Direct detection of atmospheric atomic bromine leading to mercury and ozone depletion

• DOI: 10.1073/pnas.1900613116
• Publication Date: 2019-06-29T00:15:46Z
• Authors: Siyuan Wang; Stephen M. McNamara; Christopher W. Moore; Daniel Obrist; Alexandra Steffen; Paul B. Shepson; Ralf M. Staebler; Angela R. W. Raso; Kerri A. Pratt
• Keywords: Mercury; Ozone Depletion

Bromine atoms play a central role in atmospheric reactive halogen chemistry, depleting ozone and elemental mercury, thereby enhancing deposition of toxic particularly the Arctic near-surface troposphere. However, direct bromine atom measurements have been missing to date, due lack analytical capability with sufficient sensitivity for ambient measurements. Here we present measurements, conducted springtime Arctic. Measured levels reached 14 parts per trillion (ppt, pmol mol-1; 4.2 × 108 cm-3) were up 3-10 times higher than estimates using previous indirect not considering critical molecular bromine. Observed mercury depletion rates are quantitatively explained by measured atoms, providing field validation highly uncertain chemistry. Following complete depletion, elevated concentrations sustained photochemical snowpack emissions nitrogen oxides, resulting continued depletion. This study provides breakthrough constraining chemistry polar atmosphere, where this connects rapidly changing surface pollutant fate.