Based on the five typical mangrove species in the mangrove wetland of Shenzhen Bay, the contents and distributional characteristics of iron plaques (Fe) and the Mn, Pb, Zn, Cu, As, Cr, Cd, Ni, Co, and Sb enrichment of the iron plaques on mangrove plant roots were investigated. The results show that:① There is a significant difference in the contents of iron plaques among the five mangrove species, and the contents in the species follow the order:Acanthus ilicifolius > Aeagiceras corniculatum > Bruguiera gymnorrhiza > Kandelia obovate > Heritiera littorlis; the content ranged from 0.37 g·kg-1 to 10.81 g·kg-1. ② Iron plaques have a certain enrichment effect on the heavy metals in the sediments. The contents of heavy metals in the iron plaques vary with the plant species, being the highest in A. ilicifolius and the lowest in H. littorlis. This enrichment also varies with the element species:Mn content changed from 0.11 g·kg-1 to 2.67 g·kg-1; the highest contents of Pb, Zn, Cu, As, and Cr changed from 117.44 mg·kg-1 to 189.69 mg·kg-1; and the highest contents of Cd, Ni, Co. and Sb changed from 34.84 mg·kg-1 to 63.34 mg·kg-1. The content of Zn in the iron plaque is negatively correlated with the other heavy metal contents (P<0.001), indicating that Zn might compete with the other elements. ③ Sediment pH significantly affects the content of iron plaque and the accumulation of Mn in the iron plaque (P<0.05). The water content and salinity of the sediments are positively correlated with the contents of heavy metals Cr and Co in the iron plaque (P<0.05). ④ The distribution of iron plaques and their heavy metal contents in different parts of the roots of the mangrove plants follow the order:root tip > root middle > root base.
Keywords: Shenzhen Bay; heavy metals; iron plaque; mangrove plants; sediments.