Total Mercury Mass Load from the Paglia–Tiber River System: The Contribution to Mediterranean Sea Hg Budget

Abstract

The Mediterranean Sea is characterized by a marked mercury (Hg) geochemical anomaly, arising in part from large Hg deposits. Mercury mass loads discharged from the Monte Amiata mining district (Central Italy) to the Mediterranean Sea through the Paglia–Tiber River system were estimated. Data from two seasons showed that up to 40 kg year−1 of Hg are drained to Tiber River and finally to the Mediterranean Sea. The mercury mass loads varied in different seasons, from 3 mg day−1 in the upper section of Paglia River in November to 42 g day−1 before the confluence with Tiber River in June. Along Tiber River, up to 15 ng L−1 of the total Hg found at a site after Rome showed that Hg can be discharged to the sea. The Alviano reservoir along Tiber River acts as a temporary trap for Hg-rich particulate, while dam operations may promote Hg release (up to 223 g day−1). The combination of hydrologic factors controlling Hg transport, the torrential regime in the upper catchment of Paglia River, the waterway steepness, together with Hg-contaminated legacy sediments in the Paglia River floodplain, make the Paglia–Tiber River system a long-lasting intermittent source of Hg to Tiber River and the Mediterranean Sea.

Tree Rings Record of Long-Term Atmospheric Hg Pollution in the Monte Amiata Mining District (Central Italy): Lessons from the Past for a Better Future

“…It was the third largest mercury (Hg) district worldwide (cumulative production of 102,000 tons; [32]), and currently hosts an important, actively exploited, geothermal field. Mining ceased in the early 1980s but left an impressive Hg contamination legacy in all environmental matrices, i.e., air, soil, sediments, water, and biota, as reported in recent years in several studies ( [33] and references therein; [34][35][36][37][38][39]). Exploitation of geothermal energy in the area started in 1959; currently, there are five active plants equipped with emission control systems (AMIS) to reduce Hg and H 2 S discharges from geothermal wells.…”

Process of mercury accumulation in urban strip river artificial wetland ecosystems: a case study of Changchun, a typical industrial city in Northeast China

“…The annual Hg export rate from surface runoff has been estimated to be 18.24 mg/m 2 (Gabriel et al, 2011). Natural conditions such as precipitation can exacerbate streambank erosion and alter the distribution of Hg along stream channels (Fornasaro et al, 2022). For example, rainfall can wash away mercury from the catchment leading to a threefold increase in mercury concentration in rivers (Gebka et al, 2018).…”