Estudo de caracterização dos ácidos húmicos e fúlvicos em perfil sedimentar e sua interação com metais pesados

Abstract

The largest district of organic matter (MO) in soils, waters and sediments occurs in the form of humic substances (SH), a heterogeneous mixture of organic compounds aggregated by weak interactions of a hydrophobic nature and by hydrogen bridges. HS can be classified, operationally, according to the solubility in aqueous medium, in humic acids (HA), fulvic acids (AF) and humines. The HA and AF stand out because they are the dominant reactive fractions. Attributed to their characteristics, they play an important environmental role, since they enable an interaction with heavy metals, largely responsible for the deterioration of numerous environmental compartments. In this sense, the present study is an integrative literature review where its general objective is to present and briefly discuss the current knowledge of AH and AF, as well as, defined as the main relationships between these and heavy metals in aquatic sedimentary profile. In order to carry out this study, a descriptive survey was carried out in the Web of science, Scopus and SciELO databases using “humic acids, fulvic acids, sediments and heavy metals” as keys. The first search resulted in a total of 95 documents, 54 of which were found by Web of Science, 0 by SciELO and 41 by Scopus. Then, the search filters “years of publication” and “type of document” were established and a new result was found. A total of 34 scientific articles came from the second search, of these, only 13 scientific articles (13.68% of the total documents) were selected and used for analysis. According to the selected articles, the alkaline extraction method, proposed by SISH, proved to be the most effective method for obtaining HA and PA, since it was the most used and the one with the greatest extraction capacity (~ 80% efficiency) , while the FTIR and UV-VIS characterization techniques were some of the most cited and used by the authors. Despite the qualitative character, these techniques proved to be very efficient in characterizing the main functional groups for HA and PA. In a complementary way, it was evidenced that the fractions of PA are more reactive components when compared to the HA, since they presented larger amount of carboxylic and phenolic groups, however, both fractions were able to interact with different metal ions, being this is the most important property of HA and AF, given that 100% of the articles reported this information. It is important to note that little is known about the reaction processes of the AH and AF fractions, however, research seeking to better clarify the origin, the structural form and the importance of these substances in aquatic sediments is increasing considerably in the academic environment