Geochemical and isotopic (U, Th) variations in lake waters in the Qinghai Lake Basin, Northeast Qinghai-Tibet Plateau, China: origin and paleoenvironmental implications

A uranium (U) geochemical study of lake water samples from Qinghai Lake, Northeast Qinghai-Tibet Plateau, China, was undertaken to assess the primary controls on lake water chemistry. The U-234/U-238 activity ratios of lake water exhibited limited spatial and vertical variations and were relatively...

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Bibliographic Details
Published in:Arabian Journal of Geosciences
Main Authors: Zhang, Pu, Cheng, Hai, Liu, Weiguo, Mo, Lingtong, Li, Xiangzhong, Ning, Youfeng, Ji, Ming, Zong, Baoyun, Zhao, Chen
Format: Report
Language:English
Published: SPRINGER HEIDELBERG 2019
Subjects:
U and Th isotopes
Lake water chemistry
Paleoenvironments
Qinghai Lake Basin
Northeast Qinghai-Tibet Plateau
China
SCAVENGING RATES
ARCTIC-OCEAN
URANIUM
TH-230
THORIUM
DISEQUILIBRIUM
PROFILES
INPUTS
U-234
Geology
Geosciences
Multidisciplinary
Arctic
Arctic Ocean
Online Access:http://ir.ieecas.cn/handle/361006/14363
http://ir.ieecas.cn/handle/361006/14364
https://doi.org/10.1007/s12517-019-4255-x
Description
Summary:A uranium (U) geochemical study of lake water samples from Qinghai Lake, Northeast Qinghai-Tibet Plateau, China, was undertaken to assess the primary controls on lake water chemistry. The U-234/U-238 activity ratios of lake water exhibited limited spatial and vertical variations and were relatively high compared to the values measured in rivers worldwide ((U-234/U-238)=1.171), lower than in the four river discharge inside the Lake Qinghai catchment. The U concentrations also varied minimally within three vertical sampling profiles and exhibited spatial patterns in surface waters that correlated with the distribution of total dissolved solid (TDS) values and salinity concentrations. These data suggest that the variability in U, TDS, and salinity are partially controlled by evaporation or a different secondary concentration pathway. Moreover, the U concentration and U-234/U-238 activity ratio indicates that the length of this procedure, which is controlled by the duration of water-rock interaction, is probably an important factor to consider when accounting for the variable salinities of lakes located in similar geographical areas. The Th-230(XS) content is primarily derived from the decay of dissolved U-234. The various (230)Thxs concentrations observed in the water column are interpreted to reflect various scavenging residence times in Qinghai Lake, ranging from 0.7 to 4years. The lower water mass age, such as at site 123, suggests a more rapid scavenging rate. Dissolved Th-232 is placed into the lake via the incomplete dissolution of lithogenic substances, such as dust aerosol, or other lithogenic sources (e.g., lake bed sediment or suspended riverine sediment). Water column Th-232 concentration data suggest that the Th concentrations of the lake water are controlled by three processes: (1) the dissolution of aerosol dust, (2) the dissolution of riverine and lake bed sediment, and (3) the scavenging of Th from the water.

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