Volatile methylsiloxanes (VMSs) are massively produced chemicals that comprise a wide range of industrial and household applications. The presence of cyclic and linear VMSs in several environmental matrices and ecosystems indicates persistence associated with a potential of (bio)accumulation and food web transfer with possible toxicological effects. Due to the high anthropogenic pressure in its vicinities particularly in summer, coastal areas in Southern European countries are potential hotspots for the presence of VMSs. The massive afflux of tourists and consequent increase of the use of personal care products (PCPs) with VMSs in their formulations highlight the importance of VMSs assessment in such areas. In this study, different species of marine vegetation (algae and seaweed) were collected in three different geographical areas, covering the Atlantic Ocean (North coast of Portugal), as well as the Mediterranean Sea (coasts of the Region of Murcia, Spain and of the city of Marseille, France). Samples were analysed for the determination of 4 cyclic (D3, D4, D5, D6) and 3 linear (L3, L4, L5) VMSs employing a QuEChERS extraction methodology, followed by gas chromatography/mass spectrometry (GC/MS) quantification. VMSs were detected in 92% of the 74 samples analysed, with the sum of the concentrations per sample ranging from below the limit of detection (LOD) to 458 ± 26 ng•g −1 dw (dry weight). A strong predominance of cyclic VMSs over linear ones was verified in almost all samples studied, with D5 and D6 found at higher concentrations. Seasonal variation was also assessed and despite higher levels of VMSs being identified mostly in summer months, clear seasonal trends were not perceived. It was also noted that generally the higher incidence of VMSs occurred in samples from urban and industrialized areas or in the vicinities of WWTPs, suggesting a direct input from these sources in the levels of siloxanes observed.

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Sewage sludge valorization in agricultural fields is in many countries a circular economy strategy to handle the disposal issues of this complex residue. Many countries regulate the content of heavy metals and other agrochemical parameters in sewage sludge, establishing threshold limits for its application in agricultural fields. This requires the employment of robust, timesaving, and cost-effective analytical tools suitable for multielemental analysis at trace levels. Inductively coupled plasma optical emission spectrometry (ICP-OES) is a powerful instrumental technique with proven success in this field. In this laboratory experience, students perform a multielemental analysis of sewage sludge samples, by sample acidic digestion in a closed microwave system followed by ICP-OES analysis. Validation of the analytical method is also proposed, evaluating the linear response of an external calibration with internal standardization and using a certified reference material for evaluation of recovery and precision. The method is to be applied to a real sewage sludge sample to assess its nutrient content and to compare levels of heavy metals with enforced regulations. This work was successfully carried out in an analytical chemistry class with undergraduate students of chemical, environmental, and bioengineering bachelor degree courses. Most students reached the proposed learning goals, obtaining good or very good classifications in all evaluated parameters in the assessments of laboratory performance and final group reports.

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