Rare Earth Elements abundance, fractionation, and anomalies in the sediments of the Cananéia-Iguape Estuarine-Lagoon Complex in Brazil
The Cananéia-Iguape Estuarine-Lagoon Complex (CIELC) is an extremely productive coastal ecosystem. It encloses the Valo Grande channel, built 160 years ago, which introduces water from the Ribeira River directly into the estuarine system, contributing to important biogeochemical changes in the regi...
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| Main Authors: | , , |
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| Format: | Article |
| Language: | English |
| Published: |
Instituto Oceanográfico da Universidade de São Paulo
2024-04-01
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| Series: | Ocean and Coastal Research |
| Subjects: | |
| Online Access: | https://www.journals.usp.br/ocr/article/view/222828 |
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| Summary: | The Cananéia-Iguape Estuarine-Lagoon Complex (CIELC) is an extremely productive coastal ecosystem. It encloses
the Valo Grande channel, built 160 years ago, which introduces water from the Ribeira River directly into the estuarine
system, contributing to important biogeochemical changes in the region. Many nutrients arrive at the estuary through
this channel, as well as metals and other slightly soluble elements that become part of the sediments. This study
aims to evaluate the processes that govern the distribution of rare earth elements (REE) in the sediments of the
complex by using fractionation patterns, anomalies, and the geochemical signature of minerals to evaluate sources,
natural levels, and the possible anthropogenic forcing to which CIELC is subjected. ∑REE* ranged from 14.2 to 285
mg kg-1 and showed a distribution related to depositional/textural characteristics influenced by the regional and local
lithological setting and a possible contamination. The REE/Al ratio indicated enrichment in the sea adjacent to the
estuary and at stations in the Ribeira River and Valo Grande. While the Hf/Al ratio indicated natural enrichment related
to the presence of heavy minerals in most of these stations, this ratio fails to justify enrichment at some stations in
the northern part of the estuary and the Ribeira River. Fractionation patterns and anomalies allowed us to identify
the main heavy minerals related to REE enrichment at CIELC. Cerium (Ce) anomalies showed a possible relation
with biologically mediated Ce+3 to Ce+4 oxidation processes in the most productive areas of the estuary. Europium
(Eu) anomalies were strongly associated with different mineral assemblies in several CIELC sectors. Abundance,
fractionation patterns, and REE anomalies corroborate the categorization of CIELC sediments as part of a pristine
system in its southern region and as subject to anthropogenic influences in its northern area.
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| ISSN: | 2675-2824 |