铊同位素及环境示踪研究进展

Thallium Isotopes and Environmental Tracing

近年来随着多道接收电感耦合等离子体质谱仪(MC-ICPMS)的广泛应用,铊(Tl)同位素成为当前非传统同位素地球化学研究热点之一。本文综述了Tl同位素的最新研究进展。Tl是自然界迄今为止发现的具有同位素自然分馏效应的最重的元素之一。自然界中Tl同位素分馏值ε205Tl(ε205Tl指样品与标准物质NIST SRM 997 Tl的205Tl/203Tl值的万分偏差)的变化为-6.8^+4.8,陨石中ε205Tl值为-18.8^+29.7。Tl同位素可用于示踪低温过程中的物质迁移、海洋沉积物沉积过程等,也可用于指示古气候的变化,以及佐证特定时期有机碳输出量。因此,Tl同位素可为深入了解局域海洋沉积环境的氧化还原条件、碳循环和海洋化学演化等提供新信息,将在地学与环境科学研究中得到广泛应用。

With the advent of multiple-collector inductively coupled plasma mass spectrometry（MC-ICPMS） in recent years,the new unconventional Tl stable isotope geochemistry has been developed,and Tl isotope has become a new isotopic tracer in earth science.This paper reviews the recent progress of Tl stable isotope studies.Thallium is identified to be the heaviest element with natural isotope fractionation.The natural range of ε205Tl（ε205Tl represents the deviation of the 205Tl/203Tl ratio of a sample from the NIST SRM 997 Tl isotope standard in parts per 104） varies from-6.8 to ＋14.8 in earth materials,and from-18.8 to ＋29.7 in meteorites.Tl isotope can be used as a tracer to reveal material transport in low temperature process,depositional processes of marine materials,palaeoclimate changes,and changes of organic carbon output.Therefore,Tl isotope can be used as a powerful tool in understanding redox conditions of local depositional environment,biogeochemical cycling of carbon,and geochemical evolution of oceans.It is believed that,with further studies of the thallium isotope fractionation mechanism,thallium isotopes will be applied widely in earth and environmental sciences.