An Empa research study on nanomaterials for example, carbon nanotubes has revealed that carbon nanotubes inhibit the growth of green algae by reducing the amount of space and light supplied to the plant but the material does not affect the plant lethally.
Carbon nanotubes are not poisonous to green algae, but they do slow the growth of these organisms at high concentrations because they cause clumping which leads to the algae receiving less light. Left: intact algae (green) in a clump of carbon nanotubes (black). Right: "normal" photosynthetic activity of the algae (red) made visible by fluorescence.
A significant amount of carbon nanotubes have been disposed into the surroundings, as their production has been increasing in recent years. A team of researchers from the Agroscope Reckenholz-Taenikon Research Station and Empa is now studying the impacts of carbon nanotubes on the environment when they are disposed in lakes and waterways.
During the project, the research team has devised a standard chemical process for the measurement of the photosynthetic activity and growth of green algae while being exposed to carbon nanotubes. When carbon nanotubes were mixed to the algae suspension, the team noticed the darkening of the suspension’s color and the formation of clusters by the plant with the nanomaterial, but did not see the absorption of the nanomaterial by the algae. The team also found that the algae maintained their usual photosynthesis levels at elevated carbon nanotube concentrations.
The research team concluded that the growth of the algae gets affected, as they get minimum light due to clustering caused by the addition of carbon nanotubes. To confirm this, the team developed two more tests to quantify the agglomeration and shadowing impacts of the nanomaterial on the algae. The results proved that the growth of the algae is slowed down by these two effects.
The shadowing and agglomeration effects were noticed at higher concentrations of carbon nanotubes of over 1 mg/L. However, higher concentrations are yet to be reached in the surroundings. The research findings are helpful to study other nanomaterials to assure the protection of human beings and their surroundings.