Complex effect of CNTs on environment
16 Dec 2011 by Evoluted New Media
Carbon nanotubes (CNTs) are found in an increasing number of products because they have a higher tensile strength than steel, are harder than diamond and conduct electricity better that copper. However, exactly how they affect our aquatic ecosystems is unknown. Up to 100,000 times thinner than a human hair, carbon nanotubes could be used in solar cells, plastics, batteries, medical technology and the purification of drinking water. But while these nanoparticles have a whole host of useful properties, research suggests they inhibit the growth of green algae by depriving it of light and space.
Researchers from Empa and Agroscope Reckenholz-Taenikon (ART) Research Station measured the growth and photosynthetic activity of green algae exposed to CNTs and found that, even in high concentrations of CNTs, the algae maintained normal levels of photosynthesis.
However, growth rates were reduced when NCTs were added to an algae suspension. This caused the colour to darken, and the NCTs to form clumps with the algae depriving them of light and caused slowing growth.
The researchers found no evidence that the nanotubes were absorbed by the plants, leading them to conclude that the CNTs are non-toxic to green algae as earlier studies had implied.
“Our study shows how difficult it is to understand in detail the effect of nanomaterials on organisms,” said Fabienne Schwab, an Empa and ART researcher.
Although the research shows that algae does not enjoy the ideal growth conditions in the presence of carbon nanotubes, the clumping and shadowing effects were observed at elevated levels – around 1 milligram per litre – much higher than any concentration likely in the environment.
The results – published in Environmental Science & Technology – will be used to help test other nanoparticles to guarantee the safety of humans and the environment, but Bernd Norwack, Empa researcher believes that until comprehensive, long term results are available for complex organisms such as green algae, nanoparticles should not be released into the environment.
Are Carbon Nanotube Effects on Green Algae Caused by Shading and Agglomeration?
