M. Sierra

Universidad de La Laguna

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Eduardo Juan Soriano-Sierra

Universidade Federal de Santa Catarina

Marcelo Giovanela

Universidade de Caxias do Sul

E. Chinea

Universidad de La Laguna

P. Esparza

Universidad de La Laguna

NÂ

Nito Ângelo Debacher

Universidade Federal de Santa Catarina

Eduardo Humeres

Universidade Federal de Santa Catarina

M. Ewald

Université de Bordeaux

Olivier François Xavier Donard

Centre National de la Recherche Scientifique

Tomás R. Belderraín

Universidad de Huelva

Andreia Neves Fernandes

Universidade Federal do Rio Grande do Sul

Cooperative Institutions

Universidade Federal de Santa Catarina

Centre National de la Recherche Scientifique

Universidad de La Laguna

Université de Bordeaux

Observatorio de la Inmigración de Tenerife

Universidade de Caxias do Sul

Laboratoire de Chimie

Universidade Federal do Rio Grande do Sul

Universidade de São Paulo

Laguna Research

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Elemental compositions, FT-IR spectra and thermal behavior of sedimentary fulvic and humic acids from aquatic and terrestrial environments

GEOCHEMICAL JOURNAL (2004)

Marcelo Giovanela E. Parlanti Eduardo Juan Soriano-Sierra Marly S. Soldi M. Sierra

Studies on elemental analysis, Fourier transform infrared spectroscopy (FT-IR) and thermal decomposition (thermogravimetry, TG; and derivative thermogravimetry, DTG) of sedimentary fulvic (FA) and humic acids (HA) from marine, estuarine, lacustrine and terrestrial environments are presented. In general, H/C and N/C atomic ratios, as well as the infrared spectra, reflected the extent of the influence of algal and/or terrestrial organic matter sources on the samples, the aquatic (both, marine and freshwater) humic substances (HS) being richer in nitrogen and more saturated, than terrestrial materials. Comparison of properties of FA and HA from the same parent sediments showed that the latter are relatively richer in nitrogen and unsubstituted aliphatic chains and poorer in carboxylic groups. FT-IR spectra showed that the nitrogen present is mostly as forming part of amide groups. Concerning thermal degradation, two main steps were observed for all samples: the first, relative to the loss of moisture, being located between 40°C and 100°C and the second between 270°C and 440°C. FT-IR spectra of the samples which had been heated to 90°C, 400°C and 900°C showed that, upon heating, the carboxyl content decreases (especially for FA), the aliphaticity decreases and the aromaticity increases (especially for HA), indicating that the 270°C-470°C degradation step might be related to decarboxylation and unsaturation losses. In spite of this, both kinds of HS, were shown to be highly thermo-resistant materials retaining most of their typical original infrared spectral features, even after being heated to 400°C.

Thermogravimetry

Degree of unsaturation

Nontronite

Amide

Differential thermal analysis

Sedimentary organic matter

10.2343/geochemj.38.255

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Citations (106)

Construção e otimização de um reator de baixo custo para a fotodegradação da matéria orgânica em águas naturais e sua aplicação no estudo da especiação do cobre por voltametria

Química Nova (2001)

Maria Lucia Arruda Moura Campos Lígia C. Mello Dilson R. Zanette M. Sierra Anderson Bendo

BY VOLTAMMETRY.This work describes the construction of a home-made low-cost reactor, using easily available materials, capable of destroying efficiently dissolved organic matter.Just 30 minutes of irradiation were sufficient to destroy more than 99% of the humic acids present in a solution of 4 mg C L -1 .Copper speciation was evaluated in natural waters of different salinities to test the reactor's efficiency in destroying organically complexed metal species.The effect of the organic matter concentration, salinity, dissolved oxygen and temperature in the photo-oxidation process is discussed.

10.1590/s0100-40422001000200018

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Citations (12)

Fluorescence Properties of Well-Characterized Sedimentary Estuarine Humic Compounds and Surrounding Pore Waters

Environmental Technology (2000)

M. Sierra Marcelo Giovanela Eduardo Juan Soriano-Sierra

Structural and spectroscopic properties of sedimentary estuarine humic compounds (HC) and surrounding pore waters were investigated. Elemental analysis showed that sedimentary HC exhibit a molecular design compatible with a mixed continental-marine environment. In some respects, they are well correlated with the marine organic matter (e.g. low C/H ratio), while in others they are better associated to terrestrial material (e.g. high C/N ratio). High rates of microbiological activity, combined with a tide-dependent contribution of an aliphatic marine-like source of organic matter, may account for such results. Chemical anomalies were not observed in samples from polluted sites, indicating that moderate anthropogenic disturbances will affect chemical processes related to humic compounds rather than their chemical design. With respect to fluorescence properties, sedimentary humus exhibits a single and wide emission peak (λex = 313 nm), with λmax ∼ 431 nm for fulvic acid and λmax ∼ 446 nm for humic acids. For humic acids a shoulder at around 515 nm is also observed. HC corrected excitation spectra (λem = 445 nm) are similar to those previously observed for HC from aquatic environments, presenting two peaks of variable intensities, the first being more intense, located around 250 nm, and the second located in the range 320-350 nm. Pore waters extracted from the same sediment samples as those of HC exhibited fluorescence properties comparable to that of fulvic acids but exhibiting emission maxima around 424 nm. The significance of hydrophilic substances in relation to the fluorescence properties of natural waters is discussed.

Humus

Sedimentary organic matter

10.1080/09593332108618046

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Citations (12)

Chemical and spectroscopic characterization of humic acids extracted from the bottom sediments of a Brazilian subtropical microbasin

Journal of Molecular Structure (2010)

Marcelo Giovanela Janaína da Silva Crespo Maria Lúcia Pereira Antunes Daniela Santini Adamatti Andreia Neves Fernandes

Carbon fibers

Thermogravimetry

Characterization

Reactivity

10.1016/j.molstruc.2010.07.038

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Citations (110)

The photolysis of colloidal iron in the oceans

Nature (1991)

Mark L. Wells Lawrence M. Mayer Olivier F. X. Donard M. Sierra Steve G. Ackelson

Lability

10.1038/353248a0

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Citations (125)

Fluorescence and DOC contents of pore waters from coastal and deep-sea sediments in the Gulf of Biscay

Organic Geochemistry (2001)

M. Sierra Olivier François Xavier Donard H. Etcheber Eduardo Juan Soriano-Sierra M. Ewald

Humus

10.1016/s0146-6380(01)00100-0

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Citations (42)

Characterization of Brazilian Peat Samples by Applying a Multimethod Approach

Spectroscopy Letters (2013)

Francine Girardello Régis Guégan Valdemar I. Esteves I. J. R. Baumvol M. Sierra

ABSTRACT Peat is a mixture of compounds formed by the decomposition of plant residues and mineral materials that have accumulated at the bottom of ponds and flooded depressions in riverine areas. Due to their extreme heterogeneity and natural variety, the physical and chemical properties of peat can vary widely within or between deposits, and the characterization of isolated samples is still a challenging task that requires the combination of several chemical and spectroscopic methodologies. In this study, the structural characteristics of two Brazilian peat samples were evaluated using scanning electron microscopy (SEM), elemental (CHNS-O) and thermal (TGA) analysis, X-ray diffraction (XRD), and infrared (FT-IR) and solid-state 13C-nuclear magnetic resonance (13C-NMR) spectroscopies. Although the samples originated from the same peatland, the data showed that the studied samples have distinct chemical properties and that the stage of decomposition played an important role in the differences observed.

Characterization

10.1080/00387010.2012.702184

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Citations (15)

Solar degradation of contaminants in water: TiO2 solar photocatalysis assisted by up-conversion luminescent materials

Solar Energy Materials and Solar Cells (2016)

E. Chinea M. Sierra J. Méndez‐Ramos P. Acosta-Mora J.C. Ruiz-Morales

ZBLAN

Titanium Dioxide

Human decontamination

10.1016/j.solmat.2016.06.010

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Citations (50)

Mechanisms of Acid Decomposition of Dithiocarbamates. 1. Alkyl Dithiocarbamates

The Journal of Organic Chemistry (1998)

Eduardo Humeres Nito Ângelo Debacher M. Sierra José Dimas Franco Aldo Schutz

The acid decomposition of some substituted methyldithiocarbamates was studied in water at 25 °C in the range of Ho −5 and pH 5. The pH−rate profiles showed a bell-shaped curve from which were calculated the acid dissociation constants of the free and conjugate acid species and the specific acid catalysis rate constants kH. The Brønsted plot of kH vs pKN, the dissociation constant of the conjugate acid of the parent amine, suggests that the acid cleavage occurs through two mechanisms that depend on the pKN. The plot presents a convex upward curve with a maximum at pKN 9.2, which is consistent with the cleavage of the dithiocarbamate anion through a zwitterion intermediate and two transition states. For pKN < 9.2, the N-protonation is slower than the C−N bond breakdown. Inverse SIE showed that the zwitterion is formed through a late transition state. At pKN > 9.2, the C−N bond breakdown is the slowest step, and according to the inverse SIE, the transition state changes rapidly with the increase of pKN to a late transition state. The plot shows a minimum at pKN ∼10, indicating that a new mechanism emerges at higher values, and it is postulated that it represents a path of intramolecular S to N proton-transfer concerted with the C−N bond breakdown. The thiocarbonyl group acts as a powerful electron-withdrawing group, decreasing the basicity of the nitrogen of the parent amine by 14.1 pK units.

Conjugate acid

Zwitterion

Bond cleavage

Acid dissociation constant

10.1021/jo971869b

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Citations (72)

CCDC 867111: Experimental Crystal Structure Determination

The Cambridge Structural Database (2012)

C. Martin M. Sierra E. Alvarez Tomás R. Belderraín P.J. Perez

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

10.5517/ccy39bn

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