Influence of Plant on Geochemical Cycling of Iron and the Magnetic Properties of Intertidal Sediments in the Yangtze Estuary

HAN Xiao-fei; ZHANG Wei-guo; CHEN Man-rong; YU Li- zhong

One core (CYLWA-1) from Phragrmites australis vegetated tidal flat, the Yangtz e Estuary, is selected to investigate the effect of plant on geochemical cycling o f iron and the magnetic properties of the sediments. The results show that Fe ²⁺ dominates in most layers of the sediments and increases with depth, except at a depth of 14～20 cm, where Fe³⁺ dominates due to the abundant distribution of live roots. In the oxidized layer of 14～20 cm, χ _fd, χ _ARM and χ _ARM /SIRM decline, sug gesting coarsening of ferrimagnetic minerals. On the contrary, the obvious incre ase in B _CR and SIRM/ χ indicates relative increase of imperfect an ti-ferromagneti c minerals. It is suggested that ferrimagnetic minerals be transformed into impe rfect anti-ferromagnetic iron oxides under oxidizing environment.

Influence of Plant on Geochemical Cycling of Iron and the Magnetic Properties of Intertidal Sediments in the Yangtze Estuary

1. Department of Geography, East China Normal University, Shanghai 200062;

2. State Key Laboratory of Estuarine and Coastal Research, East China Normal Uni versity, Shanghai 200062;

3. Department of Geography, Yangzhou University, Yangzhou Jiangsu 225009

Received Date: 2002-01-04

Rev Recd Date: 2002-03-06

Publish Date: 2003-09-10

Key words:

Abstract: One core (CYLWA-1) from Phragrmites australis vegetated tidal flat, the Yangtz e Estuary, is selected to investigate the effect of plant on geochemical cycling o f iron and the magnetic properties of the sediments. The results show that Fe ²⁺ dominates in most layers of the sediments and increases with depth, except at a depth of 14～20 cm, where Fe³⁺ dominates due to the abundant distribution of live roots. In the oxidized layer of 14～20 cm, χ _fd, χ _ARM and χ _ARM /SIRM decline, sug gesting coarsening of ferrimagnetic minerals. On the contrary, the obvious incre ase in B _CR and SIRM/ χ indicates relative increase of imperfect an ti-ferromagneti c minerals. It is suggested that ferrimagnetic minerals be transformed into impe rfect anti-ferromagnetic iron oxides under oxidizing environment.

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Influence of Plant on Geochemical Cycling of Iron and the Magnetic Properties of Intertidal Sediments in the Yangtze Estuary

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