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5.1 EnvironmentalTransportation
Many plastic materials that enter the environment will not remain stationary.
Instead theywill be transported between environmental compartments (e.g. from
land to freshwater and from freshwater to marine environments), with varying
residence times in each. For example, the movement from land to river systems
willdependuponprevailingweatherconditions,distancetoaspecificriversite,and
land cover type. The collection of plastic litter at roadside habitats is easily
observed, and the regular grass cutting practices of road verges in some countries
means that littered items are quickly disintegrated bymowing equipment [8]. The
movement ofMPs from land towatermay thenoccur throughoverland run-off or
dispersion (via cutting action) to roadside ditches. Themovement of bulk plastics
andMPswithin the riverine systemwill be governed by its hydrology (e.g. flow
conditions, daily discharge) and the morphology (e.g. vegetation pattern) at a
specific river site thatwillhavea largeeffectuponthepropagationof litterbecause
of stranding and other watercourse obstructions such as groynes and barrages
[2]. Compared to larger plastics, MPs may also be subject to different rates of
degradation as they will be transported and distributed to various environment
compartments at quicker rates than macroplastics. The formation of
MP-associated biofilms has been investigated for LDPE in marine setting
[62]. Transport to sediments and the formation of biofilms over the surface of
MPs may also limit rates of degradation as this removes exposure to light. The
modelling of MP fate and transportation in freshwaters is discussed further in
Kooi et al. [63],whileMP-associatedbiofilmare discussed inHarrison et al. [64].
5.2 EnvironmentalPersistence andDegradation
Themajority of our current understanding regardingplastic degradationprocesses
isderivedfromlaboratorystudies thatoften investigateasinglemechanismsuchas
photo-, thermal, or bio-degradation [65]. There is limited information on the
degradationofplastics under environmentally relevant conditionswhere anumber
ofdegradationmechanismsoccurat together.Where information isavailable these
studieshave tended to focusonweight loss, changes in tensile strength,breakdown
of molecular structure, and identification of specific microbial strains to utilise
specific polymer types. The degradation processes are defined in accordancewith
the degradationmechanismunder investigation (e.g. thermal degradation) and the
experimental result generated. In contrast, particle formation rates are often not
investigated.This is importantbecausepolymers suchasPEdonot readilydepoly-
merise and generally decompose into smaller fragments. These fragments then
further disintegrate into increasingly smaller fragments eventually forming nano-
plastics [66–68].
MicroplasticsAreContaminants ofEmergingConcern inFreshwater. . . 7
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