Cyanobacteria and natural organic matter associated with the biogeochemical cycle of arsenic in the saline-alkaline lakes of the Nhecolândia Pantanal

Author(s)

Marianna Alves Cancian

• Document type: Master's Dissertation
• Press: Campinas, SP.
• Institution: Universidade Estadual de Campinas (UNICAMP). Instituto de Química
• Defense date: 2024-02-23

Examining board members

Anne Hélène Fostier; Marcia Cristina Bisinoti; Marli de Fátima Fiore

• Advisor: Anne Hélène Fostier

Abstract

Arsenic is widely distributed in natural environments and the degree of toxicity, availability and mobilization of As in the environment depends on its speciation. Results obtained in other studies have shown that: 1) the waters of the alkaline lagoons of the Nhecolândia Pantanal systematically show high concentrations of dissolved As (up to 3 mg L-1); 2) despite the extreme conditions, these lagoons harbor an abundant microbial community; 3) phytoplankton organisms have a low bioconcentration factor (BCF) in relation to arsenic; 4) this low BCF may be related to the bioavailability of As species associated with the role of dissolved organic matter in this environment, as metal/metalloid complexation can occur in the aquatic environment. Therefore, this work aimed to elucidate the role of two species of cyanobacteria (Anabaenopsis sp. and Limnospira sp.) in the process of bioaccumulation and biotransformation of As in the saline-alkaline lagoons of the Pantanal, and to characterize and elucidate the role of dissolved organic matter in the process of interaction with As(III) and As(V) species. The results obtained showed that the cyanobacteria had low BCF in relation to As. Anabaenopsis sp. and Limnospira sp. were able to assimilate As(V) and carry out the biotransformation process. Although As(V) was found to be the dominant species both in the culture medium and in the cultured cyanobacteria, it was also possible to detect and quantify As(III), monomethylarsonic acid (MMA(V)) and dimethylarsinic acid (DMA(V)), in addition to detecting other organo-arsenical species that could not yet be identified. The results obtained so far suggest that As(III) and As(V) species are complexed by dissolved organic matter. Thus, DOM may play a fundamental role in the mobility and availability of As in this environment. In addition, the results obtained in the characterization of DOM showed that different sources of natural organic matter, i.e. the different saline-alkaline lagoons, resulted in different DOM molecular structures with different properties (AU)

• FAPESP's process: 21/05927-1 - Speciation, bioaccumulation and biotransformation of arsenic by cyanobacteria (Arthrospira sp. and Anabaenopsis sp.) from the saline-alkaline lakes of the Pantanal of Nhecolândia
• Grantee: Marianna Alves Cancian
• Support Opportunities: Scholarships in Brazil - Master