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Biosorption Of Cadmium And Chromium By Chlorella Vulgaris And Its Physiological And Biochemical Responses Under The Combined Stress Of Cadmium And Chromium

Posted on:2019-09-26Degree:MasterType:Thesis
Country:ChinaCandidate:C Y RenFull Text:PDF
GTID:2370330545981775Subject:Biochemistry and Molecular Biology
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In recent years,with the rapid development of industry and the continuous expansion of human activities,the level of heavy metal pollution continues to deepen,and water metal pollution is particularly prominent.The heavy metal pollution of water not only causes the death of aquatic organisms,but also threatens the activities of human beings seriously.Therefore,the removal of heavy metal pollution from water has become an urgent problem to be solved.At present,Most of the current treatment methods will remove some of the heavy metals,and they will cause secondary pollution.The biosorption method is an excellent adsorption method with high efficiency and no secondary pollution.As an excellent biosorbent,microalgae not only has a high adsorption rate,but also has a strong tolerance to heavy metals.Therefore,the study based on Chlorella vulgaris,CdCl2·2H2O and CrCl3·7H2O provide heavy metal ions,the adsorption rate of Chlorella vulgaris under different conditions was investigated,the optimum adsorption conditions were selected and the variation of the adsorption rate of Chlorella vulgaris was studied when the two heavy metals were composited and single treated.At the same time,the toxic effects of Chlorella vulgaris on heavy metals were studied by studying the physiological and biochemical characteristics of Chlorella vulgaris under the heavy metal stress,such as growth status,chlorophyll content,osmotic regulator and antioxidant enzyme activities.The experimental results are as follows:1.Chlorella vulgaris under the combined stress of heavy metal Cd2+and Cr3+,the temperature was 30°C,pH was 5.5,the concentration of Cd2+and Cr3+was 0.4+4mg/L,Chlorella vulgaris biomass was 0.59 g/L the maximum adsorption rate,and under these condition,Chlorella vulgaris could grow normally.2.The adsorption rate of the two heavy metal ions by Chlorella vulgaris combined with Cd2+and Cr3+reached 84.5%and 75.2%respectively,but lower than those of the two ions treated with Chlorella vulgaris alone.And in the coexistence of two ions,the adsorption rate of Cd2+was greater than that of Cr3+.3.Under the combined stress of Cd2+and Cr3+,the biomass and chlorophyll content of Chlorella vulgaris were lower than that of the control group.When the concentration was higher than 0.5+5 mg/L,the biomass and chlorophyll content were significantly lower than the control.It shows that different concentrations of Cd2+and Cr3+have inhibitory effects on the growth and reproduction of Chlorella vulgaris.4.The contents of soluble protein and free proline in Chlorella vulgaris cells increased firstly and then decreased with increasing concentrations of heavy metal ions,and reached the peak at the concentration was 0.4+4 mg/L.The changed of soluble sugar content showed a downward trend with the increase of heavy metal ion concentration,and when the concentration was higher than 0.5+5 mg/L,the downward trend was obvious.5.The MDA content of Chlorella vulgaris increased firstly and then decreased with the increase of the concentration of heavy metal Cd2+and Cr3+.The highest concentration was reached at a concentration of 0.6+6 mg/L,which was approximately3 times that of the control group.6.With the increase of the concentration of heavy metal Cd2+and Cr3+,the content of H2O2 and activity of CAT,POD and SOD in Chlorella vulgaris cells first increased and then decreased.In summary,when the pH was 5.5,temperature was 30°C,concentration of Cd2+and Cr3+was 0.4+4 mg/L,and Chlorella vulgaris biomass was 0.59 g/L,the absorption rate of Chlorella vulgaris with two kinds of ions reached the maximum value,It indicated that the Chlorella vulgaris had good adsorption effect when the heavy metal Cd2+and Cr3+coexisted,and the Chlorella vulgaris had certain biological tolerance to the combined stress of Cd2+and Cr3+.
Keywords/Search Tags:Heavy metal, Chlorella vulgaris, Biosorption, Growth status, Osmotic regulators, Antioxidant activity
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