A combination method to study the effects of petroleum on soil microbial activity.

TAM III multi-channel calorimetry was applied to study the effect of different concentrations petroleum on soil microbial activity and community. The microbial activities of the soil samples were recorded as power-time curves. The thermokinetic parameters such as microbial growth rate constant k, total heat evolution Q(T), metabolic enthalpy ∆H (met) and mass specific heat rate J(Q/S) were calculated. Results showed that petroleum had a certain extent effects to soil microorganisms. The results indicate that the soil microbial activity was promoted with a petroleum concentration lower than 0.52 % ± 0.24 %, but inhibited with further increase in petroleum.

Hematite enhances the removal of Cr(VI) by Bacillus subtilis BSn5 from aquatic environment.

In the present study, we investigated the removal of Cr(VI) and the associated bacterial activity in the systems containing Bacillus subtilis BSn5 (B. subtilis BSn5) and hematite. The microcalorimetry was used to study the effect of hematite on the normal physiological functions of B. subtilis BSn5 towards the removal of Cr(VI) for the first time. The results of the heat flux and the sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) showed that hematite does not affect the normal physiological functions of B. subtilis BSn5, and can help the strains maintain their activity in the presence of Cr(VI). More importantly, the relative capacity and intensity of Cr(VI) and total Cr removal by B. subtilis BSn5 in the presence of hematite were higher than that in the absence of hematite. The enhancement effect could be associated with their mineral adsorption, biosorption, Fe(II) reduction, bioreduction and immobilization functions. This study demonstrates the possibility of reducing the toxicity of Cr(VI) and enhancing the Cr(VI) removal efficiency in contaminated environments using a combination of hematite and B. subtilis BSn5.