Introduction—Biointeractions of Nanomaterials - Biointeractions of Nanomaterials - page 22

Source

Nanocomposites

Functionalized
nanoparticles

Nanoparticles

Aggregates

Bio-uptake

Transportation

Deposition Deposition Deposition eposition

FIGURE 1.11 Fate of nanomaterials in the environment. (Reprinted with permission from Farré, M., J.
Sanchís, and D. Barceló. 2011. TrAC Trends in Analytical Chemistry 30 (3): 517-527.)

The marine environment is composed of various colloids and natural organic matter. The
marine environment can be contaminated with NMs by coastal runoffs and atmospheric deposition
(Figure 1.12). The coastal environment is dynamic in terms of the presence of organic matter and
specific physicochemical characteristics. For example, the presence of greater amounts of organic
matter near the coast can lead to a change in the temperature and salinity with depth (Yamashita
et al. 2007). These characteristics may influence aggregation, and aggregates of NMs can sink to
the ocean floor. It is uncertain whether NMs accumulate at the interface between cold and warm
currents (Figure 1.12) or if they are recycled by biota. If they accumulate at the interface of cold
and warm currents, they may pose a risk to aquatic species that feed at this zone, such as vertically
migrating tuna. On the other hand, if the NMs are in the sediments, they induce risk to species
living at the bottom of the sea or ocean. At the surface of the ocean, NMs may get entrapped as
a microlayer due to the surface tension properties of water; this again poses a risk of toxicity to
marine birds, mammals as well as other organisms living or coming in contact with the ocean sur-
face (Simkiss 1990, Wurl and Obbard 2004).
Physicochemical properties such as pH, ionic strength, or the presence of organic ligands in
the water, affects the toxicity of NMs. The results of toxicity in seawater cannot be applied to
freshwater, as seawater is more alkaline, has a higher ionic strength, and has a different com-
position of marine bacteria that may accumulate NMs (Kennedy et al. 2004, Singaravelu et al.
2007).