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Radiogenic 32P as a new dating tool to determine groundwater ages of 50–1000 years

Year: 2024
Type: article
Abstract: Groundwater age has significant hydrogeological implication for groundwater renewal and solute transport. The period between 50 to 1000 years, marked by increased human activity, which is also a gap of groundwater dating. Cosmogenic 32 Si with a half-life of 144±11 a, is the only viable dating tool for this range but is seldom used due to complex pretreatment and time-consuming and expensive detection. Radiogenic 32 P, as a daughter isotope of 32 Si, decays by emitting high-energy β - particles and is easily detected. 32 Si and 32 P reaches radioactive equilibrium within 3 months, meaning they maintain consistent activity levels in groundwater aged between 50 and 1000 years. Therefore, 32 P can be used to date groundwater in the range of 50–1000 a. 32 P is enriched and extracted using Mg(OH) 2 co-precipitation method. The 32 P solution is then mixed with a solvent mixture containing Triton X-100 and Permafluor and detected using an ultra-low background liquid scintillation spectrometer. The counting time ranges from 2500 to 3000 min with an efficiency of 65 %, and the 32 P count peak surface is observed between channels 600 and 900. Comparing the 32 P ages with the 14 C and 32 Si ages of groundwater samples from the Jianghan Plain, Central China, reveals that 32 P ages and 14 C ages exhibit similar trends, and the 32 P ages and 32 Si ages are approximately consistent in the range of 50–1000 a. Therefore, radiogenic 32 P dating groundwater in the range of 50–1000 a is feasible, convenient and reliable.
DOI: 10.1016/j.jhydrol.2024.132120
Language: English
Open Access status: hybrid
Estimated APC paid: $3,790
OpenAlex ID: W4402913049
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Cites: 31
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Related to: 10