期刊
JOURNAL OF ENVIRONMENTAL SCIENCES
卷 88, 期 -, 页码 326-337出版社
SCIENCE PRESS
DOI: 10.1016/j.jes.2019.09.018
关键词
Dissolved organic carbon; Sulfate; Calcium; Ester group; Bidentate
资金
- National Natural Science Foundation, China
- National Science Foundation, Sri Lanka (NSFC-NSF SL) [21861142020]
- Program of China-Sri Lanka Joint Research and Demonstration Center for Water Technology
- China-Sri Lanka Joint Center for Education and Research by Chinese Academy of Sciences, China
- Chinese Academy of Sciences-The World Academy of Sciences (CAS-TWAS) President's Fellowship Program for International Ph.D. students
It has recently been proposed that recalcitrant dissolved organic carbon (DOC) in groundwater plays a potent etiological role in the peculiar distribution of chronic kidney disease of unknown etiology (CKDu). This study aims to elucidate the interactions of Ca2+ and SO42- with a model organic fraction of humic acid (SHA) to determine the possible relationship of CKDu incidence with the DOC in drinking water. XPS and FT-IR methods respectively determined the surface functional groups and chemical composition of protonated dissolved organic carbon (HDOC) in a CKDu high-risk zone (HR) of Sri Lanka and in SHA. Higher surface C composition (87.9%) and lower O (11.4%) were observed for HDOC from the HR region than for SHA (C: 73.8%, O: 24.7%). Aromatic C with less O-containing functional groups was observed in HDOC. The IR band at 1170 cm(-1) confirms the formation of organic sulfonate (C-SO3-) on SHA. A band at 1213 cm(-1) due to organic sulfonate in HDOC from the CKDu HR region was also identified. The IR band at 866 cm(-1) evidenced the formation of CaCO3 on SHA above pH 7.4. XPS data confirmed the presence of sulfur oxidation states corresponding to SO32- and SO42- at 168.9 eV and 170.1 eV binding energies, respectively. The binding energies at 347 eV and 351 eV for Ca 2p(3/2) and Ca 2p(1/2) eV, respectively, confirmed the bidentate complexation of Ca2+ with COO- and sulfonate groups on SHA. The organic sulfonate formed is postulated as a uremic toxicant. (C) 2019 The Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences. Published by Elsevier B.V.
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