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| Author(s): |
Eliete dos Santos Sousa
Total Authors: 1
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| Document type: | Doctoral Thesis |
| Press: | Piracicaba. |
| Institution: | Universidade de São Paulo (USP). Centro de Energia Nuclear na Agricultura (CENA/STB) |
| Defense date: | 2013-04-08 |
| Examining board members: |
Reynaldo Luiz Victoria;
Ricardo de Oliveira Figueiredo;
Marisa de Cassia Piccolo
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| Advisor: | Reynaldo Luiz Victoria |
| Abstract | |
In the largest basin of the planet, the Amazon river carries large amounts of particulate and dissolved carbon to the oceans. This traditional view of rivers as carriers of carbon to the oceans has been reviewed in the last decades due to new results showing that CO2 emissions to the atmosphere from these systems can surpass C transport in discharge in one order of magnitude. Several studies have been conducted to evaluate the processes controlling these emissions. However they still remain a major source of uncertainty. The main objective of this study was to quantify CO2 evasive fluxes in rivers and streams of Southwestern Amazon (Purus river basin, Acre state), taking into account chemical and physical characteristics of each system, as well as seasonality in this region and, thus, contribute to improve estimates of carbon emissions throughout the Amazon basin. The results showed that during low water the rivers have relatively high bicarbonate concentrations, indicating that carbonate weathering is an important carbon source. Dissolved inorganic carbon isotopic composition corroborated these results. However, in streams the main carbon source is soil organic matter. Seasonality has a strong influence on pCO2 and consequently on CO2 fluxes, with the highest values occurring in the rainy season. However there was no seasonal variability in respiration rates, which shows that other factors than respiration are also influencing CO2 fluxes. During the dry period, increases in chlorophyll a indicate that photosynthetic processes also play an important role in the C balance of these systems. (AU) | |