Editorial Feature

Nanomaterials - Fate of Nanomaterials in the Environment

Aug 28 2009

Updated on 16th January 2020 by Reginald Davey

The field of nanotechnology is an area of scientific research that has the potential to improve many areas of life and technological development. However, like any industry, there are potential risk factors that must be mitigated. One of the main areas of concern that pertain to this relatively new area of technology is the effect of nanomaterials upon the environment, avoiding their release into the atmosphere, water table, and soil.

Image Credit: Anucha Cheechang/Shutterstock.com

As more products containing nanomaterials are developed, there is more potential for their release. Sources of potential nanomaterial release include:

Direct or indirect release from the manufacture and processing of nanomaterials
Releases from oil refining processes
Release of nanomaterials incorporated into products fabricated for consumer use such as fertilizer and those in the pharmaceutical industries.
Release resulting from the disposal of consumer products containing nanoscale materials

This article will give an overview of what is known or can be inferred about the fate of nanomaterials in the environment.

The fate of Nanomaterials in the Atmosphere

As well as their physical and chemical characteristics, there are several factors and processes which influence the fate of airborne particles. The processes central to understanding the potential atmospheric transport of particles are agglomeration, diffusion, wet and dry deposition, and gravitational settling. These processes are relatively well understood for ultrafine particles and can be applied to nanomaterials. On the other hand, in some cases, intentionally produced nanomaterials may behave differently from incidental ultrafine particles. Also, there may be differences between nanomaterials that are aged and freshly generated.

Regarding the length of time particles remain airborne, particles with aerodynamic diameters in the nanoscale range, may follow the laws of gaseous diffusion when released into the air. Airborne particles can be classified by size and behavior into three general groups: Small particles (less than 80 nm) intermediate-sized particles (80-2000 nm) and large particles (over 2000 nm in size.)

As the physical size of particles is a critical property of nanomaterials, it is a priority to maintain the size of particles during their handling and use.

The fate of Nanomaterials in Soil

Once nanomaterials are released into the soil, their fate depends upon their chemical and physical characteristics. Soil strongly absorbs these materials due to their high surface area. Once in the soil, they may be rendered immobile, or there is the possibility that they may travel farther than larger particles, before being trapped in the soil matrix due to being small enough to fit into the small spaces between soil particles.

Absorption rates of nanoparticles within soil depend on their size, chemistry, applied particle surface treatment, and the conditions under which they are applied.

The fate of Nanomaterials in Water

Factors that control the fate of nanomaterials in water include aqueous dispersibility or solubility, nanomaterial interactions between the natural and anthropogenic chemicals in the system, and biological and abiotic processes.

Particles in the upper layers of aquatic environments, in water droplets in the atmosphere, and on soil surfaces are exposed to sunlight. Light-induced photoreactions are often critical in determining the environmental fate of chemical substances. These reactions may change the chemical and physical properties of nanomaterials and therefore alter their behavior in aquatic environments.

Potential Risks from the Release of Nanomaterials into the Environment

There are potential risks that may arise from the release of deliberately produced nanomaterials into the environment via one of the routes described above. Even though the understanding of these risks is incomplete, there is the possibility that nanoparticles can accumulate in the environment and make their way into the food chain via absorption into biological cells with unknown consequences.

Clearly, as this is still a relatively new area of scientific development, these risks must be understood and ways of preventing their unwanted release must take priority in nanomaterial research. As new and novel nanomaterials are produced, this will need to be of central focus.