Effects Of Environmental Factors On The Availability Of Lead And Cadmium By The Heavy Metal-resistant Bacterial Strain J34

Phytoremediation is a relatively safe, economic and easily operated technique forextracting heavy metals from polluted soils, owever, phytoremediators, the plants used forremediation, generally grow slowly, having small biomass and difficulty to absorb andenrich HMs fixed in soils. Using chemical matters such as chelating agents and surfactantsto enhance phytoremediation is comparatively available but usually expensive andunfriendly to environment. Therefore, it is very important to search for amicrobe-strengthened phytoremediation approach to enhance plant remediation economically.In this paper, tested strain J34 has been investigated for its influence of heavy metals-lead & chromium. The tested strain has been primarily identified as an Erwinia sp., andcould grow in pH range of 5.5 to 9.0. It has the optimal growth rate at pH 7.2. Its optimalincubation period is about 17 hour. The tested strain J34 has a good yield of acid; the lowestpH value could be about 3.1. Its acid metabolites were produced at stationary phase. Thetested strain could utilize a majority of carbon& nitrogen source, and especially the onessupplied in the experiment. It is showed that the concentrations of precipitable heavymetals-lead & chromium increase with the decrease of pH in the culture through the shakeflask experiment When added with PbCO₃ 0.0516g, 0.1012g and CdCO₃0.01536g,0.03072g separately, the pH value of the culture could decrease to 3.25, 2.8, 3.39 and3.65.The concentration of effective lead could come to 0.75765mg.L^-1 and 2.3576 mg.L^-1,which are 5.6 and 20.6 times of the control. The concentration of effective chromium couldcome to 5.02115mg.L^-1 and 5.34245mg.L^-1, which are 7.6 and 5.2 times as much as control.The tested strain produces considerable organic acid under shake flask experimentalconditions. The amount of produced organic acids increases with the concentration ofheavy metals increase, and amber acid gets maximum concentration within the six known organic acids. The solution culture shows the impact of strain J34 on the heavy metalabsorption of Indian mustard and tomato. The chromium concentration of above ground ofIndian mustard increases 19.06% and 43.41%, while that of tomato increases 31.24% and20.08% as much as control when incubated with J34 in Cd 5&10mg. L^-1 solution. The leadconcentration of above ground of Indian mustard increases 14.89% and 55.57%, while thatof tomato increases 23.93% and 19.08% as much as control when incubated with J34 in Pb100&200mg. L^-1 solution. It is indicated that in acid red soil with Pb concentration of 200mg.kg^-1 & 400 mg.kg^-1, the soluble Pb concentration of tested one are higher 123%&84.7%than the control; while with Cd concentration of 50 mg.kg-1&100 mg.kg^-1, the soluble Cdconcentration of tested one are higher 33.3%&10% than the control. It is also showed thatin neutral red soil with Pb concentration of 200 mg.kg^-1& 400 mg.kg^-1, the soluble Pbconcentration of tested one are higher 80.7%&34.9% than the control; while with Cdconcentration of 50 mg.kg^-1&100 mg.kg^-1, the soluble Cd concentration of tested one arehigher 44.6%&33.9% than the control. It is demonstrated that in alkaline red soil with Pbconcentration of 200 mg.kg^-1& 400 mg.kg^-1, the soluble Pb concentration of tested one arehigher 32.2%&55.4% than the control; while with Cd concentration of 50 mg.kg^-1&100mg.kg^-1, the soluble Cd concentration of tested one are higher 44.2%&25.2% than thecontrol. Organic fertilizer experiment showed that under the different conditions of organicfertilizer: no organic fertilizer (Group A), 1mg.kg^-1 organic fertilizer (Group B) and2mg.kg^-1 organic fertilizer (Group C), the Cd concentrations of above ground of Indianmustard are 47.3%, 47.1% and 62.4% higher than the control when faced to singlecadmium stress, while that of rape are 42.8%, 38.9%, 9.68% higher than the control.