Study Finds Gold Nanoparticles Can Bind with Cyanide in Freshwater Environment


Unknown to others, scientists had found gold nanoparticles that can bring danger into aquatic life. / Photo by: Nelro via Wikimedia Commons


Nanoparticles are used in many industries and consumer products. But little is known about their effects on the environment once the products that contain them are discarded. Researchers at Carnegie Mellon University found that a particular nanoparticle can be toxic to aquatic life.

To study the consequences of nanoparticle use, a research team led by Professor Greg Lowry looked into gold nanoparticles. Initially, they tracked down the tiny materials dissolving in freshwater domains and found that the process released gold ions, which could be toxic to certain microorganisms.

"This study has opened our eyes to the importance of plants and the plant microbiome in determining the fate of engineered nanomaterials in freshwater environments. These plants, and biofilms, in general, are important sinks for nanomaterials and are a fascinating compartment to study," said Lowry, a professor of civil and environmental engineering at CMU.

To learn the mechanism behind it, the team conducted experiments using a mesocosm, a controlled natural freshwater environment. The mesocosm housed elements found in the uncontrolled environment, such as soil, water, sediments, plants, fishes, insects, and microorganisms.

They released very low amounts of gold nanoparticles in the mesocosm each week to replicate the long-term, low-dose exposure that happens in the real world. Six months later, the mesocosm showed that 70 percent of the gold nanoparticles had accumulated in the plants, while the rest had dissolved and turned into other forms of gold.

Further inspection showed that the biofilm made by bacteria and other microorganisms produced cyanide, a chemical that interacted with gold. The chemical reaction between the two substances resulted in gold-cyanide and other complex gold forms.

The researchers concluded that the gold transformation must be studied more, but they considered its potential toxic effects to some organisms.