Effect Of The Combination Of Cadmium Resistant Bacterium And Mineral Materials On Uptake And Transfer Of Cadmium In Paddy Soil

The cadmium resistant bacterium strain H6 was studied in this paper,which have been isolated by our laboratory.Strain H6 was identified by 16S rRNA analysis and protein crystallization dying experiment.The effects of initial pH,temperature,rotational speed and inoculation quantity of bacteria on the growth of strain were studied by single factor experiments.Then combined cadmium resistant bacterium(J)with mineral materials(G)to prepare soil amendment,which was applied in paddy soil.The laboratory incubation experiments and pot experiments were carried out to explore the effects of the combination of cadmium resistant bacterium and mineral materials(G+J)on soil basic physicochemical properties,chemical fractions of cadmium and the adsorption and accumulation of cadmium in rice.The main results were as follows:(1)Strain H6 was identified as Bacillus cereus.The optimum growth conditions of strain H6 were as follows:initial pH 6.0?8.0,28?,rotational speed of 120?210 r·min-1,inoculation of 1%-5%.(2)The results of the laboratory incubation experiments showed that,the application of G+J treatments were more effective than single treatments of G and J to increase soil pH values and to decrease the contents of TCLP and CaCl2 extractable Cd.With the increase in the amount of different amendments,the soil pH values were increased by 0.43?2.25,0.36?2.06 units in soil with G+J and G treatments,respectively,while the soil pH values had no significant changes in soil with J treatments.Compared with the control soil,as results of application of G+J,G and J,the contents of TCLP extractable Cd were decreased by 68.41%?77.46%,28.86%?69.68%and 10.05%?46.06%,the contents of CaCl2 extractable Cd were decreased by 4.67%?92.53%,24.38%?94.09%and 1.27%-5.90%,the contents of acid-extractable Cd were decreased by 16.40%?27.98%17.54%?22.16%and 14.79%?22.34%,and the contents of organic-bound Cd were increased by 52.19%?121.83%,38.41%?155.62%and 158.18%?425.46%,respectively(p<0.05).(3)The results of pot experiments indicated that the application of G+J,G and J decreased the Cd contents in various rice tissues of Huanghuazhan and H You 518 with different degrees.Moreover,under certain conditions,the combined application of G and J could further decrease Cd contents in brown rice.With treatments of G+J and G,through increased soil pH values,the contents of TCLP and CaCl2 extractable Cd were decreased in paddy soil,and then Cd contents in brown rice were decreased.Although soil pH values had.no significant changes in soil with J treatments,both TCLP and CaCl2 extractable Cd contents in soil were reduced,which indicated that bioavalibility of soil Cd contents could be reduced by J treaments.Furthermore,under the treatments of G+J,G and J,Cd contents in brown rice could be decreased by reducing the Cd transport ability of husks.The treatment of G4+J4 had the best activity on reducing Cd contents in brown rice of Huanghuazhan and H You 518,which significantly reduced by 55.70%and 44.83%,respectively.(4)The ability of Cd uptake,accumulation and translocate in different genotypic rice were different.With the application of G4+J4,G4 and J4,the ability of Cd transport from roots to stems of H You 518 were stronger than Huanghuazhan,while the ability of Cd transport from husks to brown rice of Huanghuazhan was stronger than H You 518.The bioconcentration fators of Cd in stems were in the order:H You 518>Huanghuazhan,and in brown rice were:Huanghuazhan>H You 518.When the application of treatment was G4+J4,the translocation factors of husks to Cd and the bioconcentration factors of Cd in brown rice of two rice varieties were the lowest.