Changes of humic acids structure on selected key monitoring localities of arable soils

Abstract

Soil fertility is largely determined by the content and quality of soil organic matter. SlovakRepublic monitoring system includes evaluation of soil humus content, basic humic parameters and also chemical structure of humic acids (HA). Changes in humic acids structure on five selected key localities during monitoring period (1994–2000) are presented in this study. Among soil types, essentially between Chernozem and Planosol, in elemental analysis, optical parameter and 13C NMR parameters significant differences determined by Student’s test were observed (Tables 2 and 3). During monitoring period small oxidation trend mainly on Calcaric Fluvisol and Planosol HA expressed by increase of oxygen content and O/C, O/H ratio was observed. Oxidation trends during monitoring period confirm also position of Calcaric Fluvisol and Planosol HA on van Krevelen diagram. Changes in optical parameter E<sup>1%</sup><sub>6</sub>and content of carboxylic groups for the period of monitoring were negligible. Some changes throughout monitoring in <sup>13</sup>C NMR parameters were recorded. On all observed HA considerable decrease of carbon in region 106–143 ppm, characteristic for aromatic and olefinic carbon with C–C, C–H bond, was observed. Spectroscopic parameters are in good agreement with elemental analysis and carboxylic groups. Joint relationships between changes in determined parameters are expressed by significant linear correlations. Predominantly between parameters calculated from <sup>13</sup>C NMR spectra and data of elemental analysis and optical parameter E<sup>1%</sup><sub>6</sub>highly significant linear correlations (R > 0.93) are found (Table 4). 

Humic acids characterization by EDXS and ¹³C NMR spectroscopy

“…Carbon content in our samples was lower and decreased in order: Luvi-haplic Chernozem > Compost > Haplic Luvisol > Haplic Cambisol > Leptic Cambisol > Eutric Cambisol. Our fi ndings corresponded with our previous work Pospíšilová et al, (2008Pospíšilová et al, ( , 2009, and with literature data given by Fujitake et al, (1999) and Barančíková et al, (1997Barančíková et al, ( , 2002.…”

“…Higher concentration of aromatic carbon moieties was characteristic for HA isolated from Luvi-haplic Chernozem, compost and Haplic Luvisol. Obtained results corresponded with literature (Pena-Mendez et al, 2005, Barančikova et al, 1997, 2002 and our previous work Pospíšilová et al (2008Pospíšilová et al ( , 2009 Kollárová a Plíva (2008). Základní půdní charakteristiky a frakční slo-…”

Fractionation of humus and optical properties of humic acids originating from different soil types

“…7 a, b. These fi ndings corresponded with literature data (Senesi, 1993;Gieguzynska et al, 1998;Barančíková et al, 1997Barančíková et al, , 2002Sierra et al, 2005).…”

“…An inverse relationship is observed between Q 4/6 and the mean residence time of humus (= the lowest mean residence time is given by the highest values of colour quotient). The last can be also interpreted that the most humifi ed and highly condensed aromatic substances are of more ancient origin (Gieguzynska et al, 1998;Barančíková, 2002). FTIR spectroscopy offered insight into structural characteristics of HAs preparations.…”

The influence of humic acid quality on the sorption and mobility of heavy metals

“…On the basis of C HA /C FA and Q The basic chemical parameter for humic acid is elemental analysis. As you can see from Table 4, the highest content of C and the lowest content of H and also the lowest H/C ratio characteristic of the aromatic structure in HA from Chernozem, Chernitsa and Andosol were found and are typical of these soil types (Barančíková et al 1997b, Barančíková 2002. Metal binding also increased with higher proportions of nonprotonated aromatic carbon (Preston 1996).…”