Remediation of Lead Contaminated Soil by Employing Rye Grass, Lead Resistant Bacteria and Graphene Adsorbent

Abstract

Soil contamination with heavy metals is a serious environmental problem posing the enormous threat to human beings and the environment. The persistence and recalcitrant nature of these heavy metals in soil is an important issue as it leads to slow and reduced remediation of the contaminated soil. The major aim of the sustainable remediation is to reduce the harmful level of lead within the safe limits. The use of the phytoremediation, bioaugmentation and nanoremediation proves to be efficient approaches in the remediation of lead. To access the effectiveness and potential of these remedial approaches various treatments were designed: the individual and combination of individual treatments of phytoremediation, bioaugmentation and nanoremediation involving the rye grass, lead resistant bacterial strains and graphene nanoplatellets. The influence of applied treatments on the rye grass and on bacterial population were also assessed. Results showed that phyto + bio + nanoremediation was more effective in treating the lead contaminated soil and have improved the grass physiological growth accompanied by increase in chlorophyll a, b and carotenoid content and the reduced content of MDA and H2O2 in association with the improved activities of antioxidants (CAT, APX, GPX, SOD). Improved soil nutrients content and catalase activity and microbial activity was observed in phyto + bio + nanoremediation. Sequential extraction results indicated low amount of different lead fractions present in soil of phyto + bio + nanoremediation treatment after the fresh soil illustrating that this cumulative treatment was more effective in remediating the lead contaminated soil compared to other treatments. In present study treatment SS + P + LS3 + GNP (100 mg kg-1) showed the highest removal rate of lead from contaminated soil, that is 91.8 % and the CFU noted to be higher as compared to other treatments that is 5.70 * 107 ± 4.97* 103. There is no such study that focuses on the integration of rye grass, lead resistant bacterial strains and graphene for the reclamation of lead contaminated soil. Cumulative potential of phytoremediation, bioremediation and nanoremediation in remediation of lead contaminated soil proves to be greater than the individual remediation methods. Key words: Lead, Rye grass, Graphene nanoplatellets, Nano-remediation, Bioaugmentation, Phytoremediation, Sequential extraction