## 3 Materials and Methods
### Research Activity in the Augusta Bay Performed by ISMAR-CNR Bologna
Precision, estimated by repeated analyses of the same sample, ranged between 2.05 and 3.07%. Radionuclide profiles for cores L, A, D, H, G, and F are reported in Figure 2b. Hg was extracted following the procedure outlined in the EPA 3051A REV.1 ([[https://www.epa.gov/sites/default/files/2015-12/documents/3051a.pdf](https://www.epa.gov/sites/default/files/2015-12/documents/3051a.pdf)]([https://www.epa.gov/sites/default/files/2015-12/documents/3051a.pdf](https://www.epa.gov/sites/default/files/2015-12/documents/3051a.pdf)), accessed on 6 June 2023), including drying at 40 \({}^{\circ}\)C, acid microwave extraction, centrifugation, and evaporation. Concentrations were determined following the method EPA 6010 C, by use of an inductively coupled plasma-atomic emission spectrometer (ICP-AES) Spectro Ciroos. Reproducibility, obtained with repeated measurements of the same sample, was 8.2%. Recovery, defined with the SRM MESS-1, was 81%. The analytical detection limit was 0.1 mg kg\({}^{-1}\). For HCB analyses, dried samples were spiked with \({}^{13}\)C\({}_{12}\)-HCB (CLM351; Cambridge Isotope Laboratories, Woburn, MA, USA) as internal standard, extracted by ASE 200 (DIONEX, Sunnyvale, CA, USA; with an n-hexane/dichloromethane solution), and cleaned up using the automatic system, Dioxin Prep (Fluid Management System Inc., Lexington, KY, USA), as defined by method EPA 8270 ([https://19 january2017 snapshot.epa.gov/sites/production/files/2015-07/documents/epa-8270d.pdf](https://19 january2017 snapshot.epa.gov/sites/production/files/2015-07/documents/epa-8270d.pdf), accessed on 6 June 2023). High resolution gas chromatography mass spectrometry (HRGC-MS) analyses were performed on an HP 6890 plus gas chromatograph coupled to a Micromass Autospec Ultima mass spectrometer. The SRM solution for quantification was EC1668 (Cambridge Isotope Laboratories, Woburn, MA, USA). Recovery (calculated with three \({}^{13}\)C\({}_{12}\)-labeled PCBs from SRM EC4979) was 86%, while reproducibility was 2.1%. The analytical detection limit was 1 mg kg\({}^{-1}\). Hg and HCB concentrations were calculated with respect to dry weight. For the purpose of this paper, only results of radionuclide dating and chemical measurements (Hg and HCB) are summarized. Details of the other measurements can be found in [27]. Research Activity in the Venice Lagoon and the Porto Marghera Industrial Area Performed by ISMAR-CNR Bologna  
A series of published papers and documents issued by public authorities were reviewed in order to define the state of the art of scientific studies. References are reported in detail in [28; 45; 46; 47; 48]. Sediment cores considered in this paper provide a comprehensive view of the potential that can be expressed by sedimentary records involved in environmental forensic studies: (1) cores E1 and M3 represent a lagoon site near the Tresse Islet sampled in 1996 and a salt marsh of the Northern lagoon collected in 1998, respectively; (2) core C9 was collected in 1996 in the 2 nd Industrial Area, and (3) core C12 was collected in the same year in the 1 st Industrial Area (Figure 1b). Sediment cores were analysed for chronology and ancillary parameters, with the same methods reported in Section 3.2. Analysis performances were similar to those reported for chronologies. The analysis of PCDD/Fs on freeze dried sediments included the spiking with a series of 15 \({}^{13}\)C-labelled PCDD/F congeners as internal standards, then a Soxhlet-extraction with toluene, as determined by the EPA 3540 method ([[https://www.epa.gov/sites/production/files/2015-12/documents/3540c.pdf](https://www.epa.gov/sites/production/files/2015-12/documents/3540c.pdf)]([https://www.epa.gov/sites/production/files/2015-12/documents/3540c.pdf](https://www.epa.gov/sites/production/files/2015-12/documents/3540c.pdf)), accessed on 6 June 2023).