利用多元地球化学示踪剂解析东海外陆架水团结构及营养盐来源

Trace elements play significant roles in marine biogeochemical cycles, and this has been a growing impetus for a comprehensive understanding of their distributions and internal cycling in the ocean. "An International Study of the Marine Biogeochemical Cycles of Trace Elements and their Isotopes (GEOTRACES)" has been established recently. Rare Earth Elements (REEs) are an extremely coherent elemental group in terms of chemical behavior with understood similarities and systematic changes across the group, and are well suited for "tracing" complicated oceanographic phenomenon and geochemical processes. The variation of fluxes and mixing fractions of different water masses in the East China Sea outer shelf is the primary factor to determining the nutrient transport and primary production. It is an urgent issue to clarify the status of the marine ecosystem of the East China Sea outer shelf by appropriately studying the water mass structure and nutrient sources. In this study, the high resolution water mass structure will be characterized by using multi-geochemical tracers (e.g. salinity, temperature, dissolved oxygen, pH, ?18O isotope and REEs). Understanding the sources and contributions of different water masses through the internal consistency of the systematic variation of REEs can provide the scientific basis for the assessment of primary productivity and improve marine ecological environment.

东海外陆架的水团来源不同，其流量及比例的变化是决定东海营养盐供给状况的主要因素，因此阐明海水水团结构，掌握营养盐起源、不同水团的传送混合比及其时空变化，是正确评估人类活动和气候变化对东海陆架区域生态环境影响的重要依据。过去的研究已经利用箱式模型估算了东海陆架海域营养盐的来源，但是因为方法的制约，目前还缺乏海洋观察和实测证据。稀土元素（REEs）的化学性质相近却略有不同，利用REEs可以解决由单一元素的性质和分布不能解释的海洋化学现象和地球化学过程的问题。本项目采用多元地球化学示踪法（盐度、温度、溶解氧、pH等常规分析法以及氧同位素和REEs示踪法）来构建高分辨率水团结构，利用相邻稀土元素的化学相似性和有规律的变化性，了解东海营养盐起源、传送混合比及其时空变化，为正确评估初级生产力和改善海洋生态环境提供科学依据。本研究也可以推动新的国际科学计划GEOTRACES在中国的发展。