Preliminary Research On Blastofiltration Of Cd From Water

Phytoremediation, based on the theory of botanic tolerance and accumulation of certainpollutant, is a new developing ecological technique primarily used to clean pollutedenvironment. Rhizofiltration and blastofiltration are usually applied to phytoremediation ofheavy metal polluted water at present.The study used maize, sunflower and castor-oil plant as experimental materials toinvestigate the ecological effects of phytofiltration for 1mg·L-1, 2mg·L-1, 5mg·L-1 and10mg·L-1 Cd solutions (solutions without Cd as control), and the changes of physiological andbiochemical indexes of seedlings under Cd stress.The results showed that: (1) With the trial time lasting, Cd content in solution decreased,and the removal rate declined. The processes of Cd removal for seedlings of eachconcentration were almost completed in 48h. The removal rates of the three kinds of seedlingsat 72h could almost achieve more than 80%, indicating such a fast and effective action for Cdremoval from water. The removal effects of sunflower and castor-oil plant were better thanthose of maize at lower Cd concentrations (1mg·L-1 and 2mg·L-1), whereas the best removaleffects at higher Cd concentrations (5mg·L-1 and 10mg·L-1) were those of castor-oil plant,followed by maize and sunflower. So sunflower might be better used for removal of low Cdconcentration water.(2) Root absorbed the most proportion of Cd for all these three kinds of seedlings at everytreatment, and very little was transformed to stem and leaf, especially in the solutions of lowCd concentrations (1mg·L-1and 2mg·L-1). So rhizofiltration was the main mechanism of Cdremoval from water. From analyzing Cd content in seedlings (or roots) per gram andbio-enrichment coefficient of root at every concentration, the ability of Cd accumulation forthe three kinds of seedlings could be drawn as follow: sunflower>castor-oil plant >maize.(3) The physiological and biochemical indexes, such as plasma membrane permeability,root activity, content of chlorophyll and free proline, for seedlings exposed to Cd for 72h hadchanged to different degree compared with control, especially for the 5mg·L-1 and 10 mg·L-1Cdtreatments. Sunflower and castor-oil plant had greater tolerance than maize through generalanalysis of Cd accumulation and the changes of physiological and biochemical indexes.In conclusion, seedlings of maize, sunflower and castor-oil plant resorting to the functionof rhizofiltration could quickly and effectively remove Cd from water, and showed greattolerance to Cd stress for short term through physiological and biochemical mechanisms.Terrestrial plants with prosperous roots may have a good application prospect inphytoremediation of heavy metal polluted water.