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

Abstract

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.

Influence of river floods on the humification process in the bottom sediments from the Goczałkowice reservoir

“…This fact of 1650/1720 ratio decrease may be explained as the dissociation of the COOH group to COO -and the formation of transition metal complexes in the structure of the analyzed humic acids (Table 3; Fig. 5) (Giovela et al 2004, Polak et al 2005. The results of these analyses confi rm the suggested infl uence of metals in samples of the extracted humic acids.…”

Genesis of structural features of humic acids from the sediments of a high productive coastal zone

“…On evaluating the atomic ratios of HAs from mudbank sediments, it has been hypothesized that HAs were originally derived from terrestrial like sources, and later on severely modified under the prevailing conditions of mudbank prone coastal regions. Higher H/C ratio is typical of HAs of marine origin, and being less aerated as compared to terrestrial HAs, its aliphatic rich organic moiety is quite certain (Rashid, 1985;Giovanela et al, 2004). The degree of carboxylation during humification process is generally reflected through higher O/C ratio.…”

“…As compared to absolute values indicating elemental composition, atomic ratios are of higher discriminating character in defining HAs in turn of its sources and diagenetic behaviors, and also the environmental conditions under which it was derived (Visser, 1983;Giovanela et al, 2004). On evaluating the atomic ratios of HAs from mudbank sediments, it has been hypothesized that HAs were originally derived from terrestrial like sources, and later on severely modified under the prevailing conditions of mudbank prone coastal regions.…”

3D-fluorescence spectroscopic analysis of HPLC fractionated estuarine fulvic and humic acids

“…Exhaustive examination of the infrared spectral properties, as well as of the acidity contents, of these same samples, has provided strong evidence of the presence of amide linkages. 31,32,37 Figure 6. Single emission spectra (λ exc = 270 nm) for the HPLC fractions.…”