Microplastic Pollution in Benthic Midstream Sediments of the Rhine River

Abstract

Rivers are major transport vectors for microplastics (MP) toward the sea. However, there is evidence that MP can temporarily or permanently be inhibited from migrating downstream by retention in sediments or ingestion by organisms. MP concentrations, compositions, and fate within the different compartments of the fluvial environment are poorly understood. Here, benthic, midstream sediments of two undammed, open-flowing stretches were investigated in the Rhine River, one of the world’s busiest inland waterways. Twenty-five samples were collected at ten sites via riverbed access through a diving bell or dredging. We performed the first comprehensive analysis of riverbed sediment aliquots that avoids visual selection bias using state-of-the art automated micro-Fourier-transform infrared spectroscopy (μFTIR) imaging. MP numbers ranged between 0.26 ± 0.01 and 11.07 ± 0.6 × 103 MP kg–1 while MP particles <75 μm accounted for a mean numerical proportion ± SD of 96 ± 6%. MP concentrations decreased with sediment depth. Eighteen polymers were identified in the size range of 11–500 μm; the acrylates/polyurethane/varnish (APV) cluster was found at all sites (mean numerical proportion, 70 ± 19%), possibly indicating particulate pollution from ship antifouling paint. Overall, polymers denser than freshwater (>1 g cm–3) dominated (85 ± 18%), which contrasts the large proportions of low-density polymers previously reported in near-surface compartments of the Rhine.

Review of Microplastic Pollution in the Environment and Emerging Recycling Solutions

“…The prevalence of microplastics is difficult to exaggerate. MP has been found in samples varying from 1000 to more than 5000 meters deep in the ocean [2], as well as in the Laurentian Great Lakes of the US [3], freshwater lakes in Mongolia [4], and sediment samples from the river Rhine in Germany [5]. They thus can be found in both the aqueous and sedimentary environments in a broad geographic section of the world.…”

“…They thus can be found in both the aqueous and sedimentary environments in a broad geographic section of the world. In addition, microplastics are theorized to collect in river waterways on their pathway towards entering the ocean --thus transferring inland consumer products into the ocean as microplastic particles [5][6][7][8]. Researchers in China attempted to define the extent to which particle concentration differs from inland water sources to the ocean and concluded that inland freshwater sources displayed higher particle concentrations than oceanic or estuarine test sites [9].…”

Critical Assessment of Analytical Methods for the Harmonized and Cost-Efficient Analysis of Microplastics

“…The overall time demand for one sample depends on the system and method used, the targeted resolution (e.g., by using binning on high-resolution lenses) 51 and the data analysis. Of the filters available on the market, aluminum oxide filters were the cheapest option ($US$5-20 per filter), 35,51,52,71,73,74,78,161,192,193,213,233,234 and metal-coated and silicon filters 40,159,185 are more expensive ($US$20-50 per filter) while the price for FT-IR transparent windows 76,203,235 is driven by the chosen diameter ($US$50-100 per window). The drawback of using aluminum oxide is the wavenumber limitation towards 3600-1250 cm À1 compared to other filter materials (3600-900 cm À1 for FPA, even lower for MCT) which yields more spectral information in the fingerprint region.…”

Sensors Applied for the Detection of Pesticides and Heavy Metals in Freshwaters

“…Even though freshwater only occupied less than 3% of all the water on earth, our daily life is more associated with freshwater than saltwater. However, many freshwater ecosystems have been polluted by anthropogenic activities including the three most dominating contributors: human settlements, industries, and agriculture [1][2][3]. For example, more than 100,000 chemicals (e.g., pesticides) are registered nowadays, and most of them are related to our daily life; these chemicals can inevitably enter freshwaters [4].…”