象山港部分金属元素的百年沉积记录及物源指示意义

Distribution and sources of some metals in the sediment core from Xiangshan bay, East China Sea

  • 摘要: 本文利用X荧光光谱仪测定了象山港沉积物柱状样中常量元素Ti、K、Ca、Fe、Mn和微量元素Pb、Rb的含量。通过210Pb定年,分析了象山港近百年来元素的沉积记录变化特征。结合沉积物粒径、有机碳、无机碳、总氮等理化参数,通过计算富集系数和主成分分析,探讨了沉积物中金属元素的物源和环境指示意义。研究结果表明:象山港沉积物中的金属元素Ti、K、Ca、Fe、Mn、Pb、Rb的含量分别为0.45%~0.52%、2.14%~2.58%、2.48%~3.13%、4.54%~5.83%、546×10-6~868×10-6、23×10-6~37×10-6、113×10-6~130×10-6,与中国其他近岸海域具有很好的可比性。象山港沉积物中的金属元素Ti、K、Ca、Fe、Mn、Rb主要来源于陆源碎屑物质,没有出现明显的富集;而沉积物中的Pb自1980年以来出现了富集现象,其含量在近年来可能受到了人类活动的影响。金属元素Ti、K、Fe、Mn、Rb、Pb易于在有机质含量丰富的沉积物中赋存,而Ca则以无机碳酸钙的形式赋存于象山港底质中。通过与百年来长江流域夏季降水变化的比较,发现陆源性金属元素的沉积记录异常与历史降水异常年份具有耦合性。

     

    Abstract: Major and trace elements in marine sediment can reflect the sources of marine substances, environment and climate changes.In the present study, a sediment core was collected and the contents of metals in the core were analyzed using X-fluorescence spectrometer in order to investigate the temporal distribution of these elements in Xiangshan bay, East China Sea.Combined with the distribution of organic carbon, inorganic carbon, total nitrogen and grain size, the sources of metals in the core were discussed according to the enrichment factor and principle component analysis.The results show that the metal contents range from 0.45% to 0.52% for Ti, from 2.14% to 2.58% for K, from 2.48% to 3.13% for Ca, from 4.54% to 5.83% for Fe, from 546×10-6 to 868×10-6 for Mn, from 23×10-6 to 37×10-6 for Pb, and from 113×10-6 to 130×10-6 for Rb.They were comparable to those obtained from the other offshore regions of China.Lead was significantly enriched since 1980s, which is suggested to be influence by human activities in the recent years.No obvious enrichment was observed for K, Ca, Fe, Mn and Rb and their main sources are mineral particles derived from the erosion and weathering of the surrounding basement. Metals of Ti、K、Fe、Mn、Rb and Pb are prone to be enriched in the sediments rich in organic matters, while Ca is deposited as inorganic calcium carbonate in the core.Comparing with the annual change of precipitation during summer in the Yangtze valley, it is suggested that mineral sourced metals are good indicator for the abnormal precipitation in geological time.

     

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