Chasing quicksilver northward: mercury chemistry in the Arctic troposphere

The tropospheric boundary layer chemistry of Hg has been simulated using a two-phase photochemical box model to see if our current (experimental and theoretical) understanding of Hg-(g)(0) reaction rates can account for the depletion events seen during Arctic spring, when the so-called 'bromine explosion' in the model is constrained by the measured ozone depletion rate. The simulations reveal that the observed rate of Hg-(g)(0) depletion can be accounted for; however, the measured concentrations of gas-phase oxidised Hg and Hg-P (Hg associated with particulate matter) cannot. Simulating the emission of Hg-(g)(0) from the snow pack to mimic the observed concentration recovery after a depletion event suggests the net Hg deposition from a depletion event is all but irrelevant.