镉同位素体系及其在地球科学和环境科学中的应用

镉是典型的亲硫元素,常赋存于各种硫化物矿床中.在环境体系中,镉是微生物所需的营养物质,其元素的循环受生物活动的影响.已有研究表明蒸发/冷凝过程、生物及无机过程都会导致镉同位素发生分馏,因此镉同位素研究在地球科学、环境科学具有独特的应用前景.与此同时,多接收器电感耦合等离子体质谱(MC-ICP-MS)技术的应用成功地实现了地质样品中镉同位素组成的高精度测量,使得镉同位素地球化学研究获得了蓬勃发展.本文基于当前最新研究成果,对镉同位素体系进行了详细综述,重点探讨镉的地球化学行为及同位素分馏机制,镉同位素在各物质储库中的分布特征及其在地球科学、环境科学中的应用,镉同位素测试技术.镉同位素地球化学的研究尚处于起步阶段,深入开展镉同位素分馏机理、完善镉同位素在各物质储库中的分布、建立统一的同位素标准体系的研究,将推动镉同位素在地球科学和环境科学领域的广泛应用.

A Review of the Isotope System of Cadmium and Its Applications in Geosciences and Environmental Sciences

Cadmium is a typical chalcophile element which occurs in various sulfide deposits. In the environmental system, cadmium as the nutritional requirement is utilized for the growth of microorganisms, and its cycle is greatly affected by the biological process. Several recent publications have shown that mass differences between Cd isotopes result in isotopic fractionation during the evaporation/condensation processes, biological and inorganic processes. These results demonstrate that Cd isotopes can be used as a tracer in geosciences and environmental sciences. The Multiple Collector-Inductively Coupled Plasma-Mass Spectrometry (MC-ICP-MS) has successfully been used for high-precision measurements of cadmium isotopic compositions in the geological samples, which makes a rapid advance in the geochemical research of the cadmium isotope. In this paper, based on current publications, a review of the cadmium isotopic system is provided in detail, with emphasis on the geochemical behaviour of cadmium and its isotope fractionation mechanism, the distribution characteristics in the natural reservoirs, analytical technique and the applications in the geosciences and environmental sciences. The geochemical research of the cadmium isotope is just in its infancy; conducting an investigation into the cadmium isotope fractionation mechanism, the distribution characteristics in natural reservoirs and a unified cadmium isotope standard calibration system could promote the application of the cadmium isotope in geosciences and environmental sciences.