Recent accumulation of atmospheric mercury in peatlands of Tierra del Fuego, Southern South America, Argentina.

SAPKOTA, A.; RABASSA, J. O.; FENG, X.; BING, H.; PONCE, J. F.; FERNÁNDEZ, M.

Rio Cuarto

Congreso; V Congreso Argentino de Cuaternario y Geomorfología; 2012

Ombrotrophic peat has been widely used to estimate the global depositional flux of atmospheric mercury deposition both during the industrial age and the preindustrial age. A peat core of 1.5 m length from the Harberton peat bog, Beagle Channel, Tierra del Fuego, was collected to reconstruct the past atmospheric mercury deposition rates for about the last 2000 years. Based on the available age date, it is estimated that the collected peat core, i.e. 1.5 m, represents the Hg accumulation rates beginning 1200 cal yr BP (around 750 AD) to the present day, with a peat accumulation rates of ~1mm/yr. Assuming the average peat density of ombrotrophic nature, that is, 0.1 g/cm3, the atmospheric depositional fluxes of Hg ranges between 0.88 and 4.80 µg/m2/yr. Despite the calculated rates were similar with the observed direct measurements of modern wet mercury deposition rates in remote areas (1 – 4 µg/m2/yr), the Hg deposition in the Harberton peat bog was found to be increasing for the last ca. 100 yrs. The possible reason for the enhanced Hg in the top could be the combined effect of increased anthropogenic Hg emission as well as recent volcanic eruptions such as Mt. Hudson in 1991. For the rest of the core, despite the cycling nature of Hg, two enhanced peaks were observed at ca. 55 cm and 120 cm which could be due to volcanic emissions as well. In any case, Sub-Antarctic peatlands are very promising environments in terms of providing detailed records with past atmospheric geochemical information. The Hg concentration of the studied section will be compared with the pollen, phytolith and diatom content of the same sections of the core.