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Recommendation forModelValidation Validationwould require sufficientdata to
verify the credibility of themodelwith statistical rigor. Formassflowormultime-
diamodels, limiteddataper systemyet forahighnumberofaquatic systemswould
bepreferred.Forspatiotemporally resolvedmodels,however, itwouldbepreferred
to sampleonecatchment indetail. Suchacase studycatchmentcould thenbeused
to calibrate andvalidatemodels,whichcould later beapplied toother catchments.
As for process parameters, little is known yet especially about the time scales of
aggregation, fragmentation, and biofouling. Thismeans that experimentalwork is
needed, afterwhich the parameter values obtained from these experiments can be
applied inmodels.Thedevelopmentof fatemodels for freshwatermayalsobenefit
fromexperimentalandmodelstudiesonmarineplasticaggregation, fragmentation,
andbiofouling.
5.2 Comparing theModels:WhatModel forWhich
Question?
Intheprevioussections,wedescribeddifferentcategoriesofmodels indetail.Here,
webrieflydiscusswhat categoryofmodel is needed forwhich typeof questionor
application. In essence, this categorization does not differ from that for soluble
chemicals or engineerednanomaterials.
For emission-based regional estimates of environmental concentrations of plas-
ticdebris,massbalance,massflow,andespeciallymechanisticmultimediamodels
are adequate. Recently, for nanoparticles suchmodels have been developed, like
the SB4N model [63, 72, 73] and the MendNano model [106]. It is highly
recommended that suchmechanisticmultimediamodels are adapted for plastic as
well.Beingneither temporalnor spatiallyexplicit, suchmodels are screening level
models that can be used to assess relative concentrations among classes of nano-
and microplastics or among plastic emission scenarios. Hence, such models are
useful tocalculate regionalaverageorbackgroundconcentrations (PECs,predicted
environmental concentrations) for different plastic types, for different regions, or
fordifferent futureemissionscenarios.Multimediaparticlemodelscanalsobeused
todetect theparameters towhich themodel output ismost sensitiveor toquantify
uncertainty in PECs, which than can be applied in probabilistic risk assessments
(discussedbelow).
Comparedtotheoutputprovidedbymultimediamodels,morerealisticestimates
of local environmental fate and concentrations can be obtainedwith spatiotempo-
rally explicit models. However, fate models that are spatially explicit only yield
betterestimates ifdataonspatialvariability inemission intensitiesareavailable.At
present, there is only limited information on such spatial variation. Furthermore,
estimating regional average concentrations still requires definition of what is
defined as “a region.”Differentmodels use different scales,whichmeans that the
research question defineswhatmodel ismost adequate. Global rivermodels like
Modeling theFate andTransport of PlasticDebris inFreshwaters:Reviewand. . . 143
Freshwater Microplastics
Emerging Environmental Contaminants?
- Title
- Freshwater Microplastics
- Subtitle
- Emerging Environmental Contaminants?
- Authors
- Martin Wagner
- Scott Lambert
- Publisher
- Springer Open
- Date
- 2018
- Language
- English
- License
- CC BY 4.0
- ISBN
- 978-3-319-61615-5
- Size
- 15.5 x 24.1 cm
- Pages
- 316
- Categories
- Naturwissenschaften Chemie