Bioremediation of Pb-Contaminated Soil Based on Microbially Induced Calcite Precipitation

Lead (Pb) has been recognized as one of the most emerging hazardous heavy metals among environmental pollutants. Among which, soil lead pollution is very serious in many cities of China. The soil of Urumqi, an economically quickly developing city in northwestern arid China, is known to be highly contaminated with lead. On a worldwide scale, elevated levels of lead represented the greatest risk to human health. So a novel technique for the removal of such toxic metals from soils is highly desired.

Conventional methods for heavy metal removal have several disadvantages, such as less effective metal-ion removal, high regent requirements and the problem of the safe disposal of the materials. Bacterial methods for the removal of lead from contaminated sites provide an attractive alternative to physicochemical methods and have been employed for a long time. According to the previous studies, biomineralization based on microbially induced calcite precipitation (MICP) provides a promising technique to remediate toxic metals from contaminated soils with additional advantages on current bioremediation techniques.

Therefore, Pb bioremediation in soils which collected from a farmland of Urumqi was investigated using the calcite-precipitating bacterium Kocuria flava. The bacterium was able to grow on nutrient agar media supplemented with 50 mM Pb²⁺ [Pb(NO3)2].

The results showed that incubating contaminated soil with K. flava CR1 could reduce the active Pb, alleviate the Pb stress, and stabilize the Pb contaminated soil. The omnipresence of MICP and the ability of its products to trap heavy metals may provide a new in situ remediation method for contaminated soil. This process can be widely used in the remediation of heavy metals, even in arid areas where phytoremediation can not be successful. Moreover, MICP is not sensitive to redox potential, which makes this process highly effective in bioremediation. The MICP process used in this study could not only immobilize Pb ions in soils, but also effectively improve soil microbial activities and their metabolic capacity. This research provides insight into the geochemistry occurring in the MICP-based Pb-remediated soils, which will help in remediation decisions.

This work was supported by the Knowledge Innovation Program of the Chinese Academy of Sciences, Program of 100 Distinguished Young Scientists of the Chinese Academy of Sciences, National Natural Science Foundation of China, and the Chinese Academy of Sciences Fellowships for Young International Scientists.

The main finding has been published on Journal of Microbiology and Biotechnology, 2012, 22(2): 244-247. The paper is also archived at http://www.ncbi.nlm.nih.gov/pubmed/22370357.