钾同位素示踪地表过程:进展与挑战

Potassium isotopes trace Earth's surface processes:Progress and challenges

地表化学风化过程影响着不同时间尺度大气CO_(2)浓度和全球气候变化,因此有效示踪地表风化是表生过程研究的重要科学问题之一。钾(K)元素无化合价变化,主要赋存于硅酸盐岩中,在表生地质过程中其同位素通常会发生显著分馏,因此K同位素体系具有示踪地表过程的巨大潜力。然而,K同位素研究尚在起步阶段,其分馏机制及其控制因素等尚不清楚。本文从K的分布、主要储库的K同位素组成,以及K同位素在风化过程中的分馏行为等方面,系统总结了K同位素示踪地表过程的主要研究进展,提出了大小流域相结合、多同位素体系联用,并量化人类活动对K同位素分馏产生的影响,以此来减少K同位素示踪地表过程的不确定性的建议。

Chemical weathering processes at the Earth’s surface influence atmospheric CO_(2)and thus affect global climate change on different time scales.Therefore,how to effectively trace weathering processes is one of the important scientific issues in the field of supergene geochemistry.Potassium(K)has one valence state,is mainly hosted in silicate rocks and experiences distinct isotopic fractionation during supergene geochemical processes.These advantages allow K isotope systems to be a potential tracer for Earth's surface processes.However,the study of K isotopes is still in its early stage,so that there is no consensus on its fractionation mechanism and controlling factors.In this paper,the progress of K isotopes tracing Earth's surface processes is systematically reviewed from the aspects of K distribution,K isotopic compositions in major reservoirs,and fractionation behaviors of K isotopes during chemical weathering.Finally,in order to better understand the tracing of the Earth's surface processes using K isotopes,this study suggests combining large and small catchments,using multi-isotope systems,and quantifying the effects of human activities on K isotopic fractionation.