Journal
SCIENCE OF THE TOTAL ENVIRONMENT
Volume 603, Issue -, Pages 461-471Publisher
ELSEVIER
DOI: 10.1016/j.scitotenv.2017.06.114
Keywords
Soil; Dissolved organic matter; Water-soluble organic matter; Three Gorges Reservoir; Characterization; Natural organic matter
Categories
Funding
- National Natural Science Foundation of China [41403079, 41171198]
- Chongqing Research Program of Basic Research and Frontier Technology [cstc2015jcyjA20021]
- Fundamental Research Funds for the Central Universities from the Ministry of Education of China [XDJK2015B035]
- Swedish Research Council [621-2014-5370]
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Soil-derived dissolved organic matter (DOM) has a major influence in biogeochemical processes related to contaminant dynamics and greenhouse gas emissions, due to its reactivity and its bridging role between the soil and aquatic systems. Within the Three Gorges Reservoir (TGR, China) area, an extensive water-fluctuation zone periodically submerges the surrounding soils. Here we report a characterization study of soil-derived DOM across the TGR areas, using elemental and optical analysis, infrared spectroscopy (FTIR), pyrolysis-GC-MS (Py-GC-MS) and thermally assisted hydrolysis and methylation (THM-GC-MS). The results showed that the soil DOM from the TGR area is a mixture of allochthonous (i.e., plant-derived/terrigenous) and autochthonous (i.e., microbial) origins. The terrigenous DOM is composed primarily of phenolic and aliphatic structures from lignin and aliphatic biopolymers (i.e. cutin, suberin), respectively. Multivariate statistics differentiated between two fractions of the microbial DOM, i.e. chitin-derived, perhaps from fungi and arthropods in soil, and protein-derived, partially sourced from algal or aquatic organisms. Molecular proxies of source and degradation state were in good agreement with optical parameters such as SUVA(254), the fluorescence index (FI) and the humification index (HIX). The combined use of elemental analysis, fluorescence spectroscopy, and Py-GC-MS provides rigorous and detailed DOM characterization, whereas THM-GC-MS is useful for more precise but qualitative identification of the different phenolic (cinnamyl, p-hydroxyphenyl, guaiacyl, syringyl and tannin-derived) and aliphatic materials. With the multi-methodological approach used in this study, FTIR was the least informative, in part, because of the interference of inorganic matter in the soil DOM samples. The soil DOM from the TGR's water fluctuation zone exhibited considerable compositional diversity, mainly related to the balance between DOM source (microbial- or plant-derived), local vegetation and anthropogenic activities (e.g., agriculture). Finally, the relationship between DOM composition and its potential reactivity with substances of environmental concerns in the TGR area are also discussed. (C) 2017 Elsevier B.V. All rights reserved.
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