河蚬及其环境水体87Sr/86Sr对比研究

87Sr/86Sr has been widely used in researches as a biogeochemical tracer in multiple disciplines. The isotopic fractionation in both analytical and natural processes has routinely calibrated by the fractionation of 88Sr/86Sr. This practice, however, was suggested by some recent studies to be inadequate to address the fractionation of 87Sr/86Sr as it has been believed before. This finding casts doubt on the theories and models that were based on the analysis of the Sr isotope composition. To solve this problem, efforts have been made to develop new calibration method. Whatever method the development may lead to, however, it must be subjected to test of the natural processes, or the same problem as in the 88Sr/86Sr calibration would probably be unavoidable. Here we propose to tackle this problem through comparison of the 87Sr/86Sr before and after the fractionation in biogeochemical processes in a variety of environmental background. By comparing 87Sr/86Sr between the Asian Clam, Corbicula fluminea, and the ambient water in the major drainage basins of China, namely the Yellow river, Huai river, Yangtze river and Xijiang river, we aim to examine whether there exist discrepancies between the measured values of 87Sr/86Sr as Sr is passed down from the ambient water to the clam shell through the food chains. The successful implementation of this project will provide answer to the question around the 87Sr/86Sr analysis, but also to the doubt over the relevant theories and models.

87Sr/86Sr作为最常用的示踪手段被广泛应用于众多学科研究中。其在自然过程和仪器分析中的分馏作用长期用88Sr/86Sr校正。但最近发现该方法可能存在较大缺陷，由此而影响到建立在87Sr/86Sr研究基础上众多理论模式的可靠性，更影响到今后87Sr/86Sr示踪方法的应用。为此国际上开始探索新的校正方法。此举虽然必要，但自然过程的检验不可缺少。本项目提出了利用不同环境条件下生物地球化学作用前后87Sr/86Sr的对比进行验证研究的思想，拟通过中国黄河、淮河、长江和西江等江河流域双壳动物河蚬及其环境水体87Sr/86Sr的分析和统计对比，检验水体Sr经食物链进入河蚬壳体后同位素组成观测值是否与水体之间存在差异。项目的成功实施可以对上述质疑给出答案，从而检验传统Sr同位素分析方法对其分馏作用的校正程度，并对建立在87Sr/86Sr研究基础上相关理论体系和模式的可信性做出判断。