In The Yangtze Estuary Reed Comparative Study Of Heavy Metal Accumulation In Spartina Alterniflora

In this paper, a comparison of heavy metal levels in vegetations was made between indigenous Phragmites australis and exotic Spartina alterniflora in intertidal wetlands of Yangtze Estuary. The compact of vegetation on the physiochemical conditions of surrounding sediments was also studied.The main conclusions are as follows:Eh values in vegetated sediments are relatively lower in surface sediments and higher in subsurface layers with abundant roots. Magnetic parameters S.₁₀₀ and SIRM/x also indicate such a variation in redox conditions with depth. It is shown that sediments vegetated by Spartina alterniflora have higher Eh values but lower pH values, which are probably caused by densier roots and therefore higher oxygen leakage of this vegetation.There are no obvious differences in particle size comparison and sedimentation rate in sediments colonized by this two species. This is linked to the fact that this two species are grown intermingled with each other, and sampled sediments are close to each oather.Analyses of organic carbon(TOC), nitrogen (TN), C/N, δ¹³C indicate no obvious differences in sediments vegetated by this two species. δ¹³C analysis confirms that Phragmites australis is C3 vegetation while Spartina alterniflora is C4 vegetation. The C/N ration and δ¹³C of the sediments are quite similar to the values of suspended matters of the Yangtze River, but different from that of Spartina alterniflora. It is suggested that the organic matters in the sediments is mainly derived from the catchment.The concentrations of Fe, AI,Zn, Cr, Cu and V in vegetated surface sediments show significantly seasonal variations, which are highest in October but lowest in July in general. Except for Mn, which is higher in Phragmites australis vegetated sediment , the remaining elements show no differences in sediments colonized by this two species. After normalization by particle size, vertical variations of metal concentrations in cores surrounding the two plants are similar.Except for Mn, Zn and Cu, metal concentrations in the tissues of the two species followed the order as roots>leaves>stems. Both Phragmites australis...