles to confine electrons in cavities smaller than their natural wavelengths.
Some have argued that wide use of such structures will result in the nanoparticles' accumulating in the natural environment, with potentially negative results. Turco sought to test that speculation by dosing soil samples from working farms with different levels of nanoparticles, then measuring the effect on the microorganisms in the soil that break down organic compounds.
The tests, conducted at the Purdue University Agriculture Research and Education Center over a six-month period, showed no adverse impact on the soil, even at relatively high concentrations, of 1,000 parts per million. Carbon dioxide levels, soil respiration and the size and composition of soil bacteria communities showed no ill effects, according to Turco's study.
He notes that previous studies, which turned up problems in soil exposed to nanoparticles, were conducted in laboratories. "Others did their studies in a purified culture," Turco said. "You can't look at the effects of manufactured nanoparticles in isolation. You have to put them in a natural environment."
Turco suspects the exposure level and toxicity of fullerenes are naturally regulated in real-world soil environments. But he adds the caveat that he tested only a few types of nanoparticles and that further tests must be done on a broader array of particles before conclusions can be drawn.
Turco is a professor with the Purdue Department of Agronomy and the director of the Indiana Water Resources Research Center. Other researchers involved in the study were Larry Nies, a civil engineering professor; Bruce Applegate, a food science associate professor; research soil microbiologist Marianne Bischoff; and research assistant Zhonghua Tong of the Purdue Laboratory for Soil Microbiology. All are members of the Purdue Nanoscale Interdisciplinary Research Team.
The National Science Foundation and the Environmental Protection Agency provided funding for Turco's research.