O papel da matéria orgânica e do hidromorfismo na dinâmica do mercúrio em diferentes solos da Amazônia Central
Mercury dynamics in fluvial basins can be influenced by pedagogical processes and interactions with soil organic matter. In the Brazilian Amazon soils have been shown to contain elevated levels of Mercury and play an importante role in the regional mercury cycle. Two classes of soils, hydromorphic p...
| Autor principal: | Sousa, Otávio Peleja de |
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| Grau: | Dissertação |
| Idioma: | por |
| Publicado em: |
Instituto Nacional de Pesquisas da Amazônia - INPA
2020
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| Acesso em linha: |
https://repositorio.inpa.gov.br/handle/1/11256 http://lattes.cnpq.br/7976215069171360 |
| Resumo: |
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Mercury dynamics in fluvial basins can be influenced by pedagogical processes and interactions with soil organic matter. In the Brazilian Amazon soils have been shown to contain elevated levels of Mercury and play an importante role in the regional mercury cycle. Two classes of soils, hydromorphic podzols and latosols, both widely distributed in the Amazon Region, differ in their mercury loads and interact in distinct manners with organic matter. The interaction between mercury and organic matter is still poorly understood in these soils. The objective of the present study was to investigate the roles of hydromorphism and organic matter in the dynamics of mercury is first order stream basins draining these distinct soil types (hydromorphic podzol and latosol) in the Central Brazilian Amazon. Samples of soil and filtered stream water were collected from two first order stream basins, one containing predominantly hydromorphic podzols (Campina Reserve, Campina Stream) and one containing primarily latosols (Ducke Reserve, Barro Branco Stream). In each basin, vertical profiles of soil were sampled in three compartments along a topo-sequence (plateau, slope and lowland). Samples of filtered stream water and soils (fine <63 μm and coarse >63 μm) were analyzed for total mercury (HgTF and HgT) by CVAFS (MERX, Brooks Rand®) and CVAAS (FIMS 400, Perkin Elmer®), respectively. Samples of soil and water were also analyzed for water extractable organic carbon (COEA) and dissolved organic carbon, respectively, and specific UV absorption (SUVA254). Independent of topographic compartment and soil type, HgT concentrations were always highest in the fine fraction. HgT levels in podzols varied from 28-531 ng/g in the fine fraction and from 2-46 ng/g in the coarse fraction. In latosols, HgT varied from 221-340 ng/g in the fine fraction and from 25-107 ng/g in the coarse fraction. HgT concentrations in the podzol increased with declining elevation (plateau<slope<lowland), reflecting the progressive migration and accumulation of fine eluvial particals, rich in HgT, along the toposequence. The levels of COEA and SUVA254 in the podzols were positively correlated with HgT in both the fine fraction (Spearman; r=0,81 and 0,75, respectively) and the coarse fraction (r=0,66 e 0,86, respectively). The average concentration of HgTF in the stream draining podzols (9,6±3,7 ng/L) was significantly higher (t= 3,30; p=0,0035) than that in the stream draining latosols (4,9±2,8 ng/L). Postive correlations were observed between HgTF and SUVA254 (R2=0,95; p<0,001) and between HgTF and COD(R2= 0,94; p<0,001) in the stream draining hydromorphic podzols. Similar correlations were not found in the stream draining latosols. These results indicate that latosols are efficient at sequestering HgT and organic matter, while hydromorphism and organic matter dynamics in podzols play a fundamental role in mobilizing and exporting mercury to the Amazon river system. |