China 
Africa 
Explore chapters and articles related to this topic
Isotope Techniques in Flood Analysis
Published in Saeid Eslamian, Faezeh Eslamian, Flood Handbook, 2022
Samir Al-Gamal, Saeid Eslamian
In a strict sense, the term “Rayleigh fractionation” should only be used for chemically open systems where the isotopic species removed at every instant were in thermodynamic and isotopic equilibrium with those remaining in the system now of removal. Furthermore, such an “ideal” Rayleigh distillation is one where the reactant reservoir is finite and well mixed and does not re-react with the product (Clark and Fritz, 1997). However, the term “Rayleigh fractionation” is commonly applied to equilibrium closed systems and kinetic fractionations as well (as described below) because the situations may be computationally identical.
Sulfur isotopic characteristics of the Zhaxikang Sb–Pb–Zn–Ag deposit in southern Tibet
Published in Australian Journal of Earth Sciences, 2021
D. Wang, Y. Zheng, R. Mathur, H. Ren
Combined with geology, mineralogy, Fe–Zn–Cd isotope and geochronology evidence, the S isotope values show the evolution of the Zhaxikang deposit:The sulfur isotope fractionation between stage 2 sulfides and the first pulse of ore-forming fluid has achieved equilibrium during precipitation; and the kinetic Rayleigh fractionation related to vapour–liquid partitioning is the main cause for sulfur isotope variations for the second pulse of mineralisation.The sulfur source for the first pulse of mineralisation is mainly seawater sulfur mixed with some mantle-derived sulfur, and the sulfur for the second episode of mineralisation originated from mantle-derived sulfur overprinting sulfur in earlier formed sulfides and wall rocks.The first pulse of mineralisation is related to multiple seafloor volcanic events during the synsedimentary period (220–130 Ma) with submarine hydrothermal sedimentation (metasomatism) genesis, and the second pulse of mineralisation is associated with magmatic-hydrothermal activity during the post-collision period (25 Ma to now) that overprinted and transformed the first pulse of mineralisation.
Decoding the marine biogeochemical cycling of mercury by stable mercury isotopes
Published in Critical Reviews in Environmental Science and Technology, 2023
Lin Yang, Ben Yu, Deming Han, Kun Zhang, Hongwei Liu, Cailing Xiao, Ligang Hu, Yongguang Yin, Jianbo Shi, Guibin Jiang
The reduction of Hg2+ is a critical part of the cycling of marine mercury. This results in the evasion of Hg0 to the atmosphere and simultaneously competes for the substrate in methylation. The reduction can be mediated by both the biological and abiotic pathways in aquatic environments. By a series of Hg2+-resistant (mer-mediated pathway) bacterial strains and a Hg-sensitive metal-reducing anaerobe, biological reduction produced a negative MDF (for δ202Hg up to 2‰) in the product following Rayleigh fractionation (Kritee et al., 2007, 2008). More attention was focused on the light participating abiotic reduction (Bergquist & Blum, 2007; Chandan et al., 2015; Kritee et al., 2009, 2018; Rose et al., 2015; Yang & Sturgeon, 2009; Zheng & Hintelmann, 2009, 2010). The euphotic zone, where there appeared to be a great degree of photoreduction, generally received more sunlight exposure. Higher δ202Hg signatures of surface seawater than deeper layers were observed in Arctic coastal waters (Strok et al., 2015). The reduction of Hg2+ led to the preferential depletion of lighter isotopes, leaving residuals with positive δ202Hg signatures (Bergquist & Blum, 2007; Zheng & Hintelmann, 2010). This process has drawn broad attention, and a series of studies have explored isotope fractionation in the aqueous-phase reduction of Hg2+ initiated by dissolved organic matter (DOM) (Bergquist & Blum, 2007; Zheng & Hintelmann, 2009, 2010). The experimental findings in terms of MDF were consistent with the observation in natural water samples (positive MDF in the residue Hg2+).
Major ion hydrogeochemistry and health risk of groundwater nitrate in selected rural areas of the Guanzhong Basin, China
Published in Human and Ecological Risk Assessment: An International Journal, 2023
Duoxun Xu, Peiyue Li, Xin Chen, Shengfei Yang, Pei Zhang, Fa Guo
The evaporation fraction can be determined using the stable hydrogen and oxygen isotope data based on the Rayleigh fractionation principle (Qian et al. 2012, Qian et al. 2014). The calculation in this study assumes that rainwater is the origin of groundwater, as rainfall is an important recharge source of groundwater. Following the infiltration of rainwater from the unsaturated to saturated zone, the water flows through the aquifer media and experience evaporation during the flow process. The calculation results showed the evaporation fraction of groundwater in the study area ranged from 4 to 13% and 4 to 11% according to the hydrogen and oxygen isotopes, respectively.