Analytical Methods And Distribution Characteristics Of Microplastics In Typically Marine Commercial Organisms

Microplastics?defined as particles<5 mm in diameter?in the marine environment has received a lot of attention as an emerging pollutant.Microplastics would be ingested by marine organisms due to their smaller particle sizes.Ingested microplastics would enrich and transfer from low-level organisms to high-level organisms along the food chain and might eventually affect human health.A pretreatment method was established for separating microplastics from marine organisms.Successive stereo microscopy and micro-Fourier transform infrared spectroscopy equipped with attenuated total reflection??-ATR-FT-IR?in combination with scanning electron microscopy-energy dispersive spectroscopy?SEM-EDS?were implemented to optimize the microplastics detection system.This method was applied to detect microplastics in marine commercial organisms.The relationship between the integrated characteristics of microplastics in typically marine commercial shellfish and regional,species and seasonal differences were discussed preliminarily.1)Separation and detection methods for microplastics in marine commercial organismsIn this study,10%KOH solution in combination with hot filtration were established for separating microplastics from marine commercial organisms.We found 10%KOH digestion system had higher digestion efficiency.With this digestion system,the recoveries of polypropylene?PP?,polyethylene?PE?,polystyrene?PS?and polyvinyl chloride?PVC?ranged from 96.7%to 98.6%,with relative standard deviation?RSD,n=3?of?3.2%.This method had the advantages of simple,high efficiency,low damage to microplastics in the sample,and could meet the detection requirement.Successive stereo microscopy and?-ATR-FT-IR in combination with SEM-EDS were implemented to optimize the multi-technology system for microplastics detection.The combination method could provide a guarantee for the accuracy of microplastic identification results.The separation and detection technology were implemented to analyze microplastics in both the soft tissue and the digestive tract of bivalves and fish collected from the markets in Qingdao and Dongying.The distribution characteristics of microplastics in the marine organisms were analyzed,and the surface morphology of ingested microplastics was characterized.This combining multiple technologies successfully eliminated non-plastic particles ingested by marine organisms.The applicability of the separation and identification technology was further verified.2)Microplastics distribution characteristics in typically marine commercial shellfishIn order to investigate the accumulation of microplastics in commercial marine shellfish,microplastics in the Chlamys farreri?Mytilus galloprovincialis?Crassostrea gigas and Ruditapes philippinarum sampled from 5 markets of Qingdao were detected.Microplastics were observed in over 62.5%of bivalve samples.The average abundance of microplastics in different bivalves purchased from different markets varied between 0.9 and 19.4 items/individual or between 1.3 and 21.1 items g^?1?wet weight of the digestive system?.More granular microplastics were found in the R.philippinarum than other three bivalves which contained more fibrous microplastics.White microplastics were predominant in the R.philippinarum,while black microplastics were dominant in other three bivalves.Microplastics of less than 500?m coming from different bivalves were dominated.The number of microplastics decreased with increasing microplastics sizes.The most common polymer type of microplastics in the bivalve samples was rayon.The morphology of fibrous microplastics ingested by bivalves exhibited heterogeneity of rough surface and scratches.Oxygen-containing functional groups were formed on the surface of some microplastics.Microplastics in 7 kinds of marine commercial shellfish sampled from both the Qingdao City of Shandong Province and the Xiamen City of Fujian Province were detected.Microplastics were observed in over 70%of shellfish samples.The average abundance of microplastics in different bivalves from Qingdao varied between 1.2and 4.1 items/individual or between 0.8 and 4.4 items/g?wet weight of the digestive system?,while those in the shellfish from Xiamen ranged from 1.3 to 6.0items/individual and from 2.1 to 4.0 items/g.Most shellfish species ingested the fibrous microplastics and the black,white and transparent microplastics.The number of microplastics decreased with increasing microplastics sizes.Microplastics of less than 500?m were in the range of 22.7%to 66.7%.The popular microplastics polymer types were rayon and polyethylene terephthalate?PET?in the shellfish sampled from Qingdao,while the predominant microplastics polymer types in the shellfish sampled from Xiamen were rayon and polyvinylidene fluoride?PVDF?.The characteristics of surface morphology were different between the PET fiber and rayon fiber.3)Statistical analysis based on the integrated characteristics of microplastics ingested by shellfish1)The correlation of integrated characteristics of microplastics between Cr.gigas and Ch.farreri or R.philippinarum or M.galloprovincialis was high.According to the results of pairwise comparisons,we found that these correlation coefficients were greater than or equal to 0.5 accounting for 100%,92%,and 84%,respectively.The correlation of integrated characteristics of microplastics between R.philippinarum and M.galloprovincialis or Ch.farreri was low.The pairwise comparisons indicated that correlation coefficients were greater than or equal to 0.5accounting for 32%and 48%,respectively.2)The regional differences of integrated characteristics of microplastics in R.philippinarum,Meretrix lusoria,Scapharca subcrenata,mussel,and Busycon canaliculatu were more obvious.3)The seasonal variations of integrated characteristics of microplastics in M.galloprovincialis and Cr.gigas were more obvious.Mussel showed distinctly regional and seasonal variations.Hence,mussel could be used as a bioindicator of marine microplastics pollution.In conclusion,the microplastics pollution level in marine commercial organisms were revealed in this study.The relationship between the microplastics characteristics in typically marine commercial shellfish and regional,species,and seasonal differences were analyzed from the perspective of integrated characteristics of microplastics,including shape,color,size,and polymer type.The aim of this study is to provide technical support for marine microplastics environmental/ecological risk assessment and to provide basic data for the assessment of microplastics contamination and seafood safety in marine organisms.