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Atmospheric deposition (wet and dry) and nutrient cycles in Amazon Basin

Luciene Lara, Instituto de Fisica, Universidade de São Paulo, (Presenting)
Theotonio Pauliquevis, Instituto de Fisica, Universidade de São Paulo,
Paulo Artaxo, Instituto de Fisica, Universidade de São Paulo,

Wet and dry deposition plays an essential role in the functioning of the biogeochemical cycles of carbon and nitrogen since it acts as a source of nutrients to ecosystems. This paper describes the relationship between biogenic emissions from tropical forests and the concentration organic acids and nitrogen in rainwater and aerosols. We also addressed how the anthropogenic activities are changing the concentration and deposition patterns of carbon and nitrogen in Brazil. For that, it was collected rainwater and aerosol (fine and coarse mode) samples in different sites in Brazil. Land cover and land-use changes are probably responsible for the spatial variability found in precipitation and aerosol chemistry. The origin of the free acidity in rainwater is different in each site and come out to be linked to the land cover. Organic acids appear to control the acidity in remote areas while in other sites inorganic acidity has been detected. In addition, land-use changes, mostly the conversion of primary forest to pasture or croplands by biomass burning, are altering the concentration and the pattern of organic acids in rainwater. The composition of rainwater and aerosols in the disturbed sites appears to be controlled mostly by two sources: biomass burning and industrial emissions, and in the remote areas by biogenic emissions and marine influence. Additionally, nitrogen deposition was significantly higher in the disturbed sites and organic carbon deposition was significantly lower in these sites. Indeed, N wet deposition increases from an annual rate of 3.0 kg.N.ha-1.yr-1 in pristine areas to an annual rate of 5.6 kg.N.ha-1.yr-1 in disturbed regions. Moreover, the pattern of organic acids such as the rate of formate to acetate also has been changed due to biomass burning. We can anticipate that these large perturbations in the nitrogen and carbon deposition patterns have important deleterious consequences for the ecosystem functioning.

Science Theme:  ND (Nutrient Dynamics)

Session:  1B: Nutrient Cycling in Terrestrial and Aquatic Systems

Presentation Type:  Oral

Abstract ID: 101

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