Effect Of Sulfur Forms Alteration On Activity Of Heavy Metal During The Reclamation And Desalination Of The Tidal Flat

In this paper, the tidal flat of Pearl River estuary were leached by fresh water to reachedeight different salinity levels. The alteration of sulfur forms in different sediment depth of eachsalinity level was investigated. Studies of the effect of sulfur forms alteration on the toxicity andbioavailability of heavy metals can provide some theoretical foundation for the restoration andsafety use of the tidal flat contaminated by heavy metals.The results show that: after leaching, the total sulfur contents, water soluble sulfur contentsand HCl-Soluble sulphur contents reduce, the Extractable-soluble sulphur contents remainconstant and the acid-volatile sulphur contents increase, compared with the control treatment.Among the eight treatments, the contents of total sulfur, water soluble sulfur, HCl-Solublesulphur and acid-volatile sulphur in the sediments decrease gradually during desalinationprocesses, the extractable-soluble sulphur contents remain constant in these processes.Accordingto the Spearman relationship analysis, there was remarkable negative correlation(r=-0.733～-0.933,p<0.01)between the redox potential and the acid-volatile sulphur contents.The total sulfur contents and the HCl-Soluble sulphur contents first increase and thendecrease as the increase of the sediment depth from0-65cm, among them,the total sulfurcontents of35-50cm reached the highest and the HCl-Soluble sulphur contents of20-35cmreached the highest; the contents of water soluble sulfur and acid-volatile sulphur increase as theincrease of the sediment depth from0-65cm. Nevertheless, the extractable-soluble sulphurcontents don't change along with the increase of the sediment depth.The alteration of the ratio of simultaneously extracted mentals(SEM) and acid volatilesulfide(AVS) in soil during desalination shows that: Fe,Cu,Zn,Pb,Mn and Ni in soil werepotentially harmful and bioavailable. Although the increase of AVS in the early desalination stagecan reduce the activity of the heavy metals, it will increase again owning to the decrease of theAVS in the later desalination stage. The transformation of sulfur forms has more significantimpact on Pb and Ni, followed by Fe, Cu, Zn and Mn,and no significant impact can be found onthe Cd activity when the sulfur forms change during the desalination processes.