TY - JOUR
T1 - Mechanistic insights into iodine enrichment in groundwater during the transformation of iron minerals in aquifer sediments
AU - Li, Junxia
AU - Wang, Yuting
AU - Xue, Xiaobin
AU - Xie, Xianjun
AU - Siebecker, Matthew G.
AU - Sparks, Donald L.
AU - Wang, Yanxin
N1 - Funding Information:
The research work was financially supported by National Natural Science Foundation of China (Nos. 41521001 and 41502230 ), the Ministry of Education of China (111 project), the Fundamental Research Funds for the Central Universities , China University of Geosciences, Wuhan (No. CUGGC07 ) and National Science Foundation Experimental Program to Stimulate Competitive Research (No. EPS-0814251 ). We thank Hongchen Jiang and Liuqin Huang, China University of Geosciences, Wuhan, for their generous supply on Fe reducing bacterial MR-1. This research used resources of the Advanced Photon Source, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357. We thank beamline scientists Tianpin Wu and Lu Ma at beamline 9-BM-B, C at APS, for their assistance on data acquisition.
Publisher Copyright:
© 2020 Elsevier B.V.
PY - 2020/11/25
Y1 - 2020/11/25
N2 - Long-term intake of groundwater with elevated iodine concentration can cause thyroid dysfunction in humans; however, little is known on the mechanisms controlling the fate of iodine in groundwater systems. In this study, the groundwater and aquifer sediment samples from the Datong basin, a geologic iodine-affected area, were collected to perform the batch incubation experiments to understand the release and enrichment of iodine in groundwater systems. The results showed that the groundwater from the deep confined aquifer had a total iodine concentration of 473 μg/L, higher than that of shallow groundwater, and iodide is the dominant species of iodine. The deep confined aquifer was characterized by the reducing conditions. Meanwhile, a higher ratio of Fe(II) to total Fe was observed in bulk deep aquifer sediments (59%) in comparison with that of shallow sediments (33%). The results of batch incubation experiments showed that during the reductive transformation of Fe minerals in shallow aquifer sediments, iodide concentration in solution was gradually increasing from 24.7 to 101.5 μg/L after 10 days. It suggests that the transformation of Fe minerals in aquifer sediments acts as a diver causing the release of iodine from sediment into groundwater, which was further supported by the features Fe K-edge EXAFS before and after the batch experiments. Moreover, the changes in iodine species from iodate or organic iodine into iodide during the release further promotes the release of sediment iodine, which was supported by the developed geochemical models. The prevalence of reducing condition in deep aquifer favors the enrichment of released iodide. This study provides new insights into the mechanisms of iodide enrichment observed in deep confined aquifer.
AB - Long-term intake of groundwater with elevated iodine concentration can cause thyroid dysfunction in humans; however, little is known on the mechanisms controlling the fate of iodine in groundwater systems. In this study, the groundwater and aquifer sediment samples from the Datong basin, a geologic iodine-affected area, were collected to perform the batch incubation experiments to understand the release and enrichment of iodine in groundwater systems. The results showed that the groundwater from the deep confined aquifer had a total iodine concentration of 473 μg/L, higher than that of shallow groundwater, and iodide is the dominant species of iodine. The deep confined aquifer was characterized by the reducing conditions. Meanwhile, a higher ratio of Fe(II) to total Fe was observed in bulk deep aquifer sediments (59%) in comparison with that of shallow sediments (33%). The results of batch incubation experiments showed that during the reductive transformation of Fe minerals in shallow aquifer sediments, iodide concentration in solution was gradually increasing from 24.7 to 101.5 μg/L after 10 days. It suggests that the transformation of Fe minerals in aquifer sediments acts as a diver causing the release of iodine from sediment into groundwater, which was further supported by the features Fe K-edge EXAFS before and after the batch experiments. Moreover, the changes in iodine species from iodate or organic iodine into iodide during the release further promotes the release of sediment iodine, which was supported by the developed geochemical models. The prevalence of reducing condition in deep aquifer favors the enrichment of released iodide. This study provides new insights into the mechanisms of iodide enrichment observed in deep confined aquifer.
KW - Datong basin
KW - Groundwater
KW - Iodine enrichment
KW - Iodine species
KW - Iron minerals
UR - http://www.scopus.com/inward/record.url?scp=85088501649&partnerID=8YFLogxK
U2 - 10.1016/j.scitotenv.2020.140922
DO - 10.1016/j.scitotenv.2020.140922
M3 - Article
C2 - 32736101
AN - SCOPUS:85088501649
VL - 745
JO - Science of the Total Environment
JF - Science of the Total Environment
SN - 0048-9697
M1 - 140922
ER -