地球与环境

文章摘要

渭河沉积物的磁学特征及其对降雨量的响应

Magnetic Characteristics of Fluvial Deposit at the Baoji Section of the Weihe River and Its Response to Rainfall

投稿时间：2018-07-26 修订日期：2018-12-05

DOI：10.14050/j.cnki.1672-9250.2019.47.061

中文关键词: 渭河;沉积物;环境磁学;降雨量

英文关键词: Weihe River;sediment;environmental magnetism;Rainfall

基金项目:陕西省教育厅重点科学研究计划项目（17JS004）。

作者	单位
张俊辉^1,2, 刘滨¹, 李东兴¹, 周雄辉¹, 康秀丽¹, 林青¹, 王彦虎¹, 姜珊¹	1. 宝鸡文理学院地理与环境学院, 陕西宝鸡 721013 2. 宝鸡文理学院陕西省灾害监测与机理模拟重点实验室, 陕西宝鸡 721013

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中文摘要:

沉积物中的磁性矿物对气候环境变化敏感响应。渭河WH1617剖面沉积物进行全面系统的磁性特征分析表明，沉积物中的磁性矿物含量相对较低，主要载磁矿物为磁铁矿和磁赤铁矿，同时含有赤铁矿，磁晶粒以多畴为主。非磁滞剩磁磁化率与饱和等温剩磁的比值（χ_ARM/SIRM）与降雨量呈现较好的正相关性，进一步分析表明χ_ARM/SIRM可作为代用指标用来揭示渭河流域1957~2010年以来的降水量变化。其中，1957~1969年，χ_ARM/SIRM值减小，表明磁性矿物粒径变粗，降雨量递减；1969~1985年，χ_ARM/SIRM值递增，表明磁性矿物粒径变细，降雨量递增；1985~1995年，χ_ARM/SIRM值减小，磁性矿物粒径变粗，降雨量相对减少；1995~2010年，χ_ARM/SIRM值递增，磁性矿物粒径变细，降雨量波动递增，但增幅不大。通过morlet小波分析表明渭河流域近现代降雨量存在8 a和19 a的主周期变化，χ_ARM/SIRM存在8 a和16 a的主周期变化，两者的周期变化特征较为一致，进一步表明χ_ARM/SIRM在渭河沉积物中作为降水代用指标的有效性。

英文摘要:

Magnetic minerals in sediment are sensitive to changes of climate and environment. A comprehensive and systematic analysis of the magnetic characteristics of the WH1617 sediment profile in the Weihe River shows that the magnetic minerals in sediments are mainly magnetite and magnetic hematite, whose grains are mainly multi-domains (MD) and whose contents are relatively low. The χ_ARM/SIRM ratio (non-hysteresis residual magnetism magnetization to saturated isothermal residual magnetism) shows a good positive correlation with rainfall and could be used as a proxy to reveal the variation of precipitation in the Weihe River basin in the period of 1957-2010. Briefly, during 1957-1969, χ_ARM/SIRM kept decreasing and magnetic mineral particles became thicker, indicating a downtrend of rainfall; during 1969-1985, χ_ARM/SIRM increased and magnetic mineral particles became thinner, indicating an uptrend of rainfall; during 1985-1995, χ_ARM/SIRM decreased and magnetic mineral particles became thicker, indicating a downtrend of rainfall; during 1995-2010, χ_ARM/SIRM value incremented and magnetic mineral particles became thinner, indicating a modest increment of rainfall. The Morlet wavelet analysis shows that there exists two major rainfall periods of 8a and 19a in the Weihe River basin, which is consistent with two main periods, 8a and 16a, in χ_ARM/SIRM variations, therefore, it is suggested that the χ_ARM/SIRM ratio in sediment of the Weihe River could be a substitute proxy of the regional precipitation.

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