Anthropogenic mercury signals in lake sediments from southernmost Patagonia, Chile

Abstract

Atmospheric mercury fluxes to terrestrial and aquatic surfaces in the Northern Hemisphere have increased since the Industrial Revolution. However fluxes are not well characterized for the Southern Hemisphere, since environmental archives are comparatively scarce. Mercury records from 210Pb-dated sediment cores of three South Patagonian lakes were investigated in order to reveal the influence of anthropogenic activities on atmospheric mercury deposition in remote lakes of the Southern Hemisphere. Comparison with indicators of organic matter sources (carbon and nitrogen/carbon ratios) and a conservative mineral soil element (zirconium) in the sediments revealed that soil erosion is an important process contributing mercury to these lakes and influenced variation in concentrations through time. However, at ~1900AD mercury accumulation increased independent from soil erosion and peaked from 1980 to 2000AD. We attribute this to an increase in atmospheric mercury deposition in this remote region of the Southern Hemisphere. Mean flux ratios, which reflect the increase in modern mercury accumulation compared to pre-1850AD, lie within a range of 1.4 to 2.4. These values indicate an increase in atmospheric mercury deposition slightly lower than predictions derived from global mercury models that suggest an increase in Hg deposition by a factor of 2 to 3.