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The distribution of acid-volatile sulfide (AVS) and simultaneously extracted metals (SEM) were studied in sediments collected from mangrove forest, forest fringe and adjacent mudflat in the Zhangjiang Estuary, China. The aim was to examine the spatial distribution of AVS and SEM in sediments of the Estuary and determine the influence of mangrove trees on AVS and SEM concentrations in the sediments. The results indicated that AVS concentrations in forest sediments were significantly lower than those in mudflat sediments. There was a significant positive correlation between AVS values and moisture contents in forest sediments, while LOI played an important role in AVS concentrations of mudflat sediments. In the forest sediment core, the peak value of AVS appeared deeper in the sediment profile compared to it appeared in the mudflat core. The distribution of SEM showed different trends from that of AVS, and potential toxicity existed in the upriver forest sediments., (Copyright 2010 Elsevier Ltd. All rights reserved.)

The speciation distribution of cadmium (Cd) in mangrove (Kandelia candel (L.) Druce) rhizosphere sediment was investigated after different contents of Cd being loaded. The study results indicated that root induced changes of Cd bioavailability in the rhizosphere. Exchangeable and carbonate bound Cd in the rhizosphere sediments were lower than these in the bulk sediments, whilst an increase in Fe-Mn oxides bound and O.M/sulfide bound fractions occurred in the rhizosphere sediment. Increased levels of Cd in sediments resulted in higher Cd concentrations in mangrove plants, and the order of accumulation was: roots > hypocotyls > stems and leaves.