Dissolved Organic Matter Sources in High Arsenic Groundwater From a Sand‐Gravel Confined Aquifer

Abstract

High arsenic (As) groundwater (>10 μg/L) has been recognized as a global environmental issue threatening up to 220 million people throughout the world (Podgorski & Berg, 2020). Chronic intake of high-As groundwater may cause severe arsenicosis, such as skin lesions and cancers (Hug et al., 2020). Many works in the literature have revealed that high-As groundwater mainly occurs in Late Pleistocene-Holocene anoxic aquifers with

Characteristics of Dissolved Organic Matter in Uranium Hosting Aquifers and Potential Molecular Transformation During Neutral In Situ Leaching

“…Microorganism and DOM play important roles in adsorption, complexation, and reduction of U in the mineralization (Bone et al., 2017; Zhang et al., 2021c; Zhang et al., 2021d). BIX values were all greater than 1.0 (average 1.12; SD 0.15) in BM groundwater, indicating a biological origin of DOM and a strong biological activity (Gao et al., 2023). C3 was the main component of DOM in BM, accounting for approximately 47.96%, which was labile tyrosine‐like components with microbial origin (Zeng et al., 2023).…”

“…During mining, DOM increased its saturated degree and oxidation state. The gradual decrease in (DBE−O)/C wa from 0.05 to −0.02 and the increase in NOSC wa from −0.67 to −0.36 (Tables S2‐S3 in Supporting Information ) from BMRock to production wells were observed (DBE−O)/C and NOSC were used to reflect the degree of unsaturation (Phungsai et al., 2018; Zhang et al., 2021d) and redox state (Gao et al., 2023) of DOM, respectively. For a given compound, the higher positive value of (DBE−O)/C implies the higher degree of unsaturation, while the higher positive value of NOSC represents the higher oxidized state (Zhang, et al., 2021d).…”

“…Excitation wavelengths were set between 250 and 400 nm, and emission wavelengths were set between 300 and 550 nm. Biological index (BIX), fluorescence index (FI), humification index (HIX), and SUVA 254 were calculated, which can reflect the source of DOM, native microbial activities, degree of humification, and aromaticity of OM, respectively (Gao et al., 2023; Guo et al., 2019).…”

Natural Attenuation of Groundwater Uranium in Post-Neutral-Mining Sites Evidenced from Multiple Isotopes and Dissolved Organic Matter

“…Dissolved Fe(II), S(−II), NH 4 + , and NO 2 − concentrations were determined in situ using a portable spectrophotometer (DR1900 HACH, USA). 21 Concentrations of major cations, anions, and trace elements were determined by ICP-AES (iCAP6300, Thermo, USA), ion chromatography (ICS2000, Dionex, USA), and ICP-MS (7500CE, Agilent, USA), respectively. The δ 34 S and δ 18 O values of SO 4 2− were determined at the Beijing Createch Testing Technology Co., Ltd. with a Finnigan MAT-253 Plus (Thermo, USA) isotope ratio mass spectrometer.…”

“…This was further supported by the decreases in BIX and SUVA 254 from M0 (median 1.31 and 10.6, respectively) to PM (median 1.09 and 4.71, respectively) (Figure S3b) since microbial degradation of DOM decreased DOC concentrations and SUVA 254 values. 21…”