NDLI: Application of diffusive gel-type probes for assessing redox zonation and mercury methylation in the Mekong Delta sediment

Content Provider	World Health Organization (WHO)-Global Index Medicus
Author	Hong, Yongseok Dan, Nguyen Phuoc Kim, Eunhee Choi, Hyo-Jung Han, Seunghee
Spatial Coverage	Vietnam
Description	Author Affiliation: Hong Y ( Department of Environmental Engineering, Daegu University, Daegu, Republic of Korea.)
Abstract	The vertical profiles of $PO_{4}^{3−},$ Mn, Fe, $S^{2−},$ Hg, and $CH_{3}Hg^{+}$ in sediment pore water were investigated using DGT and DET probes in the Tien River, the northern branch of Vietnam's Mekong Delta. Although some of the DGT measurements could be lower than the actual pore water concentrations due to the depletion of the species, the measurements provided information for understanding redox zonation and Hg methylation. The gradual increases in the measured species concentrations with the sediment depth were observed and the diffusive fluxes of the species to overlying water were expected. The vertical profiles suggested that (1) $SO_{4}^{2−}$ seemed to be reduced before $Fe^{3+},$ or the two electron acceptors were reduced simultaneously; (2) the release of $PO_{4}^{3−}$ was more closely related to $S^{2−}$ than Fe release; and (3) Hg methylation was active in the micro-niche between the aerobic and anaerobic transition zones. The maximum pore water $CH_{3}Hg^{+}$ concentrations were observed at depths just above where the maximum $S^{2−}$ concentrations were detected. Hence, the maximum $CH_{3}Hg^{+}$ concentration was observed near surficial sediments (less than 1 cm from the surface) in brackish water, and at a depth of 3 cm in fresh water. The different vertical profiles led to a $CH_{3}Hg^{+}$ diffusive flux eight-times greater in brackish than in fresh water. The present study showed that the in situ application of DGT and DET probes was helpful to understand coupled biogeochemical reactions and mercury methylation by measuring pore water redox species.
File Format	HTM / HTML
ISSN	20507887
Issue Number	7
Volume Number	16
e-ISSN	20507895
Journal	Environmental Science: Processes & Impacts
Language	English
Publisher	Royal Society of Chemistry
Publisher Date	2014-07-01
Publisher Place	Great Britain (UK)
Access Restriction	Subscribed
Subject Keyword	Discipline Environmental Health Geologic Sediments Chemistry Mercury Water Pollutants, Chemical Environmental Monitoring Analysis Methylation Oxidation-reduction Rivers Vietnam Journal Article Research Support, Non-u.s. Gov't
Content Type	Text
Resource Type	Article
Subject	Environmental Chemistry Public Health, Environmental and Occupational Health Management, Monitoring, Policy and Law

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