5539
Doaa Ali Elsayed Ismael
Studies on Bioremediation of Toxic Heavy Metals in Agricultural Soil Ecosystem
Heavy Metals, Bio-Remediation, Pseudomonas aeruginosa, Saccharomyces cerevisiae, Enterobacter cloacae, Mixed Culture Consortium, Kaolinite and Bentonite, Soluble Organic Matter, Greenhouse Experiment, Field experiment
This work dealt with the bioremediation of toxic heavy metals in agricultural soil ecosystem. Three soil ecosystems irrigated with low quality water, i.e., sewage effluent, drainage water or industrial effluent for extended periods were studied. Both cultivated and un-cultivated soil ecosystems with corn were chemically and biologically characterized. The biological characters included analyses of the enumeration of major microbial groups (bacteria, actinomycetes and fungi) and enzyme activities (dehydrogenase, urease and alkaline phosphatase) in the tested soil ecosystems. The chemical characters included pH, EC and heavy metal contents. The soil quality was assessed using WHO and FAO limits of heavy metals and also geo-accumlation index was used to rank the level of contamination in each studied soil ecosystem. Speciation for the heavy metals Zn, Cu, Ni, Cd and Cr in the different soil fractions was carried out to get reliable information about the potential toxicity of heavy metals in the soil ecosystem. Results confirmed the risky impacts for irrigation with low quality water on the investigated soil ecosystem and Kafr-elSheikh soil ecosystem contained the highest concentrations of Cd, Cr, Ni and the lowest microbial activity, and hence it was selected for further study. Three microorganisms capable for heavy metals decontamination were isolated from the selected soil ecosystem and their morphological and microscopic characteristics as well as their 16S rRNA genes sequence were analyzed. The isolates were identified as Pseudomonas aeruginosa, Enterobacter cloacae and Saccharomyces cerevisiae; all are known to be used as bioremediation tools. The efficiency of different tested treatments including Pseudomonas aeruginosa, Saccharomyces cerevisiae, Enterobacter cloacae plus Rock Phosphate, Mixed culture consortium of isolated microorganisms (MCC), mixture of kaolinite and bentonite plus mixed culture consortium , mixture of kaolinite and bentonite plus Pseudomonas aeruginosa and soluble organic matter plus MCC in decontaminating heavy metals were assessed in a greenhouse experiment using the hyper-accumulator radish plant. Results confirmed that all tested remediative amendments led to a growth promotion and increased the total vegetative biomass of radish and mixed treatments were more efficient than the single ones. The maximum growth promotion was observed by application of soluble organic matter plus MCC, which increased total vegetative biomass by 117%. In a field trail, the efficiency of MCC and soluble organic matter plus MCC treatment in decontaminating heavy metals were estimated at Kafr-el-Sheikh because they exhibited high reduction in total concentrations of studied heavy metals in soil. Application of Saccharomyces cerevisiae and KB plus Pseudomonas aeruginosa were also evaluated as a promising technology in fixing the tested heavy metals, because they led to a clear reduction in availability and uptake of the tested heavy metals and caused rapid decontamination of heavy metals. The obtained results in the field experiment confirmed those of the greenhouse one.
2019
Ph.d
Ain Shams
Science