Instrumental analysis of microplastics-benefits and challenges

There is a high demand for easy, cheap, comparable, and robust methods for microplastic (MP) analysis, due to the ever-increasing public and scientific interest in (micro-) plastic pollution in the environment. Today, a multitude of methodologies for sampling, sample preparation, and analysis of MPs are in use. This feature article deals with the most prominent detection methods as well as with sampling strategies and sample preparation techniques. Special emphasis is on their benefits and challenges. Thus, spectroscopic methods, coupled with microscopy, require time-consuming sample preparation and extended measurement times, whereas thermo-analytical methods are faster but lack the ability to determine the size distribution in samples. To that effect, most of the described methods are applicable depending on the defined analytical question.

Sven Huppertsberg, Thomas P. Knepper, Analytical and Bioanalytical Chemistry, , Volume 410, Issue 25, pp 6343–6352

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Influence of Nano- and Microplastic Particles on the Transport and Deposition Behaviors of Bacteria in Quartz Sand

Plastic particles are world widely present in natural environment and are highly likely to interact with bacteria (the ubiquitous microbes in natural environment), which might affect the transport and deposition of bacteria in porous media. In this study, the significance of plastic particles from nano-scale to micron-scale (0.02-2 μm) on the transport and deposition behaviors of bacteria (Escherichia coli) in quartz sand was examined under environmentally relevant conditions in both NaCl and CaCl2 solutions at pH 6. The results showed that the presence of different-sized plastic particles did not affect bacterial transport behaviors at low ionic strength (10 mM NaCl and 1 mM CaCl2), whereas, at high ionic strength conditions (50 mM NaCl and 5 mM in CaCl2), plastic particles increased bacterial transport in quartz sand. At low ionic strength conditions, the mobility of both plastic particles and bacteria was high, which might drive to the negligible effects of plastic particles on bacterial transport behaviors. The mechanisms driving to the enhanced cell transport at high ionic strength were different for different-sized plastic particles. Specifically, for 0.02 μm nano-plastic particles, the adsorption of plastic particles onto cell surfaces and the repel effect induced by suspended plastic particles contributed to the increased cell transport. As for 0.2 μm MPs, the suspended plastic particles that induced repelling effect contributed to the increased cell transport. Whereas, for 2 μm MPs, the competition deposition sites by the plastic particles was the contributor to the increased cell transport.

HE LEI, Dan Wu, Haifeng Rong, Meng Li, Meiping Tong, and Hyunjung Kim, Environ. Sci. Technol., Just Accepted Manuscript, September 11, 2018

Nanoplastic Ingestion Enhances Toxicity of Persistent Organic Pollutants (POPs) in the Monogonont Rotifer Brachionus koreanus via Multixenobiotic Resistance (MXR) Disruption

Among the various materials found inside microplastic pollution, nanosized microplastics are of particular concern due to difficulties in quantification and detection; moreover, they are predicted to be abundant in aquatic environments with stronger toxicity than microsized microplastics. Here, we demonstrated a stronger accumulation of nanosized microbeads in the marine rotifer Brachionus koreanus compared to microsized ones, which was associated with oxidative stress-induced damages on lipid membranes. In addition, multixenobiotic resistance conferred by P-glycoproteins and multidrug resistance proteins, as a first line of membrane defense, was inhibited by nanoplastic pre-exposure, leading to enhanced toxicity of 2,2′,4,4′-tetrabromodiphenyl ether and triclosan in B. koreanus. Our study provides a molecular mechanistic insight into the toxicity of nanosized microplastics toward aquatic invertebrates and further implies the significance of synergetic effects of microplastics with other environmental persistent organic pollutants.

Chang-Bum Jeong, Hye-Min Kang, Young Hwan Lee and al., Environ. Sci. Technol., Article ASAP, September 7, 2018

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Distribution of Microplastics and Nanoplastics in Aquatic Ecosystems and Their Impacts on Aquatic Organisms, with Emphasis on Microalgae

Plastics, with their many useful physical and chemical properties, are widely used in various industries and activities of daily living. Yet, the insidious effects of plastics, particularly long-term effects on aquatic organisms, are not properly understood. Plastics have been shown to degrade to micro- and nanosize particles known as microplastics and nanoplastics, respectively. These minute particles have been shown to cause various adverse effects on aquatic organisms, ranging from growth inhibition, developmental delay and altered feeding behaviour in aquatic animals to decrease of photosynthetic efficiency and induction of oxidative stress in microalgae. This review paper covers the distribution of microplastics and nanoplastics in aquatic ecosystems, focusing on their effects on microalgae as well as co-toxicity of microplastics and nanoplastics with other pollutants. Besides that, this review paper also discusses future research directions which could be taken to gain a better understanding of the impacts of microplastics and nanoplastics on aquatic ecosystems.

Jun-Kit Wan, Wan-Loy Chu, Yih-Yih Kok, Choy-Sin Lee, Chapter, Part of the Reviews of Environmental Contamination and Toxicology book series, Springer

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Toxicities of polystyrene nano- and microplastics toward marine bacterium Halomonas alkaliphila

Nano- and microplastics have been shown to cause negative effects on marine organisms. However, the toxicities of nano- and microplastics toward marine bacteria are poorly understood. In this study, we investigated the toxic effects of polystyrene nano- and microplastics on the marine bacterium Halomonas alkaliphila by determining growth inhibition, chemical composition, inorganic nitrogen conversion efficiencies and reactive oxygen species (ROS) generation. The results showed that both nano- and microplastics inhibited the growth of H. alkaliphila in high concentrations, while nanoplastics rather than microplastics influenced the growth inhibition, chemical composition and ammonia conversion efficiencies of H. alkaliphila at concentration of 80 mg/L. The ROS generation indicated oxidative stress induced by nano- but not microplastics, and the oxidative stress induced by nanoplastics may provide a significant effect on bacteria. Furthermore, the positively charged nanoplastics (amine-modified 50 nm) induced higher oxidative stress toward bacteria than that induced by negatively charged nanoplastics (non-modified 55 nm). The increased extracellular polymeric substances as evidenced by transmission electron microscope (TEM) observation suggested the possible bacterial protective mechanisms. The present study illustrates for the first time the impact of plastics debris on the inorganic nitrogen conversion efficiencies of marine bacteria. Our findings highlight the effects of microplastics on the ecological function of marine organisms.

Xuemei Sun, Bijuan Chen, Qiufen Li, Nan Liu, Bin Xia, Lin Zhu, Keming Qu, Science of The Total Environment, Volume 642, 15 November 2018, Pages 1378–1385

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Styrene impairs normal embryo development in the Mediterranean mussel (Mytilus galloprovincialis)

This study analysed the effects of styrene, a main monomer in plastic manufacturing and acknowledged to be amongst the most common plastic leachates, on early embryo development of the Mediterranean mussel. Embryotoxicity tests showed that styrene impaired normal embryo development at concentrations (0.01 μg/L–1 mg/L) encompassing the environmental range. Occurrence of normal D-veligers was significantly reduced up to 40% of the total, and larval size was reduced of about 20%. D-veligers grown in the presence of styrene (0.1 and 10 μg/L) showed significant reduction of total Multixenobiotic resistance (MXR) efflux activity that was not apparently related to transcriptional expression of genes encoding P-glycoprotein (ABCB) and Mrp (ABCC), the two main ABC transporters of embryonal MXR system. Indeed, ABCB transcription was not affected by styrene, while ABCC was up-regulated. At these same concentrations, transcriptional profiles of 15 genes underlying key biological functions in embryo development and potential targets of adverse effects of styrene were analysed. Main transcriptional effects were observed for genes involved in shell biogenesis and lysosomal responses (down-regulation), and in neuroendocrine signaling and immune responses (up-regulation). On the whole, results indicate that styrene may affect mussel early development through dysregulation of gene transcription and suggest the possible conservation of styrene mode of action across bivalve life cycle and between bivalves and humans, as well as through unpredicted impacts on protective systems and on shell biogenesis.

Rajapaksha Haddokara Gedara Rasika Wathsala, Silvia Franzellitti, Morena Scaglione,
Elena Fabbri, Aquatic Toxicology, Volume 201, August 2018, Pages 58-65

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Turning microplastics into nanoplastics through digestive fragmentation by Antarctic krill

Microplastics (plastics <5 mm diameter) are at the forefront of current environmental pollution research, however, little is known about the degradation of microplastics through ingestion. Here, by exposing Antarctic krill (Euphausia superba) to microplastics under acute static renewal conditions, we present evidence of physical size alteration of microplastics ingested by a planktonic crustacean. Ingested microplastics (31.5 µm) are fragmented into pieces less than 1 µm in diameter. Previous feeding studies have shown spherical microplastics either; pass unaffected through an organism and are excreted, or are sufficiently small for translocation to occur. We identify a new pathway; microplastics are fragmented into sizes small enough to cross physical barriers, or are egested as a mixture of triturated particles. These findings suggest that current laboratory-based feeding studies may be oversimplifying interactions between zooplankton and microplastics but also introduces a new role of Antarctic krill, and potentially other species, in the biogeochemical cycling and fate of plastic.

Amanda L. Dawson, So Kawaguchi, Catherine K. King, Kathy A. Townsend, Robert King, Wilhelmina M. Huston, Susan M. Bengtson Nash ,Nature Communications, volume 9, Article number: 1001, 2018

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