DOI: 10.1007/s10533-013-9899-0
Scopus记录号: 2-s2.0-84897470241
论文题名: Dissolved oxygen and dissolved inorganic carbon stable isotope composition and concentration fluxes across several shallow floodplain aquifers and in a diffusion experiment
作者: Parker S.R. ; Darvis M.N. ; Poulson S.R. ; Gammons C.H. ; Stanford J.A.
刊名: Biogeochemistry
ISSN: 0168-2563
EISSN: 1573-515X
出版年: 2014
卷: 117, 期: 2018-02-03 起始页码: 539
结束页码: 552
语种: 英语
英文关键词: Dissolved inorganic carbon
; Dissolved oxygen
; Groundwater
; Respiration
; Stable isotopes
Scopus关键词: aquifer
; concentration (composition)
; dating method
; diffusion
; dissolved inorganic carbon
; dissolved oxygen
; experimental study
; floodplain
; gas exchange
; isotopic composition
; isotopic fractionation
; microbial activity
; oxic conditions
; oxygen isotope
; temperature effect
; Flathead River
; Montana
; Silver Bow Creek
; United States
; Kathetostoma giganteum
英文摘要: Recent studies have documented the occurrence of dissolved molecular oxygen (DO) in shallow groundwater that is isotopically lighter than can be explained by atmospheric gas exchange or by biogeochemical reactions that consume 16O16O faster than 16O18O. In the present study, spatial gradients in the isotopic composition of DO (δ18O-DO) and dissolved inorganic carbon (δ13C-DIC) were measured in three shallow floodplain aquifers: (1) the Nyack aquifer, of the Middle Fork of the Flathead River in northwest Montana; (2) the Silver Bow Creek floodplain in southwest Montana; and (3) the Umatilla River floodplain in northeast Oregon. The field data show general trends of increasing DIC concentration, decreasing δ13C-DIC, and decreasing DO concentration with increase in groundwater path length. These trends are consistent with consumption of DO and production of DIC by microbial respiration. Although the expected trend of an increase in δ18O-DO with increase in path length was found at an area adjacent to hyporheic recharge at the Nyack floodplain, the majority of groundwater samples collected at Nyack and from the other sites distal to recharge zones had anomalously low δ18O-DO values well below 24.2 ‰, the value corresponding to atmospheric isotopic equilibrium. At the Nyack site, 3H-3He dates were used to estimate groundwater travel time: all groundwater samples with apparent age >1 year had δ18O-DO<24.2 ‰. Previously it has been suggested that diffusion of O2 could be a viable mechanism to explain the existence of isotopically light DO in shallow groundwater. To test this hypothesis, laboratory experiments were conducted to measure the isotopic fractionation of O2 as it diffuses from air across a simulated capillary fringe (made from a floating layer of foam beads) into a stirred, initially anoxic, water column. As expected, 16O16O diffused faster than 16O18O, and the magnitude of isotope fractionation associated with diffusion increased with a decrease in temperature. Fractionation factors (α) calculated from these diffusion experiments were 1.0030 at 15-19 °C and 1.0048 at 8 °C. The combined field and laboratory data suggest that diffusion is an important mechanism to maintain aerobic conditions in shallow groundwater systems, allowing microbial respiration to continue at long distances (km scale) from the source of groundwater recharge. © 2013 Springer Science+Business Media Dordrecht. Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/83657
Appears in Collections: 气候减缓与适应 气候变化事实与影响
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作者单位: Department of Chemistry and Geochemistry, Montana Tech of The University of Montana, 1300 W. Park Street, Butte, MT, 59701, United States; Department of Geological Sciences and Engineering, University of Nevada-Reno, 1664 N. Virginia Street, Reno, NV, 89557-0138, United States; Department of Geological Engineering, Montana Tech of The University of Montana, 1300 W. Park Street, Butte, MT, 59701, United States; Flathead Lake Biological Station, Department of Biological Sciences, The University of Montana, Missoula, MT, 59812, United States
Recommended Citation:
Parker S.R.,Darvis M.N.,Poulson S.R.,et al. Dissolved oxygen and dissolved inorganic carbon stable isotope composition and concentration fluxes across several shallow floodplain aquifers and in a diffusion experiment[J]. Biogeochemistry,2014-01-01,117(2018-02-03)