Progress 10/01/02 to 09/30/08
Outputs
OUTPUTS: Our data showed that aliphatic structures, particularly the paraffinic fractions, tend to be less polar and more hydrophobic. As a result, they have high affinity for hydrophobic organic contaminants such as pyrene and phenanthrene. Once polar functional groups are added to aliphatic fractions via oxidation and coating, sorption of hydrophobic organic compounds decreased due to the reduced hydrophobicity and possibly the decreased accessibility. This also demonstrates the importance of the conformation of organic matter for retention of hydrophobic organic contaminants. PARTICIPANTS: Dr. Benny Chefetz, The Hebrew University of Jerusalem; Dr. Xilong Wang, Peking Univsersity (a former postdoctoral fellow); Dr. Beth Johnson, Post University (a former Ph.D. student) TARGET AUDIENCES: Agricultural scientists, environmentalists, college students, conservationists PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
This research greatly improves the understanding of soil organic matter chemistry and organic carbon decomposition dynamics in soils, and helps to predict the sorption, release, and fate of organic contaminants in soils including pesticides.
Publications
- Chen, D.Y., B. Xing and W.B. Xie. 2007. Sorption of phenanthrene, naphthalene and o-xylene by soil organic matter fractions. Geoderma. 139: 329-335.
- Wang, X.L. and B. Xing. 2007. Importance of structural makeup of biopolymers for organic contaminant sorption. Environ. Sci. Technol. 41: 3559-3565.
- Wang, X.L. and B. Xing. 2007. Sorption of organic contaminants by biopolymers-derived chars. Environ. Sci. Technol. 41 (24): 8342-8348.
- Kang, S.H. and B.S. Xing. 2008. Relationship of polarity and structures of organic matter with sorption capacity of hydrophobic organic compounds. Chapter 5 (p. 125-143) In Soil Mineral-Microbe-Organic Interactions: Theories and Applications, eds: Huang, Q., P.M. Huang, and A. Violante. Springer-Verlag, Berlin, pp.353.
- Wen, B., J. Zhang, S.-Z. Zhang, X.-Q. Shan, S.U. Khan and B. Xing. 2007. Phenanthrene sorption to soil humic acid and different humin fractions. Environ. Sci. Technol. 41: 3165-3171.
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Progress 10/01/06 to 09/30/07
Outputs
Aliphatic components including lipids were extracted from soil and compost samples. Sorption of organic contaminants by these components along with humic fractions was determined. In addition, Cuticular materials and their fractions from several plant species were isolated and characterized by various instrumental analyses. Competitive sorption and desorption behavior of herbicides with plant cuticular fractions were also examined. Decomposition of plant cuticular materials in soil and its effect on sorption of organic chemicals were investigated. Our research results were disseminated and shared primarily through scientific publications and presentations at regional, national and international meetings and conferences.
Impacts
Aliphatic structures are highly enriched in soil humin fraction, contributing greatly to overall sorption of hydrophobic organic chemicals (HOCs) by soil. With preferential decomposition of pectin and cutin in soil, cutan becomes increasingly important for sorption of HOCs and herbicides. NMR data indicate a rubber-like nature for cutin, which is supported by reversible and noncompetitive sorption. In addition, the rigid phase of the biopolymer can be changed by the sorbed molecules, resulting in sorptive behavior variation. Once again, our data show that the aliphatic fraction of soil organic matter can significantly influence the fate and bioavailability of HOCs including herbicides in soils. Our data help understand the structure and chemistry of plant cuticular components including cutin, cutan, and lipids and their roles in soil organic matter dynamics and carbon cycling.
Publications
- Mashayekhi, H., P. Veneman and B. Xing. 2006. Phenanthrene sorption by compost humic acids. Biology and Fertility of Soils. 42: 426-431.
- Shechter, M., B. Xing, F-D. Kkopinke and B. Chefetz. 2006. Competitive sorption-desorption behavior of triazine herbicides with plant cuticular fractions. J. Agric. Food Chem. 54: 7761-7768.
- Stimler, K., B. Xing and B. Chefetz. 2006 . Transformation of plant cuticles in soil: effect on their sorptive capabilities. Soil Sci. Soc. Am. J. 70: 1101-1109.
- Wang, X.L. and B. Xing. 2007. Roles of acetone-conditioning and lipid in sorption of organic contaminants. Environ. Sci. Technol. 41(16): 5731-5737.
- Johnson, B.J., O. Dorot, J.D. Liu, B. Chefetz and B. Xing. 2007. Spectroscopic Characterization of Aliphatic Moieties in Four Plant Cuticles. Commun. Soil Sci. Plant Anal. 38: 2461-2478.
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Progress 10/01/05 to 09/30/06
Outputs
Aliphatic components of tomato, green pepper and apple fruit cuticles, and the leaf cuticles of mature olive tree, were characterized using elemental analysis, C-13 NMR and FTIR. Cuticular fractions isolated for analyses included bulk, dewaxed, non-saponifiable, and non-hydrolyzable cuticles. Results from C-13 NMR and FTIR spectra indicate that the cuticles of all the plant materials studied are comprised of extractable lipids, polysaccharides and cutin, while the cuticles extracted from the olive leaf, pepper fruit and apple fruit also contained non-saponifiable, non-hydrolyzable residues, likely to be cutan. The aliphatic signature peaks of the apple fruit and olive leaf cutan-like materials were much weaker than those of the pepper fruit. H/C and (O+ N)/C ratios for the olive leaf, pepper fruit and apple fruit cuticle fractions indicate that their bulk cuticle, dewaxed cuticle and lipid fractions are more aliphatic than, but have a similar polarity to, their
respective cutan-like fraction. These results provide evidence that pepper fruit, apple fruit and olive leaf cuticles each contain a cutan-like fraction, but in the olive leaf and apple fruit, this fraction has a slightly different chemical structure from that of the pepper fruit, and makes up a smaller percent of the total cuticle. Incubation experiments of bulk cuticular materials in soils are underway. Isolated cuticular fractions from the incubation experiments will be used for sorption of organic contaminants. In addition, we examined sorption and conformational characteristics of reconstituted cuticular waxes of green pepper on montmorillonite. Organic carbon-normalized sorption coefficients of polyaromatic hydrocarbons (PAHs) increased with the loading of wax on the clay surface. Desorption was dependent on PAH's molecular sizes and sorbed-amounts, and wax-loading on the clay. Sorbed PAH molecules could swell the wax matrix and affect the PAH release. A novel phase transition
model in mineral-waxes-PAHs interaction system was proposed.
Impacts
An improved knowledge of plant cuticular materials will help understand soil organic matter chemistry and carbon sequestration in soils. The sorption-desorption behavior of PAHs with reconstituted-waxes on montmorillonite is potentially useful to the understanding of soil organic matter-clay complex (soil humin) because organic matter in the humin is highly aliphatic in nature (wax-like materials)
Publications
- Chen, L. and B. Xing. 2005. Sorption and conformational characteristics of reconstituted plant cuticular waxes on montmorillonite. Environ. Sci. Technol. 39: 8315-8323.
- Xing, B. and J.J. Pignatello. 2005. Sorption of organic chemicals. In Encyclopedia of Soils in the Environment. Elsevier Ltd., Editor-in-Chief: Daniel Hillel, Oxford, U.K. 2005. p. 537-547.
- Han, X., S. Wang, P. Veneman and B. Xing. 2006. Change of organic carbon content and its fractions in black soil under long-term application of chemical fertilizers and recycled organic manure. Commun. Soil Sci. Plant Anal. 37 (7&8): 1127-1137.
- Pan, B., B. Xing, W. Liu, S. Tao, et al. 2006. Distribution of sorbed phenanthrene and pyrene in different humic fractions of soils and importance of humin. Environ. Pollut. 143: 24-33.
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Progress 10/01/04 to 09/30/05
Outputs
We investigated the sorption of nonpolar and polar aromatic organic pollutants to aliphatic-rich cuticular fractions of green pepper. We also determined the sorption of phenanthrene by sequentially extracted soil humic acids and humins. The polarity and structures of cuticular fractions and humic materials were characterized by elemental analysis, FTIR and NMR. Further, we synthesized clay-humic complexes from extracted humic acid and pure clay minerals to simulate soil humin. Aliphatic fractions were preferentially adsorbed by these minerals. The humic fractions adsorbed by the tested clay minerals had greater carbon-normalized sorption coefficients than that of the bulk humic acid. Overall, polarity and accessibility seem to play a regulating role in sorption of organic contaminants.
Impacts
Relatively nonpolar, aliphatic fractions of organic matter sorb significant amounts of organic contaminants, thus they will affect the fate, bioavailability and mobility of these contaminants in soils and sediments. In addition, polarity of organic matter should be considered in the fate and risk assessment models for organic contaminants.
Publications
- Baoliang, C., E.J. Johnson, B. Chefetz, L. Zhu and B. Xing. 2005. Sorption of polar and nonpolar aromatic organic contaminants by plant cuticular materials: the role of polarity and accessibility. Environ. Sci. Technol. 39:6138-1641.
- Kang, S. and B. Xing. 2005. Phenanthrene sorption to sequentially extracted soil humic acids and humin. Environ. Sci. Technol. 39: 134-140.
- Wang, K. and B. Xing. 2005. Structural and sorption characteristics of adsorbed humic acid on clay minerals. J. Environ. Qual. 34: 342-349.
- Xing, B., J.D. Liu, X.B. Liu and X.Z. Han. 2005. Extraction and characterization of humic acids and humins from a black soil of China. Pedosphere, 15: 1-8.
- Williams, A., B. Xing, and P. Veneman. 2005. Effect of cultivation on soil organic matter and aggregate stability. Pedosphere, 15 (2): 255-262.
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Progress 10/01/03 to 09/30/04
Outputs
Tomatoes and green peppers were selected to isolate cuticular materials; the skins of both tomato and green pepper contained appreciable amounts of cuticular materials such as cutin. Preliminary spectroscopic data show that isolated cuticular materials are highly aliphatic. Further spectroscopic analysis and sorption experiments are underway. Soil organic matter (SOM) was also used to examine aliphatic organic fractions using alkaline sequential extractions. Aliphatic organic carbon content of humic acids increased with further extractions, while polarity and aromatic carbons apparently decreased. As a result, later extracted humic acids and humin fractions were more hydrophobic and aliphatic, which would make them better sorbents for organic compounds including pesticides. Sorption experiments are currently being conducted.
Impacts
Both plant cuticular materials and soil organic matter could contain a significant amount of aliphatic carbon content. These aliphatic organic materials can be strong sorbents for organic pollutants in soils and sediments.
Publications
- Wang, K.J. and B. Xing. 2004. Proton correlation times and segmental mobility of humic acids in two solvents. Soil Sci. 169: 168-175.
- Kang, S.H., D. Amarasiriwardena, P.L. Veneman, and B. Xing. 2003. Characterization of ten sequentially extracted humic acids and a humin from a soil in western Massachusetts. Soil Sci. 168: 880-887.
- Gunasekara, A.S. and B. Xing. 2003. Sorption and desorption of naphthalene by soil organic matter: Importance of aromatic and aliphatic components. J. Environ. Qual. 32: 240-246.
- Gunasekara, A.S. M.J. Simpson, and B. Xing. 2003. Identification and characterization of sorption domains in soil organic matter using structurally modified humic acids. Environ. Sci. Technol. 37: 852-858.
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Progress 10/01/02 to 09/30/03
Outputs
Aliphatic carbons can be a significant fraction of soil organic matter, particularly the paraffinic carbons due to its recalcitrant nature. We sequentially extracted one soil for its humic acids and humin and characterized them using NMR, FTIR, and UV-Visible spectrometers. We observed that later extracted humic acids have much more aliphatic structures than the early extracted humic acids. Humin (i.e., the residue after extractions) is most aliphatic in structure. We also examined sorption of naphthalene by a mineral soil and its humin and humic acid. Similarly, humin is more aliphatic than humic acid and its source soil. Organic carbon normalized sorption coefficient of naphthalene is highest for humin, indicating the importance of aliphatic components in soil organic matter. In addition, sorption hysteresis of naphthalene is larger in humin than its source soil and humic acid; it is more difficult for naphthalene to release once sorbed in humin.
Impacts
Humin is more aliphatic in structure than the other humic fractions of a soil and is a major fraction of soil organic matter. Thus, humin will strongly influence the release and efficacy of pesticides in soils. A better understanding of humin structures and sorptive characteristics will help to determine its contribution to sorption and bioavailability of organic chemicals in soils.
Publications
- Gunasekara, A.S. and Xing, B. 2003. Sorption and Desorption of naphthalene by soil organic matter: Importance of aromatic and aliphatic components. J. Environ. Qual. 32: 240-246.
- Kang, S.H., Amarasiriwardena, D., Veneman, P.L. and Xing, B. 2003. Characterization of ten sequentially extracted humic acids and a humin from a soil in western Massachusetts. Soil Sci. (in press).
- Liu, B., Han, X., Song, C., Herbert, S. and Xing, B. 2003. Soil organic carbon dynamics in black soils of china under different agricultural management systems. Commun. Soil Sci. Plant Anal. 34: 973-984.
- Xing, B. 2003. Phenanthrene sorption by humic-clay complexes. ACS Preprints of papers, Div. of Environ. Chem. 43(2): 897-901.
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