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The presence of large quantities of plastic waste and its fragmentation in various environmental compartments are an important subject of current research. In the environment, (photo ) oxidation processes and mechanical abrasion lead to the formation of microplastics. However, until now, there are no established quality assurance concepts for the analysis of microplastic (<5 mm) in environmental compartments, including sampling, processing and analysis.
The aim of the present work is the development of suitable examination methods and protocols (sampling, sample preparation and detection) to qualify and quantify microplastic in urbane water management systems. At first a fractional filtration system for sampling and the analytical tool, the so-called TED-GC-MS (thermal desorption gas chromatography mass spectrometry) were developed. The TED-GC-MS method is a two-step analytical procedure which consists of a thermal extraction where the sample is annealed and characteristic decomposition products of the polymers are collected on a solid phase. Afterwards these products are analysed using GC-MS. The developed fractional filtration for sampling and the TED-GC-MS for detection were used for quantitative analysis to screen the waste water influent and effluent of a Berlin waste water treatment plant for the most relevant polymers, polyethylene (PE), polypropylene (PP), polystyrene (PS), polyethylene terephthalate (PET) and polyamide (PA).
The results of the study revealed that the polymeres PE, PS and PP were detected in the effluent, and PE and PS were find in the raw waste water of the sewage treatment plant in Ruhleben, Berlin. Differences in polymer types and amounts were detected at different sampling dates and within different sieve fractions. Much higher amounts of polymers were observed in the raw waste water. The peak areas of the decomposition products, used for quantification of the polymers, were adjusted using so-called response factors since the TED-GC-MS method is more sensitive for PP and PS than for PE. It has been shown that PE is the most dominant polymer in the samples. Comparing the masses of polymers in the effluent and in the raw sewage, a removal of 99 % of the polymers in the water treatment plant can be assumed. These results are consistent with the literature where removal rates between 98-99 % were described.
Aufgrund der demographischen Entwicklung und dem damit verbundenen gesteigertem Bedarf an Medikamenten besteht in Deutschland das Problem des Eintrags von Rückständen und Transformationsprodukten über das Abwasser in die Umwelt. In herkömmlichen Reinigungsverfahren werden Medikamentenrückstände häufig unvollständig entfernt oder in andere teilweise toxischere Verbindungen umgewandelt (z. B. durch Ozonierung). Eine perspektivisch aussichtsreiche Möglichkeit zur Beseitigung dieser Schadstoffe ist die Oxidation zu Wasser und Kohlendioxid durch Bestrahlung des vorgeklärten Abwassers mit UV-Licht in Gegenwart von Photokatalysatoren wie z. B. TiO2.
Für vergleichende Untersuchungen der photokalalytischen Aktivität von TiO2-Submikro- und Nanopulvern im Labormaßstab wurde Methylenblau als Modellsubstanz gewählt. Kommerziell erhältliche TiO2-Pulver wurden Testlösungen zugesetzt und der zeitlich fortschreitende Abbau von Methylenblau unter Bestrahlung mit UV-Licht in beobachtet. Für die technische Nutzung der photokatalytischen Abwaserreinigung ist die Immobilisierung der eingesetzten Pulver mit der Möglichkeit der Rückgewinnung erforderlich, sowohl aus Umweltschutzgründen als auch für die Wirtschaftlichkeit des Verfahrens.
Aufbaugranulation wurde als ein prinzipiell auch großtechnisch realisierbares Verfahren der Immobilisierung gewählt. In einem Intensivmischer wurden Granulate auf der Basis von Submikrometer-SiO2 unter Verwendung eines anorganischen Binders hergestellt. Das photokatalytisch aktive TiO2 wurde in Anteilen von 10-25 Ma.-% entweder dem Ausgangspulver zugemischt oder am Ende des Granulierprozesses als Granulat-Coating aufgebracht. Eine Temperung der Granalien bei Temperaturen von maximal 300°C – 500°C erwies sich als ausreichend, um deren Stabilität beim Einsatz in Methylenblau-Lösung im Batch-Verfahren zu gewährleisten.
Tests zum Einsatz der SiO2-TiO2-Granulate als Photokatalysatoren zum Abbau von Methylenblau-Lösungen unter UV-Bestrahlung verliefen erfolgreich. Es konnte gezeigt werden, dass sich die Granalien nach erfolgtem Farbstoffstoff-Abbau aus den Lösungen rückgewinnen und erneut verwenden ließen. Die recycelten Granulate wiesen eine ähnliche photokatalytische Aktivität wie frisch hergestellte auf.
Plastics are used in many applications, such as packaging, building and construction, mobility and transport and more. Due to their favourable properties like light weight, flexible processing and low costs their production and consequently their input into natural systems has increased significantly over the last decades. In the environment (photo )oxidation processes and mechanical abrasion lead to the decomposition of the plastics. During this process microplastics (<5 mm) can be formed. It has been shown that environmental pollutants can sorb to these microplastics.[1,2] Nevertheless, knowledge on this topic is still limited.
Our work aims at the investigation of the sorption behaviour of the triazole fungicide difenoconazole to simulated microplastics made of virgin polyamide (PA), polypropylene (PP), and polystyrene (PS). Sorption experiments were planned based on a full factorial design with agitation, salinity, and pH value as parameters. The results of our study revealed that difenoconazole indeed, has sorbed to all microplastics tested here. Data analysis showed that agitation is the main influencing factor, whereas salinity and the pH value held little to no significance on the amount of sorbed difenoconazole.
To simulate the behaviour of naturally aged microplastics, sorption to cryo-milled PP and acid-treated PA was also studied. The thus treated samples were characterised by Fourier transform infrared spectroscopy (FTIR), gel permeation chromatography (GPC), and dynamic scanning calorimetry (DSC). FTIR spectroscopy did not show any changes in the chemical structure but GPC and DSC measurements indicated a systematic chain scission of the treated PA. Scanning electron microscope (SEM) images illustrate that milling of the microplastics leads to non-spherical, star-shaped particles. This fact has a huge influence on the surface properties and consequently on the absorption.
The results of our study are important in terms of i) creating realistic sorption scenarios with relevant parameters for the sorption process, as well as for ii) the choice of proper materials to simulate naturally occurring microplastics. We could show that not only the characteristics of the material like particle size distribution or surface properties are important, but also the applied analytical technique which is used for the characterization of the material . Since there is no standard methodology for microplastic identification and quantification, we suggest to combine several methods to obtain a reliable overall characterization.
Plastics and rubber are used in many applications, such as packaging, building, construction and mobility. Due to their favourable properties like light weight, flexible processing and low costs their production and consequently their input into the environment has increased significantly over the last decades. In the environment, oxidation processes and mechanical abrasion lead to the decomposition of these plastics into small fragments, called microplastic (< 5 mm). By definition, microplastics only involve thermoplastics and duroplastics but elastomers made out of synthetic polymers (e. g. styrene butadiene rubber), modified natural polymers (e. g. natural rubber) and products of synthetic polymers (e. g. tires) are also part of the current microplastic discussion. The main entry pathway of rubber into the environment is the wear of used tire treads in road traffic. Lassen et al. showed that 60 % of the microplastic emissions in Denmark into the environment come from secondary microplastics generated by tires. Rain events can cause microplastic and rubber to get from the street into the street inlets. Depending on the sewage system, these waters are sometimes not cleaned in the sewage treatment plants and reach the surface waters untreated.
To analyse microplastic particles in samples, mainly FTIR or Raman spectroscopic methods are applied at present. Rubber or tire particles in environmental samples cannot be analysed by these methods, because the added carbon black leads to annoying absorption and fluorescent effects.
We developed a thermoanalytical method, the so-called TED-GC-MS (thermal extraction desorption gas chromatography mass spectrometry), which allows the simultaneous detection of microplastic and tire wear with almost no sample preparation in about 2.5 h. The TED-GC-MS is a two-step analytical method which consists of a thermobalance and a GC-MS system. Up to 50 mg of an environmental sample is heated up to 600 °C in a nitrogen atmosphere. During pyrolysis, between 300 and 600 °C polymer-specific decomposition products are produced and collected on a solid phase. Afterwards the substances are desorbed, separated and analysed using the GC-MS.
The aim of the present work is to present the TED-GC-MS as a time efficient screening method to quantify the industrial most relevant polymers in street run-off samples. Analytical challenges in the determination of polyethylene (PE), polypropylene (PP), polystyrene (PS), polyethylene terephthalate (PET) and polyamide (PA), polymethyl methacrylate (PMMA) and styrene-butadiene-rubber (SBR) as a component of tire wear are honestly discussed.
The study area is a 200 m long section of the Clayallee in Berlin, a representative typical urban catchment area. The road run-off in this section flows through the gullies directly into a sample chamber, which directs the runoff in an open channel to the rainwater sewer of this area. The sample chamber allows a sample to be taken directly from the road run-off without mixing with the run-off from other areas. The sample chamber is equipped with an automatic sampler. The automatic sampler is controlled by a conductivity sensor to detect the storm event at an early stage. The sensor gives the sampler a signal to start the sampling program when it gets in contact with water and reaches a certain conductivity threshold. The capacity of the sample container is 100 l and the maximum delivery of the automatic sampler is 2.8 l/min.
Afterwards, the water was pumped through various stainless-steel sieves with a diameter of approximately 20 cm and mesh widths of 500, 100, 50 μm. The obtained solids were steam sterilized, freeze-dried and measured with the TED-GC-MS.
The results of the TED-GC-MS-measurements are summarized in Figure 1. It shows the polymers which were detected in 1 mg of the dry masses of various street run off samples obtained during a period of 1.5 years. We detected PMMA, PS, PP, PE and SBR, as a component of tire wear in the samples. The quantification of the polymers leads to amounts of PS, PP, PE and SBR between 0 µg and 10 µg. PMMA was only detected in traces.
Der Vortrag stellt spektroskopische und neue thermoanalytische Verfahren zum Nachweis von Mikroplastik in Umweltproben vor. Ein spezieller Fokus liegt auf dem neu entwickelten Verfahren der TED-GC-MS. Zusätzlich wird gezeigt, wie die TED-GC-MS eingesetzt werden kann, um Reifen in der Umwelt zu bestimmen.