Quantification and Clustering of Inorganic Nanoparticles in Wastewater Treatment Plants across Switzerland

Single particle Inductively Coupled Plasma Time-of-Flight Mass Spectrometry (sp-ICP-TOFMS), in combination with online microdroplet calibration, allows for the determination of number concentrations (PNCs) and masses elements individual particles. Because sp-ICP-TOFMS analyses environmental samples produce rich datasets composed both single-metal nanoparticles (smNPs) many types multi-metal NPs (mmNPs), interpretation these data is well suited to automated analysis schemes. Here, we present a approach that includes automatic detection elemental mass determinations based on unsupervised clustering mmNPs identify unique classes their element compositions. To demonstrate potential our approach, analyzed waste water collected from influent effluent five wastewater treatment plants (WWTPs) across Switzerland. We determined NPs, as PNCs, estimate NP removal efficiencies WWTPs. Through hierarchical clustering, identified conserved all WWTPs; most abundant were those Ce-La, Fe-Al, Ti-Zr, Zn-Cu. In addition, found are one or few WWTPs, which could indicate point sources anthropogenic NPs.