Characterization of bioavailable Sr isotopic composition of Jeju Island, Korea
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Geosciences Journal
GJ
Characterization of bioavailable Sr isotopic composition of Jeju Island, Korea Min-Ji Jung1,2, Sung-Gyun Yim1,2, Youn-Joong Jeong2, Gi Young Jeong3, Jong-Sik Ryu4, and Albert Chang-sik Cheong1,2* 1
Graduate School of Analytical Science and Technology, Chungnam National University, Daejeon 34134, Republic of Korea Ochang Center, Korea Basic Science Institute, Cheongju 28119, Republic of Korea 3 Department of Earth and Environmental Sciences, Andong National University, Andong 36729, Republic of Korea 4 Department of Earth and Environmental Sciences, Pukyong National University, Busan 48513, Republic of Korea 2
ABSTRACT: Stable isotope signatures of geologic, atmospheric, and hydrologic sources are transferred to the ecosystem through the food chain. The present study used Sr isotope data of soil and plant samples collected from Jeju Island to explore the roles of these sources in the local bioavailable Sr pool. X-ray diffraction and Sr isotope data revealed that the soil materials came from diverse sources such as weathered volcanic bedrock, marine carbonate sediments, and allochthonous aeolian dust. Dilute (1 M) ammonium nitrateand acetic acid-leachates of the soil samples yielded 87Sr/86Sr ratios between 0.7047 and 0.7092, which were slightly but discernably higher than ratios for Jeju volcanic rocks reported in the literature (0.7045 ± 0.0004). This indicates that relatively more radiogenic Sr, probably in carbonate and aeolian dust, was preferentially released to the leachates. Geopedological control over the bioavailable Sr pool was demonstrated by the positive 87Sr/86Sr correlation between leachable soil fractions and the corresponding plant samples. The enhanced 87Sr/86Sr ratios of plants (0.7062–0.7092, average = 0.7077 ± 0.0012) reflect the influence of seawater. These Sr isotope data provide a scientific basis for addressing archaeological and historical questions related to Jeju Island. Key words: Jeju Island, bioavailable element, Sr isotope Manuscript received July 22, 2020; Manuscript accepted September 12, 2020
1. INTRODUCTION The Rb-Sr isotope system has long been used for radiometric dating and petrogenetic investigation. Rubidium, an alkali metal belonging to group IA, consists of two naturally occurring isotopes (87Rb and 85Rb). 87Rb, which presently makes up 27.83% of Rb, decays to stable 87Sr through β− particle emission with a decay constant of 1.42 × 10−11 year−1 (Steiger and Jäger, 1977); this corresponds to a half-life of 48.8 × 109 years. Strontium, a member of the alkaline earth elements of group IIA, consists of radiogenic 87Sr and three *Corresponding author: Chang-sik Cheong Korea Basic Science Institute, Ochang Center, 162 Yeongudanji-ro, Cheongwon-gu, Cheongju 28119, Republic of Korea Tel: +82-43-240-5170, Fax: +82-43-240-5319, E-mail: [email protected] Electronic supplementary material The online version of this article (https://doi.org/10.1007/s12303-0200035-6) contains supplementary material, which is available to authorized users.
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