南黄海牡蛎壳元素组成的原位微区分析及环境指示  

In-situ microanalysis of elemental ratios in a single oyster shell from the South Yellow Sea,China and its environmental implications

作　　者：宋佳泽 黄湘通[1] 杨守业[1] 亓利剑[1] SONG Jiaze;HUANG Xiangtong;YANG Shouye;QI Lijian(State Key Laboratory of Marine Geology,School of Ocean and Earth Science,Tongji University,Shanghai 200092)

机构地区：[1]同济大学海洋地质国家重点实验室,上海200092

出　　处：《海洋地质与第四纪地质》2020年第2期70-79,共10页Marine Geology & Quaternary Geology

基　　金：国家自然科学基金项目“东海周边河流沉积物源汇体系的关键过程:沉积地球化学约束”(41730531);上海市自然科学基金“长江-东海源汇体系碎屑锆石U-Pb年代学与重矿物原位地球化学研究”(18ZR1440400)。

摘　　要：碳酸盐生物壳体的周期性生长纹层是记录气候环境变化的天然材料。随着原位微区测试技术的快速发展,高分辨率的同位素和化学元素组成的快速分析显著推动了古气候环境变化及生物地球化学研究。应用激光剥蚀等离子体质谱仪(LAICP-MS)对南黄海现代牡蛎Crassostrea gigas壳体韧带部的元素组成进行原位微区测试,利用内标元素43Ca进行元素比值的校正,探讨了牡蛎壳中化学元素特征及其环境意义。研究的长牡蛎壳体中Mg/Ca、Sr/Ca、Na/Ca比值具有显著的季节性周期变化。环境水体物理化学性质的变化对壳体生长速率影响较大,壳中白垩质方解石和叶片方解石生长层分别对应较高和较低的环境温度,白垩方解石层具有较高的Mg/Ca、Sr/Ca和较低的Na/Ca比值。Mg/Ca比值可指示牡蛎壳体生长环境水体温度,利用前人Mg/Ca比值公式计算可以恢复与器测资料相符的近岸海水温度结果。本研究对应用LA-ICP-MS分析技术开展高分辨率的生物壳体元素组成和环境示踪研究具有借鉴意义。Biogenic calcium carbonates are widely used natural archives to study environmental history and human activities as they preserve a wealth of information of climatic and environmental changes.With the NIST610 glass as the reference material and 43Ca as the internal element to calibrate,major and trace elements in a modern Pacific Oyster shell(Crassostrea gigas)taken from the offshore area of South Yellow Sea near Haimen were measured with laser ablation inductively coupled plasma-mass spectrometry(LA-ICP-MS).The primary objecitve is to reveal elemental compositions and environmental implications.Our results show very good correlations between the variations in Mg/Ca,Sr/Ca,Na/Ca ratios and the seasonal growth increments of the shell.This might suggest that variations in elemental ratios of the shell are mainly controlled by physical and chemical properties of the ambient sea water.In most cases,the chalky calcite layers in oyster shells correspond to the period of higher sea water temperature,while the foliated calcite layers are associated with the period of lower temperature.In general,the chalky calcite layers are featured by high Mg/Ca and Sr/Ca and low Na/Ca ratios.By applying Mg/Ca-temperature reconstruction equation published in literature,we obtained reliable sea surface temperature for the study area based on Mg/Ca ratios in the oyster shell,which is supported by the overall consistence between gauged water temperatures and the reconstructed.

关 键 词：牡蛎壳 CRASSOSTREA GIGAS 微量元素 LA-ICP-MS MG/CA 温度 

分 类 号：P736.14[天文地球—海洋地质]