Annual time-series of total filterable atmospheric mercury concentrations in the Arctic

Abstract

Total atmospheric mercury (TAM) is operationally defined as the sum of gaseous elemental mercury (GEM), gaseous oxidized inorganic mercury (GOIM), which is also called reactive gaseous mercury (RGM), and total filterable mercury (TFM). An annual weekly-integrated time-series of TFM concentrations in ambient air at Alert, Nunavut, Canada from March 1998 to March 1999 is reported in this paper. The observed TFM concentrations ranged from 0 to 0.37 ng m⁻³ with the highest value occurring in the spring after polar sunrise and the lowest in summer. The average values for the four seasons are 0.086 (March—May), 0.00085 (June—August), 0.0015 (September—November) and 0.013 ng m⁻³ (December 1998–February 1999) respectively. This pattern is anti-correlated to that of GEM concentration observed at the same location. The GOIM concentration, calculated using the equation [GOIM]=[TAM]−[GEM]−[TFM], is also anti-correlated with GEM concentration. The annual time-series of the TFM operational blank values shows the same temporal pattern as the TFM concentration, with values ranging from 0.00 to 0.011 ng m⁻³. These results confirm that, in the polar regions, GEM oxidation and atmospheric deposition of mercury occur mainly in the 3-month period after polar sunrise. Incisive laboratory and field experiments are needed to either confirm or rule out the springtime GEM oxidation/conversion mechanisms proposed in this paper.