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International audience; Volcanic and geothermal areas are important natural sources of mercury, with mercury concentrations in volcanic gases above the atmospheric background. Individual volcanoes exhibit variable degassing features and behavior, leading to considerable uncertainty in global geogenic mercury fluxes estimations. Likewise, studies on mercury emissions from submarine volcanic and hydrothermal sites are scarce. Nevertheless, information on those natural inputs is needed to better estimate the anthropogenic mercury enrichment, and thus for the implementation of the Minamata convention.During Spring 2021, the GEOFLAMME campaign took place at the northern end of the Mozambique channel, where we examined the influence of volcanic inputs from a volcano that had formed less than 2 years ago near Mayotte Island. Water samples were obtained with a trace metal-clean CTD rosette and all-titanium high-pressure samplers using the remotely operated vehicle Victor 6000 on board R/V Pourquoi pas?. Total mercury was measured on board via Cold Vapour Atomic Fluorescence Spectroscopy (CV-AFS) following the EPA method 1631. Exhaled fluid samples from titanium samplers followed the same analytical scheme, but at the shore laboratory.Mercury levels measured from water column showed increased concentrations near the seafloor. Total mercury measured in fluid samples from the different venting sites showed concentrations 3 to 60 times higher than surrounding seawater.Our study provides new insight to the understanding for mercury biogeochemistry, the interactions between magmatism, tectonics and fluids circulation processes, as well as the implications on the physical-chemical properties of the water column. It also improves our knowledge on present-day mercury cycling in the marine environment usingfield-based data. Ongoing work will attempt to quantify seafloor mercury inputs to the vicinity of the Mayotte Island.

Long-term monitoring data of ambient mercury (Hg) on a global scale to assess its emission, transport, atmospheric chemistry, and deposition processes is vital to understanding the impact of Hg pollution on the environment. The Global Mercury Observation System (GMOS) started in November 2010 with the overall goal to develop a coordinated global observing system to monitor Hg on a global scale, including a large network of ground-based monitoring stations, ad hoc oceanographic cruises and measurement flights in the troposphere and lower stratosphere. To date, more than 40 ground-based monitoring sites constitute the global network covering many regions where little to no observational data were available before GMOS. This work presents atmospheric Hg concentrations recorded worldwide, analyzing Hg measurement results in terms of temporal trends, seasonality and comparability within the network. Major findings highlighted a clear gradient of atmospheric Hg concentrations between the Northern and Southern Hemispheres, confirming that the gradient observed is mostly driven by local and regional sources, which can be anthropogenic, natural or a combination of both. In order to understand the atmospheric cycling and seasonal depositional characteristics of Hg, wet deposition samples were also collected at 17 selected GMOS monitoring sites providing new insight into baseline concentrations of THg concentrations in precipitation particularly in regions, such as the Southern Hemisphere and Tropical areas where wet deposition were never investigated before, opening the way for additional measurements across the GMOS network and new findings in future modeling studies highlighting the need of integrated measurements in ambient air and rainwater samples to improve our understanding of deposition processes and oxidation mechanisms. These new observations in fact, give scientists and modelers some insight into baseline concentrations of Hg concentrations in air and precipitation with the overarching benefit which clearly consists in the advancement of knowledge about Hg processes on global scale.

International audience; Over the last few years, the development of 3D printing has enabled numerous advances in research. This type of printing technology opens a vast array of possibilities in analytical chemistry, and more particularly in the field of flow analysis. Ease of fabrication and flexibility of this technology has led to the development of a new type of system for the determination of lead in natural waters. This device is composed of three units: a column for selective retention of lead, a mixing coil and a microfluidic cell for UV-Vis spectroscopy. The final goal is to get a fast system which can be used on site, with a low limit of detection and quantification.