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Identification of mobile aliphatic sorptive domains in soil humin by solid‐state 13 C nuclear magnetic resonance
Author(s) -
Simpson Myrna J.,
Johnson Philippe C. E.
Publication year - 2006
Publication title -
environmental toxicology and chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.1
H-Index - 171
eISSN - 1552-8618
pISSN - 0730-7268
DOI - 10.1897/05-152r.1
Subject(s) - solid state , humin , identification (biology) , nuclear magnetic resonance , chemistry , solid state nuclear magnetic resonance , environmental chemistry , soil water , environmental science , physics , soil organic matter , soil science , botany , biology
Many sorption studies aim to elucidate organic matter structure and contaminant sorption relationships. Through this pursuit, a great deal of insight has been gained about contaminant interactions with humic fractions, namely the fulvic and humic acid isolates. Comparatively, less is known about the structure and environmental reactivity of the humin fraction; however, researchers have reported that the humin fraction consistently produces higher sorption coefficients than the corresponding source material and other humic fractions. In this paper, we report on a study that uses solid‐state 13 C nuclear magnetic resonance (NMR) to characterize six humin samples extracted from soil. In addition, 1‐naphthol sorption was measured for each whole‐soil and humin sample. With the exception of the peat sample, the humin samples yielded significantly higher organic carbon–normalized sorption coefficients ( K oc ) compared with the whole‐soil samples. The solid‐state 13 C NMR analysis reveals the presence of amorphous, polymethylene‐rich domains in all of the humin samples. Other researchers have indicated that these domains exhibit a high affinity for hydrophobic organic contaminants. Consequently, we hypothesize that the concentration of amorphous, polymethylene‐rich domains in soil humin is responsible for the high sorption coefficients reported here and by other researchers.