Utilization Of Sediment As Substrates And Its Effect On Heavy Metals In Contaminated Soil

This study is based on the resource utilization of sediment containing flocculant which are collected from the riverway.On the one hand the different ratios of flocculant sediment and decomposed pig manure were used to obtain the suitablehorticultural substrates.On the other hand,the flocculants in sediment,polyaluminium chloride(PAC),can be explored into the passivation of heavy metals in contaminated soil,giving the results as follows:(1)The flocculant sediment feature with high density and low porosity,also with low contents of organic matter,available phosphorus and potassium,which is unsuitable for direct cultivation of plant.The different proportions of flocculant sediments and decomposed pig manure were uesed to obtain two different substrates,that is S2(80%flocculation sediment + 20%pig manure)and S3(70%flocculation sediment + 30%pig manure).With the 100%flocculant sediment as control(CK),the physical and chemical properties of substrates CK,S2 and S3 were determined.As compared with CK,the decreased density and increased porosity were observed for S2 and S3,which is more suitable for the requirement of cultivation substrates.Furthmore,the significantly increased contents were noted for organic matter,available nitrogen,phosphorus as well as potassium of both S2 and S3.As indicated in pot experiments,the cultivation effect of S2 and S3 for plant outbalance CK,with S2 working best.Also shown in FTIR,the peak strengths characteristic for Si-O-Si and Si-O-Al as well as Si-O-Mg,were changed in S2 and S3 when compared to CK.The addition of rotten pig manure changed the composition and its content in flocculant sediment.?(2)Huajiachi paddy soil and Fuyang paddy soil polluted with heavy-metal were blended with flocculation sediment,giving four different compound soil,which is the N(100%paddy soil),the NS(60%paddy soil + 40%flocculation sediment),the P(100%contaminated paddy soil)as well as the PS(60%contaminated paddy soil ?40%flocculation sediment).As compared with both N and P,the addition of flocculant sediment caused the increase in the contents of EC,organic matter,alkali-hydro nitrogen and rapidly-available potassium,to a varied extent.The concentrations of Cu,Pb,Cd and Zn were significantly reduced in PS when compared to P.Rice(Jia 58,Xiushui 134)was cultivated in the above four soils,and the overall growth of rice in PS was superior to P,while the overall growth of rice in NS was weaker than N.The uptake of Cu,Pb,Cd and Zn in PS into plant organs was significantly lower than P.Therefore,the addition of flocculant sediment can significantly reduce the contents of Cu,Pb,Cd and Zn in Fuyang heavy-metal contaminated soil,so as to effectively decrease the uptake of Cu,Pb,Cd and Zn in soil into rice organs.The addition of flocculant sediment resulted in the increase of Al concentration in heavy-metal contaminated soil,and the significant decrease in soil Al/P and Cd/Al,also reduced the uptake of soil Cd into rice.