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Sci Total Environ. 2017 Dec 15;603-604:461-471. doi: 10.1016/j.scitotenv.2017.06.114. Epub 2017 Jun 23.

Composition of dissolved organic matter (DOM) from periodically submerged soils in the Three Gorges Reservoir areas as determined by elemental and optical analysis, infrared spectroscopy, pyrolysis-GC-MS and thermally assisted hydrolysis and methylation.

Author information

1
Key Laboratory of Eco-environments in Three Gorges Reservoir Region, Ministry of Education, Chongqing Key Laboratory of Agricultural Resources and Environment, College of Resources and Environment, Southwest University, Chongqing 400716, China; Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, Umeå SE-90183, Sweden. Electronic address: jiangtower666@163.com.
2
Ciencia do Sistema Terra, Departamento de Edafoloxía e Química Agrícola, Universidade de Santiago de Compostela, Campus Sur s/n, Santiago de Compostela 15782, Spain; Instituto de Ciencias del Patrimonio (Incipit), Consejo Superior de Investigaciones Científicas (CSIC), Avda. de Vigo sn, 15705 Santiago de Compostela, Spain.
3
Key Laboratory of Eco-environments in Three Gorges Reservoir Region, Ministry of Education, Chongqing Key Laboratory of Agricultural Resources and Environment, College of Resources and Environment, Southwest University, Chongqing 400716, China.
4
Qinghai Institute of Salt Lakes, Chinese Academy of Sciences, Xining 810008, China.
5
School of Chemical and Biomolecular Engineering, Georgia Institute of Technology, Atlanta, GA 30332, United States.

Abstract

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 SUVA254, 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.

KEYWORDS:

Characterization; Dissolved organic matter; Natural organic matter; Soil; Three Gorges Reservoir; Water-soluble organic matter

PMID:
28641186
DOI:
10.1016/j.scitotenv.2017.06.114
[Indexed for MEDLINE]

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