Research On The Propagation And Rapid Disposal For Fresh Biomass Of Sedum Plumbizincicola-A Cadmium And Zinc Hyperaccumulator

Among numerous soil pollution remediation technologies,phytoremediation is an outstanding one that gets more and more attention and application for its green,in-suit and wide adaptability.Sedum plumbizincicola,a zinc and cadmium hyperaccumulator,has many advantages over soil remediation,such as large biomass,high growth rate,high accumulation,wide adaptability,and so on.After years of continuous research,S.plumbizincicola,has achieved good results in the phytoextration of cadmium contaminated soil,and it shows a huge potential and broad application prospect.It should be noted that,in the process of scale application,some problems need to be overcome,such as lack of high quality seedlings.Besides,the harvest fresh biomass of S.plumbizincicola,containing high concentrations of heavy metals,need a large area and long time to dry,which may bring secondary environmental pollution.Therefore,this study was carried out from the following two aspects:how to grow seedlings effectively and efficiently,and the safe and economical disposal of the harvested biomass to avoid secondary environmental pollution.For the research on the propagation technologies,we conduct several sets of experiments on seed germination and cottage,the major findings of this study are as follows.We blended the fine soil and seeds of S.plumbizincicola in the ratio of 6:1 and sowed,germinated about 7.8±2.1 strains,and the density is relatively moderate.It overcomes the difficulty that the tiny seed causes intensive seedling.Culture substrate has an impact on the germination of the seed of S.plumbizincicola.Humus or its admixture with vermiculite or perlite are better than the farmland soil or its admixture with vermiculite or perlite.To propagate seedlings in the way of cottage,S.plumbizincicola was easy to take root.Cultivated on the substrate of humus and vermiculite(3:1),rooting situation and growth of the cutting seedlings performance best.The processing of the stem section has a significant impact on the result in the cottage of S.plumbizincicola.We found that the stem which was removed a small amount of leaves and the ones which was kept all the leaves has a high survival rate.In addition,the survival rate of the stem which was removed off all the leaves can still reach 80.9%.Fresh biomass of S.plumbizincicola,was cut and crushed to get residue and sap.Then the residue was dried quickly and the sap was treated using physical and chemical methods to make sure that the effluent Cd concentration was under corresponding standard limits.The effect of different flocculant,pH value and heavy metal capture agent on the removal rate of Cd from sap was investigated,and the optimal treatment method was obtained.The results show that after being cut and crushed,the dry time of fresh biomass decreased from half month to 2?6 days.By adding 0.3%PAC,0.1%NaOH,0.05%TMT,the Cd concentration of effluent decreased from 1.98 mg L-1 to 0.066mg L-1,lower than 0.1 mg L-1,the limited value of the "national waste water comprehensive discharge standard"(GB 8978-1996).On the basis of research in laboratory,a pilot test was carried out in the phytoremediation site in Xiangtan,Hunan Province and the anticipated effect has been achieved.Through our established rapid dehydration system,the harvested biomass was broken and crushed,then its volume reduced about 90%,the residue weight reduced by more than 60%.The corresponding effluent was disposed by water treatment system and finally the Cd concentration of effluent decreased to 0.082 mg L-1,lower than 0.1 mg L-1,the limited value of the "national waste water comprehensive discharge standard"(GB 8978-1996).This research provides important technical support for the propagation and rapid disposal for fresh biomass of S.plumbizincicola.