Spatial Distribution and Sources of Dissolved Organic Matter in High-Antimony Shallow Groundwater in the Xikuangshan Mine, Hunan, China

The origin and composition of dissolved organic matter (DOM) is crucial for fate of antimony (Sb) in aquatic systems. However, there are in which DOM compositional properties, that may better explain the biogeochemical process of Sb, have been absent. This study aimed to understand the fraction, spatial distribution, and spectral characteristics of DOM in high-Sb groundwater (commonly: >0.005 mg/L) from the Xikuangshan Mine in Lengshuijiang, Hunan, China, and explore the characteristics of DOM associated with the formation process of high-Sb groundwater. Inductively coupled mass spectrometry and excitation/emission matrix-parallel factor analysis were used to determine the Sb content, DOM composition, and fluorescence characteristics of 25 shallow groundwater samples collected in May 2021. The dissolved organic carbon (DOC) values in the shallow groundwater varied from 0.38 +/- 1.89 to 9.90 +/- 1.89 mg/L, with a mean of 2.49 mg/ L. The DOM consisted of the following four components: C1, terrestrial humus; C2, microbial humus; C3, fulvic acid; and C4, tryptophan. DOM in high-Sb groundwater usually has a high humification index, low biological index, and low fluorescence intensity values. This result will help to understand the effect of DOM on the accumulation and migration of antimony in groundwater during biogeochemical cycling.