Microbial remediation of cadmium-contaminated soils and its mechanisms: a review / 生物工程学报

Excessive levels of cadmium (Cd) in soil exert serious negative impacts on soil ecosystems. Microorganisms are a common component of soil and show great potential for mitigating soil Cd. This review summarizes the application and remediation mechanisms of microorganisms, microbial-plants, and microbial-biochar in Cd-contaminated soil. Microorganisms such as Bacillus, Acinetobacter, Pseudomonas, and arbuscular mycorrhizal fungi (AMF) can change the biological validity of Cd through adsorption, mineralization, precipitation and dissolution. Different factors such as pH, temperature, biomass, concentration, and duration have significant effects on Cd bioavailability by microorganisms. Pseudomonas, Burkholderia, and Flavobacterium can promote the uptake of Cd2+ by hyperaccumulator through promotion and activation. Biochar, a soil amendment, possesses unique physicochemical properties and could act as a shelter for microorganisms in agriculture. The use of combined microbial-biochar can further stabilize Cd compared to using biochar alone.

Planning of ecologically suitable areas for Ligusticum chuanxiong under background of soil cadmium pollution / 中国中药杂志

Chuanxiong Rhizoma is a traditional Chinese medicinal material mainly produced in Sichuan and Chongqing of China. In recent years, the cadmium content in Chuanxiong Rhizoma produced in most of the genuine producing areas has exceeded the standard, which makes Chuanxiong Rhizoma difficult to be exported. To solve the problem of excessive cadmium content in soil, this study employed the MaxEnt model to simulate the potential geographic distribution of Ligusticum chuanxiong and evaluate important environmental factors, and re-plan its ecologically suitable areas based on the mineral distribution characteristics and soil cadmium pollution status. The results showed that the places suitable for L. chuanxiong growing covered an area of 335 523.69 km~2, mainly in central and eastern Sichuan, southern Shaanxi and most parts of Chongqing. Among them, the highly suitable areas of L. chuanxiong were mainly concentrated in Chengdu, Ya'an, Deyang, and Mianyang. Solar radiation, annual precipitation, and annual range of temperature were evaluated as important variables affecting the distribution of L. chuanxiong, with the contribution rates of 62.3%, 13.3%, and 6.8%, respectively. In addition, Qionglai county, Chongqing county, Mianyang city(Youxian district and Fucheng district), Qingchuan county, and Xinjin county were classified into the first-class ecologically suitable zone, covering a total area of 2 768.87 km~2. The se-cond-class ecologically suitable zone was even wider, involving such counties as Tongjiang county, Renshou county, Jianyang county, and Nanjiang county, and the total area reached 43 616.92 km~2. The re-planning of the ecologically suitable areas for L. chuanxiong has provided strong data support for the cultivation and resource development of L. chuanxiong and also new ideas for solving the problem of excessive cadmium content in L. chuanxiong.

Effects of different passivators on growth and physiological characteristics of Ophiopogon japonicus in cadmium-contaminated soil / 中草药

Objective: To comprehensively evaluate the different passivation materials on growth and cadmium uptake and accumulation of Ophiopogon japonicus cultivated in cadmium contaminated soil of. Methods: Using one-year-old O. japonicus as experimental material, the effects of five different passivation materials (white marble Ar, straw biochar Br, fly ash Fh, bacterial residue Me, diatomite Dm) on the growth, physiological and biochemical indexes and cadmium absorption and accumulation of O. japonicus were studied by soil pot experiment. Results: The biomass, chlorophyll, soluble sugar and soluble protein of O. japonicus could be significantly increased in soils contaminated with two kinds of Cd under different passivation materials. Among them, Ar and Me were the most improved. In addition, the activities of antioxidant enzyme system of O. japonicus were significantly decreased, and the content of MDA had no noteworthy change. Different passivation materials remarkably increased the content of flavonoids in the underground part of O. japonicus, among which Ar and Fh treatments increased the most. The contents of heavy metal Cd in all parts of O. japonicus were decreased by different passivation materials, and the contents of Cd in aboveground and underground parts of O. japonicus were significantly lower than those of the control, and the effects of Ar, Br and Fh treatments were better than those of the control. Conclusion: Studies have shown that by combining and comparing treatments of different passivating materials, in terms of the biomass of O. japonicus treated with Me, the biomass improvement effect of Me was better than that of Ar and Br. Aiming at the effect of reducing Cd absorption and accumulation of O. japonicus and improving the effective component flavone of O. japonicus, it can be concluded that Ar and Fh have better effects in treating Cd polluted soil and improving the quality of O. japonicus.