Mercury (Hg) is one of the most harmful metals to the environment. This study focuses on factors that influence mercury distribution in sediments and its bioavailability. Given the history of contamination in the Tagus estuary, sediment cores were collected and pore waters were separated from two sites: one heavily contaminated, Cala do Norte (CN), and a non-contaminated, Ponta da Erva (PE). The levels of total Hg and methylmercury (MeHg) in solid sediments and dissolved Hg (HgR and HgT) and MeHg in the pore waters were analyzed and compared to other parameters in sediments. Total Hg...