Dynamic Oxidation of Gaseous Mercury in the Arctic Troposphere at Polar Sunrise

TLDR

Gaseous elemental mercury is a globally distributed air toxin with a long atmospheric residence time, so any process that shortens its lifetime can increase its potential accumulation in the biosphere. Our measurements at Barrow, AK, show that rapid, photochemically driven oxidation of boundary‑layer Hg0 after polar sunrise—likely by reactive halogens—produces oxidized mercury that deposits in the remote Arctic troposphere at concentrations exceeding 900 pg m⁻³, accumulates in snowpack in a bioavailable form, and is released during summer melt, indicating a recent, widespread polar phenomenon.

Abstract

Gaseous elemental mercury (Hg0) is a globally distributed air toxin with a long atmospheric residence time. Any process that reduces its atmospheric lifetime increases its potential accumulation in the biosphere. Our data from Barrow, AK, at 71° N show that rapid, photochemically driven oxidation of boundary-layer Hg0 after polar sunrise, probably by reactive halogens, creates a rapidly depositing species of oxidized gaseous mercury in the remote Arctic troposphere at concentrations in excess of 900 pg m-3. This mercury accumulates in the snowpack during polar spring at an accelerated rate in a form that is bioavailable to bacteria and is released with snowmelt during the summer emergence of the Arctic ecosystem. Evidence suggests that this is a recent phenomenon that may be occurring throughout the earth's polar regions.