Abdelhak Maghchiche

Nanomaterials, due to their specific physicochemical properties such as a large surface area to volume ratio and high reactivity, can accumulate and transform in different environmental compartments. In soil, nanomaterials can interact with soil particles, forming stable or unstable aggregates, which affects their mobility and bioavailability. In water, nanomaterials can remain suspended, settle, or interact with dissolved substances, altering their potential toxicity to aquatic organisms. In the air, due to their microscopic size, they can be transported over long distances, posing a risk to human health and ecosystems. The transformation of nanomaterials in all these compartments depends on factors such as pH, temperature, the presence of organic matter, and microbial activity, all of which can significantly influence their ecological and toxic effects.

Nanomaterials transform in soil, water, and air through processes like adsorption, aggregation, and chemical reactions, influenced by environmental factors, affecting their impact.

That is correct. Indeed, like other materials, nanomaterials' fate in the environment depends on biological, chemical, and physical properties of the agent and the environmental medium where they reside. A key starting point for nanoparticles (NPs), or as air pollution folks call them, "ultrafines", is aggregation or agglomeration. As the particles aggregate, they take on the characteristics of larger aerosols that ultimately are deposited to the earth's surface. Another key aspect of NPs is their relatively large surface areas. This means that adsorption is a particularly important mechanism by which substances, including pollutants, sorb to NPs. This, not only the inherent constituents of the particle, e.g., iron NPs, are important, but the substances on their surfaces are transported and transformed in the atmosphere and in other media after they deposit. As such, pollutants can move by advection within the atmosphere, surface water, groundwater, soil, and even within the structures of biota.