Page - 93 - in Freshwater Microplastics - Emerging Environmental Contaminants?

aquatic animals. InTaihuLake, recoveredmicroplasticswere found inavarietyof colors including transparent, black, white, red, yellow, green, and blue [31]. In addition, blue was the most dominant color in plankton net and surface water samples, while whitemicroplastics were themost abundant in sediments [31]. In the freshwaters ofWuhan,microplastics were found to be transparent or in blue, purple, red, or other colors, and coloredmicroplastics, accounting for 50.4–86.9% of the totalmicroplastics,weremoreabundant than transparentones [32].Fromthe estuaries of Jiaojiang, Oujiang, and Minjiang, microplastics were divided into transparent, white, black, and colored groups, and colored microplastics were identified as the most dominant [34]. It may be interesting to investigate further howcoloraffects theenvironmental fateandecologicaleffectsofmicroplastics.As an example, colorants can often influence the final thermal andUV stability of a plasticmaterial [60, 61]. 3.2.4 SurfaceTexture Once entering the environment, plastics are subject to weathering processes, and these processes will influence the surface of the microplastics (Fig. 2). Featured surface textures onmicroplastics canbeused to indicate theprocesses ofmechan- icalandoxidativeweathering[62,63].Surface texturesareusuallyexaminedusing SEM.Featuressuchasgrooves, fractures,andmechanicalpitsarebelievedtoresult frommechanical weathering,while flakes, granules, and solution pits are consid- eredasoxidativeweathering features [43].Thesurfaceoxidationofplasticscanbe confirmedusingFTIRas indicatedby theappearanceofpeaks for carbonylgroups [31, 43].Zhanget al. [23] examined the surface textures ofmicroplastics from the lakeshore sediments of the Siling Co basin, and mechanical weathering features weremoreoftenobserved,whichwereattributed to thewindyweathercondition in the studyarea.This result agreeswith theoverall trendofmicroplastics recovered fromtheGreatLakes,butdiffers fromthose recovered frombeachsands inHawaii [43,63].Hawaiihasawarmerandmorehumidclimate thannorthernTibet and the Great Lakes region and might therefore favor the oxidative weathering of the plastics. 3.3 PolymerTypesFound A variety of polymers were used in the production of plastics. Properties and performances of the plastic materials are largely determined by the polymer types they are made of. Thus, polymer types can have a great impact on the longevity and buoyancy ofmicroplastics, thus affecting their fate in the environ- ment. Polymer types are typically identifiedusingFTIRandRaman spectrometry, and less often pyrolysis-gas chromatography/mass spectrometry (Pyr-GC/MS) is used [64, 65]. Detailed reviews of the typically used techniques for the Microplastic Pollution in InlandWaters FocusingonAsia 93