Matica e Geoscienze, Universitdegli Studi di Trieste, By way of Weiss 2, 34128 Trieste, Italy; [email protected] (S.C.); [email protected] (E.P.); [email protected] (E.P.) Dipartimento di Scienze Chimiche e Farmaceutiche, Universitdegli Studi di Trieste, By way of Licio Giorgieri 1, 34127 Trieste, Italy; [email protected] Correspondence: [email protected]: Millo, C.; Bravo, C.; Covelli, S.; Pavoni, E.; Petranich, E.; Contin, M.; De Nobili, M.; Crosera, M.; Otero Sutti, B.; das Merc Silva, C.; et al. Metal Binding and Sources of Humic Substances in Recent Sediments from the Canan aIguape EstuarineLagoon Complex (SouthEastern Brazil). Appl. Sci. 2021, 11, 8466. https://doi.org/10.3390/ app11188466 Academic Editor: Anna Annibaldi Received: 7 July 2021 Accepted: 9 September 2021 Published: 12 SeptemberAbstract: The Canan aIguape estuarine agoon complex (S Paulo state, Brazil) is often a organic Resolvin E1 supplier laboratory to study metal binding by humic substances (HS) in subtropical settings. This transitional atmosphere is evolving into a freshwater environment as a result of water input from the Ribeira River, funneled through the Valo Grande Canal (Iguape). Previous mining activities in the Ribeira River basin and maritime website traffic are suspected to become potential sources of trace metals in the program. In this study, the trace metal contents of Totally free Humic Acids (FHA), Bound Humic Acids (BHA), and Fulvic Acids (FA) extracted from sedimentary organic matter had been investigated. Additionally, the sources of HS were traced making use of their stable carbon isotope compositions and C/N ratios. The outcomes suggested a mixed marine errestrial supply of FHA, BHA, and FA. Copper and Cr have been probably the most TPMPA Antagonist abundant trace metals bound to HS. On average, Cu showed concentrations of 176, 115, and 37.9 g1 in FHA, BHA, and FA, respectively, whereas Cr showed average concentrations of 47.4, 86.3, and 43.9 g1 in FHA, BHA, and FA, respectively. Marine FHA showed the highest binding capacity for trace metals, whereas terrestrial FA derived in the decay of mangrove organic matter showed the lowest binding capacity. Keywords: humic acids; fulvic acids; stable isotopes; trace metal contaminationPublisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations.1. Introduction Humic substances (HS) are essential elements of all-natural organic matter in water and sediments, where they represent essentially the most refractory fraction [1,2]. HS consist of heterogeneous mixtures of organic molecules formed through the decay of plant, animal, and microbial remains [3]. Primarily based on their solubility, HS are subdivided into 3 fractions: fulvic acids (FA, soluble in acidic and standard solutions), humic acids (HA, insoluble in acidic options), and humin (insoluble). HA, in turn, is usually subdivided into Absolutely free HA (FHA) and Bound HA (BHA), the latter getting the fraction bound to mineral surfaces by formation of cationic bridges. BHA can only be solubilised by extraction with Na4 P2 O7 , which complexes calcium and breaks cationic bridges [4]. The study of HS is relevant in coastal oceanography simply because HS can bind metals, either by complexation or by surface adsorption. This binding ability is resulting from the truth that HS consist of a mixture of carboxylated and fused alicyclic structures, which can constitute ligands for metal binding [7]. HS could be present in water either as a dissolvedCopyright: 2021 by the authors. Licensee MDPI, Basel, Switzerland. This short article is definitely an open access article di.
