DOI: 10.1016/j.epsl.2018.06.039
Scopus记录号: 2-s2.0-85049999477
论文题名: Effect of cadmium sulphide precipitation on the partitioning of Cd isotopes: Implications for the oceanic Cd cycle
作者: Guinoiseau D. ; Galer S.J.G. ; Abouchami W.
刊名: Earth and Planetary Science Letters
ISSN: 0012821X
出版年: 2018
卷: 498 起始页码: 300
结束页码: 308
语种: 英语
英文关键词: cadmium isotopes
; cadmium sulphides
; Geotraces
; Oxygen Deficient Zones
; Rayleigh fractionation
Scopus关键词: Cadmium sulfide
; II-VI semiconductors
; Ionic strength
; Oxygen
; Seawater
; Solutions
; Sulfur compounds
; Ab initio simulations
; Biogeochemical cycling
; Fractionation factors
; Geotraces
; Low oxygen conditions
; Oxygen deficient
; Rayleigh fractionation
; Sulphide precipitation
; Isotopes
; biogeochemical cycle
; cadmium
; isotopic composition
; isotopic fractionation
; isotopic ratio
; oxygen
; partitioning
; precipitation (chemistry)
; sulfide
; water mass
英文摘要: The biogeochemical cycling of cadmium (Cd) and its isotopes in the surface ocean is dominated by biological uptake into phytoplankton, while regeneration of the sinking particulate Cd governs the shapes of Cd profiles in the deeper ocean. Additionally, the water mass circulation plays an important role in the redistribution of Cd and its isotopes. Superimposed on this general cycle, it has recently been argued that cadmium sulphide (CdS) precipitation can occur in oceanic Oxygen Deficient Zones (ODZ). This has been proposed to account for the decrease in Cd/PO4 ratios and the positive Cd isotope excursion in seawater compared to sinking particles. To assess whether CdS precipitation results in a fractionation of Cd isotopes, we performed cadmium–sulphide precipitation experiments under controlled low-oxygen conditions in low (pure water) and high ionic strength (synthetic seawater) water, with variable reaction times and cadmium/sulphide ratios. Enrichment in light Cd isotopes is systematically observed in the precipitated CdS phase, in agreement with recent ab initio simulations of isotope effects associated with Cd speciation in aqueous solution. Our experimental results follow a closed-system Rayleigh fractionation model with the fractionation factor (αCdsol-CdS) for 112Cd/110Cd decreasing with increasing salinity – from 1.00026 for pure water to 1.00014 for a salinity twice that of modern seawater, indicating a salinity control on the magnitude of Cd isotope fractionation. We propose that this fractionation, varying with salinity, is controlled by isotope equilibrium between the various Cd aqueous species present in solution, with preferential involvement of free Cd2+ ion in CdS formation. The magnitude of Cd isotope fractionation in seawater (αCdsol-CdS = 1.00016) determined in our study is in accord with the Cd isotope shift observed in modern oceanic ODZ and attributed to removal by CdS. Our experiments show that CdS precipitation could have significant local impact on the cycling of Cd, and further demonstrates the utility of Cd isotopes as tracers of the sequestration of cadmium into sulphides in restricted euxinic basins, such as the Black Sea. © 2018 Elsevier B.V. Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/109765
Appears in Collections: 影响、适应和脆弱性 气候变化事实与影响
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作者单位: Max Planck Institute for Chemistry, Climate Geochemistry Department, Hahn-Meitner-Weg 1, Mainz, 55128, Germany; Institut de Physique du Globe de Paris, Sorbonne Paris Cité, Université Paris Diderot, CNRS UMR 7154, Paris, France
Recommended Citation:
Guinoiseau D.,Galer S.J.G.,Abouchami W.. Effect of cadmium sulphide precipitation on the partitioning of Cd isotopes: Implications for the oceanic Cd cycle[J]. Earth and Planetary Science Letters,2018-01-01,498