Journal of East China Normal University(Natural Science) ›› 2021, Vol. 2021 ›› Issue (2): 73-84.doi: 10.3969/j.issn.1000-5641.2021.02.008

• Estuary and Coastal Research • Previous Articles     Next Articles

Comparison of different extraction methods for alkaline earth metals and its implications: A case study of the surficial sediments from Ningbo Plain

Jing HUANG1,2, Tongtong ZHENG1,2, Aihua WANG3, Wenjing LI1,2, Zhanghua WANG1,2,*()   

  1. 1. State Key Laboratory of Estuarine and Coastal Research, East China Normal University, Shanghai 200241, China
    2. Institute of Urban Development, East China Normal University, Shanghai 200062, China
    3. Nanjing Center of China Geology Survey, Nanjing 210016, China
  • Received:2020-03-26 Online:2021-03-25 Published:2021-04-01
  • Contact: Zhanghua WANG


The concentrations and relative ratios of alkaline earth metals, such as Sr, Ba, and Ca, in sediments are widely used to discriminate marine and terrestrial environments in paleoenvironmental research. However, geochemical elements occur mostly in mineral crystal lattices (namely, the residual phase after acid extraction), which is not linked to the physical, biological, or chemical environments of the deposition processes. Hence, only selective extraction of phases can be used to interpret changes in the sedimentary environment. In this study, we collected surficial sediments from the present-day saltmarsh-tidal flat, alluvial plain, and tidal river (Yaojiang River) in Ningbo Plain and used a plasma spectrometer to measure the concentrations of Sr, Ba, and Ca in: the leachates extracted by diluted acetic acid (HAc) and diluted hydrochloric acid (HCl), the residues after acid extraction, and the bulk samples. The results showed that alkaline earth metals in the HAc-leachates were most sensitive to changes in the sedimentary environment, followed by the HCl-leachates. No variation in Sr/Ba (molar ratio) could be distinguished in the bulk samples of surficial sediments collected from different sedimentary settings. Furthermore, consistent results were obtained by using different sample amounts and measuring instruments when applying the HAc method. Significant variations in alkaline earth metals in the HAc-leachates were observed for the surficial sediments in this study. Ca and Sr showed the highest concentrations in the saltmarsh-tidal flat sediments and the lowest concentrations in the alluvial sediments; Ba concentration showed the opposite trend. We thus suggest that end-member analyses of the alkaline earth metals in HAc leachates can be used to effectively identify transgression/regression recorded in sedimentary stratigraphy in the coastal zone.

Key words: alkaline earth metals, selective extraction, end-member analysis, discrimination of sedimentary environment

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