Biomedical Engineering Reference
In-Depth Information
While most of the ecotoxicity data were obtained from aquatic studies, few
aquatic studies have been done under conditions resembling those found
in the field, including the presence of significant amount of organic matter,
high ionic strength, etc. [13,17].
The release pathways of NMs into the environment are possibly similar
to those known for other environmental contaminants such as metals and
organic compounds. The sources of manufactured NMs can be direct (inten-
tional) or indirect (accidental), as discussed in the following sections.
10.2.1 Intentional Release into Environment
Manufactured NMs may be deliberately introduced into the environment as
pesticides, or other agricultural applications, and as part of remediation tech-
nologies for decontamination of soil, water, or groundwater. Environmental
remediation of nano-enabled technologies has been presented in Chapter 5
of this topic. Several applications of NMs, including the removal of pesti-
cides, organo-chlorinated solvents, or explosives from groundwater, and
reclamation of land lost to forest fires have been investigated; however, the
potential ecotoxicological risks associated with the use of NMs in ground-
water or their dispersion on the soil surface remains a concern [10,18-20].
For instance, following their dispersion into soil, NMs could become part
of aerosols formed by wind erosion. Once in the environment, NMs could
possibly impair key ecological functions, such as nutrient recycling, water
depuration, and biomass production [10]. Ecological receptors at risk would
encompass all sensitive species that are exposed to NMs through air, water,
or soil. Geochemical cycles such as carbon (CO 2 fixation by plants and algae)
and nitrogen cycle may also be affected.
The carbon cycle could be affected as it has been speculated that some
NMs (e.g., TiO 2 ) with photo-oxidizing activity could enhance the turnover
rate of the stable organic matter in soil [16]. In addition, NMs introduced in
soils could modify soil hydrophilicity and decrease wettability, and lead to
increased problems with erosion, loss of soil fertility, and water pollution
[10]. Finally, NMs in soil, sediments, and water may also affect the bioavail-
ability of certain essential nutrients (e.g., phosphate) and change growth
rates (biomass production) in algae, phytoplankton, soil bacteria, and plants.
Soil respiration rates would then be modified, as well as soil texture-related
processes such as transport of gases (soil CO 2 transport, evapotranspiration)
or water (infiltration, soil moisture transport, surface runoff) [10].
10.2.2 Accidental Release into Environment
A significant part of the environmental contamination will occur via indi-
rect routes. The industrial NMs producers and manufacturers of prod-
ucts containing NM are among the largest sources of NM contamination.
Atmospheric emissions and effluents of conventional industrial pollutants
Search WWH ::




Custom Search