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Critical Review
Microplastics and Nanoplastics in Aquatic Environments: Aggregation, Deposition, and Enhanced Contaminant Transport Olubukola Alimi, Jeffrey Farner Budarz, Laura M Hernandez, and Nathalie Tufenkji Environ. Sci. Technol., Just Accepted Manuscript • DOI: 10.1021/acs.est.7b05559 • Publication Date (Web): 21 Dec 2017 Downloaded from http://pubs.acs.org on December 22, 2017
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Microplastics and Nanoplastics in Aquatic
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Environments: Aggregation, Deposition, and Enhanced
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Contaminant Transport
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Olubukola S Alimi, Jeffrey Farner Budarz, Laura M Hernandez, Nathalie
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Tufenkji*
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Department of Chemical Engineering, McGill University,
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Montreal, Quebec, Canada H3A 0C5
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Corresponding Author. Phone: (514) 398-2999; Fax: (514) 398-6678; E-mail:
[email protected] 20
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Abstract
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Plastic litter is widely acknowledged as a global environmental threat and poor
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management and disposal lead to increasing levels in the environment. Of recent concern
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is the degradation of plastics from macro- to micro- and even to nanosized particles
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smaller than 100 nm in size. At the nanoscale, plastics are difficult to detect and can be
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transported in air, soil and water compartments. While the impact of plastic debris on
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marine and fresh waters and organisms has been studied, the loads, transformations,
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transport, and fate of plastics in terrestrial and subsurface environments are largely
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overlooked. In this review, we first present estimated loads of plastics in different
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environmental compartments. We also provide a critical review of the current knowledge
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vis-à-vis nanoplastic (NP) and microplastic (MP) aggregation, deposition, and
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contaminant co-transport in the environment. Important factors that affect aggregation
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and deposition in natural subsurface environments are identified and critically analyzed.
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Factors affecting contaminant sorption onto plastic debris are discussed, and we show
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how polyethylene generally exhibits a greater sorption capacity than other plastic types.
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Finally, we highlight key knowledge gaps that need to be addressed to improve our
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ability to predict the risks associated with these ubiquitous contaminants in the
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environment by understanding their mobility, aggregation behavior and their potential to
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enhance the transport of other pollutants.
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1.0 Introduction
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Currently, the global production of plastics exceeds 320 million tons (Mt) per year,1 with
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production expected to double in the next 20 years.2 Of this, only 6-14% is recycled,
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meaning up to 86% ends up either in landfills (21–42%) or released into the environment
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due to mismanagement through a variety of pathways (Figure 1).2-6 Indeed, with the
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widespread use of different plastics, the current era has been referred to as the
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Plasticene.7 Plastic debris has been detected in air,8 oceans,5, 9, 10 soils,11-13 sediments,14, 15
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and surface waters worldwide.16 It is estimated that in Europe and North America, the
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amount of microplastics (MPs) transferred every year from wastewater treatment plants
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(WWTPs) to agricultural soils as biosolids is greater than the total burden of MPs
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currently present in ocean water.3
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Plastics are produced through the polymerization of various monomers and additives
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resulting in a spectrum of characteristics such as polarity and “glassiness”.17, 18 These
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differences in composition will impact their affinity for other pollutants and potential
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risks associated with them.19 The most commonly detected plastics in the environment
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are polyethylene (PE), polyvinyl chloride (PVC), polypropylene (PP), polyethylene
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terephthalate (PET) and polystyrene (PS).20
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The presence of MPs in the environment had been largely overlooked until recently;
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however, the number of studies is now growing rapidly due to the global ubiquity of
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plastic and its potential threat to human health and biota. Large plastic debris breaks
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down to form macroplastics (herein defined as >25 mm in size), mesoplastics (5-25 mm),
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MPs (
