Progress 09/01/09 to 08/31/13
Outputs
Target Audience: The primary target audiences reached during this year (a no-cost extension year) were other scientists working in the field. These inviduals were reached via oral dissemnination of the research results via presnetations at technical meetings and submission of manuscripts for publication. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided? This project has supported 2 undergraduate chemistry majors who have done research as a part of their undergraduate degree requirements, 2 postdoctoral research associates and a senior reserch staff member. The senior reserch staff meember has accepted a tenure-track university positoin in environmental chemistry. How have the results been disseminated to communities of interest? The results of this research project have been disseminated via oral presentations at regional, national and international scientific meetings. One manuscripts is in prepss and 2 others are under review. What do you plan to do during the next reporting period to accomplish the goals? This is the final project report.
Impacts
What was accomplished under these goals?
The primary findings of this project during this project year are stated below. · Similarities and differences in the self-assembly of humic acid and humin were identified. Both NOM samples have shown similarities at the second hierarchical level that mirror the similarities in the distribution of the corresponding components, HA1 and L0. We have also shown that differences at the first hierarchical level that mirror the differences in the distribution and nature of the corresponding fractions, HA2 and L1. The first hierarchical level is composed primarily of amphiphilic components and has a positive cpE in case of humic acid while for humin is composed of mainly lipids and the cpE has negative values. · The amphiphilicity of HA2, crystallinity of L1 and the mass ratio of the HA2/L1 fractions were identified as factors that affect the self-assembly process however no exact dependence of the self-assembly process on these factors has been possible to date. · The existence of these operationally defined NOM fractions (HA1, HA2 and L1) that have been isolated from both humic acid and humin using two different extractants and from two geomaterials with different chemical characteristics and geochemical histories, suggests that the hierarchical associative mechanism is one that is characteristic of NOM. · The mineralization of self-assembled samples is higher by as much as 70% compared to their corresponding physical mixtures and does not show preferential mineralization. · The mineralization enhancement follows the same trend as the extent of the self-assembly as determined by the variation in heat capacity values. The larger the change in heat capacity the more self-assembled the sample is and the more mineralized it is when compared to its corresponding physical mixture. · The extent of mineralization of the self-assembled samples was not correlated to chemical composition based on the carbon-type distribution or hydrophobicity index, both of which were derived from the samples quantitative 13C solid-state NMR spectra. In contrast, the extent of mineralization of the physical mixtures and the individual fractions did vary with chemical composition and was accompanied by preferential mineralization of alkyl carbon. · The mineralization of humic acid and its most abundant fraction (HA1) samples in the solid state at 85% relative humidity showed significantly lower values than the ones from the solution mineralization experiments. · Domains within HA0 fractions with different amounts of motion were identified using 2D WISE (WIde-line SEparation) and T2 NMR measurements. A mobile domain in a peat humic acid fraction was not apparent from T2 measurements.
Publications
- Type:
Journal Articles
Status:
Awaiting Publication
Year Published:
2014
Citation:
Khalaf, M.; Chilom, G.; Rice, J. A., 2014, Mineralization of natural organic matter: Role of chemical composition and structural organization, Soil Biology & Biochemistry, 73:96-105, http://dx.doi.org/10.1016/j.soilbio.2014.02.013
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2010
Citation:
Chilom, G.*; Nagy, Z.; Delp, S.; Huff, G.; Rice, J. A., Self-assembly of humic acid: influence of pH and chemical composition, Biogeosciences Section 04, AGU Fall Meeting, San Francisco, Dec. 2010, paper B41E-0350.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2011
Citation:
Khalaf, M.*; Chilom, G.; Rice, J. A.; Microbial utilization and transformation of humic acid and its fractions, 241rst ACS National Meeting, Anaheim, CA, March 2011, GEOC 33.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2011
Citation:
Chilom, G.; Khalaf, M.; Rice, J. A.*, Effect of self-assembly on the microbial degradation of humic acid, European Geophysical Union Congress, April 2011, Vienna, Austria, EGU2011-5049.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2011
Citation:
Chilom, G.*; Rice, J. A., Unifying characteristic of soil organic matter, 242nd ACS National Meeting, Denver, CO, Aug. 2011, ENVR 375.
- Type:
Journal Articles
Status:
Published
Year Published:
2013
Citation:
Chilom, G.; Baglieri, A.; Johnson-Edler, C. A.; Rice, J. A., 2013, Hierarchical self-assembling properties of natural organic matters components, Organic Geochemistry, 57, 119-126, http://dx.doi.org/10.1016/j.orggeochem.2013.02.008.
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Progress 09/01/10 to 08/31/11
Outputs
OUTPUTS: Three fractions referred to as the non-amphiphilic humic, the amphiphilic fraction and the lipid fraction were isolated from NOM samples using a combination of organic solvent and aqueous alkaline extractions. Microbial degradation studies were performed for fractions of humic acid and their corresponding physical mixtures isolated from Leonardite and Guanella peat (Objective 1 & 2). The two materials are both reach in organic carbon but have different carbon-type distribution, with leonardite being primarily aromatic and Guanella being primarily aliphatic. Humic acid fractions and mixtures were analyzed before and after short term degradation experiments by solid state 13C NMR. Long term experiments of microbial degradation of these materials and two more isolated from Pahokee peat and Poinsett soil are in progress. Self-assembly of materials isolated from Leonardite, Pahokee and Guanella peat was described by the value of the excess heat capacity of these materials (Objective 4). The heat capacity of the composite formed at first level of organization and of its components, amphiphilic and lipid fractions were determined by differential scanning calorimetry. Correlations between the magnitude of the excess heat capacity and properties of these materials, such as carbon-type distribution, composition, surfactant character and crystallinity, were made. Work for the fourth system, Poinsett soil, is in progress. The 2D WISE (WIde-line SEparation) solid-state NMR spectra of the fractions and its corresponding mixtures in both hydrated and dehydrated samples were measured. Using spin-diffusion 2D WISE spectroscopy, spin diffusion between different types of proton sites was detected based on changes in the linewidths of the 1H resonances. The 1H T1 and T2 of the samples were also measured. A NMR spin-echo acquisition sequence was used to determine the relaxation time T2. The spin-echo is generated by two pulses separated by a time, τ. Using an echo with a long τ (200 μs), the protons with long T2 (fast motion) were selectively measured. (Objective 3). The results of these experiments were presented in papers at the Spring and Fall ACS National Meeting (2011), and the European Geophysics Union 2011 Annual Meeting. PARTICIPANTS: Gabriela Chilom (co-PI), Research Associate, South Dakota State University; James Rice (co-PI), Professor, South Dakota State University; Jay S. Shore (co-PI), Associate Professor, South Dakota State University; Moustafa Khalaf, Postdoctoral Research Associate, South Dakota State University; Zoltan Nagy, Postdoctoral Research Associate, South Dakota State University. TARGET AUDIENCES: Environmental scientists, environmental chemists and global change scientists. PROJECT MODIFICATIONS: None anticipated at this time
Impacts
Regardless of their origin, nature or pretreatment, natural organic matter has in common the ability to self-assembly into supramolecular structures that are controlled by a rather small portion of its components. These components are identified as amphiphilic humic-like and lipid components. Similar excess heat capacity values were found for Leonardite and Pahokee peat and smaller values were found for Guanella. Distribution of the three fractions was similar for Leonardite and Guanella but their characteristics, in terms of amphiphilic character and crystallinity were similar for leonardite and Pahokee. The self-assembly of these materials depends more on the relative properties of the fractions than on the ratio of amphiphilic and lipid components. In addition, not all the fractions of humic acid showed the same degradability. The amphiphilic fraction of humic acid was the one most mineralized, suggesting that properties like organization might have a major impact on mineralization of humic samples. A comparison of the intensities and the linewidths of the 1H slices of the 1H-13C WIdeline Separation (WISE) NMR spectra indicate that there is spin diffusion between different components of the samples suggesting that they are multiple domains in most of the samples, excluding the lipid fraction. Further work is necessary to try to determine an estimate of domain size and to determine what types of domains these may be. The observation of both broad and narrow 1H resonances in the spin echo experiment is significant because it is related to the morphology of the sample and it may be possible to obtain more detailed understanding of the domains in the samples by using 2D NMR techniques to measure the proximity of the protons to each and protons to carbon types using the narrow and broad resonances. The narrow resonances were not apparent in the 2D WISE spectra, because the parameters used to measure these spectra were optimized to ensure that the measured carbon signals came from carbon in very close proximity to the hydrogen.
Publications
- No publications reported this period
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Progress 09/01/09 to 08/31/10
Outputs
OUTPUTS: Using a combination of organic solvent and aqueous alkaline extractions various NOM samples and were separated into three fractions referred to as the non-amphiphilic humic (HA1), the amphiphilic (HA2) fraction and the lipid fraction (L1). The carbon-type distribution of each fraction was determined for each material by 13C DPMAS solid-state NMR. Fractions of humic acid isolated from four materials, Leonardite, Guanella peat, Pahokee Peat and Poinsett soil were prepared and based on their calculated distribution the physical mixtures were prepared. All these samples will be used for the microbial biodegradation studies (Objective 1 and 2) that are in progress. The microbial inoculum was isolated from a soil and its growing kinetic was determined using glucose as the mineralizable substrate. Leonardite humic acid samples at various degrees of deprotonation were prepared by drying from solutions of pH values between 2 and 11, and fractionated using the same combination of organic solvent and aqueous alkaline extractions described earlier (Objective 4). The variation of the fractions' distribution and carbon-type composition with pH was determined. The amphiphilic fraction was also characterized by tensiometry and the lipid fraction by differential scanning calorimetry. The variation of surfactant character of HA2 and crystallinity of L1 with pH were determined. Interactions specific to first level of organization between the amphiphilic and lipid fractions of Leonardite, were assessed by using 2D WISE (WIde-line SEparation) solid-state NMR spectroscopy. 2D WISE is a 1H-13C heteronuclear correlation technique where broad dipolar-coupled 1H resonances are measured. From these broad dipolar-coupled 1H resonances, correlation times of the molecular motion of different domains of the individual fractions were estimated and compared to the ones of the composite material (Objective 3). The results of these experiments were presented in papers at the AGU Fall Meeting (2009), 45th Midwest Regional Meeting of the American Chemical Society (ACS) (2010), the 239th ACS National Meeting (2010), and the Soil Science Society of America 2010 Annual Meeting. PARTICIPANTS: James Rice (PI), Professor, South Dakota State University, Gabriela Chilom (co-PI), Research Associate, South Dakota State University, Jay S. Shore (co-PI), Associate Professor, South Dakota State University, Moustafa Khalaf, Postdoctoral Research Associate, South Dakota State University, Zoltan Nagy, Postdoctoral Research Associate, South Dakota State University, Gary Huff, Undergraduate Research Assistant, South Dakota State University, Sara Delp, Undergraduate Research Assistant, University of Wisconsin- Platteville, Andrea Baglieri, Assistant Professor, University of Catania, Italy. TARGET AUDIENCES: Other biogeochemists and soil scientists PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
NOM has a positive role in the environment regardless of its origin or chemical composition that is due to its organization and the interactions between its individual components. NOM is present in a self-assembled supramolecular-state that is controlled by a small portion of its components that define its core. This "core" consists of lipids and amphiphilic components, chemically similar to their parent material, that self-assemble in nanoparticles and then further engage the non-amphphilic humic to form supramolecular structures. While the non-amphphilic humic components are difficult to control, the amphiphilic and lipid components are manageable so it opens the opportunity of controlling the NOM's behavior depending on the application desired. NOM organization varies with the pH. Based on the data obtained from Leonardite and Guanella peat, the higher the pH the L0 nanocomposite amount decreased, the contribution of lipids to it increases and the surfactant character of amphiphilic components increased too. Changes in the self-assembled state were observed with pH varied over environmental values. In addition the data showed that the core of NOM is defined by the strength of surfactant character and degree of lipid crystallinity as major factors that control its self assembly. This finding was also supported by the 2D WISE NMR study which showed that the mobility of aliphatic carbon from lipids increased upon interaction with the surfactant components. While we do not expect that the crystalline matrix to change considerably upon interaction we suggest that pockets of amorphous carbon are formed inside the matrix that interacts with the amorphous carbon of the surfactant. To test this hypothesis experiments are currently underway using various samples of NOM.
Publications
- Chilom, G., Baglieri,A., Rice, J.A. (2009) Effect of Soil Organic Matter Self-Assembly on Carbon Biodegradability, AGU Fall Meeting, San Francisco, December 2009.
- Delp, S., Chilom, G., Nagy, Z., Rice, J.A. (2010). Influence of pH on the self-assembly of humic acid, ACS regional Meeting, Wichita, KS, October 2010.
- Huff, G., Nagy, Z., Chilom, G., Rice, J.A. (2010) Self-assembly of Humic Acid: Influence of Composition, ACS regional Meeting, Wichita, KS, October 2010.
- Chilom, G., Baglieri,A., Rice, J.A. (2010) Comparative study of composite materials isolated from the humic acid and humin of a mineral soil, ACS National meeting San Francisco 2010.
- Chilom, G., Nagy, Z., Rice, J.A. (2010) Size Separation and Characterization of Fractions Involved in Humic Acid Self-Assembly, SSSA Annual Meeting, Long Beach, CA, Nov 2010.
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