Environmental Engineering Reference
In-Depth Information
Table 15.10 Environmental/solvent conditions affecting NM's BA by aquatic biota.
Examples/
References*
l.NPshave
salinity-
dependent
bioavailability
and toxic
effects
(Kashiwada,
2006).
2. Solvent
properties
affect the
physical-
chemical
behavior of
NMs in
environ. &
physiological
media
(Espinasse et
al., 2007;
Wangetal.,
2008a).
a Numbers in this column do not correspond the bullets in the other two columns.
Observation/Effects on BA of
NMs/Contaminants
• Light stimulates photocatalyzed reactions which
affect BA by aquatic biota. Temperature tends to
increase rates of both uptake and elimination.
BCF increases with an increase in temperature.
• pH influences the uptake rate of organic acids
and bases, ZPCs of NMs (see Table 15.1 1), and
K o w of NMs. In fish, BCF values of a given
compound tend to be lower in salt water.
• DO consumption influences metabolic activity.
At a lower DO, the water flow rate increases to
maintain O 2 consumption, providing more NMs
for adsorption.
• Both SS and DOM influence the rate of
magnitude of NMs transport across biological
membranes. Uptake of nonionic NMs by biota
may be reduced in the presence of DOM or
humic-like materials. Sorption, entrapment, or
sequestering of nonionic NMs on or within SS or
DOM reduces their bioavailability.
• Many solvent properties (e.g., density/viscosity)
affect biosorption of NMs. Solvent motivated
biosorption occurs when the NM is hydrophobic.
• Water Quality
Fate, Behaviors and Risk of NMs in Organisms. To further evaluate factors
and conditions shown in Table 15.8 that affect NM fate and behaviors in organisms,
results of some previous studies will be discussed even though most of these studies
focused on the risk, rather than fate and behaviors, associated with applications of
different NMs. Recent studies have shown that the risk associated with NMs might be
greater and the fate and behaviors of NM in organisms are much more complicated than
we have thought because NMs may cause different responses once they get into the host.
Several sets of evidence to support this statement are described as follows, along with
some preliminary studies on related mechanisms.
The first set of evidence is obtained from studies on inhaled or injected NPs
entering systemic circulation and migrating to various organs and tissues. Recently, it
has been found that inhaled NP effects are no longer confined to the lung, since particles
are suggested to translocate to the blood while lung inflammation invokes systemic
responses (Borm, 2002). The behavior of particles of different sizes and the related
mechanisms are very complex. Churg et al. (1998) reported that small TiC>2 NPs (21 nm)
persist in the tissues (rate tracheal explants) as relatively large aggregates, whereas the
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