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4 Particles as aVector forCo-pollutants
One of the possible environmental processes, often discussed for both engineered
nanomaterials andmicroplastics, is their ability to act as vectors for other pollut-
ants. Through their use in, for example, consumer products and medical and
industrial applications, engineered nanomaterials and primary microplastics will
comeintocontactwithotherchemicalsubstances,suchaspreservatives,surfactants
and active ingredients in pharmaceutical drugs. Finally, throughdifferent disposal
routes, the particles will come into contact with environmental contaminants
present in, for example, waste water streams and landfill leachate. As a conse-
quence, intentional and unintentionalmixing of the particleswith other chemical
compounds takesplacebefore, duringandafter their intendeduse.By thisprocess,
an otherwise inert and non-toxic particle potentially becomes a carrier of toxic
compounds. At the same time hydrophobic pollutantswith a lowwater solubility
becomemore mobile when sorbed to plastic particles, whichmay increase their
transport andconsequently impact their distributionandbioavailability [34]. It has
beenshownthatengineerednanomaterialscansorbandtransportorganicpollutants
in the aquatic environment [35–37]. Similarly, nano- andmicroplastics have the
potential toact asvectors forhydrophobicorganicchemicals, as recently reviewed
byRochman [38].
With an increased surface area-to-volume ratio, smaller particleswill generally
havea largercapacity for adsorptionofchemical substances (onan ‘adsorptionper
particle mass’ basis). At the same time, their small sizemay facilitate uptake by
organisms and even potential translocation into different parts and organs. This
vector function is governed by the properties of the pollutant and the particle
[39]. Important particle properties include chemical composition, porosity, size
and surface properties (coating, charge).Weathering processes can both increase
and decrease sorption [40]. The formation of cracks and increased surface rough-
ness leads to an increased surface area and, therefore, a potentially increased
sorption capacity. Counteracting this, weathering may also change crystallinity,
increasedensity andhardness and change surface charge. For instance, changes in
surface charge as a result of weathering can increase the sorption of some sub-
stances anddecrease the affinity for others [41].
Plastic towaterpartitioningcoefficients (logKpw) forvariousorganicchemicals
(logKow from0.90 to8.76)havebeencollected forpolydimethylsiloxane (PDMS),
lowdensityPE (LDPE), highdensityPE (HDPE), ultra-highmolecularweight PE
(UHMWPE), PP, PS and PVC [41]. Regression analysis showed generally good
correlationsbetween logKowand logKpwand linear proportionality forLDPEand
HDPE. This analysis suggests that the partitioning of chemicals into plastics is
driven by hydrophobic interactions – similar to the partitioning of chemicals into
animal lipids [41].At thesametime,pollutantsmayadhere to theparticle surfaces.
For example, it has been found that nanoplastics have a capability to adsorb
hydrophobicpollutants,aprocesswhichcanpotentiallybeexploited in theremoval
of chemicals from contaminated soil and water [42]. Hence, for nano- and
32 S.Rist andN.B.Hartmann
Freshwater Microplastics
Emerging Environmental Contaminants?
- Titel
- Freshwater Microplastics
- Untertitel
- Emerging Environmental Contaminants?
- Autoren
- Martin Wagner
- Scott Lambert
- Verlag
- Springer Open
- Datum
- 2018
- Sprache
- englisch
- Lizenz
- CC BY 4.0
- ISBN
- 978-3-319-61615-5
- Abmessungen
- 15.5 x 24.1 cm
- Seiten
- 316
- Kategorien
- Naturwissenschaften Chemie