Maize (C4 plant) stover was incubated for two years in a wheat (C3-cropped) soil. • Average 54.6%... more Maize (C4 plant) stover was incubated for two years in a wheat (C3-cropped) soil. • Average 54.6% organic C of HAs and 35.7% that of FAs were of maize origins. • Fractions from sequential exhaustive extractions were spectroscopically characterised. • Humin, isolated in DMSO/sulfuric acid was predominantly aliphatic in nature. • The humic substances studies enabled investigations of SOM dynamics.
Purpose Dissolved organic matter (DOM), a heterogeneous mixture of low concentrations of organic ... more Purpose Dissolved organic matter (DOM), a heterogeneous mixture of low concentrations of organic matter draining from soils, plays a significant role in soil C cycling and in nutrient and pollutant transport. DOM from undisturbed soil profiles has rarely been studied. Hydrophobic acids (Ho) and hydrophilic acids (Hi), the major components of DOM, were recovered, using XAD-8 and XAD-4 resins in series, from waters draining in winter and in spring periods from well-drained and poorly drained Irish grassland soil profiles in lysimeters. Materials and methods Waters were collected from 45 soil undisturbed lysimeters at the Teagasc Research Centre, Johnstown Castle, Wexford, Ireland. Four Irish representative soils had been collected as undisturbed 1.0-m-deep monoliths, transported to the experiment site and arranged randomly in an experimental facility. Water collections were carried out in winter and spring periods. The DOM was isolated and fractionated using an XAD-8 and XAD-4 resins in-tandem procedure, and hydrophobic acids (Ho) and hydrophilic acids (Hi) were isolated. The amounts of DOM recovered in the winter period were much greater than those in the spring period, and the soil types had only minor influences on the DOM concentrations recovered. The Ho and Hi fraction contents ranged from 62 to 90 and 10 to 28%, respectively, of the total DOM content extracted. The Hi acids were most enriched in 13 C, and considered to reflect greater microbial inputs. The neutral sugar (NS) contents for the Ho and Hi fractions were in the range of 15 to 52 μg mg -1 , with the Hi fraction most enriched. The amino acids (AAs) for the Ho and Hi fractions varied from 0.6 to 2.4%, and the total AAs and NS of the Ho acids were well correlated. The DOM fractions from the drainage waters contained much less AAs and NS than the corresponding fractions in the parent soils. The solid-and liquid-state NMR data indicated organic structures with low aromaticity, significant amounts of carbohydrate and with lesser amounts of peptide structures, and with long-chain methylene (CH 2 ) n and methine (-CH-) groups. Conclusions The application of a variety of wet chemistry and of spectroscopy procedures has given a more in-depth awareness of the compositions of the DOM in the drainage waters from four different soils in 1.0-m-deep lysimeter arrangements. Based on wet chemistry analyses, and FTIR and liquid-and solid-state NMR spectrometry, it is clear that there are some differences between the compositions of the DOM fractions recovered. Alkyl functionalities dominated the structures. These included significant amounts or O-alkyl (predominantly carbohydrate), and with lesser (and variable amounts in the different fractions) aromatic structures (to which aromatic amino acid components were considered to be significant contributors), and with no evidence for lignin-derived structures The results suggest that, during residence in the soil solution, microbiological processes transform the SOM components released into products that are greatly different from their materials of origin in the SOM.
In-situ combustion (ISC) process has drawn more and more attention in the development of heavy oi... more In-situ combustion (ISC) process has drawn more and more attention in the development of heavy oil reservoir due to its high efficiency and oil recovery. Although numerous studies have been reported that oil properties exhibit significant changes during the combustion process, the reaction mechanisms and the evolution of oil components are still not well understood. In this work, the compounds of produced oils collected from a three dimensional simulated production model (container) at different duration times after combustion being initiated and the original oil were characterized at the molecular level using gas chromatography (GC), gas chromatography -mass spectrometry (GC-MS) and high-field Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR MS). Both aromatic and acidic components were analyzed. The aromatic components showed relatively more stable characteristics than that of acidic components, no obvious changes in aromatic compounds distributions were observed by the positive ion atmospheric pressure photoionization (APPI) FT-ICR MS analysis. Small aliphatic acids were detected in the ISC oils which were responsible for the high total acid numbers (TAN). The acidic O x (x=1-3) compounds, which have major contributions to the increase in TAN, were generated in greater abundances compared to that of the original crude oil. The carbon number distributions of the O 1 and O 2 classes in the produced Page 1 of 16 ACS Paragon Plus Environment Energy & Fuels oils significantly shifted to a lower carbon number region, with the dominant distribution from 15 -45 at the initial state to 10 -40 at the longest duration time. The double bond equivalent (DBE) values decreased during the combustion process. The generated acidic O 1 components with DBE values less than 4 were also found in negative ion electrospray (ESI) analysis, indicating the oxidation of hydrocarbons to alcohols.
PurposeDissolved organic matter (DOM) composition is influenced by and modulates biogeochemical p... more PurposeDissolved organic matter (DOM) composition is influenced by and modulates biogeochemical processes, yet DOM characterization techniques are challenged by its heterogeneous properties and structures. In this paper, ultrahigh electrospray ionization Fourier transform ion cyclotron resonance (ESI-FTICR) mass spectrometry is used to characterize previously isolated and well-characterized four DOM fractions from a water reservoir in the southwestern part of the USA.Materials and methodsAbout 50–60 L water samples were collected from Lake Pleasant (a water reservoir of Colorado River) and isolated and fractionated using a sequential isolation and fractionation procedure. DOM was firstly fractionated to the colloids and soluble permeate, then hydrophobic acids (HPO-A) and neutrals (HPO-N) plus amphiphilic acids (AMP-A) and neutrals (AMP-N) were fractionated using the resin-in-tandem procedure. Approximately 0.7 mg sample was dissolved in 250 μL methanol/water mixture (1:1, v/v) and diluted twice with 0.1 % (by volume) NH4OH (in 1:1 methanol/water, v/v) and measured by ESI-FTICR in negative ion mode.Results and discussionIn the m/z range of <700, among the sum of 4107 peaks, HPO-N contained the most assigned 1763 molecules and HPO-A, AMP-N, and AMP-A contained 971, 990, and 293, respectively. Acid fractions were relatively more oxygenated than the corresponding neutrals. Except for the major assigned CHO molecules, a high portion of heteroatom-containing molecules were assigned in the neutral fractions. Van Krevelen and Venn diagrams analyses showed significant molecular differentiation among the fractions. Among the assigned formulas, the Venn diagram indicated only a small portion (<4 %) of distinct formulas overlapped. S-containing molecules were efficiently ionized and identified in the neutrals. Some of the S1-containing compounds with high signal magnitudes are tentatively assigned to alkylbenzene sulfonates and their biodegradation and biotransformation derivatives indicating anthropogenic input on site.ConclusionsBy using the XAD resin-in-tandem approach and FTICR-MS, numbers of DOM molecules in fractions were distinctly separated, accordingly the complexity of DOM was reduced. Furthermore, to a great extent, the compositions and structures of each fraction in the molecular level are remarkably different as evidenced by only small portion of molecules overlapping.
An awareness of the transformation of plant residues returned to cultivated soils is vital for a ... more An awareness of the transformation of plant residues returned to cultivated soils is vital for a better understanding of carbon cycles, the maintenance of soil fertility and the practice of a sustainable agriculture. The transformation of maize (Zea mays L) straw residues into soil organic matter (SOM) in a one year incubation experiment was studied in a soil that had been under long term cultivation with wheat (Triticum aestivum L) for >30years. A novel sequential exhaustive extraction and fractionation procedure isolated a series of fractions of SOM. The samples were characterized by elemental and δ(13)C analyses, by amino acids and neutral sugars analyses, by Fourier transformed infrared (FTIR) spectrometry, and by solid state (13)C nuclear magnetic resonance (NMR) spectroscopy and with chemical shift anisotropy (CSA) -filter and dipolar dephasing (DD) spectral editing NMR techniques. The δ(13)C data indicated that 59% and 38% of the newly transformed organic carbon was in the...
Dodecylbenzene sulfonic acid (DBSA), the acid form of sodium dodecylbenzenesulfonate (SDBS), is o... more Dodecylbenzene sulfonic acid (DBSA), the acid form of sodium dodecylbenzenesulfonate (SDBS), is often identified and detected in soils. However, it still has less awareness of the sorption behavior of DBSA with soil organic matter. In this paper, the sorption behaviors of DBSA on two different types of soils (Mollisol and Alluvial soils) and soil humic acids (HAs) were studied and compared, and the mechanisms of HAs and DBSA interactions were discussed. Sorption dynamics and isotherms were studied using the batch equilibrium method. The sorption kinetics was relatively slow, and the sorption equilibrium can be reached within 10 h. In the designed concentration range of DBSA in this work, the maximum DBSA sorption capacities on the Alluvial soil HA (AHA) and the Mollisol soil HA (MHA) were 115.0 and 112.2 mg/ g, respectively, which were higher than those of the Alluvial soil (AS) and Mollisol soil (MS). The sorption isotherms were well fitted by the Freundlich equation. The sorption capacity of the AHA was greater than that of the MHA, AS and MS. Furthermore, the sorption complexes of HAs and DBSA were characterized using elemental analysis, micro-Fourier transform infrared spectroscopy (FTIR), solid-state 13 C nuclear magnetic resonance (NMR) spectroscopy and electron spin resonance spectroscopy (ESR), it reveals that the sorption of DBSA on HAs mainly occurred on the C=O, C-O and aromatic functional groups. Moreover, the sorption data indicated that the sorption behavior was complicated, probably due to the formation of H bonds, hydrophobic interactions and electron donoracceptor mechanisms.
Humin, the most recalcitrant and abundant organic fraction of soils and of sediments, is a signif... more Humin, the most recalcitrant and abundant organic fraction of soils and of sediments, is a significant contributor to the stable carbon pool in soils and is important for the global carbon budget. It has significant resistance to transformations by microorganisms. Based on the classical operational definition, humin can include any humic-type substance that is not soluble in water at any pH. We demonstrate in this study how sequential exhaustive extractions with 0.1 M sodium hydroxide (NaOH)+6 M urea, followed by dimethylsulphoxide (DMSO)+6% (v/v) sulphuric acid (H 2 SO 4 ) solvent systems, can extract 70-80% of the residual materials remaining after prior exhaustive extractions in neutral and aqueous basic media. Solid-state 13 C NMR spectra have shown that the components isolated in the base+urea system were compositionally similar to the humic and fulvic acid fractions isolated at pH 12.6 in the aqueous media. The NMR spectra indicated that the major components isolated in the DMSO+H 2 SO 4 medium had aliphatic hydrocarbon associated with carboxyl functionalities and with lesser amounts of carbohydrate and peptide and minor amounts of lignin-derived components. The major components will have significant contributions from longchain fatty acids, waxes, to cuticular materials. The isolates in the DMSO+H 2 SO 4 medium were compositionally similar to the organic components that resisted solvation and remained associated with the soil clays. It is concluded that the base+urea system released humic and fulvic acids held by hydrogen bonding or by entrapment within the humin matrix. The recalcitrant humin materials extracted in DMSO+H 2 SO 4 are largely biological molecules (from plants and the soil microbial population) that are likely to be protected from degradation by their hydrophobic moieties and by sorption on the soil clays. Thus, the major components of humin do not satisfy the classical definitions for humic substances which emphasise that these arise from microbial or chemical transformations in soils of the components of organic debris.
Neste trabalho faz-se a divulgação do potencial de carvões e resíduos orgânicos parcialmente carb... more Neste trabalho faz-se a divulgação do potencial de carvões e resíduos orgânicos parcialmente carbonizados visando obter materiais que mimetizam a matéria orgânica do solo das Terras Pretas de Índio da Amazônia, e que sirvam como condicionadores de solo e seqüestrem carbono de forma recalcitrante e reativa. Pesquisas desenvolvidas por grupos brasileiros e estrangeiros têm contribuído para o entendimento do surgimento e utilização das Terras Pretas de Índio da Amazônia. Aqui são divulgados resultados de estudos químicos no sentido do desenvolvimento do conhecimento científico e tecnológico e de inovação no aproveitamento de subprodutos orgânicos, principalmente de indústrias de biocombustíveis, carvão vegetal metalúrgico e outros, buscando imitar a excelente performance da chamada Terras Pretas de Índio da Amazônia. The potential of charcoal and of partially combusted organic waste to mimic the soil organic matter of the Terras Pretas de Índios (Amazonian Dark Earths) from the Amazon Region is discussed. These materials serve as soil conditioners and as sequesterers of carbon in recalcitrant and in reactive forms. Studies carried out by Brazilian and by international groups have contributed to the emergence of an awareness of the compositions and of the uses of these materials. In this contribution we report on chemical studies that are leading to the development of a scientific and technological awareness, and of innovations that will have value in finding novel uses in applications to soil of chars from organic wastes such as those from the biofuel industry, and from metallurgical and various coal plant residues.
Titanium dioxide nanoparticles increasingly will be used in commercial products and have a high l... more Titanium dioxide nanoparticles increasingly will be used in commercial products and have a high likelihood of entering municipal sewage that flows to centralized wastewater treatment plants (WWTPs). Treated water (effluent) from WWTPs flows into rivers and lakes where nanoparticles may pose an ecological risk. To provide exposure data for risk assessment, titanium concentrations in raw sewage and treated effluent were determined for 10 representative WWTPs that use a range of unit processes. Raw sewage titanium concentrations ranged from 181 to 1233 µg L(-1) (median of 26 samples was 321 µg L(-1)). The WWTPs removed more than 96% of the influent titanium, and all WWTPs had effluent titanium concentrations of less than 25 µg L(-1). To characterize the morphology and presence of titanium oxide nanoparticles in the effluent, colloidal materials were isolated via rota-evaporation, dialysis and lyophilization. High resolution transmission electron microscopy and energy dispersive X-ray analysis indicated the presence of spherical titanium oxide nanoparticles (crystalline and amorphous) on the order of 4 to 30 nm in diameter in WWTP effluents. This research provides clear evidence that some nanoscale particles will pass through WWTPs and enter aquatic systems and offers a methodological framework for collecting and analyzing titanium-based nanomaterials in complex wastewater matrices.
SummaryA comprehensive sequential extraction procedure was applied to isolate soil organic compon... more SummaryA comprehensive sequential extraction procedure was applied to isolate soil organic components using aqueous solvents at different pH values, base plus urea (base‐urea), and finally dimethylsulfoxide (DMSO) plus concentrated H2SO4 (DMSO‐acid) for the humin‐enriched clay separates. The extracts from base‐urea and DMSO‐acid would be regarded as ‘humin’ in the classical definitions. The fractions isolated from aqueous base, base‐urea and DMSO‐acid were characterized by solid and solution state NMR spectroscopy. The base‐urea solvent system isolated ca. 10% (by mass) additional humic substances. The combined base‐urea and DMSO‐acid solvents isolated ca. 93% of total organic carbon from the humin‐enriched fine clay fraction (<2 μm). Characterization of the humic fractions by solid‐state NMR spectroscopy showed that oxidized char materials were concentrated in humic acids isolated at pH 7, and in the base‐urea extract. Lignin‐derived materials were in considerable abundance in t...
Humin is the most recalcitrant and least understood fraction of soil organic matter. By definitio... more Humin is the most recalcitrant and least understood fraction of soil organic matter. By definition, humin is that fraction not extracted by traditional aqueous alkaline soil extractants. Here we show that g70% of the traditional humin fraction is solubilized when 0.1 M NaOH + 6 M urea and dimethyl sulfoxide (DMSO) + 6% H 2 SO 4 are used in series after conventional extraction. Multidimensional solution-state NMR is applied in this study to gain an understanding of the major constituents present in these "solubilized humin fractions". The spectra indicated strong contributions from five main categories of components, namely. peptides, aliphatic species, carbohydrates, peptidoglycan, and lignin. Diffusion edited spectroscopy indicated that all species are present as macromolecules (or stable aggregate species). Although the distribution of the components is generally similar, peptidoglycan is present at significant levels supporting a higher microbial contribution to humin than to humic and fulvic fractions. The abundance of plant-and microbial-derived materials found does not exclude "humic" materials (e.g., oxidized lignin) or the presence of novel compounds at lower concentrations but suggests that a large proportion of humin is formed from classes of known compounds and parent biopolymers.
Highly water-soluble hydroxylated fullerene derivatives are being investigated for a wide range o... more Highly water-soluble hydroxylated fullerene derivatives are being investigated for a wide range of commercial products as well as for potential cytotoxicity. However, no analytical methods are currently available for their quantification at sub-ppm concentrations in environmental matrices. Here, we report on the development and comparison of liquid chromatography-ultra violet/visible spectroscopy (LC-UV/vis) and mass spectrometry (LC-MS) based detection and quantification methods for a commercial fullerols. We achieved good separation efficiency using an amide-type hydrophilic interaction liquid chromatography (HILIC) column (plate number >2000) under isocratic conditions with 90% acetonitrile as the mobile phase. The method detection limits (MDLs) ranged from 42.8 ng/mL (UV detection) to 0.19 pg/mL (using MS with multiple reaction monitoring, MRM). Other MS measurement modes achieved MDLs of 125 pg/mL (single quad scan, Q1) and 1.5 pg/mL (multiple ion monitoring, MI). Each detection method exhibited a good linear response over several orders of magnitude. Moreover, we tested the robustness of these methods in the presence of Suvanee River fulvic acids (SRFA) as an example of organic matter commonly found in environmental water samples. While SRFA significantly interfered with UVand Q1-based quantifications, the interference was relatively low using MI or MRM (relative error in presence of SRFA: 8.6% and 2.5%, respectively). This first report of a robust MS-based quantification method for modified fullerenes dissolved in water suggests the feasibility of implementing MS techniques more broadly for identification and quantification of fullerols and other water-soluble fullerene derivatives in environmental samples.
Maize (C4 plant) stover was incubated for two years in a wheat (C3-cropped) soil. • Average 54.6%... more Maize (C4 plant) stover was incubated for two years in a wheat (C3-cropped) soil. • Average 54.6% organic C of HAs and 35.7% that of FAs were of maize origins. • Fractions from sequential exhaustive extractions were spectroscopically characterised. • Humin, isolated in DMSO/sulfuric acid was predominantly aliphatic in nature. • The humic substances studies enabled investigations of SOM dynamics.
Purpose Dissolved organic matter (DOM), a heterogeneous mixture of low concentrations of organic ... more Purpose Dissolved organic matter (DOM), a heterogeneous mixture of low concentrations of organic matter draining from soils, plays a significant role in soil C cycling and in nutrient and pollutant transport. DOM from undisturbed soil profiles has rarely been studied. Hydrophobic acids (Ho) and hydrophilic acids (Hi), the major components of DOM, were recovered, using XAD-8 and XAD-4 resins in series, from waters draining in winter and in spring periods from well-drained and poorly drained Irish grassland soil profiles in lysimeters. Materials and methods Waters were collected from 45 soil undisturbed lysimeters at the Teagasc Research Centre, Johnstown Castle, Wexford, Ireland. Four Irish representative soils had been collected as undisturbed 1.0-m-deep monoliths, transported to the experiment site and arranged randomly in an experimental facility. Water collections were carried out in winter and spring periods. The DOM was isolated and fractionated using an XAD-8 and XAD-4 resins in-tandem procedure, and hydrophobic acids (Ho) and hydrophilic acids (Hi) were isolated. The amounts of DOM recovered in the winter period were much greater than those in the spring period, and the soil types had only minor influences on the DOM concentrations recovered. The Ho and Hi fraction contents ranged from 62 to 90 and 10 to 28%, respectively, of the total DOM content extracted. The Hi acids were most enriched in 13 C, and considered to reflect greater microbial inputs. The neutral sugar (NS) contents for the Ho and Hi fractions were in the range of 15 to 52 μg mg -1 , with the Hi fraction most enriched. The amino acids (AAs) for the Ho and Hi fractions varied from 0.6 to 2.4%, and the total AAs and NS of the Ho acids were well correlated. The DOM fractions from the drainage waters contained much less AAs and NS than the corresponding fractions in the parent soils. The solid-and liquid-state NMR data indicated organic structures with low aromaticity, significant amounts of carbohydrate and with lesser amounts of peptide structures, and with long-chain methylene (CH 2 ) n and methine (-CH-) groups. Conclusions The application of a variety of wet chemistry and of spectroscopy procedures has given a more in-depth awareness of the compositions of the DOM in the drainage waters from four different soils in 1.0-m-deep lysimeter arrangements. Based on wet chemistry analyses, and FTIR and liquid-and solid-state NMR spectrometry, it is clear that there are some differences between the compositions of the DOM fractions recovered. Alkyl functionalities dominated the structures. These included significant amounts or O-alkyl (predominantly carbohydrate), and with lesser (and variable amounts in the different fractions) aromatic structures (to which aromatic amino acid components were considered to be significant contributors), and with no evidence for lignin-derived structures The results suggest that, during residence in the soil solution, microbiological processes transform the SOM components released into products that are greatly different from their materials of origin in the SOM.
In-situ combustion (ISC) process has drawn more and more attention in the development of heavy oi... more In-situ combustion (ISC) process has drawn more and more attention in the development of heavy oil reservoir due to its high efficiency and oil recovery. Although numerous studies have been reported that oil properties exhibit significant changes during the combustion process, the reaction mechanisms and the evolution of oil components are still not well understood. In this work, the compounds of produced oils collected from a three dimensional simulated production model (container) at different duration times after combustion being initiated and the original oil were characterized at the molecular level using gas chromatography (GC), gas chromatography -mass spectrometry (GC-MS) and high-field Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR MS). Both aromatic and acidic components were analyzed. The aromatic components showed relatively more stable characteristics than that of acidic components, no obvious changes in aromatic compounds distributions were observed by the positive ion atmospheric pressure photoionization (APPI) FT-ICR MS analysis. Small aliphatic acids were detected in the ISC oils which were responsible for the high total acid numbers (TAN). The acidic O x (x=1-3) compounds, which have major contributions to the increase in TAN, were generated in greater abundances compared to that of the original crude oil. The carbon number distributions of the O 1 and O 2 classes in the produced Page 1 of 16 ACS Paragon Plus Environment Energy & Fuels oils significantly shifted to a lower carbon number region, with the dominant distribution from 15 -45 at the initial state to 10 -40 at the longest duration time. The double bond equivalent (DBE) values decreased during the combustion process. The generated acidic O 1 components with DBE values less than 4 were also found in negative ion electrospray (ESI) analysis, indicating the oxidation of hydrocarbons to alcohols.
PurposeDissolved organic matter (DOM) composition is influenced by and modulates biogeochemical p... more PurposeDissolved organic matter (DOM) composition is influenced by and modulates biogeochemical processes, yet DOM characterization techniques are challenged by its heterogeneous properties and structures. In this paper, ultrahigh electrospray ionization Fourier transform ion cyclotron resonance (ESI-FTICR) mass spectrometry is used to characterize previously isolated and well-characterized four DOM fractions from a water reservoir in the southwestern part of the USA.Materials and methodsAbout 50–60 L water samples were collected from Lake Pleasant (a water reservoir of Colorado River) and isolated and fractionated using a sequential isolation and fractionation procedure. DOM was firstly fractionated to the colloids and soluble permeate, then hydrophobic acids (HPO-A) and neutrals (HPO-N) plus amphiphilic acids (AMP-A) and neutrals (AMP-N) were fractionated using the resin-in-tandem procedure. Approximately 0.7 mg sample was dissolved in 250 μL methanol/water mixture (1:1, v/v) and diluted twice with 0.1 % (by volume) NH4OH (in 1:1 methanol/water, v/v) and measured by ESI-FTICR in negative ion mode.Results and discussionIn the m/z range of <700, among the sum of 4107 peaks, HPO-N contained the most assigned 1763 molecules and HPO-A, AMP-N, and AMP-A contained 971, 990, and 293, respectively. Acid fractions were relatively more oxygenated than the corresponding neutrals. Except for the major assigned CHO molecules, a high portion of heteroatom-containing molecules were assigned in the neutral fractions. Van Krevelen and Venn diagrams analyses showed significant molecular differentiation among the fractions. Among the assigned formulas, the Venn diagram indicated only a small portion (<4 %) of distinct formulas overlapped. S-containing molecules were efficiently ionized and identified in the neutrals. Some of the S1-containing compounds with high signal magnitudes are tentatively assigned to alkylbenzene sulfonates and their biodegradation and biotransformation derivatives indicating anthropogenic input on site.ConclusionsBy using the XAD resin-in-tandem approach and FTICR-MS, numbers of DOM molecules in fractions were distinctly separated, accordingly the complexity of DOM was reduced. Furthermore, to a great extent, the compositions and structures of each fraction in the molecular level are remarkably different as evidenced by only small portion of molecules overlapping.
An awareness of the transformation of plant residues returned to cultivated soils is vital for a ... more An awareness of the transformation of plant residues returned to cultivated soils is vital for a better understanding of carbon cycles, the maintenance of soil fertility and the practice of a sustainable agriculture. The transformation of maize (Zea mays L) straw residues into soil organic matter (SOM) in a one year incubation experiment was studied in a soil that had been under long term cultivation with wheat (Triticum aestivum L) for >30years. A novel sequential exhaustive extraction and fractionation procedure isolated a series of fractions of SOM. The samples were characterized by elemental and δ(13)C analyses, by amino acids and neutral sugars analyses, by Fourier transformed infrared (FTIR) spectrometry, and by solid state (13)C nuclear magnetic resonance (NMR) spectroscopy and with chemical shift anisotropy (CSA) -filter and dipolar dephasing (DD) spectral editing NMR techniques. The δ(13)C data indicated that 59% and 38% of the newly transformed organic carbon was in the...
Dodecylbenzene sulfonic acid (DBSA), the acid form of sodium dodecylbenzenesulfonate (SDBS), is o... more Dodecylbenzene sulfonic acid (DBSA), the acid form of sodium dodecylbenzenesulfonate (SDBS), is often identified and detected in soils. However, it still has less awareness of the sorption behavior of DBSA with soil organic matter. In this paper, the sorption behaviors of DBSA on two different types of soils (Mollisol and Alluvial soils) and soil humic acids (HAs) were studied and compared, and the mechanisms of HAs and DBSA interactions were discussed. Sorption dynamics and isotherms were studied using the batch equilibrium method. The sorption kinetics was relatively slow, and the sorption equilibrium can be reached within 10 h. In the designed concentration range of DBSA in this work, the maximum DBSA sorption capacities on the Alluvial soil HA (AHA) and the Mollisol soil HA (MHA) were 115.0 and 112.2 mg/ g, respectively, which were higher than those of the Alluvial soil (AS) and Mollisol soil (MS). The sorption isotherms were well fitted by the Freundlich equation. The sorption capacity of the AHA was greater than that of the MHA, AS and MS. Furthermore, the sorption complexes of HAs and DBSA were characterized using elemental analysis, micro-Fourier transform infrared spectroscopy (FTIR), solid-state 13 C nuclear magnetic resonance (NMR) spectroscopy and electron spin resonance spectroscopy (ESR), it reveals that the sorption of DBSA on HAs mainly occurred on the C=O, C-O and aromatic functional groups. Moreover, the sorption data indicated that the sorption behavior was complicated, probably due to the formation of H bonds, hydrophobic interactions and electron donoracceptor mechanisms.
Humin, the most recalcitrant and abundant organic fraction of soils and of sediments, is a signif... more Humin, the most recalcitrant and abundant organic fraction of soils and of sediments, is a significant contributor to the stable carbon pool in soils and is important for the global carbon budget. It has significant resistance to transformations by microorganisms. Based on the classical operational definition, humin can include any humic-type substance that is not soluble in water at any pH. We demonstrate in this study how sequential exhaustive extractions with 0.1 M sodium hydroxide (NaOH)+6 M urea, followed by dimethylsulphoxide (DMSO)+6% (v/v) sulphuric acid (H 2 SO 4 ) solvent systems, can extract 70-80% of the residual materials remaining after prior exhaustive extractions in neutral and aqueous basic media. Solid-state 13 C NMR spectra have shown that the components isolated in the base+urea system were compositionally similar to the humic and fulvic acid fractions isolated at pH 12.6 in the aqueous media. The NMR spectra indicated that the major components isolated in the DMSO+H 2 SO 4 medium had aliphatic hydrocarbon associated with carboxyl functionalities and with lesser amounts of carbohydrate and peptide and minor amounts of lignin-derived components. The major components will have significant contributions from longchain fatty acids, waxes, to cuticular materials. The isolates in the DMSO+H 2 SO 4 medium were compositionally similar to the organic components that resisted solvation and remained associated with the soil clays. It is concluded that the base+urea system released humic and fulvic acids held by hydrogen bonding or by entrapment within the humin matrix. The recalcitrant humin materials extracted in DMSO+H 2 SO 4 are largely biological molecules (from plants and the soil microbial population) that are likely to be protected from degradation by their hydrophobic moieties and by sorption on the soil clays. Thus, the major components of humin do not satisfy the classical definitions for humic substances which emphasise that these arise from microbial or chemical transformations in soils of the components of organic debris.
Neste trabalho faz-se a divulgação do potencial de carvões e resíduos orgânicos parcialmente carb... more Neste trabalho faz-se a divulgação do potencial de carvões e resíduos orgânicos parcialmente carbonizados visando obter materiais que mimetizam a matéria orgânica do solo das Terras Pretas de Índio da Amazônia, e que sirvam como condicionadores de solo e seqüestrem carbono de forma recalcitrante e reativa. Pesquisas desenvolvidas por grupos brasileiros e estrangeiros têm contribuído para o entendimento do surgimento e utilização das Terras Pretas de Índio da Amazônia. Aqui são divulgados resultados de estudos químicos no sentido do desenvolvimento do conhecimento científico e tecnológico e de inovação no aproveitamento de subprodutos orgânicos, principalmente de indústrias de biocombustíveis, carvão vegetal metalúrgico e outros, buscando imitar a excelente performance da chamada Terras Pretas de Índio da Amazônia. The potential of charcoal and of partially combusted organic waste to mimic the soil organic matter of the Terras Pretas de Índios (Amazonian Dark Earths) from the Amazon Region is discussed. These materials serve as soil conditioners and as sequesterers of carbon in recalcitrant and in reactive forms. Studies carried out by Brazilian and by international groups have contributed to the emergence of an awareness of the compositions and of the uses of these materials. In this contribution we report on chemical studies that are leading to the development of a scientific and technological awareness, and of innovations that will have value in finding novel uses in applications to soil of chars from organic wastes such as those from the biofuel industry, and from metallurgical and various coal plant residues.
Titanium dioxide nanoparticles increasingly will be used in commercial products and have a high l... more Titanium dioxide nanoparticles increasingly will be used in commercial products and have a high likelihood of entering municipal sewage that flows to centralized wastewater treatment plants (WWTPs). Treated water (effluent) from WWTPs flows into rivers and lakes where nanoparticles may pose an ecological risk. To provide exposure data for risk assessment, titanium concentrations in raw sewage and treated effluent were determined for 10 representative WWTPs that use a range of unit processes. Raw sewage titanium concentrations ranged from 181 to 1233 µg L(-1) (median of 26 samples was 321 µg L(-1)). The WWTPs removed more than 96% of the influent titanium, and all WWTPs had effluent titanium concentrations of less than 25 µg L(-1). To characterize the morphology and presence of titanium oxide nanoparticles in the effluent, colloidal materials were isolated via rota-evaporation, dialysis and lyophilization. High resolution transmission electron microscopy and energy dispersive X-ray analysis indicated the presence of spherical titanium oxide nanoparticles (crystalline and amorphous) on the order of 4 to 30 nm in diameter in WWTP effluents. This research provides clear evidence that some nanoscale particles will pass through WWTPs and enter aquatic systems and offers a methodological framework for collecting and analyzing titanium-based nanomaterials in complex wastewater matrices.
SummaryA comprehensive sequential extraction procedure was applied to isolate soil organic compon... more SummaryA comprehensive sequential extraction procedure was applied to isolate soil organic components using aqueous solvents at different pH values, base plus urea (base‐urea), and finally dimethylsulfoxide (DMSO) plus concentrated H2SO4 (DMSO‐acid) for the humin‐enriched clay separates. The extracts from base‐urea and DMSO‐acid would be regarded as ‘humin’ in the classical definitions. The fractions isolated from aqueous base, base‐urea and DMSO‐acid were characterized by solid and solution state NMR spectroscopy. The base‐urea solvent system isolated ca. 10% (by mass) additional humic substances. The combined base‐urea and DMSO‐acid solvents isolated ca. 93% of total organic carbon from the humin‐enriched fine clay fraction (<2 μm). Characterization of the humic fractions by solid‐state NMR spectroscopy showed that oxidized char materials were concentrated in humic acids isolated at pH 7, and in the base‐urea extract. Lignin‐derived materials were in considerable abundance in t...
Humin is the most recalcitrant and least understood fraction of soil organic matter. By definitio... more Humin is the most recalcitrant and least understood fraction of soil organic matter. By definition, humin is that fraction not extracted by traditional aqueous alkaline soil extractants. Here we show that g70% of the traditional humin fraction is solubilized when 0.1 M NaOH + 6 M urea and dimethyl sulfoxide (DMSO) + 6% H 2 SO 4 are used in series after conventional extraction. Multidimensional solution-state NMR is applied in this study to gain an understanding of the major constituents present in these "solubilized humin fractions". The spectra indicated strong contributions from five main categories of components, namely. peptides, aliphatic species, carbohydrates, peptidoglycan, and lignin. Diffusion edited spectroscopy indicated that all species are present as macromolecules (or stable aggregate species). Although the distribution of the components is generally similar, peptidoglycan is present at significant levels supporting a higher microbial contribution to humin than to humic and fulvic fractions. The abundance of plant-and microbial-derived materials found does not exclude "humic" materials (e.g., oxidized lignin) or the presence of novel compounds at lower concentrations but suggests that a large proportion of humin is formed from classes of known compounds and parent biopolymers.
Highly water-soluble hydroxylated fullerene derivatives are being investigated for a wide range o... more Highly water-soluble hydroxylated fullerene derivatives are being investigated for a wide range of commercial products as well as for potential cytotoxicity. However, no analytical methods are currently available for their quantification at sub-ppm concentrations in environmental matrices. Here, we report on the development and comparison of liquid chromatography-ultra violet/visible spectroscopy (LC-UV/vis) and mass spectrometry (LC-MS) based detection and quantification methods for a commercial fullerols. We achieved good separation efficiency using an amide-type hydrophilic interaction liquid chromatography (HILIC) column (plate number >2000) under isocratic conditions with 90% acetonitrile as the mobile phase. The method detection limits (MDLs) ranged from 42.8 ng/mL (UV detection) to 0.19 pg/mL (using MS with multiple reaction monitoring, MRM). Other MS measurement modes achieved MDLs of 125 pg/mL (single quad scan, Q1) and 1.5 pg/mL (multiple ion monitoring, MI). Each detection method exhibited a good linear response over several orders of magnitude. Moreover, we tested the robustness of these methods in the presence of Suvanee River fulvic acids (SRFA) as an example of organic matter commonly found in environmental water samples. While SRFA significantly interfered with UVand Q1-based quantifications, the interference was relatively low using MI or MRM (relative error in presence of SRFA: 8.6% and 2.5%, respectively). This first report of a robust MS-based quantification method for modified fullerenes dissolved in water suggests the feasibility of implementing MS techniques more broadly for identification and quantification of fullerols and other water-soluble fullerene derivatives in environmental samples.
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