Metal Binding and Sources of Humic Substances in Recent Sediments from the Cananéia-Iguape Estuarine-Lagoon Complex (South-Eastern Brazil)

Abstract

The Cananéia-Iguape estuarine–lagoon complex (São Paulo state, Brazil) is a natural laboratory to study metal binding by humic substances (HS) in subtropical settings. This transitional environment is evolving into a freshwater environment due to water input from the Ribeira River, funneled through the Valo Grande Canal (Iguape). Past mining activities in the Ribeira River basin and maritime traffic are suspected to be potential sources of trace metals in the system. In this study, the trace metal contents of Free Humic Acids (FHA), Bound Humic Acids (BHA), and Fulvic Acids (FA) extracted from sedimentary organic matter were investigated. Moreover, the sources of HS were traced using their stable carbon isotope compositions and C/N ratios. The results suggested a mixed marine–terrestrial source of FHA, BHA, and FA. Copper and Cr were the most abundant trace metals bound to HS. On average, Cu showed concentrations of 176, 115, and 37.9 μg g−1 in FHA, BHA, and FA, respectively, whereas Cr showed average concentrations of 47.4, 86.3, and 43.9 μg g−1 in FHA, BHA, and FA, respectively. Marine FHA showed the highest binding capacity for trace metals, whereas terrestrial FA derived from the decay of mangrove organic matter showed the lowest binding capacity.

Sinking particles in the photic zone: relations with biogeochemical properties in different sectors of the Cananéia-Iguape Estuarine-Lagoon Complex (CIELC)-Brazil

“…In contrast to the Valo Grande region, the water exchanges with wetland ecosystems (mostly mangrove) in the southern estuarine sectors of CIELC (Cananéia Bay, Batatais mangrove creek, and Ararapira channel) seemed to drive, at a certain level, the lower TRIX values (oligotrophic conditions) and the predominance of DON (relative to DIN) and ammonium (within the DIN pool). In this (most preserved) CIELC area, the increase in DON could be related to the decomposition of mangrove vegetation into yellow substances (humic and fulvic acids), as evinced by Millo et al (2021). Besides, oligotrophic mangrove creeks are areas of regeneration, thus tending to show a higher proportion of DON (relative to DIN) and ammonium (within the DIN pool) (Dittmar and Lara, 2001;Fortune et al, 2022).…”

“…Photochemical microbial activity on Dissolved Organic Matter (DOM) may release DON from humic acid (Dell'Anno et al, 1999). Millo et al (2021), analyzing stable isotopes from sampled CIELC surface sediments, showed strong evidence that fulvic acids (the fraction of the humic substance that is soluble in acidic and basic solutions) originated from the decay of organic matter derived from local mangroves (Ararapira Channel and Cananéia Bay). Besides, it is important to note that the average concentration of DON (≈16 µmol L -1 ) in the southern sectors resembles the annual average concentration of DON (≈20 µmol L -1 ) found by Dittmar and Lara (2001) in a large mangrove tidal creek in Northern Brazil.…”

Research in a RAMSAR site: The Cananéia-Iguape-Peruíbe estuarine-lagoon complex, Brazil

“…Some previous studies carried out in the CIELC have monitored the environmental properties of this region, such as Besnard (1950), Kato (1966aKato ( , 1966bKato ( , 1966c, Teixeira (1968), Tundisi and Teixeira (1968), Miyao et al (1986), Miyao and Harari (1989), Braga (1995), Tessler and Souza (1998), Braga and Chiozzini (2008), and Maluf (2009). In recent decades, several scientific studies have been carried out to understand the oceanographic dynamics of the CIELC, considering the circulation patterns of the adjacent shelf and tidal inflows (Camargo and Harari, 1994;Mesquita and Harari, 2003); the physical and chemical properties of the water Chiozzini et al, 2010;Azevedo and Braga, 2011;Aguiar et al, 2013;Souza et al, 2011aSouza et al, , 2011bEschrique et al, 2014;Haytsmann, 2018;Mindaugas et al, 2023); sedimentary and geomorphological characterization and metal inputs (Mahiques et al, 2009;2013;2014;Cornaggia et al, 2018;Tramonte et al, 2018); geochemical aspects (Amorim, et al 2008;Barcellos et al, 2005;Aguiar et al, 2008;Perretti and Braga, 2022;Sutti et al, 2022;Millo et al, 2021); the composition of the ichthyofauna (Sadowsky, 1974;Tanji, 1981, 1983;Rios, 2001;Contente, 2013;<...…”

Special Issue on Contaminants in Coastal Environments: From the Sediment-Water Interface to the Trophic Chain

“…However, strong interactions between MeHg and organic carbon underlined the negligible risk of increased mobility and the potential bioaccumulation of MeHg in the aquatic trophic chain. Millo et al [2] analyzed metal binding by humic substances (HS) in a subtropical transitional environment affected by past mining activities and maritime traffic, which are thought to be potential sources of trace metals in the system. The results suggested a mixed marine-terrestrial source of HS with copper and chromium as the most abundant trace metals bound to HS.…”