Application of activated carbon traps to quantify mercury emissions in volcanic and hydrothermal environments

Mercury (Hg) is classified by the World Health Organization as one of the top ten chemicals of major public health concern due to its high toxicity and propensity for bioaccumulation. While anthropogenic emissions have been extensively studied, natural contributions such as volcanic degassing remain poorly constrained. Volcanic activity is a significant natural source of Hg, contributing approximately 340 Mg yr-1 [Bagnato et al. 2007; Yin et al. 2024], primarily in the form of gaseous elemental mercury (Hg0, GEM). The Hg undergoes long-range global transport, necessitating a more precise quantification of these natural inputs. Several studies have been carried out to understand the volcanic Hg budget using techniques such as Au traps and Lumex RA-915 mercury analyzer [Edwards et al. 2020 and reference therein]. This study aims to test activated carbon traps across different geological settings to quantify the concentration of the Hg outflux. Sampling has been conducted at Vulcano Island, Campi Flegrei, Paternò and Montecchie. After sampling, all activated carbon traps have been analysed using a Milestone Direct Mercury Analyzer (DMA-80) Tricell available at the Earth Sciences Department of Sapienza University of Rome. The sampling procedure has consisted of exposing the traps under controlled flow rate varying from 0.5 to 5 L min-1 and for different duration from 6 to 120 min. Traps have been located both in the vicinity of and above fumaroles. Furthermore, soil gas measurements have been carried out using a pump and syringe system for gas extraction. Preliminary results obtained from the different geological contexts show Hg quantities ranging from 0.23 ng at Montecchie up to 272 ng in the soil gases of Pisciarelli (Campi Flegrei) as a function of exposure time and flux. Similar values are also recorded in Paternò with 0.24 ng of Hg both at 6 and 12 minutes. Our data will be discussed in terms of establishing a protocol for the use of activated carbon traps in different geological environments and to be able to contribute to the volcanic and hydrothermal Hg monitoring.