The use of the 210Pb method for preliminary evaluating the sedimentation rate in Amazon river mouth

Annals of Warsaw University of Life Sciences – SGGW
Land Reclamation No 42 (1), 2010: 149–157
(Ann. Warsaw Univ. of Life Sci. – SGGW, Land Reclam. 42 (1), 2010)

The use of the 210Pb method for preliminary evaluating the sedimentation rate in Amazon river mouth

SOPHIE ALTHAMMER1, ERICH FOßHAG1, HARALD MARTIN HOFFMANN1, JOSÉ REINALDO CARDOSO NERY2, DANIEL MARCOS BONOTTO3
1Institute for Physical Chemistry and Radiochemistry, Mannheim University of Applied Sciences, Germany
2Universidade Federal do Amapá (UNIFAP), Brasil
3Departamento de Petrologia e Metalogenia, Universidade Estadual Paulista (UNESP), Brasil

Abstract: This investigation reports the preliminary results for determining the sedimentation rate at the Amazonas River mouth, Brazil, by the 210Pb method. The CIC (constant initial concentration) of unsupported/excess 210Pb model was successfully applied to one sediments core. The measurements were made in a sediments core comprising ten samples 10 cm – thick each. The year of the sampling (2006) was used as reference for the establishment of the rate of sedimentation from the beginning of the top of the testimony. However, the atmospheric conditions and climate in Amapá State, Brazil, claimed for optimization of the results. Because the Channel North is opened into the Atlantic Ocean, it exhibits a huge water volume, causing a permanent motion of sediments and water. So, heavy waves are formed at the water surface, stirring the upper sand strata. Only at a depth of 40–50 cm the profi le tends to be more homogeneous, where it is mostly composed by fi ne sand and very fi ne sand. Thus, it is reasonable utilize the CIC model from 210Pb data, which allows estimate a sedimentation rate corresponding to 0.61 g/cm²yr and a mean linear rate of 0.8 cm/yr. The 238U and 210Pb activities in the sediments allowed the reconstruction of the sedimentation processes over a period of about 130 years.

Key words: sedimentation rate, unsupported/excess 210Pb model, 210Pb-method, Amazonas River mouth

Streszczenie: Zastosowanie metody 210Pb do wstępnej oceny intensywności sedymentacji w ujściu rzeki Amazonki. W pracy przedstawiono wyniki badań przebiegu procesu sedymentacji w obszarze ujściowym rzeki Amazonki. Do oceny intensywności sedymentacji wykorzystano model CIC (Constant Initial Concentration) aktywności 210Pb, którą badano w dziesięciu 10-cm warstwach osadu pobranego w 2006 roku. Zastosowana metoda pozwoliła na ocenę przebiegu procesu sedymentacji osadów w okresie 130 lat. Górne warstwy osadów o miąższości 40–50 cm posiadają zaburzoną strukturę i aktywność 210Pb, spowodowaną okresowym oddziaływaniem fal oceanicznych i wód słonych. Dolne warstwy osadu, w których dominują piaski bardzo drobne i drobne, posiadają homogeniczną strukturę oraz liniowo zmienną aktywność 210Pb. Stwierdzono, że średnia intensywność sedymentacji w analizowanym obszarze wynosi 0,61 g⋅cm–²⋅rok–1, co odpowiada warstwie o miąższości 0,8 cm⋅rok–1.

Please use the following format to cite the selected article:
ALTHAMMER S., FOßHAG E., HOFFMANN H.M., JOSÉ REINALDO CARDOSO NERY, BONOTTO D.M. The use of the 210Pb method for preliminary evaluating the sedimentation rate in Amazon river mouth. Annals of Warsaw University of Life Sciences – SGGW. Land Reclamation No 42 (1), 2010: 149–157

Authors’ addresses:
Sophie Althammer, Erich Foßhag, Harald Martin Hoffmann
Institute for Physical Chemistry and Radiochemistry,
Mannheim University of Applied Sciences,
Paul-Wittsack-Straße 10, 68163 Mannheim, Germany
e-mail: sophie.althammer@daimler.com
e.fosshag@hs-mannheim.de
H.Hoffmann@hs-mannheim.de

José Reinaldo Cardoso Nery
Universidade Federal do Amapá (UNIFAP) Campus
Marco Zero, Rodovia Juscelino Kubitschek,
68902-280 Macapá, Amapá
Brasil
e-mail: jrnery@unifap.br

Daniel Marcos Bonotto
Departamento de Petrologia e Metalogenia
Universidade Estadual Paulista (UNESP)
Câmpus de Rio Claro, Av. 24-A No 1515, C.P. 178
13506-900 Rio Claro, São Paulo
Brasil
e-mail: dbonotto@rc.unesp.br

ALTHAMMER S., FOßHAG E., HOFFMANN H.M., JOSÉ REINALDO CARDOSO NERY, BONOTTO D.M. The use of the 210Pb method for preliminary evaluating the sedimentation rate in Amazon river mouth

DOI 10.2478/v10060-008-0073-7