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While plastics have become indispensable in our daily lives over the last decades, the input into the environment has been increasing concurrently. Plastics often end up in the environment because of intensive use and poor waste management practice. They are subjected to aging and fragmentation and finally be deposited as microplastic particles or in short microplastics (MP). MP are defined as particles originating from synthetic polymers between 1 µm and 5 mm.
Although the pervasive abundance of MP in aquatic environments has been demonstrated comprehensively, less is known about the occurrence and fate of MP in terrestrial ecosystems. It is still unclear if soil functions as a MP source or a sink for aquatic environments. MP can either be transported into water bodies by soil erosion or be retained in soils. The few studies published are not comparable because of non-existent harmonized and standardized methods for sampling, sample preparation, and analysis.
For an assessment of a potential exposure situation of MP, the determination of a mass content in the soil is crucial. Consequently, spectroscopic methods like Raman or FTIR are not suitable, as they deliver information about the shape and size of individual particles. Therefore, we show the application of ThermoExtractionDesorption-GasChromatography-MassSpectrometry (TED-GC-MS) for MP analysis in the soil. In this method, the soil sample is heated up to 600 °C in a nitrogen atmosphere. The decomposition gases are sorbed on a solid phase, then transferred to a GS-MS system where they are desorbed, separated and identified. The method allows the rapid identification of individual polymers through the detection of specific decomposition products, but also the quantitative determination of the MP mass. Besides thermoplastics, elastomers originated from tire abrasion, can be detected.
In the present study, several terrestrial ecosystems in south-west Germany were systematically sampled. Subsequent sample preparation included sieving in fractions of 5-100 µm, 100-1000 µm, and 1-5 mm. MP were extracted by density separation using ZnCl2 solutions. The detection was done by TED-GC-MS measurements. Data of agricultural areas and floodplains are presented exemplarily. A quantitative assessment of highly occurring MP from littering as well as tire abrasion is conducted.
Mikroplastik (MP) findet sich in aquatischen Ökosystemen weltweit und es konnte gezeigt werden, dass hydrophobe organische Schadstoffe an MP angereichert werden. Es ist bekannt, dass teilkristalline und amorphe Polymere unterschiedliche Sorptionsver-halten aufweisen. Der Einfluss des Alterungszustandes der MP-Partikel auf das Sorptionsverhalten ist nicht hinreichend geklärt. In dieser Studie wurden amorphes Polystyrol (PS) und teilkristallines Polypropylen (PP) in Form von Industriepellets gezielt gealtert und mikroskopisch sowie mittels XPS, FTIR und DSC charakterisiert. Anschließend wurde in Batchexperimenten die Sorption von potenziell wassergefährdenden Kraftstoffbestandteilen (Ether und BTEX) an den Pellets mittels Headspace-Gaschromatografie untersucht.
Die Präsenz von Mikroplastik in aquatischen Ökosystemen ist ein globales Problem und steht zunehmend im Fokus der Öffentlichkeit. In mehreren Studien konnten Anreicherungen hydrophober, organischer Schadstoffe an MP nachgewiesen werden. Der Einfluss des Alterungszustandes der MP-Partikel auf das Sorptionsverhalten von hydrophoben organischen Substanzen ist nicht hinreichend geklärt.
Ziel der vorliegenden Arbeit war die Untersuchung des Sorptionsverhaltens von Schadstoffen mit Bedeutung für limnische Gewässer an künstlich gealterten Partikeln relevanter Polymere. Das Modell verwendete die Aromaten Benzol, Toluol, Ethylbenzol und Xylol (BTEX) sowie Etherverbindungen. Diese Substanzen sind oder waren Bestandteile in unterschiedlichen Kraftstoffen und finden sich daher in vielen aquatischen Ökosystemen weltweit. Als Sorbentien kamen teilkristallines Polypropylen (PP) und amorphes Polystyrol (PS) in Form von Industriepellets zum Einsatz. Die Pellets wurden jeweils sowohl unbehandelt als auch mittels UV-Bestrahlung künstlich gealtert verwendet und mikroskopisch sowie mittels XPS, FTIR und DSC charakterisiert. Die Alterung führte bei PS zu einer verringerten Sorptionskapazität, während bei PP keine Veränderung im Sorptionsverhalten beobachtet wurde.
Tire wear (TW) constitutes a significant source of microplastic in terrestrial ecosystems. It is known that particles emitted by roads can have an effect up to 100 m into adjacent areas. Here, we apply for the first-time thermal extraction desorption gas chromatography-mass spectrometry (TED-GC/MS) to determine TW in soil samples by detection of thermal decomposition products of styrene-butadiene rubber (SBR), without additional enrichment. Additionally, zinc contents were determined as an elemental marker for TW. Mixed soil samples were taken along three transects along a German motorway in 0.3, 2.0, and 5.0 m distance from the road. Sampling depths were 0–2, 2–5, 5–10, and 10–20 cm. Four fine fractions, 1 000–500, 500–100, 100–50, and <50 μm, were analyzed.
TW contents based on SBR ranged from 155 to 15 898 mg kg−1. TW contents based on zinc were between 413 and 44 812 mg kg−1. Comparison of individual values of SBR and zinc reveals SBR as a more specific marker. Results confirm that most TW ends up in the topsoil within a 2 m distance.
The sampling strategy resulted in representative data for a larger area. Standard deviations of quadruple TED-GC/MS determination of SBR were <10% for all grain size fractions. TED-GC/MS is a suitable analytical tool for determining TW in soil samples without the use of toxic chemicals, enrichment, or special sample preparation.
Tire wear particles (TW) are generated by the abrasions of tires on the road surface through traffic. These particles can be transported by air and surface runoff and might also infiltrate the soil and consequently affect terrestrial ecosystems. The estimated tire wear (TW) emissions are immense, with 1.33 106 t a-1 in Europe. Despite this, only little is known about the environmental contents or the fate of TW.
One reason for this knowledge gap is the challenging analysis of TW in environmental samples. Detection of TW with spectroscopic methods is problematic due to high fluorescence interferences caused by contained black carbon. One analytical approach is to use zinc (Zn), a typical additive in tires, as a specific marker for the quantification of tire wear. However, any Zn originating from the sample matrix must be separated beforehand and requires elaborate sample preparation.
Car tires consist partly of synthetic rubbers, such as styrene-butadiene-rubber (SBR). This SBR could be identified and quantified via Thermal-Extraction-Desorption-Gas Chromatography-Mass Spectrometry (TED-GC-MS). This newly developed and fast screening method allows the simultaneous detection of microplastics and TW mass contents and requires minimal to no sample preparation. Firstly the sample is thermally extracted in a thermobalance under a nitrogen atmosphere. The resulting specific decomposition products are sorbed on a solid phase adsorber, which is then transferred to a GC-MS via an autosampler, where the products are desorbed, separated and identified. Cyclohexenylbenzene is used as a specific marker for SBR.
Here we investigated top layer soil samples, collected at the roadside of highly frequented German highways. Samples were analyzed without sample preparation, and SBR was detected in all investigated samples in mass contents ranging from 67.2 to 2230 mg kg-1. A correlation between SBR and Zn content in the soil was confirmed, while the correlation between SBR and Corg was hardly pronounced. We successfully demonstrated the application of TED-GC-MS as a screening method for tire wear in soil samples.
The present study will discuss these analytical results in detail as well as sampling parameters like sampling depth and distance to the roadside, and the effect of the particle size on the particle transport by water runoff and air.
Background: The ubiquitous occurrence of microplastic particles in marine and aquatic ecosystems was intensively investigated in the past decade. However, we know less about the presence, fate, and input paths of microplastic in terrestrial ecosystems. A possible entry path for microplastic into terrestrial ecosystems is the agricultural application of sewage sludge and solid bio-waste as fertilizers. Microplastic contained in sewage sludge also includes Polyethylene terephthalate (PET), which could originate as fiber from textile products or as a fragment from packaging products (foils, bottles, etc.). Information about microplastic content in such environmental samples is limited yet, as most of the used analytical methods are very time-consuming, regarding sample preparation and detection, require sophisticated analytical tools and eventually need high user knowledge.
Results: Here, we present a simple, specific tool for the analysis of PET microplastic particles based on alkaline extraction of PET from the environmental matrix and subsequent determination of the monomers, terephthalic acid, using liquid chromatography with UV detection (LC-UV). The applicability of the method is shown for different types of PET in several soil-related, terrestrial environmental samples, e.g., soil, sediment, compost, fermentation residues, but also sewage sludge, suspended particles from urban water management systems, and indoor dust. Recoveries for model samples are between 94.5 and 107.1%. Limit of determination and limit of quantification are absolute masses of 0.031 and 0.121 mg PET, respectively. In order to verify the measured mass contents of the environmental samples, a method comparison with thermal extraction-desorption-gas chromatography–mass spectrometry (TED-GC/MS) was conducted. Both methods deliver similar results and corroborated each other. PET mass contents in environmental samples range from values below LOQ in agriculture soil up to 57,000 mg kg−1 in dust samples.
Conclusions: We demonstrate the potential of an integral method based on chemical extraction for the Determination of PET mass contents in solid environmental samples. The method was successfully applied to various matrices and may serve as an analytical tool for further investigations of PET-based microplastic in terrestrial ecosystems.
Microplastics are small plastic fragments that are widely distributed in marine and terrestrial environments. While the soil ecosystem represents a large reservoir for plastic, research so far has focused mainly on the impact on aquatic ecosystems and there is a lack of information on the potentially adverse effects of microplastics on soil biota. Earthworms are key organisms of the soil ecosystem and are due to their crucial role in soil quality and fertility a suitable and popular model organism in soil ecotoxicology.
Therefore, the aim of this study was to gain insight into the effects of environmentally relevant concentrations of microplastics on the earthworm Eisenia andrei on multiple levels of biological organization after different exposure periods. Earthworms were exposed to two types of microplastics: (1) polystyrene-HBCD and (2) car tire abrasion in natural soil for 2, 7, 14 and 28 d. Acute and chronic toxicity and all subcellular investigations were conducted for all exposure times, avoidance behavior assessed after 48 h and reproduction after 28 d. Subcellular endpoints included enzymatic biomarker responses, namely, carboxylesterase, glutathione peroxidase, acetylcholinesterase, glutathione reductase, glutathione S-transferase and catalase activities, as well as fluorescence-based measurements of oxidative stress-related markers and multixenobiotic resistance activity. Multiple biomarkers showed significant changes in activity, but a recovery of most enzymatic activities could be observed after 28 d. Overall, only minor effects could be observed on a subcellular level, showing that in this exposure scenario with environmentally relevant concentrations based on German pollution levels the threat to soil biota is minimal. However, in areas with higher concentrations of microplastics in the environment, these results can be interpreted as an early warning signal for more adverse effects. In conclusion, these findings provide new insights regarding the ecotoxicological effects of environmentally relevant concentrations of microplastics on soil organisms.