Optimization, performance, and application of a pyrolysis-GC/MS method for the identification of microplastics

Plastics are found to be major debris composing marine litter; microplastics (MP, < 5 mm) are found in all marine compartments. The amount of MPs tends to increase with decreasing size leading to a potential misidentification when only visual identification is performed. These last years, pyrolysis coupled with gas chromatography/mass spectrometry (Py-GC/MS) has been used to get information on the composition of polymers with some applications on MP identification. The purpose of this work was to optimize and then validate a Py-GC/MS method, determine limit of detection (LOD) for eight common polymers, and apply this method on environmental MP. Optimization on multiple GC parameters was carried out using polyethylene (PE) and polystyrene (PS) microspheres. The optimized Py-GC/MS method require a pyrolysis temperature of 700 °C, a split ratio of 5 and 300 °C as injector temperature. Performance assessment was accomplished by performing repeatability and intermediate precision tests and calculating limit of detection (LOD) for common polymers. LODs were all below 1 μg. For performance assessment, identification remains accurate despite a decrease in signal over time. A comparison between identifications performed with Raman micro spectroscopy and with Py-GC/MS was assessed. Finally, the optimized method was applied to environmental samples, including plastics isolated from sea water surface, beach sediments, and organisms collected in the marine environment. The present method is complementary to μ-Raman spectroscopy as Py-GC/MS identified pigment containing particles as plastic. Moreover, some fibers and all particles from sediment and sea surface were identified as plastic.

Ludovic Hermabessiere, Charlotte Himber, Béatrice Boricaud, Maria Kazour, Rachid Amara, Anne-Laure Cassone, Michel Laurentie, Ika Paul-Pont, Philippe Soudant, Alexandre Dehaut, Guillaume Duflos, Analytical and Bioanalytical Chemistry, , Volume 410, Issue 25, pp 6663–6676

The article


Microplastic pollution on Caribbean beaches in the Lesser Antilles

Here we investigate microplastics contamination on beaches of four islands of the Lesser Antilles (Anguilla, St. Barthélemy, St. Eustatius and St. Martin/Maarten). These islands are close to the North Atlantic subtropical gyre, which contains high levels of microplastics. On average 261 ± 6 microplastics/kg of dry sand were found, with a maximum of 620 ± 96 microplastics on Grandes Cayes, Saint Martin. The vast majority of these microplastics (>95%) were fibers. Levels of microplastics differed among islands, with significantly lower levels found in St. Eustatius compared to the other Islands. No difference in microplastic levels was found between windward and leeward beaches. Our research provides a detailed study on microplastics on beaches in the Lesser Antilles. These results are important in developing a deeper understanding of the extent of the microplastic challenge within the Caribbean region, a hotspot of biodiversity.

Thijs Bosker, Lucia Guaita, Paul Behrens, Marine Pollution Bulletin, Volume 133, August 2018, Pages 442–447

The article

Microplastics in mussels sampled from coastal waters and supermarkets in the United Kingdom

Global contamination of the marine environment by plastic has led to the discovery of microplastics in a range of marine species, including those for human consumption. In this study, the presence of microplastics and other anthropogenic debris in seawater and mussels (Mytilus edulis) from coastal waters of the U.K., as well as supermarket sources, was investigated. These were detected in all samples from all sites with spatial differences observed. Seawater samples taken from 6 locations (in triplicates) displayed 3.5 ± 2.0 debris items/L on average (range: 1.5–6.7 items/L). In wild mussels sampled from 8 locations around the U.K. coastal environment, the number of total debris items varied from 0.7 to 2.9 items/g of tissue and from 1.1 to 6.4 items/individual. For the supermarket bought mussels, the abundance of microplastics was significantly higher in pre-cooked mussels (1.4 items/g) compared with mussels supplied live (0.9 items/g). Micro-FT-IR spectroscopy was conducted on 136 randomly selected samples, with 94 items characterized. The spectra found that 50% of these debris items characterized were microplastic, with an additional 37% made up of rayon and cotton fibers. The microplastic levels detected in the supermarket bought mussels present a route for human exposure and suggests that their quantification be included as food safety management measures as well as for environmental monitoring health measures.

J. Li, C. Green, A. Reynolds and al., Environmental Pollution, Volume 241, October 2018, Pages 35–44

The article

Separation and Identification of Microplastics in Digestive System of Bivalves

A pretreatment method was established for separating microplastics from digestive system of bivalve sample. Qualitative and quantitative analysis of microplastics was carried out by micro-Fourier transformed infrared (μ-FT-IR) spectroscope and Stereo microscope. The method was applied to analyze the microplastics in the digestive system in Chlamys farreri and Mytilus galloprovincialis. The results showed that the digestion system of using 10% KOH had high 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 ≤ 3.19%. We collected Chlamys farreri from local markets (n = 50) and Mytilus galloprovincialis from both local markets (n = 50) and wild environments (n = 15) in Qingdao, China. The results showed that microplastics were found in over 80% of the individuals purchased from the market and 40% of the wild collected individuals. The average abundance of microplastics in Chlamys farreri purchased from different markets varied between 5.2 and 19.4 items/individual or between 3.2 and 7.1 items g−1 (wet weight of digestive system), while in Mytilus galloprovincialis, the numbers varied between 1.9 and 9.6 items/individual or between 2.0 and 12.8 items g−1. Farmed mussels (Mytilus galloprovincialis) contained more microplastics (average 1.9 items per individual, 3.17 items g−1) than wild mussels (average 0.53 items individual, 2.0 items g−1). Three shapes of microplastics, including fibers, fragments and granules were separated from the samples above. Among which, fibrous microplastics, being the most dominant ones, took up 84.11% of total microplastics. The average size of fibrous microplastics ((0.66 ± 0.70) mm) was larger than that of the other two shapes of microplastics. The number of microplastics decreased with increasing microplastic sizes. Microplastics of less than 500 μm coming from different markets were in the range of 26% to 84%. And it was found that the most common polymer component in the samples was cellophane (CP), followed by polypropylene (PP). The method has some advantages such as simplicity, high efficiency, and low damage to the microplastics in the sample, and can be used to detect and analyze microplastics in seafood.

J. F. Ding, J. X. Li, C. J. Sun and al., Chinese Journal of Analytical Chemistry, Volume 46, Issue 5, May 2018, Pages 690-697

The article

Spatial occurrence and effects of microplastic ingestion on the deep-water shrimp Aristeus antennatus

Microplastic (MP) ingestion has been reported in a wide variety of organisms, however, its spatial occurrence and effects on wild populations remain quite unknown. The present study targets an economically and ecologically key species in the Mediterranean Sea, the shrimp Aristeus antennatus. 39.2% of the individuals sampled had MP in their stomachs, albeit in areas close to Barcelona city the percentage reached values of 100%. Overall, MP ingestion was confirmed in a wide spatial and depth (630–1870 m) range, pointing out the great dispersion of this pollutant. The benthophagous diet and close relationship with the sea bottom of A. antennatus might enhance MP exposure and ultimately lead to accidental ingestion. Detailed analysis of shrimps’ diet revealed that individuals with MP had a higher presence of endobenthic prey. Microplastic fibers are probably retained for long periods due to stomach’s morphology, but no negative effects on shrimp’s biological condition were observed.

E. Carreras-Colom, M. Constenla, A. SolerMembrives and al., Marine Pollution Bulletin, Volume 133, August 2018, Pages 44-52

The article

Sticky tape and simulations help assess microplastic risk

Tiny pieces of plastic, now ubiquitous in the marine environment, have long been a cause of concern for their ability to absorb toxic substances and potentially penetrate the food chain. Now scientists are beginning to understand the level of threat posed to life, by gauging the extent of marine accumulation and tracking the movement of these contaminants. (…)

N. Grover, Horizon EU magazine, 23/04/2018

The news

Two forage fishes as potential conduits for the vertical transfer of microfibres in Northeastern Pacific Ocean food webs

We assessed the potential role played by two vital Northeastern Pacific Ocean forage fishes, the Pacific sand lance (Ammodytes personatus) and Pacific herring (Clupea pallasii), as conduits for the vertical transfer of microfibres in food webs. We quantified the number of microfibres found in the stomachs of 734 sand lance and 205 herring that had been captured by an abundant seabird, the rhinoceros auklet (Cerorhinca monocerata). Sampling took place on six widely-dispersed breeding colonies in British Columbia, Canada, and Washington State, USA, over one to eight years. The North Pacific Ocean is a global hotspot for pollution, yet few sand lance (1.5%) or herring (2.0%) had ingested microfibres. In addition, there was no systematic relationship between the prevalence of microplastics in the fish stomachs vs. in waters around three of our study colonies (measured in an earlier study). Sampling at a single site (Protection Island, WA) in a single year (2016) yielded most (sand lance) or all (herring) of the microfibres recovered over the 30 colony-years of sampling involved in this study, yet no microfibres had been recovered there, in either species, in the previous year. We thus found no evidence that sand lance and herring currently act as major food-web conduits for microfibres along British Columbia’s outer coast, nor that the local at-sea density of plastic necessarily determines how much plastic enters marine food webs via zooplanktivores. Extensive urban development around the Salish Sea probably explains the elevated microfibre loads in fishes collected on Protection Island, but we cannot account for the between-year variation. Nonetheless, the existence of such marked interannual variation indicates the importance of measuring year-to-year variation in microfibre pollution both at sea and in marine biota.

J. M. Hipfner, M. Galbraith, S. Tucker and al., Environmental Pollution, Volume 239, August 2018, Pages 215-222

The article