Analysis of environmental microplastics by vibrational microspectroscopy: FTIR, Raman or both?

The contamination of aquatic ecosystems with microplastics has recently been reported through many studies, and negative impacts on the aquatic biota have been described. For the chemical identification of microplastics, mainly Fourier transform infrared (FTIR) and Raman spectroscopy are used. But up to now, a critical comparison and validation of both spectroscopic methods with respect to microplastics analysis is missing. To close this knowledge gap, we investigated environmental samples by both Raman and FTIR spectroscopy. Firstly, particles and fibres >500 μm extracted from beach sediment samples were analysed by Raman and FTIR microspectroscopic single measurements. Our results illustrate that both methods are in principle suitable to identify microplastics from the environment. However, in some cases, especially for coloured particles, a combination of both spectroscopic methods is necessary for a complete and reliable characterisation of the chemical composition. Secondly, a marine sample containing particles <400 μm was investigated by Raman imaging and FTIR transmission imaging. The results were compared regarding number, size and type of detectable microplastics as well as spectra quality, measurement time and handling. We show that FTIR imaging leads to significant underestimation (about 35 %) of microplastics compared to Raman imaging, especially in the size range <20 μm. However, the measurement time of Raman imaging is considerably higher compared to FTIR imaging. In summary, we propose a further size division within the smaller microplastics fraction into 500–50 μm (rapid and reliable analysis by FTIR imaging) and into 50–1 μm (detailed and more time-consuming analysis by Raman imaging).

Andrea Käppler, Dieter Fischer, Sonja Oberbeckmann, Gerald Schernewski, Matthias Labrenz, Klaus-Jochen Eichhorn, Brigitte Voit, Analytical and Bioanalytical Chemistry, pp 1–15, 8 October 2016

The article

Distribution of small plastic fragments floating in the western Pacific Ocean from 2000 to 2001

Sampling was conducted at 31 sites in the western Pacific Ocean from 2000 to 2001 with the aim of collecting plastic fragments with a neuston net (mesh size 1.00 mm × 1.64 mm). Small plastic fragments including microplastics (small fragments in the size range of 1.1–41.8 mm) were collected at multiple survey sites. Waters with high densities of small fragments were observed between 20°N and 30°N to the south of Japan and between 20S and 30S to the northeast of New Zealand (maxima of 6.63 × 102 and 2.03 × 102 pieces/ha, respectively). These waters are located to the west of the Ekman convergence zones related to trade winds in the subtropical gyres of the North and South Pacific Oceans. Nearly no small plastics were observed in the tropical circulation of the western Pacific Ocean.

Keiichi Uchida, Ryuichi Hagita, Toshifumi Hayashi, Tadashi Tokai, Fisheries Science, pp 1–6, 7 October 2016

The article

Mapping marine debris across coastal communities in Belize: developing a baseline for understanding the distribution of litter on beaches using geographic information systems

Monitoring of marine debris (also known as marine litter) is an essential step in the process to eradicate ecological dangers in marine ecosystems caused by humans. This study examines marine debris in the Caribbean country of Belize using geographic information systems (GIS) to develop (1) a detailed data library for use on handheld Global Positioning System (GPS) units and tablets with mobile mapping applications for deployment in the field and (2) a freely available, online mapping portal to share data with Belizeans to encourage future citizen science efforts. Four diverse communities were targeted ranging from larger more populated towns, to smaller villages across central and southern Belize: San Pedro, Caye Caulker, Punta Gorda, and Monkey River. Fieldwork was conducted over 1 month, during which data points were collected in 50-m surveys followed by debris cleanup and removal. Features in our database included material, quantity, item, brand, and condition. Over 6000 pieces of debris were recorded in GIS for further analysis, and 299 gal of debris were removed from the shores of Belize. The most abundant form of debris observed was plastic (commonly bottles) across all locations; plastic comprised 77.6 % of all debris items observed. Through GIS, a detailed snapshot understanding of debris patterns across multiple settings in Belize was documented. Ongoing collaborations with local organizations in Belize have demonstrated significant interest and utility for such GIS approaches in analyzing and managing marine debris. The data, methodology, visual representations, and online mapping platform resulting from this research are a first step in directly supporting local Belizean community advocacy and policy, while contributing to larger institutional strategies for addressing marine debris issues in the Caribbean.

Paulita Bennett-Martin, Christy C. Visaggi, Timothy L. Hawthorne, Environmental Monitoring and Assessment, October 2016, 188:557

Large microplastic particles in sediments of tributaries of the River Thames, UK – Abundance, sources and methods for effective quantification

Sewage effluent input and population were chosen as predictors of microplastic presence in sediments at four sites in the River Thames basin (UK). Large microplastic particles (1 mm–4 mm) were extracted using a stepwise approach to include visual extraction, flotation and identification using Raman spectroscopy. Microplastics were found at all four sites. One site had significantly higher numbers of microplastics than other sites, average 66 particles 100 g− 1, 91% of which were fragments. This site was downstream of a storm drain outfall receiving urban runoff; many of the fragments at this site were determined to be derived of thermoplastic road-surface marking paints. At the remaining three sites, fibres were the dominant particle type. The most common polymers identified included polypropylene, polyester and polyarylsulphone. This study describes two major new findings: presence of microplastic particles in a UK freshwater system and identification of road marking paints as a source of microplastics.

Alice A. Horton, Claus Svendsen, Richard J. Williams, David J. Spurgeon, Elma Lahive, Marine Pollution Bulletin, Available online 28 September 2016, In Press

The article

Microplastics in the Southern Ocean

A field survey to collect microplastics with sizes < 5 mm was conducted in the Southern Ocean in 2016. We performed five net-tows and collected 44 pieces of plastic. Total particle counts of the entire water column, which is free of vertical mixing, were computed using the surface concentration (particle count per unit seawater volume) of microplastics, wind speed, and significant wave height during the observation period. Total particle counts at two stations near Antarctica were estimated to be in the order of 100,000 pieces km− 2.

Atsuhiko Isobe, Kaori Uchiyama-Matsumoto, Keiichi Uchida, Tadashi Tokai, Marine Pollution Bulletin, Available online 26 September 2016, In Press

The article

Microplastic fragments and microbeads in digestive tracts of planktivorous fish from urban coastal waters

We investigated microplastics in the digestive tracts of 64 Japanese anchovy (Engraulis japonicus) sampled in Tokyo Bay. Plastic was detected in 49 out of 64 fish (77%), with 2.3 pieces on average and up to 15 pieces per individual. All of the plastics were identified by Fourier transform infrared spectroscopy. Most were polyethylene (52.0%) or polypropylene (43.3%). Most of the plastics were fragments (86.0%), but 7.3% were beads, some of which were microbeads, similar to those found in facial cleansers. Eighty percent of the plastics ranged in size from 150 μm to 1000 μm, smaller than the reported size range of floating microplastics on the sea surface, possibly because the subsurface foraging behavior of the anchovy reflected the different size distribution of plastics between surface waters and subsurface waters. Engraulis spp. are important food for many humans and other organisms around the world. Our observations further confirm that microplastics have infiltrated the marine ecosystem, and that humans may be exposed to them. Because microplastics retain hazardous chemicals, increase in fish chemical exposure by the ingested plastics is of concern. Such exposure should be studied and compared with that in the natural diet.

Kosuke Tanaka & Hideshige Takada, Scientific Reports 6, Article number: 34351 (2016)

The article