Do nanoparticles affect the health of the soil ecosystem?

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Source: European Commission, Environment DG

New research reveals that many microorganisms, including bacteria and protozoa, show little sensitivity to fullerene nanoparticles applied to soil samples. However, fast-growing bacteria decreased in number and the genetic diversity of bacteria and protozoa altered slightly. This could affect the bottom of the food chain, which may have long-term implications for the overall health of the soil ecosystem.

Nanotechnology collectively describes technology and science which utilises nanoscale particles. Despite their benefits, introduction of nanoparticles into the environment might have significant impacts as they may be extremely resistant to degradation and have the potential to accumulate in bodies of water or in soil.

The study observed the behaviour of C60 fullerenes, also know as 'Bucky Balls', in soil. These are a type of carbon nanomaterial currently used in some cosmetics with expected future use in pharmaceuticals. Other types of carbon nanomaterials have a promising future for use in a range of environmental applications, including environmental sensors, renewable energy technologies and pollution prevention strategies. Laboratory tests on C60 fullerenes provide a good indicator of how other types of carbon nanomaterials will behave in the environment, as they all display similar physical and chemical characteristics.

In water, nanoparticles cluster together to form larger particles, aggregates, which may behave differently when released into the environment. In order to investigate the impact of fullerenes on soil microorganisms, the researchers prepared suspensions of aggregated C60 fullerenes, applied them to soil at varying concentrations and assessed how they affected the growth and diversity of soil dwelling microorganisms over time.

The study demonstrated that microbial biomass and respiration rate (an indication of the activity of soil microorganisms) were unaffected by nanoparticle treatments. Soil protozoans, such as amoeba, were slightly sensitive to nanoparticle applications. However, fast growing bacteria decreased up to 4 fold in number. Protozoa feed on bacteria, so a reduction in bacterial biomass could disrupt the bottom of the food chain in the soil ecosystem. Additionally, the researchers noticed a very small, but persistent, change in the genetic diversity of both the bacterial and protozoan community, caused by the fullerenes.

It is possible that the water-repelling nature of fullerenes means that they limit bacterial growth by adsorbing vitamins and minerals, which are essential for bacterial growth, from the soil.

Interactions between microorganisms in the soil ecosystem are very complicated and the impact of fullerenes on fast-growing bacteria may affect the balance of these interactions and in turn the overall health and function of the soil. Researchers recommend that further studies of the long-term fate of fullerene nanoparticles are needed before they are released into the environment. In addition there are many different types of nanoparticles so the effects of all types should be considered when setting environmental regulations for their release.

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