Microplastics contaminating drinking water is a growing issue that has been the focus of a few recent studies, where a major bottleneck is the time-consuming analysis. In this work, a micro-optofluidic platform is proposed for fast quantification of microplastic particles, the identification of their chemical nature and size, especially in the 1–100 µm size range. Micro-reservoirs ahead of micro-filters are designed to accumulate all trapped solid particles in an ultra-compact area, which enables fast imaging and optical spectroscopy to determine the plastic nature and type. Furthermore, passive size sorting is implemented for splitting the particles according to their size range in different reservoirs. Besides, flow cytometry is used as a reference method for retrieving the size distribution of samples, where chemical nature information is lost. The proof of concept of the micro-optofluidic platform is validated using model samples where standard plastic particles of different size and chemical nature are mixed.

Microplastics (MP) have been detected in almost all matrices, including drinking water, and assessing the contamination of drinking water with this type of pollution is of the utmost sanitary importance. This study aims to evaluate MP contamination of inlet river water and drinking water at three drinking water treatment plants (DWTPs) in the Paris region in France. Each plant performs water treatment processes that are efficient for particulate matter removal such as coagulation-flocculation, sand filtration, and granular activated carbon filtration. One of the plants also has a parallel water treatment file that uses microfiltration and nanofiltration processes. This file was investigated to assess its efficiency compared to the others. To our knowledge, this study is the first to investigate MP contamination in a DWTP using nanofiltration processes. The drinking water distribution network was also investigated, with samples taken at three network points. Microplastics contamination of sizes 25–5,000 μm was characterized using micro-Fourier transform infrared spectroscopy (μ-FTIR) in large volume samples (500 L) with complete mapping of each sample. Concentrations ranging from 7.4 to 45.0 MP/L were found in inlet water while concentrations ranging from blank level (0.003 MP/L) to 0.260 MP/L were found in outlet drinking water (overall removal rate above 99%). Polyethylene, polypropylene, and polyethylene terephthalate were the main polymers found both at the inlet and outlet, but ratios varied significantly at the outlet. No MP were detected in four out of the six samples from the nanofiltration file, and were not found to have significantly different concentrations compared to blank level. Concentrations in the distribution network were higher overall than at the corresponding DWTP outlet, although a high degree of variation between samples was observed. Our results suggest that membrane processes of microfiltration and nanofiltration are more efficient than typical treatment processes, and also that a MP re-contamination within the distribution network itself might occur.

<p>Air masses loaded with mineral dust and originating from the Sahara arrive frequently in Europe, which has multiple impacts on global and regional cycles. However, the occurrence of these processes may further accelerate in the future in response to climate change, and more knowledge is therefore required on the characteristics of the particles transported during these massive dust transport and deposition episodes. Furthermore, questions arise regarding the content of this dust in radionuclides, in relationship with the atmospheric nuclear bomb testing conducted around the world between the 1950s and the 1970s in general, and those tests conducted by France in the Sahara in the early 1960s in particular.</p><p>The Saharan dust episode that took place from 13<sup>th</sup> to 16<sup>th</sup> March 2022 led to the occurrence of dense dust deposition across multiple European countries, which raised concerns among the population regarding the potential radioactivity content of this dust. To address this question with a representative sample set, a participative science campaign to collect dust across Europe was launched on Twitter on 17<sup>th</sup> March 2022. Thanks to this initiative, 110 dust samples could be collected along a transect from Southern Spain to Austria.</p><p>This unique sample bank was regrouped at University Paris-Saclay, France, to conduct a set of physico-chemical analyses on a selection or on the totality of these dust samples including particle size, colourimetry, mineralogy and fallout radionuclides.</p><p>Backward trajectories of air masses that have led to these deposits were calculated, and this analysis confirm their potential origin from Algeria. <sup>137</sup>Cs was detected in all dust samples, with variable activity concentrations. A strong relationship was found between the particle size of the analysed particles and the <sup>137</sup>Cs activity concentrations, which is consistent with the literature on this topic. Particle size was found to decrease with increasing distances from the source. The colour and mineralogy analyses demonstrated that the dust collected in Austria showed different properties than those samples collected in Spain, France, Luxembourg and Germany, which likely indicates that this material did not fully consist of Saharan dust deposited during the March 2022 episode. Accordingly, the following interpretations did not take the properties of Austrian dust into account.</p><p>The mineralogical analyses confirmed the potential origin of the dust from the Maghreb region, including a vast area in Southern Morocco and Southern Algeria. In contrast, the analysis of plutonium isotopic ratios (<sup>240</sup>Pu/<sup>239</sup>Pu) and <sup>137</sup>Cs/<sup>239+240</sup>Pu activity ratios, which provide diagnosis tools to investigate the source of artificial radionuclides, in a selection of dust samples collected between Southern Spain and Luxembourg showed that the dust signature was consistent with that of the global fallout largely dominated by the nuclear tests conducted by the USA and the Soviet Union. The <sup>137</sup>Cs contained in the dust transported and deposited during this episode was therefore very likely not associated with the French nuclear tests conducted in the early 1960s in Sahara.</p><p>In the future, elemental geochemistry analyses will provide additional information on their source provenance. All results will also be published in open-access database and disseminated to the public.</p>