Microplastic in Water Cycle - Sampling, Sample Handling, Analysis, Occurrence, Removal and Validation; Subproject: Microplastic in Environmental Samples: Identification and Quantification by Raman Microspectroscopy / MiWa

Objectives

• Harmonization of sampling and sample handling
• Analysis of microplastic in sediments and groundwater
• 2D and 3D analysis of microplastic in biota

Method of Approach

• Raman microspectroscopy & Raman imaging
• Munich Plastic Sediment Separator (MPSS)

Description

Microplastics (MP) in freshwater ecosystems are of emerging scientific and public concern. Plastics (the colloquial term for synthetic polymers) are used extensively and in a wide range of applications. Besides its numeral benefits plastics are a problem if deposited in the environment. Degradation of bigger parts is one major reason for the occurrence of MP (“secondary MP”). The other major pathway is the direct spillage of so-called primary particles from consumer products. MP are particles made of synthetic polymers that have a certain size. Until now, most scientists speak of MP when a particle is between 5 mm and 1 µm large. A widely accepted definition has not yet been given.

Research groups around the world use a lot of different approaches to determine MP contamination in sediment and water bodies. They not only differ in terms of sampling, but also in sample handling and analysis. Several methods were applied for the analysis of MP. The variety includes mere optical inspection, thermal decomposition methods coupled with GC/MS or spectroscopic methods like IR or Raman. Optical identification alone is especially unsound for small particles, because it leads to false positive or false negative results strongly depending on the person conducting the inspection. Thermal methods for the identification of MP are quite new and the future will unravel its potential. Spectroscopic methods are now the most widely applied methods. Due to fingerprint spectra they give an unambiguous way for the identification of the polymer type. Raman has (besides others) the advantage over IR that it is able to identify MP down to 1 µm whereas IR is only able to identify particles with a maximum size of 20 µm.

In this project we plan to improve sampling, sample handling and analysis of MP in sediment and groundwater. Therefore, we intensively work together with our partners from universities and public authorities. Sampling is the crucial part of the whole analytical process. Errors in this part hamper all the following steps. It is therefore of paramount concern to establish a standardized or at least harmonized method for sampling. Sample handling is the second step of the analytical process. Within this step it is necessary to determine method specific losses and/or to identify the generation of artefacts. The Munich Plastic Sediment Separator (MPSS), which was developed at our institute (in cooperation with Bayreuth University), is used to separate MP from sediments. Although this is a method applied by several research groups it is necessary to improve the separation process. Organic as well as inorganic matrix substances need to be addressed. If groundwater is affected by pollution with MP, will be examined by the application of the Crossflow Ultrafiltration, which was developed at the IWC for the identification of viruses. The third part of this project is the development of a suitable method for the identification of MP with RM. Although this is possible now it is a time and labor consuming process. We want to improve the identification to make it faster and easier.

We also plan to determine the fate of MP in biota. The toxicity pattern of MP is a field of debate. There are studies that claim to have found no effect of MP at all, but there are also studies that show worrisome adverse effects on organisms. The possible toxicity of MP may arise from its mere physical impact on the gut system or the additives it contains. Possible may be as well a concentration effect of toxic organic substances on MP. Ingested MP may release these substances in the intestines of organisms to induce a high level of stress. Within this project, we aim to determine where MP is located inside small organisms (aquatic invertebrates, snails, etc.). Therefore, we collaborate with scientists studying toxicity patterns. RM will serve as a non-destructive 2D and 3D imaging tool. It enables us to look inside intact biota samples. Due to the applied confocal measuring procedure, we are able to ascertain the position of MP down to a few micrometers. This should allow us to differentiate between MP that is only attached to the gut system and MP that is translocated into cells. The latter is hypothesized to happen for MP smaller than 10 µm.

For further information on the aim and scope of the project MiWa see the homepage http://www.nawam-miwa.de/

For the former DFG project please see "Microplastic Particles in Aquatic Ecosystems"