TY - JOUR
T1 - Redox processes and occurrence of arsenic in a volcanic aquifer system of Kumamoto Area, Japan
AU - Hossain, Shahadat
AU - Hosono, Takahiro
AU - Ide, Kiyoshi
AU - Matsunaga, Midori
AU - Shimada, Jun
N1 - Funding Information:
This study was funded under the Core Research for Evolutional Science and Technology project (CREST) by the Japan Science and Technology Agency (JST) with additional from the Grant-in-Aid for young scientists (A) (no. 24681007). The authors wish to thank Dr. Kotaro Nakata of Central Research Institute of Electric Power Industry (CRIEPI) laboratory for rendering help in DOC analyses and Kumamoto city government office for supplying the sediment core samples. Special thanks are extended to Dr. Makoto Kagabu, Kumamoto University for his help in illustrating some maps and figures for this manuscript. We are grateful to Dr. Yang for his cordial help during sample collection. Finally, we are paying sincere thanks to two anonymous reviewers for their constructive and useful review comments to improve this manuscript.
Publisher Copyright:
© 2016, Springer-Verlag Berlin Heidelberg.
PY - 2016/5/1
Y1 - 2016/5/1
N2 - Sources, distributions, and controlling factors for mobilization of arsenic (As) in Kumamoto basin were investigated relating to the determination of redox processes of the study area. Groundwater and sediment core samples were analyzed. Nitric acid digestion and sequential leaching experiment of sediment core samples revealed that the source of As in the groundwater is geogenic and leached primarily due to the sediment–water interactions. Unlikely, similar relations of total As with total Fe, Mn, and Al in acid extracts, leaching experiments showed a positive relation of Astotal with Fetotal and Altotal indicated that Fe and Al oxides/hydroxides are abundant and may be the major adsorbent of As in low pH condition. Arsenic concentrations in groundwater ranges from 0.1 to 60.6 μg/l. High As concentrations occurred in anaerobic stagnant groundwaters from Kumamoto plain area with high dissolved Fetotal, Mntotal, and Altotal, moderately dissolved HCO3 −, PO4 3−, SO4 2−, and low concentrations of NO3 − and DOC suggesting the reducing condition of subsurface aquifer. There is a range of As(III)/As(T) ratios from mostly arsenate to mostly arsenite. Groundwater pH was relatively high, and high As occurred at higher pH range. It is assumed that desorption of As from metal oxide surfaces was facilitated by the elevated pH, which is considered as an important process for As mobilization. In addition to this, a wide range of δ34SSO4 values (8.3–57.6 ‰) indicates that sulfur is undergoing redox cycling mediated by microbial activities. Following δ34SSO4 results, it is anticipated that dissolved As is coprecipitated as sulfides in the presence of dissolved Fe(II) in some places, though at this moment, there is no direct evidence of coprecipitation or sequester of As with Fe and sulfide ion. Finally, a combination of the following three variables are considered potentially important causes for the high dissolved As concentrations in groundwater of Kumamoto area—(1) high groundwater pH, (2) anoxic redox conditions, and (3) stagnant groundwater in younger age sediments, which have not been well flushed since burial.
AB - Sources, distributions, and controlling factors for mobilization of arsenic (As) in Kumamoto basin were investigated relating to the determination of redox processes of the study area. Groundwater and sediment core samples were analyzed. Nitric acid digestion and sequential leaching experiment of sediment core samples revealed that the source of As in the groundwater is geogenic and leached primarily due to the sediment–water interactions. Unlikely, similar relations of total As with total Fe, Mn, and Al in acid extracts, leaching experiments showed a positive relation of Astotal with Fetotal and Altotal indicated that Fe and Al oxides/hydroxides are abundant and may be the major adsorbent of As in low pH condition. Arsenic concentrations in groundwater ranges from 0.1 to 60.6 μg/l. High As concentrations occurred in anaerobic stagnant groundwaters from Kumamoto plain area with high dissolved Fetotal, Mntotal, and Altotal, moderately dissolved HCO3 −, PO4 3−, SO4 2−, and low concentrations of NO3 − and DOC suggesting the reducing condition of subsurface aquifer. There is a range of As(III)/As(T) ratios from mostly arsenate to mostly arsenite. Groundwater pH was relatively high, and high As occurred at higher pH range. It is assumed that desorption of As from metal oxide surfaces was facilitated by the elevated pH, which is considered as an important process for As mobilization. In addition to this, a wide range of δ34SSO4 values (8.3–57.6 ‰) indicates that sulfur is undergoing redox cycling mediated by microbial activities. Following δ34SSO4 results, it is anticipated that dissolved As is coprecipitated as sulfides in the presence of dissolved Fe(II) in some places, though at this moment, there is no direct evidence of coprecipitation or sequester of As with Fe and sulfide ion. Finally, a combination of the following three variables are considered potentially important causes for the high dissolved As concentrations in groundwater of Kumamoto area—(1) high groundwater pH, (2) anoxic redox conditions, and (3) stagnant groundwater in younger age sediments, which have not been well flushed since burial.
KW - Arsenic mobility
KW - Groundwater
KW - Kumamoto
KW - Metal oxides
KW - Redox processes
KW - Sulfur isotopes
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U2 - 10.1007/s12665-016-5557-x
DO - 10.1007/s12665-016-5557-x
M3 - Article
AN - SCOPUS:84964556595
SN - 1866-6280
VL - 75
JO - Environmental Earth Sciences
JF - Environmental Earth Sciences
IS - 9
M1 - 740
ER -