Atmospheric mercury monitoring data across Italy: A multi-year national dataset (2020 - 2023).

In compliance with the European Air Quality Directive, an Italian monitoring network was established under the framework of the "Reti Speciali" agreement. A key component of this framework is the monitoring of atmospheric mercury (Hg) across the Italian territory. To this end, a dedicated Hg network was designed including three ground-based monitoring stations, strategically located from Northern to Southern Italy, to identify potential geographical variations. Atmospheric Hg was measured using automated instrumentation, providing high-resolution time series for Total Gaseous Mercury (TGM) or Gaseous Elemental Mercury (GEM). While all three stations monitored these primary Hg species, one master station provided advanced speciation data, including Gaseous Oxidized Mercury (GOM) and Particulate-bound Mercury (PBM). The measurements carried out within this network produced a comprehensive four-year dataset (2020-2023), establishing the first preliminary baseline for atmospheric Hg concentrations in Italy. These Hg data are supplemented by concurrent meteorological measurements at each station, enabling multi-parameter analysis. The provided integrated dataset supports a extensive characterization of atmospheric Hg behaviour across the Italian peninsula, enabling the assessment of emission reduction policies mandated by the Minamata Convention on Mercury.