Lake Maggiore is a southern subalpine lake located across the border between Italy and Switzerland. It is well studied since 1972 thanks to a monitoring program funded by the International Commission for the Protection of Italian-Swiss Waters (CIPAIS; https://www.cipais.org/web/). This program comprises the analysis of trace elements and persistent organic pollutants (POPs) in sediments of the lake and of the main tributaries and in different bioindicators: zooplankton, lake molluscs, riverine benthic invertebrates, fish. This lake is characterized by legacy DDT and mercury contamination deriving from industrial activities. However, several different anthropogenic pressures act as potential sources of contamination. The present dataset (on excel file) consists of data regarding the analysis of trace elements and POPs in 16 core sediments collected in the Lake between 2014 and 2023. Sediment chronology was established using a combination of radiometric measurements (137Cs, 210Pb, 14C), changes in diatom composition and abundance (in particular, the transition from small-sized Stephanodiscus populations to Pantocsekiella comensis-dominated populations, corresponding to year 1989, and the transition from P. comensis to Stephanodiscus spp., corresponding to year 1963), and the presence of turbiditic deposits associated to exceptional floods. Analyses were carried out on whole sediment samples, which were characterized by fine grain size composition. Besides, the database comprises trace elements and POPs concentrations in freshly deposited sediments collected seasonally in the main tributaries of Lake Maggiore (Ticino tributary, Tresa, Margorabbia, Boesio, Bardello and Toce rivers) in the lake emissary (Ticino emissary) in 2022-2024. Analyses were carried out on the < 63 µm grain size fraction, for comparison between sampling sites and dates. The reported contaminant concentrations comprise: - trace elements: total mercury (THg), methylmercury (MeHg), arsenic (As), cadmium (Cd), copper (Cu), nickel (Ni), and lead (Pb); - Dichlorodiphenyltrichloroethane (DDT): and 6 congeners and isomers (o,p' DDD, p,p' DDD, o,p' DDE, p,p' DDE, o,p' DDT and p,p' DDT) and total DDT. - Polychlorinated biphenyls (PCBs): 14 congeners (PCB-18, -28+31, -44, -52, -101, -118, -138, -149, -153, -170, -180, -194, -209), and sumPCB14; - Polybrominated diphenyl ethers (PBDEs): 8 congeners (BDE-28, -47, -99, -100, -153, -154, -183, -209) and sumBDE; - Hexabromocyclododecane (HBCD); - Decabromodiphenyl ethane (DBDPE); - Polycyclic aromatic hydrocarbons (PAHs): 17 congeners (Naphthalene, Acenaphthylene, Acenaphthene, Fluorine, Phenanthrene, Anthracene, Fluoranthene, Pyrene, Benzo[a]anthracene, Chrysene, Benzo[b]fluoranthene, Benzo[k+j]fluoranthene, Benzo[a]pyrene, Perylene, Indeno[1,2,3-cd]pyrene, Dibenzo[a,h]anthracene, Benzo[ghi]perylene) and sumPAHs; - Polycyclic musk fragrances (PMFs): ADBI (Celestolide), AHDI (Phantolide), HHCB (Galaxolide), AHTN (Tonalide), HHCB-L (Galaxolidone), and sumPMFs; - Perfluoroalkyl and polyfluoroalkyl substances (PFASs): Perfluorooctane sulfonate (PFOS), Perfluorooctanoic acid (PFOA), Perfluorobutanoic acid (PFBA), Perfluorobutanesulfonate (PFBS), sum of PFAS (sum of PFOS, PFOA, PFBA and PFBS) and sum of the concentration of Perfluorodecanoic acid (PFDeA), Perfluorododecanoic acid (PFDoA), Perfluoroheptanoic acid (PFHpA), Perfluorohexanoic acid (PFHxA), Perfluorohexasulfonic acid (PFHxS), Perfluorononanoic acid (PFNA), Perfluoropentanoic acid (PFPeA) and Perfluoroundecanoic acid (PFUnA) expressed as sum of other PFAS compounds. - Total Organic Carbon (TOC). The dataset of the cores allows for detecting changes in the concentrations over the analysed periods and between different areas of the Lake, thus providing evidence for spatial and temporal variations of pollutants and expected temporal trends of contamination (see annual reports on hazardous substances in Lake Maggiore at https://www.cipais.org/web/). Data on river sediments provide a basis for identifying sources and paths of contamination. This research was founded by the International Commission for the Protection of Italian-Swiss Waters (CIPAIS), monitoring programs 2014-2016, 2017-2019, 2020-2022, and 2022-2024 (https://www.cipais.org/web/).

The site Lago Maggiore-Italy (https://deims.org/f30007c4-8a6e-4f11-ab87-569db54638fe) belongs to the Long Term Ecological Research national and international networks (LTER-Italy, LTER-Europe and ILTER).