Occurrence and Spatial Distribution of Microplastics in River Shore Sediments of the Rhine-Main Area in Germany

Plastic debris is one of the most significant organic pollutants in the aquatic environment. Because of properties such as buoyancy and extreme durability, synthetic polymers are present in rivers, lakes, and oceans and accumulate in sediments all over the world. However, freshwater sediments have attracted less attention than the investigation of sediments in marine ecosystems. For this reason, river shore sediments of the rivers Rhine and Main in the Rhine-Main area in Germany were analyzed. The sample locations comprised shore sediment of a large European river (Rhine) and a river characterized by industrial influence (Main) in areas with varying population sizes as well as sites in proximity to nature reserves. All sediments analyzed contained microplastic particles (<5 mm) with mass fractions of up to 1 g kg^–1 or 4000 particles kg^–1. Analysis of the plastics by infrared spectroscopy showed a large abundance of polyethylene, polypropylene, and polystyrene, which covered more than 75% of all polymer types identified in the sediment. Short distance transport of plastic particles from the tributary to the main stream could be confirmed by the identification of pellets, which were separated from shore sediment samples of both rivers. This systematic study shows the emerging pollution of inland river sediments with microplastics and, as a consequence thereof, underlines the importance of rivers as vectors of transport of microplastics into the ocean

Characterization of 3‑Aminopropyl Oligosilsesquioxane

The synthesis routes in the production of polysilsesquioxanes have largely relied upon <i>in situ</i> formations. This perspective often leads to polymers in which their basic structures including molecular weight and functionality are unknown [Lichtenhan, J. D.; et al. Silsesquioxane-siloxane copolymers from polyhedral silsesquioxanes Macromolecules, 1993, 26, 2141−2142, http://dx.doi.org/10.1021/ma0060a053]. For a better understanding of the polysilsesquioxane properties and applications, there is a need to develop more techniques to enable their chemical characterization. An innovative method was developed to determine the molecular weight distribution (MWD) of an oligosilsesquioxane synthesized in-house from (3-aminopropyl)­triethoxysilane. This method, which can be applied to other silsesquioxanes, siloxanes, and similar oligomers and polymers, involved separation using high performance liquid chromatography (HPLC) and detection using mass spectrometry (MS) with electrospray ionization (ESI). The novelty of the method lies on the unique determination of the absolute concentrations of the individual homologues present in the sample formulation. The use of absolute concentrations is necessary in estimating the MWD of the formulation when relative percentage, which is based solely on mass spectral ion intensities, becomes irrelevant due to the disproportionate response factors of the homologues. Determination of absolute concentration requires the use of single-homologue calibration standards. Because of commercial unavailability, these standards were prepared by efficient fractionation of the original formulation