Mercury is an important global toxic contaminant of concern that causes cognitive and neuromuscular damage in humans. It is ubiquitous in the environment and can travel in the air, in water, or adsorb to soils, snow, ice and sediment. Two significant factors that influence the fate of atmospheric mercury, its introduction to aquatic and terrestrial environments, and its bioaccumulation and biomagnification in biotic systems are the chemical species or forms that mercury exists as (elemental, oxidized or organic) and its physical phase (solid, liquid/aqueous, or gaseous). In this work, we show that previously unknown mercury-containing nanoparticles exist in the air using high-resolution scanning transmission electron microscopy imaging (HR-STEM). Deploying an urban-air field campaign near a mercury point source, we provide further evidence for mercury nanoparticles and determine the extent to which these particles contain two long suspected forms of oxidized mercury (mercuric bromide and mercuric chloride) using mercury mass spectrometry (Hg-MS). Using optical particle sizers, we also conclude that the conventional method of measuring gaseous oxidized mercury worldwide can trap up to 95% of nanoparticulate mercuric halides leading to erroneous measurements. Finally, we estimate airborne mercury aerosols may contribute to half of the oxidized mercury measured in wintertime Montréal urban air using Hg-MS. These emerging mercury-containing nanoparticle contaminants will influence mercury deposition, speciation and other atmospheric and aquatic biogeochemical mercury processes including the bioavailability of oxidized mercury to biota and its transformation to neurotoxic organic mercury.
Area of Research: Atmospheric Chemistry
This paper was published in Nature publications's Scientific Reports. (authors: Avik J. Ghoshdastidar1 & Parisa A. Ariya). View full article here
Prof. Parisa Ariya is a James McGill Professor of Atmospheric and Interfacial Chemistry, Professor at the Department of Atmospheric & oceanic Sciences as well as the Department of Chemistry at McGill. Her laboratory's research explore major fundamental, and applied research questions on chemical and physical processes involving aerosols, as well as organic and metal pollutants of relevance to the Earth's atmosphere and its interfaces. Our direct research contributions are to the fields of atmospheric sciences and climate change, specifically aerosol-cloud interaction, air pollution, atmosphere-ocean interactions, physical and analytical chemistry, sustainable chemistry and technology, nanoscience, environmental health and medicine.