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| Changes in the spectral characteristics of dissolved organic matter from paddy soil after heating |
| Received:July 24, 2017 |
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| KeyWord:dissolved organic matter;heating;humification degree;paddy soil;spectral characteristics |
| Author Name | Affiliation | E-mail | | PANG Yan-hua | School of Environmental & Safety Engineering, Changzhou University, Changzhou 213164, China | | | CHEN Li-na | School of Environmental & Safety Engineering, Changzhou University, Changzhou 213164, China
Changzhou Academy of Environmental Science, Changzhou 213022, China | | | ZHANG Sheng | School of Environmental & Safety Engineering, Changzhou University, Changzhou 213164, China | | | TU Bao-hua | School of Environmental & Safety Engineering, Changzhou University, Changzhou 213164, China | | | ZHANG Wen-yi | School of Environmental & Safety Engineering, Changzhou University, Changzhou 213164, China | | | HUANG Zhao-qin | College of Environmental and Ecologic, Jiangsu Open University, Nanjing 210036, China | | | HU Lin-chao | School of Environmental & Safety Engineering, Changzhou University, Changzhou 213164, China
Changzhou Academy of Environmental Science, Changzhou 213022, China | linchao.hu@hotmail.com |
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| Abstract: |
| Dissolved organic matter(DOM) is an important soil component. It consists of low-molecular-weight free amino acids, carbohydrates, organic acids, and high-molecular-weight enzymes, amino sugars, humus, and so on. It plays an important role in many chemical and biological processes in the soil. In this study, UV-VIS spectra, three-dimensional fluorescence, and infrared spectroscopy were used to analyze the effect of heat treatment on the structure and composition of DOM in different soils. The paddy soil samples were heated at 200℃, 250℃, and 300℃ for 2 h, 4 h, and 6 h, respectively. SUVA254, SUVA260, and SUVA280 were the absorption coefficients for unit dissolved organic carbon concentrations at 254, 260, and 280 nm, respectively. The results showed that the ultraviolet absorbance ratio(E2/E3) increased and the SUVA254, SUVA260, and SUVA280 values decreased when the temperature rose. They also indicated that the DOM aromaticity and hydrophobicity decreased when the temperature increased. Furthermore, the A253/A203 absorbance ratio increased when the temperature rose. This indicated that the aromatic ring substituents of the DOM component were mainly aliphatic chains when unheated and that the fatty substances were decomposed in large quantities when heated. The three-dimensional fluorescence spectra showed that a blue-shift in the main fluorescence peak appeared and fluorescence intensity increased. The ratio of the fluorescence peak value of fulvic acid in the ultraviolet region and the fluorescence peak in the visible region decreased. This result showed that the soil aromaticity and the molecular weight decreased after heating. The infrared spectra results showed that the amounts of carboxylic acid substances increased after heating. The aliphatic substances content increased at 200℃ and 250℃, but decreased at 300℃. These results will provide a basis for assessing the environmental risk of contaminants in soils under the influence of heat treatment. |
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