Engineered Nanomaterials as Emerging Contaminants in Water - Nanotechnologies for Water Environment Applications - page 568

was employed to evaluate the distribution of copper in different organs of mice (Chen et
al., 2007). Extraction of nC 60 from water using solid phase extraction (SPE) and
analysis in toluene by liquid chromatography with a mass spectrometer can detect nC 60
to less than 1 part per billion (Chen et al., in-press). New methods will continue to be
developed to facilitate exposure assessments in toxicity studies.
However, some NM research implies that parameters other than solely mass
concentration are important. To address these issues, new analytical methods will be
required to complement proven techniques. To characterize colloidal concentration,
size distribution, mineral composition and surface properties, it is quite common to use a
combination of different techniques (Ledin and al., 1995; Rodriguez and Armstrong,
2004; Moon et al., 2006b). For instance, UV detection, fluorescence spectroscopy, and
gravimetric analysis are applicable for determination of colloid concentration(Chin and
Gschwend, 1991; Belzile and Guo, 2006). Light scattering, photon correlation
spectroscopy, and the fractionation procedures such as ultrafiltration and size exclusion
chromatography can be utilized for the size distribution measurements (Chen and Buffle,
1996; Duker and Ledin, 1998; Cai, 1999). Atomic force microscopy, scanning electron
microscopy, transmission electron microscopy, small angle neutron scattering, X-ray
diffraction, infrared spectroscopy, and inductively coupled plasma mass spectrometry
are advantageous to obtain information about mineral constituents and general surface
properties (Chen and Buffle, 1996; Lartiges et al., 2001; Gee and Bruland, 2002;
Mavrocordatos et al., 2004; Diallo et al., 2005; Titelman et al., 2005; Chanudet and
Filella, 2006). Since typical dimensions of engineered NMs fall into the size range of
colloid, a variety of methods that have been used to investigate the physical and
chemical properties of colloids may also be applied in the characterization of NMs in
natural waters. Innovative combinations of existing and new analytical tools need to be
developed and validated to critical information such as size distribution, number,
composition, and mass values from which other critical information can be calculated
(i.e., surface area, fractal properties).
16.4.2 Processes Affecting Nanomaterials Fate in the Environment
A wide array of physical and biogeochemical processes may affect the fate of
NMs in aquatic systems (Table 16.1). Nearly all the processes have some potential
relevance for natural, incidental and engineered NMs. Aggregation is discussed in detail
(Section 16.5) because it is arguably among the most important processes as it underpins
the ability of NMs to flocculate, be removed by filters, partition into soils or
bioaccumulate. Representative effects of the other processes on nanomaterials are
outlined in Table 16.1. However, all the processes outlined in Table 16.1 occur in the
presence of transport processes (e.g., longitudinal stream and sediment movement,
groundwater flow, etc). Combined together they affect the duration of exposure of
aquatic organisms and humans (e.g., withdrawal of water from rivers) to NMs, and the