Soils as an Important Sink for Mercury in the Amazon

ISSN： 0049-6979

Source： Water, Air, and Soil Pollution, Vol.126, Iss.3-4, 2001-03, pp. : 321-337

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Abstract

This work focuses on the behaviour of mercury in lateritic soil profiles found in the Serra do Navio and Tartarugalzinho areas of the State of Amapá in Northern Brazil. The Hg contents are high in the upper horizons of the soil profiles (100–300 g kg^-1), and decrease to less than 100 g kg^-1 at depths of 200 or 300 cm. The higher levels of Hg are associated with higher Fe concentrations, particularly in the ferruginous accumulations as mottles and nodules. For each horizon of the soil profile, balance calculations were used to distinguish the amount of mercury naturally accumulated from rocks through lateritic pedogenesis (lithogenic mercury) from the anthropogenic mercury introduced in the profile through atmospheric contamination. The results show that the anthropogenic contribution is significant in the upper horizons (up to 95%% of the total Hg), and decreases downward in the soil profile. Mercury burdens were calculated for soil profiles in both upslope (272 880 and 217 440 g m^-2 for the first 70 cm) and downslope positions (118 800 and 182 160 %g m^-2 for the first 70 cm). The loss of Hg in downslope profiles seems to be related to the natural evolution of iron duricrust into latossols, which has been brought about by climatic changes toward increasing humidity in the Amazon since the Tertiary.