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.
