Propagação dos Fluxos de Sedimentos em suspensão do Rio Amazonas- Trecho Tamshiyacu (Peru) até Óbidos(Brasil)-Variabilidade Espacial e Temporal
The sediments flux in Amazon Basin have an important role on the aquatic biodiversity and richness in the floodplains because the nutrients and organic matter attached on suspended sediments are deposited in these zones. The suspended sediments have influence in the geomorphology of Amazon River too...
| Autor principal: | Cárdenas, Elisa Natalia Armijos |
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| Grau: | Tese |
| Idioma: | por |
| Publicado em: |
Instituto Nacional de Pesquisas da Amazônia - INPA
2020
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| Assuntos: | |
| Acesso em linha: |
https://repositorio.inpa.gov.br/handle/1/12676 http://lattes.cnpq.br/4352761886147088 |
| Resumo: |
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The sediments flux in Amazon Basin have an important role on the aquatic biodiversity and richness in the floodplains because the nutrients and organic matter attached
on suspended sediments are deposited in these zones. The suspended sediments have
influence in the geomorphology of Amazon River too, because where they are deposited
in zone of low turbulence new isle are create. The sediments flux have influence in
the meandering movement and sometimes this movement can cause meanders to cutoff
and create new lakes. These changes and richeness have influence in the Amazonian
population.
The Amazon Basin is considered in global terms as one of main source of suspended
sediments of Atlantic Ocean, but the Andean region and foreland provide 90% of sedi-
ments at the Amazon Basin.
The aim of this study is to understand the spatial and temporal distribution of
sediments flux in the Amazon River, therefore were select four gauging station located
along of Amazon Riven from Peru to Brazil. In each gauging station was make superfi-
cial samples each ten days and samples in the section in different times of hydrological
period. Turbidity profiles and granulometry measuring were made too in each gauging
station.
In the Andean region, it is observed a relationship between the suspended sediments
concentration and discharge, however, this relationship become a hysteresis in the plain
especially in the Óbidos gauging station located at 870 km before of mouth. This result
can be by the contribution of influx poor in suspended sediments from Guyanese and
Brazilian shields.
In 3000 km of long from Peru to Brazil plain, the suspended sediments is composed
by two well defined types of suspended sediments: fine sediments (10-20 μm) and coarse
sediments (100-250 μm). The percentage of each type of sediments in the main river is
different during the hydrologic regime. Peak of fine sediments is observed in the same
period of peak of rainfall (December to March) and peak of coarse sediments is observed
in flood period (May to July).
The Andean and sub-Andean basin gauging station show the coarse sediments in
surface due to great turbulence and low depths. Therefore, this gauging station show
a relationship between the suspended sediments concentration in surface and averagesuspended sediments concentration in section, with this relation is possible to calcu-
late the suspended sediments flux. Hence the Peruvian basin provide 540 Mt year −1 .
However in the Brazilian plain the context is different, the depth is from 40 to 100 m,
becoming almost null the presence of coarse sediments in the surface. Therefore, cannot
use the relationship between suspended sediments concentration in surface and average
suspended sediments concentration in section. When the Óbidos gauging station is
analysed, it found there is a relationship between suspended sediments concentration
in surface and average of fine suspended sediments concentration. It is observed too,
that there is the relationship between coarse suspended sediments concentration and
discharge. Therefore, it is possible to calculate of suspended sediments flux using this
two relationships. The Amazon River export 1100 Mt year − 1 of suspended sediments
at Óbidos gauging station, of which 60% correspond at fine sediments flux and 40% to
coarse sediments flux. It is observed that the suspended sediments are sensitivity of
climate variability, generally El Niño events is associate with increase of fine suspended
sediments and La Niña events increase a percentage of coarse sediments in Amazon
River.
It is using the turbidity for determinate of suspended sediments concentration, we
use this technique due the high frequency in acquisition of data. However for use
the turbidity is necessary the previous calibration. It was observed that the turbidity
signal is an addition to the signal emitted by the particles in one sample and with this
assumption the Rose model was used to separate the concentration signal obtained by
the turbidity of these two types of sediments present in the Amazon River, fine particles
and sand. Therefore, it was obtained the concentration profiles to fine sediments and the
concentration profiles to the sand. It is observed during the rising period that the fine
sediments profiles show a strong gradient, however in the flood periods this gradient
reduce come a constant in all section. These results show that turbidity and Rouse
model can be used for prediction of suspended concentration in Amazon River.
Keywords: suspended sedi |