Characterizing the multidimensionality of microplastics across environmental compartments

Understanding the multidimensionality of microplastics is essential for a realistic assessment of the risks these particles pose to the environment and human health. Here, we capture size, shape, area, polymer, volume and mass characteristics of >60 000 individual microplastic particles as continuous distributions. Particles originate from samples taken from different aquatic compartments, including surface water and sediments from the marine and freshwater environment, waste water effluents, and freshwater organisms. Data were obtained using state-of-the-art FTIR- imaging, using the same automated imaging post-processing software. We introduce a workflow with two quality criteria that assure minimum data quality loss due to volumetric and filter area subsampling. We find that probability density functions (PDFs) for particle length follow power law distributions, with median slopes ranging from 2.2 for marine surface water to 3.1 for biota samples, and that these slopes were compartment-specific. Polymer-specific PDFs for particle length demonstrated significant differences in slopes among polymers, hinting at polymer specific sources, removal or fragmentation processes. Furthermore, we provide PDFs for particle width, width to length ratio, area, specific surface area, volume and mass distributions and propose how these can represent the full diversity of toxicologically relevant dose metrics required for the assessment of microplastic risks

Toward the systematic identification of microplastics in the environment: evaluation of a new independent software tool (siMPle) for spectroscopic analysis

Microplastics (MP) are ubiquitous within the environment, but the analysis of this contaminant is currently quite diverse, and a number of analytical methods are available. The comparability of results is hindered as even for a single analytical method such as Fourier transform infrared spectroscopy (FT-IR) the different instruments currently available do not allow a harmonized analysis. To overcome this limitation, a new free of charge software tool, allowing the systematic identification of MP in the environment (siMPle) was developed. This software tool allows a rapid and harmonized analysis of MP across FT-IR systems from different manufacturers (Bruker Hyperion 3000, Agilent Cary 620/670, PerkinElmer Spotlight 400, Thermo Fischer Scientific Nicolet iN10). Using the same database and the automated analysis pipeline (AAP) in siMPle, MP were identified in samples that were analyzed with instruments with different detector systems and optical resolutions, the results of which are discussed

Microplastic in plankton of the North- and Baltic Sea

The environmental pollution with small plastic particles was recognized in the early 70s (Carpenter & Smith 1972). Today these plastics can be found in every marine habitat and are expected to have enormous negative impacts. The smaller the items get through fragmentation the more organisms can feed on them. Zooplankters cannot discriminate while feeding and can absorb POPs or other chemicals adhered to ingested plastics which then have the potential to accumulate in the marine food chain (Cole et al 2013). The term microplastic includes all plastics smaller than 5 mm: These can be released directly as primary microplastic in cosmetics and in form of lost industrial pellets or through fragmentation of larger plastic items (secondary microplastics). Introduced in the environment, plastics cannot be mineralized, but UV- radiation and physical wave actions will lead to the embrittlement and further fragmentation of plastics. Because of this even a direct stop of plastic introduction would lead to an increasing amount of microplastics in the marine environment (Cole et al 2011). Until now nonexistent methods made the detection of microscopic plastics that are smaller than 500 µm impossible and so most of the published studies focus on the visual sorting and determination of samples taken in marine sediments or at the water surface. The new combination of micro- Fourier transform infrared spectroscopy (FTIR) with a focal plane array detector (FPA) is highly promisingly for this (Harrison et al 2012). But to enable this way of analysis a sufficient sample purification is needed that removes all disturbing natural materials without affecting the plastic particles. A method was developed that combines enzymatic digestion with density separation using a ZnCl2 solution. This method allows for the first time the examination of all microscopic plastics of complete plankton samples taken from coastal waters of the German North and Baltic Sea. Although plastic introduction from the high shipping activities and additional landbased sources can be expected in the region, there is little knowledge about large- scale planktonic microplastic concentrations. 28 stations were sampled and the total concentrations of visible and microscopic plastics determined which ranged considerably from 0 to 3.5 items m-3. An outstanding high concentration of 1.3 visible plastics m-3 and the detection of same PE pellets in 2012 and 2013 at the western coast of Denmark could suggest an accumulation zone in this area. A fact that may be supported by the findings of Galgani et al (2000) who found considerably higher plastic concentrations in an 190 large area 200 km away from the Danish coast when examining sedimented macroplastics

Quantifying the Invisible - Micro- and Nanoplastics in the Urban Water Cycle

Plastic is the common name given to a wide range of synthetic or semi-synthetic organic polymers. These polymers are lightweight, durable, and cheap which explains a global production of 359 million tonnes in 2018 (PlasticsEurope 2019). However, due to several reasons plastic items can end up in the environment where its durability eventually can cause ecological, and socio-economic harm (Galgani et al. 2013, SAPEA 2019). Special attention by science, media and policy, has been given to plastic items smaller than 5 mm, so called microplastics (MP) which, to date, can be found in almost all natural habitats (Hurley et al. 2018). It has been estimated that about 80% of the environmental plastic is released by terrestrial sources (Andrady 2011, Rochman 2018), and that riverine transport plays an important role in distributing the plastic. Over the last years, numbers of studies on (micro)plastics have increased exponentially. Still, our knowledge on occurrences and types of MP in the freshwater environment remains fragmentary. Due to the even higher analytical challenges it is yet to be determined if, how and where even smaller plastics, so called nanoplastics (NP), occur and behave in the environment. This thesis focussed on assessing the presence of MP in the urban water cycle which describes how humans get, use and re-use freshwater. Accurate data on MP types and concentrations are needed to assess their related risks, to trace back their emission sources, and to mitigate these sources. For this thesis three fields of interest were defined. After a general introduction (Chapter 1), we (i) addressed analytical requirements to accurately identify MP and NP (Chapter 2 and Chapter 3). Applying herein defined criteria, (ii) Chapter 4 and Chapter 5 contain the results of two field studies examining MP in and around the effluents of WWTPs. And (iii) in Chapter 6 the removal of NP during drinking water purification was assessed experimentally. Finally, Chapter 7 provides answers to the posed research questions, and ends with an outlook section discussing which research topics should (not) be studied in the future. This was done based on the findings of previous chapters, of which main conclusions are summarized below

Quantifying the Invisible - Micro- and Nanoplastics in the Urban Water Cycle

Plastic is the common name given to a wide range of synthetic or semi-synthetic organic polymers. These polymers are lightweight, durable, and cheap which explains a global production of 359 million tonnes in 2018 (PlasticsEurope 2019). However, due to several reasons plastic items can end up in the environment where its durability eventually can cause ecological, and socio-economic harm (Galgani et al. 2013, SAPEA 2019). Special attention by science, media and policy, has been given to plastic items smaller than 5 mm, so called microplastics (MP) which, to date, can be found in almost all natural habitats (Hurley et al. 2018). It has been estimated that about 80% of the environmental plastic is released by terrestrial sources (Andrady 2011, Rochman 2018), and that riverine transport plays an important role in distributing the plastic. Over the last years, numbers of studies on (micro)plastics have increased exponentially. Still, our knowledge on occurrences and types of MP in the freshwater environment remains fragmentary. Due to the even higher analytical challenges it is yet to be determined if, how and where even smaller plastics, so called nanoplastics (NP), occur and behave in the environment. This thesis focussed on assessing the presence of MP in the urban water cycle which describes how humans get, use and re-use freshwater. Accurate data on MP types and concentrations are needed to assess their related risks, to trace back their emission sources, and to mitigate these sources. For this thesis three fields of interest were defined. After a general introduction (Chapter 1), we (i) addressed analytical requirements to accurately identify MP and NP (Chapter 2 and Chapter 3). Applying herein defined criteria, (ii) Chapter 4 and Chapter 5 contain the results of two field studies examining MP in and around the effluents of WWTPs. And (iii) in Chapter 6 the removal of NP during drinking water purification was assessed experimentally. Finally, Chapter 7 provides answers to the posed research questions, and ends with an outlook section discussing which research topics should (not) be studied in the future. This was done based on the findings of previous chapters, of which main conclusions are summarized below

Quality criteria for the analysis of microplastic in biota samples: a critical review

Data on ingestion of microplastics by marine biota are quintessential for monitoring and risk assessment of microplastics in the environment. Current studies, however, portray a wide spread in results on the occurrence of microplastic ingestion, highlighting a lack of comparability of results which might be attributed to a lack of standardisation of methods. We critically review and evaluate recent microplastic ingestion studies in aquatic biota, propose a quality assessment method for such studies, and apply the assessment method to the reviewed studies. The quality assessment method uses ten criteria: Sampling method and strategy, Sample size, Sample processing and storage, Laboratory preparation, Clean air conditions, Negative controls, Positive controls, Target component, Sample (pre-)treatment, and Polymer identification. The results of this quality assessment show a dire need for stricter quality assurance in microplastic ingestion studies. On average studies score 8.0 out of 20 points for ‘completeness of information’, and ‘zero’ for ‘reliability’. Alongside the assessment method, a standardised protocol for detecting microplastic in biota samples incorporating these criteria is provided

Quality Criteria for the Analysis of Microplastic in Biota Samples : A Critical Review

Data on ingestion of microplastics by marine biota are quintessential for monitoring and risk assessment of microplastics in the environment. Current studies, however, portray a wide spread in results on the occurrence of microplastic ingestion, highlighting a lack of comparability of results, which might be attributed to a lack of standardization of methods. We critically review and evaluate recent microplastic ingestion studies in aquatic biota, propose a quality assessment method for such studies, and apply the assessment method to the reviewed studies. The quality assessment method uses ten criteria: sampling method and strategy, sample size, sample processing and storage, laboratory preparation, clean air conditions, negative controls, positive controls, target component, sample (pre)treatment, and polymer identification. The results of this quality assessment show a dire need for stricter quality assurance in microplastic ingestion studies. On average, studies score 8.0 out of 20 points for “completeness of information” and 0 for “reliability”. Alongside the assessment method, a standardized protocol for detecting microplastic in biota samples incorporating these criteria is provided

Closing the gap between small and smaller: Towards a framework to analyse nano- and microplastics in aqueous environmental samples

Measuring concentrations and sizes of micro- and nanoplastics in the environment is essential to assess the risks plastic particles could pose. Microplastics have been detected globally in a variety of aquatic ecosystems. The determination of nanoplastics, however, is lagging behind due to higher methodological challenges. Here, we propose a framework that can consistently determine a broad spectrum of plastic particle sizes in aquatic environmental samples. Analytical evidence is provided as proof of principle. FTIR microscopy is applied to detect microplastics. Nanoplastics are studied using field-flow-fractionation and pyrolysis GC-MS that gives information on the particle sizes and polymer types. Pyrolysis GC-MS is shown to be promising for the detection of nanoplastics in an environmental samples as a mass of approximately 100 ng is required to identify polystyrene. Pre-concentrating nanoplastics by crossflow ultrafiltration enables polystyrene to be identified when the original concentration in an aqueous sample is > 20 µg L-1. Finally, we present an approach to estimate polymer masses based on the two-dimensional microplastic shapes recorded during the analysis with FTIR microscopy. Our suite of techniques demonstrates that analysis of the entire size spectrum of plastic debris is feasible

Focal plane array detector-based micro-Fourier-transform infrared imaging for the analysis of microplastics in environmental samples

Environmental context Microplastics are of increasing environmental concern following reports that they occur worldwide from the arctic to the deep sea. However, a reliable methodology that facilitates an automated measurement of abundance and identity of microplastics is still lacking. We present an analytical protocol that applies focal plane array detector-based infrared imaging of microplastics enriched on membrane filters applicable to investigations of microplastic pollution of the environment. Abstract The pollution of the environment with microplastics (plastic pieces &lt;5 mm) is a problem of increasing concern. However, although this has been generally recognised by scientists and authorities, the analysis of microplastics is often done by visual inspection alone with potentially high error rates, especially for smaller particles. Methods that allow for a fast and reliable analysis of microplastics enriched on filters are lacking. Our study is the first to fill this gap by using focal plane array detector-based micro-Fourier-transform infrared imaging for analysis of microplastics from environmental samples. As a result of our iteratively optimised analytical approach (concerning filter material, measuring mode, measurement parameters and identification protocol), we were able to successfully measure the whole surface (&gt;10-mm diameter) of filters with microplastics from marine plankton and sediment samples. The measurement with a high lateral resolution allowed for the detection of particles down to a size of 20 μm in only a fractional part of time needed for chemical mapping. The integration of three band regions facilitated the pre-selection of potential microplastics of the ten most important polymers. Subsequent to the imaging the review of the infrared spectra of the pre-selected potential microplastics was necessary for a verification of plastic polymer origin. The approach we present here is highly suitable to be implemented as a standard procedure for the analysis of small microplastics from environmental samples. However, a further automatisation with respect to measurement and subsequent particle identification would facilitate the even faster and fully automated analysis of microplastic samples.</jats:p

Ingestion and chronic effects of car tyre tread particles on freshwater benthic macroinvertebrates

Micronized particles released from car tires have been found to contribute substantially to microplastic pollution, triggering the need to evaluate their effects on biota. In the present study, four freshwater benthic macroinvertebrates were exposed for 28 days to tread particles (TP; 10-586 µm) made from used car tires at concentrations of 0, 0.1, 0.3, 1, 3 and 10% sediment dry weight. No adverse effects were found on the survival, growth and feeding rate of Gammarus pulex and Asellus aquaticus, the survival and growth of Tubifex spp., and the number of worms and growth of Lumbriculus variegatus. A method to quantify TP numbers inside biota was developed and here applied to G. pulex. In bodies and faces of G. pulex exposed to 10% car tire TP, averages of 2.5 and 4 tread particles per organism were found, respectively. Chemical analysis showed that, although car tire TP had a high intrinsic zinc content, only small fractions of the heavy metals present were bioavailable. PAHs in the TP-sediment mixtures also remained below existing toxicity thresholds. This combination of results suggests that real in situ effects of TP and TP-associated contaminants when dispersed in sediments are probably lower than those reported after forced leaching of contaminants from car tire particles