Atmospheric Mercury Depletion Events: Assessment Impact of Meteorological Parameters in the Arctic Winter

In 2001, the mercury analyzer was installed at Amderma (69.45⁰ N, 61.39⁰ E, 49 m above sea level; Yugor Peninsula) in the Nenets Autonomous Okrug (Russia) to carry out continuous measurements of gaseous elemental mercury vapor concentration in the atmospheric surface layer. The data analysis demonstrated that the atmospheric mercury depletion evens (AMDEs, concentration < 1 ng m^-3) are observed on a rather limited territory, i.e. along the coast of the Arctic seas. During observational period (2001-2015), the analyzer was placed at three locations at different distances (8.9 km – 2001-2004, 2.5 km – 2005-2010, and 200 m - 2010-2015) from the Kara Sea coast.

For the AMDEs cases, during winters of 2001-2004 the air temperature was in range from -15⁰С to -31⁰С and relative humidity – 68-84%. The dominated atmospheric transport for these cases was mainly observed from the N-N-W direction. The number AMDEs relative to all measurements was about 0.2%. For 2005-2010, the temperature ranged from -1⁰С to -37⁰С and relative humidity – 74-83%. The atmospheric transport – from the E-E-N direction. The number AMDEs relative to all measurements was 2.7%. For 2010-2013, the temperature varied from -22⁰С to -27⁰С and relative humidity – 75-87%. The atmospheric transport – mainly from the S-S-W direction. The number AMDEs relative to all measurements was 26.9%, showing substantial 10-fold increase of AMDEs compared with the previous period. As a result, all cases correspond to range of air temperatures from -1⁰C to -37⁰C and relative humidity of 68-87% for entire monitoring period considered.

For selected considered episode (29-30 Mar 2002), the air temperature varied from -26⁰C to -31⁰C, and when it decreased to the minimum, the effect of mercury depletion was detected with the lowest concentration (0.39 ng m^-3). For episode (29 Feb - 1 Mar 2007), the temperature was also decreasing from -16⁰C to -37⁰C, and at reaching the minimum, the mercury concentration was also the lowest (0.12 ng m^-3). Moreover, in Dec 2006, for the first time, a significant number of AMDEs cases (23 events) was recorded during the polar night. In Feb 2010 the longer duration (up to 40 hours) AMDEs episodes were observed compared with Jan (up to 15 hours).

Note that all AMDEs are generally observed at lower air temperatures and relative humidity values with respect to the average values.