Characterization of aqueous humic substances before and after chlorination

Hanna, John V.; Johnson, WD; Quezada, Robinson A.; Wilson, Michael; Xiao, Li

doi:10.1021/es00018a022

Cited by 43 publications

(31 citation statements)

References 13 publications

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“…Despite using samples spanning a wide range of mineralogical composition, including all major phyllosilicate species and varying contents of sesquioxides, the chemical composition of ROC in all samples was similar as revealed by 13 C-NMR. The preservation of alkyl C moieties during NaOCl and HF treatment agrees with findings that aliphatic structures are relatively resistant to chemical treatments like oxidation or acid hydrolysis (Hanna et al 1991;Westerhoff et al 1999Westerhoff et al , 2004Chefetz et al 2002). However, the fact that ROC also contained 11-18% polysaccharidetype C (O-alkyl C) following NaOCl treatment and HF extraction suggests that these polysaccharide-type materials were part of recalcitrant organic moieties.…”

Section: Chemically Resistant Organic Mattersupporting

confidence: 82%

“…The presence of lignin phenols was again confirmed by positive correlations between the absolute amounts of O-aryl C and C-aryl C, with the amounts of lignin phenols (VSC per kg soil) (r 2 = 0.53, p < 0.05; r 2 = 0.62, p < 0.01, respectively). We exclude a significant contribution of signals derived from chlorinated compounds in the aliphatic and aromatic region (Hanna et al 1991;Rajan et al 1996). Chlorination by NaOCl decreases with pH, being maximal close to pH 2, whereas we conducted the NaOCl treatment at pH 8 (Lebedev et al 2004).…”

Section: Cross-polarization Magic-angle Spinning Carbon-13 Nmrmentioning

confidence: 99%

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Stabilization of Soil Organic Matter: Association with Minerals or Chemical Recalcitrance?

et al. 2006

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Soil organic matter (OM) can be stabilized against decomposition by association with minerals, by its inherent recalcitrance and by occlusion in aggregates. However, the relative contribution of these factors to OM stabilization is yet unknown. We analyzed pool size and isotopic composition ( 14 C, 13 C) of mineral-protected and recalcitrant OM in 12 subsurface horizons from 10 acidic forest soils. The results were related to properties of the mineral phase and to OM composition as revealed by CPMAS 13 C-NMR and CuO oxidation. Stable OM was defined as that material which survived treatment of soils with 6 wt% sodium hypochlorite (NaOCl). Mineral-protected OM was extracted by subsequent dissolution of minerals by 10% hydrofluoric acid (HF). Organic matter resistant against NaOCl and insoluble in HF was considered as recalcitrant OM. Hypochlorite removed primarily 14 C-modern OM. Of the stable organic carbon (OC), amounting to 2.4-20.6 g kg À1 soil, mineral dissolution released on average 73%. Poorly crystalline Fe and Al phases (Fe o , Al o ) and crystalline Fe oxides (Fe dÀo ) explained 86% of the variability of mineral-protected OC. Atomic C p /(Fe+Al) p ratios of 1.3-6.5 suggest that a portion of stable OM was associated with polymeric Fe and Al species. Recalcitrant OC (0.4-6.5 g kg À1 soil) contributed on average 27% to stable OC and the amount was not correlated with any mineralogical property. Recalcitrant OC had lower D 14 C and d 13 C values than mineral-protected OC and was mainly composed of aliphatic (56%) and O-alkyl (13%) C moieties. Lignin phenols were only present in small amounts in either mineral-protected or recalcitrant OM (mean 4.3 and 0.2 g kg À1 OC). The results confirm that stabilization of OM by interaction with poorly crystalline minerals and polymeric metal species is the most important mechanism for preservation of OM in these acid subsoil horizons.Abbreviations: CPMAS 13 C-NMR -cross-polarization magic-angle spinning 13 C nuclear magnetic resonance spectroscopy; FR -fluoride reactivity; OC -organic C; OM -organic matter; MOC and MN -mineral-protected organic C and N; ROC and RN -chemically resistant (recalcitrant) organic C and N; SSA -specific surface area; XRD -x-ray diffraction; TEM -transmission electron microscopy

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Section: Chemically Resistant Organic Mattersupporting

confidence: 82%

Section: Cross-polarization Magic-angle Spinning Carbon-13 Nmrmentioning

confidence: 99%

Stabilization of Soil Organic Matter: Association with Minerals or Chemical Recalcitrance?

et al. 2006

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“…It may be possible to detect contaminants such as oil at natural abundance, and massive inputs of lignite and coal dust from mining operations were easily detected in SOM (Schmidt et al 1996Rumpel et al 1998). In a different type of environmental application, Hanna et al (1991) used 13 C CPMAS NMR to show large effects of chlorination on the structure of aquatic humic substances. Benoit and Preston (2000) investigated the fate of fully ring-labeled atrazine (6-chloro-N-ethyl-N-isopropyl-1,3,5-triazine-2,4-diamine) in a 3-mo laboratory incubation with soil and fresh or composted straw.…”

Section: C-13 Labeling and Xenobioticsmentioning

confidence: 99%

Carbon-13 solid-state NMR of soil organic matter - using the technique effectively

Preston¹

2001

Can. J. Soil. Sci.

112

105

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).Preston, C. M. 2001. Carbon-13 solid-state NMR of soil organic matter -using the technique effectively. Can. J. Soil Sci. 81: 255-270. Solid-state 13 C CPMAS NMR offers many options for characterizing carbon in soil organic matter (SOM). Its effectiveness, however, is often limited by a poor understanding of the techniques, and lack of hands-on access and training opportunities for students. Of nearly 250 modern NMR systems in Canada, approximately one is genuinely available for SOM studies, and there is poor communication between NMR operators and SOM users. While quantitative reliability can be addressed to some extent by multiple contact-time experiments or single-pulse (Bloch decay) spectra, it is also important to consider the effects of spectrometer background, spinning sidebands (especially with higher magnetic fields) and processing operations such as linebroadening, phasing and baseline correction. In many studies, more consideration needs to be given to instrument specifications, the type of information needed, and whether sample fractionation or pretreatment should be used. Structural information can be greatly enhanced by dipolar-dephasing and sideband suppression sequences. Sequences based on relaxation differences can reveal pools of carbon with different structures. Data analysis can be enhanced by principal component analysis, spectrum deconvolution and difference spectra. Studies of xenobiotics and C metabolism can be greatly aided by 13 C-labeling. However, a key limitation to SOM applications remains the gap in culture and expectations of the users.Key words: Soil organic matter, 13 C CPMAS NMR, Bloch decay, dipolar dephasing, spinning sidebands Preston, C. M. 2001. Analyse de la matière organique du sol par RMN au 13 C électronique -de l'importance de bien utiliser la technique. Can. J. Soil Sci. 81: 255-270. La RMN CPMAS 13 C électronique permet de caractériser le carbone présent dans la matière organique du sol (MOS) de diverses manières. Il arrive souvent cependant que cette technique perde de son efficacité parce qu'on la connaît mal et parce que les étudiants n'ont pas eu la chance de l'examiner ou de l'expérimenter. Sur les 250 systèmes modernes de RMN existant au Canada, un seul, à peu près, est vraiment réservé à l'étude de la MOS; de plus, la communication passe mal entre les opérateurs de systèmes RMN et les utilisateurs de MOS. Bien qu'on puisse remédier dans une certaine mesure au problème de la fiabilité quantitative en multipliant les expériences sur la durée de contact ou en recourant au spectre obtenu après une seule impulsion (décroissance de Bloch), il ne faut pas négliger les effets de l'arrière-plan du spectromètre, de la rotation des bandes latérales (surtout quand le champ magnétique est puissant) et des opérations de traitement comme l'élargissement des lignes, la mise en phase et la correction de la ligne de base. Dans de nombreux cas, on devrait accorder plus d'attention aux paramètres de l'instrument, au genre de données requises et à la nécessité de fractionner et...

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“…Phenols are frequently detected in source water with the highest average concentration of 10 g/L and 11 kinds of them have been classified as priority pollutants in USEPA [10]. Moreover, it has been proved that phenols are the main configurations composing of humic substances, which are regarded as the important NOM in source water [11][12][13].…”

Section: Introductionmentioning

confidence: 99%