Mercury fluxes in a natural forested Amazonian catchment (Serra do Navio, Amapa State, Brazil)

Mercury (I-Ig total) fluxes were calculated for rainwater, throughfall and stream water in a small catchment located in the northeastern region of the Brazilian Amazon (Serra do Navio, Amapa State), whose upper part is covere d by a natural rainforest and lower part was altered due to deforestation a nd activities related to manganese mining. The catchment area is 200 km fro m the nearest gold mining (garimpo). Minimum and maximum Hg concentrations were measured monthly from October 1996 to September 1997 and were 3.5-23.4 ng l(-1) for rainwater, 16.5-82.7 ng l(-1) for throughfall (March-August 1 997) and 1.2-6.1 and 4.2-18.8 ng l(-1) for stream water, in natural and dis turbed areas, respectively. In the natural area, the inputs were 18.2 mu g m(-2) year(-1) in rainwater and 72 mu g m(-2) year(-1) in throughfall. This enrichment was attributed to dry deposition. The stream output of 2.9 mu g m(-2) year(-1) indicates that Hg is being recycled within the forest as ot her chemical species or is being retained by the soil system, as confirmed by the cumulative Hg burden in the 0-10 cm surface layer, which was 36 480 mu g m When the disturbed area of the catchment was included, the stream ou tput was 9.3 mu g m(-2), clearly indicating the impact of the deforestation of the lower part of the basin on the release of mercury. The Hg burden in the disturbed area was 7560 mu g m(-2) for the 0-10 cm surface layer. (C) 2000 Elsevier Science B.V. All rights reserved.