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| Distribution of Fixed-NH4+-N in Luochuan Loess Section |
| RAO Wen-bo1,2, LI Xiao-biao1, GAO Zhen-min1, LUO Tai-yi1 |
1. The State Key Laboratory of Ore Deposit Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550002, China;
2. The Graduate School, Chinese Academy of Sciences, Beijing 100039, China |
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Abstract Fixed-NH4+-N content varies between 120 μg·g-1 and 202 μg·g-1 in Luochuan loess-palaeosol sequences. Fixed-NH4+-N content in interbeded palaeosols is higher than that of the loess. There are three big fluctuations in values of fixed NH4+-N content in the Luochuan loess section during the last 130 ka. Fixed-NH4+-N content is the highest in the S1 palaeosoil developed in the last interglacial period. Secondly, fixed-NH4+-N content is slightly lower in the S0 layer formed in the post-glacial period. Thirdly, fixed-NH4+-N content is the lowest in Malan loess formed in the last glacial period. In addition, there are three small oscillations in the values of fixed-NH4+-N content in the Malan loess. The curve of fixed-NH4+-N in the loess and interbeded paleosols much corresponds to climate variation in the Chinese Loess Plateau. The curve of fixed-NH4+-N exhibits a similar oscillation in amplitude and in frequency with that of magnetic susceptibility and the <2 μm fraction in the S0L1S1 sequence. These characteristics show that fixed-NH4+-N is closely related to climate conditions, and further reveal that fixed-NH4+-N in the Luochuan loess section can record the information of climate change to some degree.
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Received: 08 May 2003
Published: 20 December 2004
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2004, Vol. 24 
