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Title: Deposição do mercúrio através da serapilheira na Mata Atlântica, Parque Estadual da Pedra Branca, RJ
Keywords: Deposição Atmosférica;  Floresta Tropical;  Mercúrio;  Mata Atlântica;  Atmospheric Deposition;  Tropical Rainforest;  Mercury;  Trace Element;  Atlantic Florest
Issue Date: 25-Feb-2008
Abstract: The Atlantic Forest, a hotspot in the world with a great diversity of plants and animals, is located in the most industrialized region of Brazil, a potential source of chemical elements for the atmosphere. Recently, was described the Hg litterfall input to the soil mainly, after the stomatal (leaf pores) uptake, acting as an important way to transport this pollutant from air to soil. This flux of mercury is more notable in tropical forests, which have the higher annual litter production. The aim of this work was quantify the total concentration of Hg in litterfall, and estimate how much was deposited in the Parque Estadual da Pedra Branca, na cidade do Rio de Janeiro. Leaves of the five most predominant species were analyzed to assess the Hg concentrations by canopy leaves and test the correlations with foliar anatomical parameters, such as stomatal and trichomatic frequency. The annual mean of Hg concentration was 237, 7+ 52 ng g-1 and the flux was 184, 2 + 98 μg m-2 over a 7,6 t.ha-1 of litter production. The past two months temperature was correlated to the monthly concentration deviation, showing the relation with biochemistry process ruling the plant growing. The monthly precipitation had a strong negative correlation with the Hg concentrations of the higher temperature months. These correlations confirm the dependency on physiological events, controlled by biochemistry processes that rule the stomatal opening, being optimal during high temperatures and soil with no water deficiency. The green foliage Hg concentration revealed a great interespecific variation, from 60 ng g-1 - Metternichia principes, 84 ng g-1 - Colubrina. glandulosa,170 ng g-1 - Cordia trichotoma, 190 ng g-1 - Piptadenia gonoacantha to 215 ng g-1 - Alchornea iricurana. There was a clear positive correlation between these concentrations and the stomatal density of these species, except by the species with trichomes, showing one more evidence of the stomatal uptake and the superficial trichomes adsorption roles. These results are very high even to a polluted urban area, and show the complexity of phenological and climatic phenomena that rules the Hg uptake in tropical forests. This potential uptake of Mata Atlantica must be considered for their conservation and preservation, once the Hg soil destination came from litter, is unknown. Due to the global Hg pollutant status, the development of international laws, to Hg air emissions, is crucial.
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