Xiaoyu Yu

Shifts in the relative abundance of bacteria after wine-lees-derived biochar intervention in multi metal-contaminated paddy soil

The impact of biochar application on soil ecological functions depends on the diversity of soil conditions and of the feedstocks from which biochar is obtained. Moreover, little information is available on the effect of biochar on dynamic changes in microorganisms with the development of rice plants in multi-metal-contaminated paddy soil amended with wine-lees-derived biochar. In this paper, biochar obtained from the pyrolysis of wine lees at 600°C was used to investigate the potential role of biochar in maintaining soil ecological functions, with consideration of the alteration of the microbial population over periods of rice growth. Biochar increased the soil nutrient availability, suppressed the toxicity of heavy metals and benefited the rice growth. Enzymic activities initially increased and then decreased with increasing biochar addition as well as with the growth stage. High-throughput sequencing results indicated that biochar application shifted the soil microbial community, increased the bacterial diversity and reduced the bacterial richness. The relative abundances of Actinobacteria, Firmicutes, Proteobacteria, Planctomycetes and Cyanobacteria increased with increasing biochar addition, whereas the abundance of Gemmatimonadetes decreased at higher biochar applications. With increasing biochar application, Nitrospirae, which were lowest in the 1% biochar addition treatment, first decreased and then increased. The results from this study indicated that biochar addition increased N2 fixation and improved C cycling. Redundancy analysis (RDA) indicated that RI (potential ecological risk index), AN (available nitrogen) and AP (available phosphorus) were the most important factors for bacteria and accounted for 68.7%, 58.3% and 52.4% of the variation, respectively. Therefore, the reduction of metal toxicity and the improvement of soil fertility are important mechanisms for higher bacterial abundances.

Grey relational analysis for evaluating the effects of different rates of wine lees-derived biochar application on a plant–soil system with multi-metal contamination

In this study, grey relational analysis (GRA) was used to investigate the effects of different application rates of wine lees-derived biochar on a plant–soil system with multi-metal contamination. A pot experiment was conducted to determine rice growth in multi-metal-contaminated soil amended with samples of wine lees-derived biochar, and 47 indicators (including soil properties, microbial activity, and plant physiology) were selected as evaluation indexes to assess the plant–soil system. The results indicated that higher wine lees-derived biochar application rates (2% W/W) were favorable for soil fertility, the bioconcentration factor (BF), and the mobility factor (MF, %) (with the exception of Cr, Zn, and Hg), but an application of 1% produced the highest plant growth, enzymatic activities, and bacterial diversity. The richness of the bacterial communities was reduced in the soil amended with the wine lees-derived biochar. According to the GRA assessment, the 1% application rate of wine lees-derived biochar was more suitable for restoring the holistic plant–soil system than were the application rates of 0, 0.5, and 2% (W/W). Furthermore, this study shows that GRA is a useful method for evaluating plant–soil systems.

The factors affecting biochar application in restoring heavy metal-polluted soil and its potential applications

ABSTRACT Heavy metal soil contamination is being given more and more attention due to increasing threats of heavy metals to soil quality, ecological function and human health. Biochar application is an effective way to remove toxic metals due to its high efficiency and low price. Electrostatic adsorption is the primary adsorption mechanism. The absorption ability and stability of biochar is the key to its adsorption performance. The extent of the restoration efficiency is dependent on many factors. The biomass, pyrolysis temperature and application rate affect the number of binding sites. The ageing process and soil properties significantly affect the biochar stability. For long-term purposes, biochar derived from woody residues and pyrolysed at high temperatures is the best available material. In addition, the application of alkaline and electronegative biochar to clay-rich, acidic and As- or Cr-contaminated soil should to be treated with caution.