Abstract
Two kinds of biochars, one derived from corn straw and one from pig manure, were studied as carriers of a mutant genotype from Bacillus subtilis (B38) for heavy metal contaminated soil remediation. After amendment with biochar, the heavy metal bioavailability decreased. Moreover, the heavy metal immobilization ability of the biochar was enhanced by combining it with B38. The simultaneous application of B38 and pig manure-derived biochar exhibited a superior effect on the promotion of plant growth and the immobilization of heavy metals in soil. The plant biomass increased by 37.9% and heavy metal concentrations in the edible part of lettuce decreased by 69.9–96.1%. The polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) profiles revealed that pig manure-derived biochar could enhance the proliferation of both exotic B38 and native microbes. These results suggest that B38 carried by pig manure-derived biochar may be a promising candidate for the remediation of soils contaminated by multiple heavy metals.
Highlights
Heavy metal pollution in farmland has become a serious environmental issue in China and other developing countries[1]
Six treatments were designed for the study: a control (S), soil amended only with B38 (SB), soil amended only with corn straw derived biochar (SC), soil amended with both B38 and corn straw-derived biochar (SCB), soil amended only with pig manure-derived biochar (SP), and soil amended with both B38 and pig manure-derived biochar (SPB)
Corn straw-derived biochar used as a carrier could promote the activity of B38, but it reduces the improvement effect of soil fertility compared with the corn straw-derived biochar alone
Summary
Heavy metal pollution in farmland has become a serious environmental issue in China and other developing countries[1]. UV-irradiation induced mutation is the simplest and most effective physical mutation method, and it has been widely used in the breeding of microbes for industrial use[7,8,9] This technology has seldom been used in mutation for improving the heavy metal resistibility of microorganisms[10,11]. Another limitation of bioaugmentation is that the contaminated soils are usually nutrient deficient and cannot support the rapid growth of the bioaugmented microbes[12]. A lower pyrolysis temperature is favorable for stabilizing the heavy metals and releasing P, K, Ca and other plant nutrients to soil[21] Such a capability may depend on the original feedstock of the biochar[22,23]. Biochar can be utilized as a fertilizer as well as a heavy metal stabilizer
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