DOI: 10.1016/j.earscirev.2019.01.016
论文题名: Source and evolution of dissolved boron in rivers: Insights from boron isotope signatures of end-members and model of boron isotopes during weathering processes
作者: Mao H.-R. ; Liu C.-Q. ; Zhao Z.-Q.
刊名: Earth Science Reviews
ISSN: 00128252
出版年: 2019
卷: 190 起始页码: 439
结束页码: 459
语种: 英语
中文关键词: Biological cycling
; Boron isotopes
; Continental weathering
; Mass balance model
; Reservoirs
; River
英文关键词: biogeochemical cycle
; boron isotope
; chemical weathering
; dissolution
; isotopic composition
; isotopic fractionation
; mass balance
; precipitation (chemistry)
; river water
; steady-state equilibrium
; water chemistry
英文摘要: The evolution of atmospheric CO 2 and the pH of the ocean can be reconstructed by the boron isotopic composition (δ 11 B) of marine carbonates, which is influenced by the δ 11 B of the seawater. Boron (B) in the ocean is primarily affected by continental weathering through rivers. Thus, it is essential to understand the behavior of B and B isotopes in rivers and the factors affecting riverine B, which require a better understanding of sources and processes of B in river systems. This review evaluates the inventories of B reservoirs contributing to rivers and investigates the processes regulating the B isotope geochemistry of rivers. B is widespread at the Earth's surface and shows a wide range of concentrations between reservoirs. Different reservoirs also exhibit significant variations in B isotopic compositions. Mixing and Rayleigh effects are mainly responsible for the variations in the δ 11 B values of meteoric precipitation, which result in marine (δ 11 B = +37 ± 7‰), anthropogenic (δ 11 B = +9 ± 10‰), and mixing types (δ 11 B = +17 ± 13‰) of meteoric precipitation. The contribution of B to rivers from carbonate dissolution is negligible. Marine and non-marine evaporites have distinct δ 11 B values (marine δ 11 B: + 27 ± 9.4‰ and non-marine δ 11 B: −2 ± 8.6‰) that primarily reflect their different depositional environments. S-type granites that are tourmaline-free have an estimated δ 11 B value of −14.2 ± 4.9‰ and a Na/B value of 140 ± 34. Non-S-type granites have a δ 11 B value of −8.9 ± 6.7‰ and a Na/B value of 1190 ± 170. Intraplate basalts exhibit a δ 11 B value of −5.2 ± 4.4‰ and a Na/B value of 3300 ± 770. Subduction-related basalts have a δ 11 B value of + 0.3 ± 7.3‰ and a Na/B value of 1060 ± 830. Shale has high B contents of siliciclastic sedimentary rocks (104 ± 92 ppm). The inferred δ 11 B values of marine and continental shales are −8‰ and −16‰, respectively. The effects of metamorphism can vary widely depending on the geologic setting and type of protolith. The δ 11 B values of wastewater are investigated based on their industrial, agricultural, and urban sources. This inventory of B reservoirs can be useful for studies on rivers on a continental scale. In regolith and groundwater, B isotopic fractionation mainly occurs due to water-rock interactions and the biological cycle of B, whereas adsorption on sediments leads to minor B isotopic fractionation in rivers. In groundwater, the reactive transport model reveals that the δ 11 B value of river water is sensitive to hydrological conditions. In regolith, the steady-state mass balance model is used to predict the B isotope behavior of soil solution in different weathering regimes. In the supply-limited regime (where chemical weathering is limited by tectonic forcing), the precipitation of secondary minerals controls the variations in the δ 11 B values of soil solution, leading to an increase in the difference in the δ 11 B values between soil solution and parent rock (δ 11 B diss −δ 11 B rock ) with lower denudation rates, whereas secondary mineral dissolution produces the opposite change in δ 11 B. In the kinetically limited regime (where chemical weathering is limited by climate), the biological cycle controls the variations in the δ 11 B values of soil solution, and the δ 11 B values of soil solution generally become closer to those of parent rock with higher denudation rates. The relationship between the denudation rates and δ 11 B diss −δ 11 B rock is thus not monotonous, indicating that additional constraints are required to distinguish between the two regimes. Understanding of B isotope geochemistry of rivers can be improved by better constraints on B end-member estimates, investigation of the B isotopic fractionation caused by weathering and biological cycling in regolith, and assessment of atmospheric and biological sub-cycle. © 2019 Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/165874
Appears in Collections: 气候变化与战略
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作者单位: State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, 550081, China; University of Chinese Academy of Sciences, Beijing, 100049, China
Recommended Citation:
Mao H.-R.,Liu C.-Q.,Zhao Z.-Q.. Source and evolution of dissolved boron in rivers: Insights from boron isotope signatures of end-members and model of boron isotopes during weathering processes[J]. Earth Science Reviews,2019-01-01,190