Characterization of Ten Sequentially Extracted Humic Acids and a Humin From a Soil in Western Massachusetts

Abstract

Humic substances are mixtures of macromolecules with varied structures and chemical compositions that are affected by differences in parental biomaterials and environmental conditions. This study used elemental analysis, diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), and solid-state 13 C nuclear magnetic resonance spectroscopy (NMR) to identify the chemical and structural heterogeneity of 10 humic acids (HAs) and a humin. The HAs were obtained by progressively extracting solution from a soil in western Massachusetts, eight times with 0.1 M Na 4 P 2 O 7 and two times with 0.1 M NaOH. The humin was the residual fraction after 10 base extractions. As indicated by solid state NMR analysis, the aliphatic carbons (0 ϳ 108 ppm) of the HAs increased gradually from 50% in fraction 1 (F-1) to 62% in fraction 9 (F-9) and 70% for the humin, but the aromatic carbons (108 ϳ 162 ppm) were highest in F-1. The band assigned to aliphatic carbon (2930 cm ؊1 ) in the DRIFTS spectra gradually increased with further extractions, and the relative intensity of this peak was the highest in humin. The atomic C/H ratio declined from 1.1 for F-1 to 0.6 for F-10 and the humin, consistent with the spectroscopic analyses. In addition, both elemental and spectroscopic data reveal that the last extracted HA and humin contained relatively lower contents of polar functional groups such as carboxylic and phenolic groups. This study shows significant chemical, structural, and molecular differences among the 10 sequentially extracted HAs and humin, even from a single soil. (Soil Science 2003;Volume 168:880-887)

Nuclear Magnetic Resonance Analysis of Natural Organic Matter

“…However, because it is insoluble, most researchers opt to use solid -state 13 C NMR methods to analyze the structure of humin (Preston et al, 1989 ;Almendros et al, 1996 ;Nierop et al, 1999 ;Kang et al, 2003 ;Guignard et al, 2005 ;Xing et al, 2005 ;Keeler et al, 2006 ;Simpson and Johnson, 2006 ). Traditionally, there have been fewer NMR studies of soil humin than other NOM fractions (humic and fulvic acids).…”

“…For example, several studies have shown that the humin fraction yields higher sorption values than does its corresponding source material (Nearpass, 1976 ;Garbarini and Lion, 1986 ;Chiou et al, 2000 ;Salloum et al, 2001 ;Kang and Xing, 2005 ;Bonin and Simpson, 2007 ). Solid -state 13 C NMR studies of humin have demonstrated that humin has functional groups similar to those of the whole soil or sediment from which it was isolated; however, the humin fraction has been observed to be higher in aliphatic and substituted aliphatic carbon but lower in aromatic carbon than corresponding humic acids (Almendros et al, 1991b(Almendros et al, , 1996Nierop et al, 1999 ;Salloum et al, 2001 ;Kang et al, 2003 ;Guignard et al, 2005 ;Wang and Xing, 2005b ;Keeler et al, 2006 ;Simpson and Johnson, 2006 ;Bonin and Simpson, 2007 ). A comparison of the 13 C CPMAS NMR spectra from two types of soil and corresponding humin isolates are shown in Figure 15.8 .…”

Capillary Electrophoretic Determination of Selected Phenolic Compounds in Humic Substances of Well Waters and Fertilizers

“…With regard to T-FA, the low C/H atomic ratio (0.53) may imply an enrichment of alkyl groups with high hydrogen saturation. 29,30 The rank of oxygen magnitude for HAs was found to be T-FA > A-HA > Y-HA > T-HA ≅ S-HA2 > S-HA1 > W-HA after analysis. The O/C ratio is normally considered an indicator of alkoxyl, carbonyl, and carboxylic contents.…”

“…The O/C ratio is normally considered an indicator of alkoxyl, carbonyl, and carboxylic contents. 26,29 In general, the C/N ratio is an index of possible microbial activity and natural contributor. Samples A-HA and T-HA may be derived from terrestrial plant materials, as their C/N ratios exceeded 15.…”

Synthesis and Characterization of paramagnetic (poly styrene-coacrylamide) hydrogel: used as adsorbent for removal of pesticide (chlorpyrifos)

“…Due to their wide applications, these pesticides are often detected in fresh water exceeding permissible levels and cause harmful impact on human health [1]. The pesticides form a strong class of water pollutants as they are mostly non-biodegradable and carcinogenic in nature [2][3]. Therefore toxicity of pesticides and their degradation products are making these chemical substances a potential hazard by contaminating the environment [4].…”