RESUMO
This paper presents the results of the first international comparative study of commonly applied analytical methods for microplastic analysis. Although it was shown that the comparability between previously published studies is highly limited, there are ambitious efforts regarding the standardization of microplastic analysis. This comparative study serves as a first step to assess the suitability of frequently used methods in microplastic research. Furthermore, it highlights obstacles when conducting a comparative study for microplastics. Results from 17 laboratories from eight different countries are compared. Samples comprised of five different types of microplastic reference particles with diameters ranging from 8 µm to 140 µm suspended in ultrapure water. Microscopy, Fourier-transform infrared microspectroscopy (µ-FTIR), Raman microspectroscopy (µ-Raman), thermo-extraction-and-desorption- or pyrolysis- combined with gas chromatography coupled to mass spectrometry (Σ-GC/MS), scanning electron microscopy and particle counter were compared regarding results on total particle number, polymer type, number of particles and/or particle mass for each polymer type. In the scope of this comparative study, for the identification of polymer type µ-Raman and Σ-GC/MS performed best. The quantification of polymer mass for identified polymer types was questionable for Σ-GC/MS, whereas other methods failed to determine the correct polymer mass. Quantification of particle number per identified polymer type was evaluated successful for µ-FTIR and the quantification of total particle numbers was best for microscopy and to a lesser extent for µ-FTIR. Remarkable was the large variance of results between the methods but also within the methods. The latter is likely due to individual interpretations of methods and preparation protocols, in particular in regard to the handling of blank values. Results strongly emphasize the need for standardization and validation of analytical methods in microplastic research both on a global scale as well as in the context of individual laboratories.
RESUMO
In Germany information on the occurrence of MTBE in groundwaters is scarce. In order to assess the German situation, in 1999 a monitoring programme on MTBE in groundwater was set up. Within this survey 170 wells were examined, which are used as groundwater monitoring points or which are foreseen for drinking water extraction in emergency cases or for irrigation purposes. In rural areas MTBE was found only in 9% of all samples in concentrations above the limit of determination (LOD) of 0.05 microg L(-1). In urban areas MTBE was detected in 49% of all wells under investigation and the median concentration was calculated to 0.17 microg L(-1). In one case a maximum MTBE concentration of almost 700 microg L(-1) was detected. As a first result of this survey one can conclude, that MTBE is regularly present in German groundwaters under urban areas. Although investigations about the occurrence of MTBE in German groundwaters have to be extended in future, this first snapshot can lead to the assumption, that MTBE concentrations due to diffuse sources are lower than the ones found in the USA. Nevertheless, e.g. accidental spills can lead to elevated MTBE concentrations.
