Fluxos de mercurio gasoso na interface solo/atmosfera na Bacia do Rio Negro utilizando camaras dinamicas de fluxo / Hg fluxes en the soil/air interface in the Negro River Basin (Amazon) by using dynamic flux chamber

AUTOR(ES)

Gabriella Magarelli

DATA DE PUBLICAÇÃO

2006

RESUMO

The aim of this thesis was to quantify the soil/air exchange of mercury in the Negro River Basin by using a Dynamic Flux Chamber. The methodological study showed that the flux chamber was efficient to compare the Hg fluxes in the different sites. However, the humidity inside the chamber and the low flushing flow rate could have subestimated the Hg fluxes. Hg fluxes found at the flooding forest and at the non-flooding forest were low but they are in agreement with literature reports. At the forest sites, the evasive diurnal Hg fluxes (mean of 1.3 ± 1.3 pmol m-2 h-1) were equivalent to the nocturnal fluxes (mean of -1.3 ± 1.2 pmol m-2h-1), concluding that the forest soils of the Negro River Basin do not export Hg to the atmosphere.What occurs is a Hg cycling of about 0.7 t y-1 inside the forest. The deposition of Hg to the forests soils from litterfall showed to be the most significative Hg input to the forest, whose value was 26.6 t y-1. The deforested sites of the Negro River Basin presented Hg fluxes in the soil/air exchange higher than the forest sites (12.3 ± 9.9 pmol m-2 h-1). This led to an important conclusion that the absence of vegetal covering significantly enhances Hg soil emissions, both in areas of flooding and in nonflooding soils. At the Negro River Basin, considering 1% of desforestation, the Hg mass exported to the atmosphere from the deforested soils would be 0.13 t ano-1. Besides the importance to estimating the Hg0 fluxes at the air/soil interface for a Hg biogeochemistry study of the Negro River Basin, the understanding of the factors that could affect these Hg fuxes is very important. Among the environmental paramethers studied, the soil temperature, the solar radiation and the soil organic matter were the paramethers which showed the highest correlations with the Hg fluxes. Key-words: mercury fluxes, soil/air exchange, flux chamber, Amazon, soil temperature

ASSUNTO(S)

soil-atmosphere mercurio mercury solo-atmosfera

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