Decreasing trends in total gaseous mercury observations in baseline air at mace head, ireland from 1996 to 2011

Abstract

The Mace Head dataset comprises the longest existing time series of atmospheric mercury measurements with high time resolution in the temperate marine background atmosphere, starting in September 1995. For this study, the concentrations of total gaseous mercury in baseline air masses arriving at Mace Head, Ireland have been analyzed for possible trends in the atmospheric mercury background concentration over a 16-year period (i.e., 1996-2011). Statistical analyses have revealed a significant negative (downwards) trend of -0.027 +/-0.01 ng/m(3) yr(-1), or -1.4 to 1.8% per year. Furthermore, evidence of a seasonal cycle was found with somewhat higher concentrations during the winter time and somewhat lower concentrations during summer.