Development of analytical strategies for the monitoring of persistent anthropogenic pollutants in aqueous matrices and marine environments

The growing scientific and political interest in marine pollution has led the European Union to launch a 2030 mission called Restore our Ocean and Waters, which aims to protect and restore the health of our oceans and waters, through research and innovation, citizen engagement and blue investments. In addition to plastic pollution which is so important that it is in the world’s press almost every day, contamination by persistent organic pollutants is also relevant to human health. In fact, the modern concept of health, the concept of Planetary Health, is based on the idea that human health is inextricably linked to the health of the environment. For this reason, the Istituto Superiore di Sanità has signed with the Italian Navy a Memorandum of Understanding to implement a project called "Sea Care" The project started in 2022 with the aim of sampling seawater all over the world, exploiting the Italian Navy fleet, in order to generate extensive knowledge on persistent chemical contamination and its biological impacts in collaboration with other partners such as the Emilia Romagna Regional Environmental Protection Agency, the Sapienza University of Rome and the University of Padua. Among the numerous chemical contaminants being studied, the PhD project focuses on the research and quantification of alkylphenols (APEs), compounds that can act as endocrine disruptors in animal organisms and humans, which is why the European Union (EU Directive 2013/39) has included some of them in the list of priority and hazardous substances for aquatic environments and humans. In the environment, the ethoxylated form, which is mainly used in industry to exploits its surfactant properties, tends to degrade by losing the ethoxyl group. Nonylphenol (NP) and octylphenol (OP) are the ones that attract the most attention because of their toxicological properties. Alkylphenols are molecules that can have several isomeric forms, in particular nonylphenol has as many as 550, including stereoisomers. The conformation of these molecules is capable of interacting with the aryl receptor of cell membranes with the effect of mimicking 17-ß-estradiol, thus interfering with the endocrine metabolism of this natural hormone. The aim of this work, is to improve the knowledge of alkylphenol contamination in seawater by two main ways: a traditional analytical method, in gas-chromatography-mass spectrometry (GC-MS), and an innovative spectroscopic method, based on near infrared spectroscopy (NIR). The former allows the isomeric speciation of nonylphenol and the assessment of the toxicological weight of different isomers, the latter is much faster and more user-friendly and it could be installed directly on board a ship in the future, but both aim to fill the knowledge gap on marine alkylphenol contamination and its impact on human health. Both methods have been developed and validated: the GC-MS acquisition follows a solid phase extraction with HLB disks and uses a 60 m long column to be able to separate nonylphenol isomers. The GC-MS analysis performed on 43 real seawater samples, collected during 2022 Sea Care campaign in the Atlantic Ocean, Arctic Ocean, Mediterranean Sea, Red Sea and Persian Gulf, proves that nonylphenols and 4t-octylphenol are present in offshore marine environments, both in superface and in deep waters, including those within the EU, despite the existence of legislation that strictly limits the use of these molecules in industrial applications. The NIR method was developed using a transmittance MicroNIR first on distilled water and then on reconstituted seawater (in 33% NaCl solution), and in both cases the ability of the technique to discriminate blank samples from those fortified with different analysis concentrations, either singly or in a mixture, was evaluated, and subsequently quantification models were developed that showed promising results in both matrices. Chemometric analysis methods such as Principal Component Analysis (PCA), Partial Least Square-Discriminant Analysis (PLS-DA) and Partial Least Squares Regression (PLS) were used to develop these models, and the results show that, even in reconstituted water, the models are able to quantify both analytes with limits of detection (LOD) and quantification (LOQ) comparable to those of traditional GC-MS techniques. It can therefore be concluded that MicroNIR technology can be used as a rapid screening technique for the quantification of persistent organic pollutants such as alkylphenols in an aqueous matrix, even in the presence of high levels of salts, and this opens up interesting scenarios for possible application directly on board ship, as part of the Sea Care Project and beyond.