Effects of Pseudomonas alkylphenolica KL28 on immobilization of Hg in soil and accumulation of Hg in cultivated plant.

Abstract

The available content of mercury (Hg) in farmland soil is directly related to the safety of agricultural products. Meanwhile, humans may accumulate high concentrations of Hg through the food chain, resulting in health damage. Regarding the remediation technologies of Hg-contaminated soil, research and development is mainly concentrated on the immobilisation of Hg in soil and efficient extraction by accumulators. Therefore, in this work, the highly Hg-tolerant strain Pseudomonas alkylphenolica KL28 was used to study the removal effect of Hg in a solution, immobilization effect of Hg in soil, and its effect on growth, Hg accumulation and photosynthetic characteristics of Brassica campestris L. KL28 could effectively remove Hg2+ in the solution, with the removal ratio of 96.0% at 24h. This strain could reduce decreases in shoots' and roots' dry weights by 31% and 16%, respectively, at a Hg concentration of 20mg/L. The available Hg in the soil decreased to 4.7-9.4% in 8 days treated with KL28 bacterial solution at a dosage of 100 L/hm2. Meanwhile, with increases in Hg concentrations, Fv/Fm, Y(II), Y(I) and Y(NPQ) in the leaves of B. campestris showed a downward trend while Y(ND) and Y(NO) displayed an upward trend. Under the stress of 20mg/L Hg2+, KL28 could reduce the Fv/Fm from 11.2 to 6.1%. KL28 could effectively remove Hg in the solution, immobilize Hg in soil, promote growth, decrease Hg accumulation and affect photosynthetic characteristics of B. campestris, indicating its potential use in Hg contaminated soils.