Modeling the quenching of fluorescence from organic matter in Amazonian soils

Amanda Maria Tadini; Stephane Mounier; Débora Marcondes Bastos Pereira Milori

doi:10.1016/j.scitotenv.2019.134067

Modeling the quenching of fluorescence from organic matter in Amazonian soils

Sci Total Environ. 2020 Jan 1:698:134067. doi: 10.1016/j.scitotenv.2019.134067. Epub 2019 Aug 28.

Authors

Amanda Maria Tadini¹, Stephane Mounier², Débora Marcondes Bastos Pereira Milori³

Affiliations

¹ Embrapa Agricultural Instrumentation, São Carlos, SP, Brazil; Institute of Chemistry of São Carlos, University of São Paulo, São Carlos, SP, Brazil; Laboratoire MIO - Equipe CEM, Université de Toulon, CS 60584, 83041 Toulon CEDEX 9, France. Electronic address: amandatadini@hotmail.com.
² Laboratoire MIO - Equipe CEM, Université de Toulon, CS 60584, 83041 Toulon CEDEX 9, France.
³ Embrapa Agricultural Instrumentation, São Carlos, SP, Brazil.

PMID: 31783454
DOI: 10.1016/j.scitotenv.2019.134067

Abstract

Knowledge of the interactions of soil organic matter (SOM) with metal species is important in order to obtain information concerning the fates of the metals in environment, whose reactive functional groups present in SOM can provide high complexation capacity. The aim of this study was to evaluate the interactions involving humic acids (HA) and fulvic acids (FA), extracted from Amazonian soils, with Cu(II) and Al(III) ions, using fluorescence quenching spectroscopy. The obtained results showed that the data for the humic fractions of the Amazonian Spodosols could be fitted with one to one complexation model, which provided the best representation of the changes in fluorescence quenching after addition of Cu(II) or Al(III) ions. It was found that the HA presented fewer complexation sites and lower stability constants, compared to the FA samples. Furthermore, the FA showed selective interaction with the metals, while the HA fraction was less selective and could be associated its homogeneous structure. The results showed that the humic acids required 10 times more carbon in their structures than fulvic acids for complexing a metal atom. This behavior can be associated to the fact that the Fulvic Acid fraction has higher mobility and greater interaction during the profile when compare humic acids. Hence, given the diversity of metals to which the HA has affinity, this soil fraction appears to be mainly responsible for soil fertility, while the FA fraction has higher mobility and greater interaction with water.

Keywords: Amazonian Spodosol; Complexation; Humic fractions; Mobility.