Microplastics have recently been stated as being remarkable contaminants of all environmental matrices. The lack of consistent and standardised methods and protocols used to evaluate and quantify microplastics present in riverine systems made a comparison among different studies a critical issue. Based on literature research and the practical expertise of the authors, this work presents a complete collection and analysis of procedures concerning the monitoring of microplastics in riverine environments, focusing on their sampling and analytical protocols to identify, quantify, and characterise them. Further details regarding the advantages and disadvantages of each analytical technique described, such as general recommendations and suggestions, are provided to give practical support for analytical procedures. In particular, microplastics studies consist firstly of their sampling from the aquatic compartment (aqueous and solid phase). Based on the goal of the research, specific devices can be used to collect particles from different matrices. It follows their quantification after extraction from the environmental matrix, adopting different protocols to isolate microplastics from a large amount of organic matter present in a riverine system. In the end, additional qualitative analyses (e.g., RAMAN and FTIR spectroscopy, GC-MS) are required to identify the chemical composition of particles for a better image regarding the abundance of polymer types, their origin, or other information related to manufacturing processes.

Microplastic abundances have been studied intensively in the last years in marine and freshwater environments worldwide. Though several articles have been published about the Mediterranean Sea, only few studies about the Black Sea exist. The Black Sea drains into the Mediterranean Sea and may therefore significantly contribute to the Mediterranean marine pollution. So far, only very few articles have been published about micro-, meso- and macroplastic abundances in the Western Black Sea. In order to fill this knowledge gap and to decipher the number of plastics on the water surface, 12 samples were collected from surface waters with a neustonic net (mesh size 200 μm) in the Black Sea close to the Danube Delta and the Romanian shore. Organic matter was digested and plastic particles were isolated by density separation. The results of visual inspection, pyrolysis GC-MS (for microplastics) and ATR-FTIR (for mesoplastics >5 mm) revealed an average concentration of 7 plastic particles/m³, dominated by fibers (∼76%), followed by foils (∼13%) and fragments (∼11%). Only very few spherules were detected. The polymers polypropylene (PP) and polyethylene (PE) dominated which is in line with other studies analyzing surface waters from rivers in Western Europe as well as in China. Statistical analyses show that the plastic concentration close to the mouth of the Danube River was significantly higher than at four nearshore regions along the Romanian and Bulgarian coastline. This could be explained by plastic inputs from the Danube River into the western part of the Black Sea.

The complex aquatic system of dam reservoirs is known to trap emerging pollutants as microplastics (MPs) in sediments and water column. Considering the knowledge gaps in this type of environment, we investigated the amount and distribution of MPs in the surface water layer, as well as in the surface and deep sediments of the Siriu Reservoir in the Buzău River system, which is located in the southern area of the Eastern Carpathians, Romania. There was a discrepancy between MP abundancy in both water and sediment samples collected near the reservoir (5.3 MPs/m³, 315.5 MPs/kg) and at several kilometers downstream of the dam (1.4 MPs/m³, 132.5 MPs/kg). The chronological accumulation of MPs in the lacustrine sediments was determined by analyzing 5 cm intervals of a 50 cm length core extracted from the reservoir bed. By comparing the concentration of MPs identified in each interval with the solid debit volumes registered in the last decade, we found that flood events could be traced easily due to abundant MP accumulation. Morphologically, the particles were observed mainly as fibers and fragments. Fourier transform infrared spectroscopy (FT-iR) investigations identified most of the MPs as polypropylene (28%), polyethylene (26%), and polyethylene terephthalate (19%).

This paper focuses on the natural and anthropogenic radioactivity of sediment samples from key spots located in the Lower Danube area and the Danube Delta region. The idea of the study is to confirm that gamma spectrometry is an efficient method for geological sample characterization in terms of isotopic ratios and also for evaluating the impact of nuclear activi- ties, namely testing artificial contamination. This is a preliminary study meant to analyze the relevance of a database for reference sediments from the Danube River built via gamma ray spectrometry.