Key Laboratory of Plant Nutrition and Fertilizer in South Region, Ministry of Agriculture, Institute of Agricultural Resources and Environment, Guangdong Academy of Agricultural Sciences, Guangzhou 510640, China.
Department of Soils and Water, Faculty of Agriculture, Al-Azhar University, Assiut 71524, Egypt.
Biomolecules. 2021 Mar 17;11(3):448. doi: 10.3390/biom11030448.
Heavy metals (HMs) toxicity represents a global problem depending on the soil environment's geochemical forms. Biochar addition safely reduces HMs mobile forms, thus, reducing their toxicity to plants. While several studies have shown that biochar could significantly stabilize HMs in contaminated soils, the study of the relationship of soil properties to potential mechanisms still needs further clarification; hence the importance of assessing a naturally contaminated soil amended, in this case with Paulownia biochar (PB) and Bamboo biochar (BB) to fractionate Pb, Cd, Zn, and Cu using short sequential fractionation plans. The relationship of soil pH and organic matter and its effect on the redistribution of these metals were estimated. The results indicated that the acid-soluble metals decreased while the fraction bound to organic matter increased compared to untreated pots. The increase in the organic matter metal-bound was mostly at the expense of the decrease in the acid extractable and Fe/Mn bound ones. The highest application of PB increased the organically bound fraction of Pb, Cd, Zn, and Cu (62, 61, 34, and 61%, respectively), while the BB increased them (61, 49, 42, and 22%, respectively) over the control. Meanwhile, Fe/Mn oxides bound represents the large portion associated with zinc and copper. Concerning soil organic matter (SOM) and soil pH, as potential tools to reduce the risk of the target metals, a significant positive correlation was observed with acid-soluble extractable metal, while a negative correlation was obtained with organic matter-bound metal. The principal component analysis (PCA) shows that the total variance represents 89.7% for the TCPL-extractable and HMs forms and their relation to pH and SOM, which confirms the positive effect of the pH and SOM under PB and BB treatments on reducing the risk of the studied metals. The mobility and bioavailability of these metals and their geochemical forms widely varied according to pH, soil organic matter, biochar types, and application rates. As an environmentally friendly and economical material, biochar emphasizes its importance as a tool that makes the soil more suitable for safe cultivation in the short term and its long-term sustainability. This study proves that it reduces the mobility of HMs, their environmental risks and contributes to food safety. It also confirms that performing more controlled experiments, such as a pot, is a disciplined and effective way to assess the suitability of different types of biochar as soil modifications to restore HMs contaminated soil via controlling the mobilization of these minerals.
重金属（HMs）毒性是一个全球性问题，取决于土壤环境的地球化学形态。生物炭的添加可以安全地减少 HMs 的可移动形态，从而降低其对植物的毒性。虽然有几项研究表明生物炭可以显著稳定污染土壤中的 HMs，但研究土壤性质与潜在机制之间的关系仍需要进一步澄清；因此，评估自然污染土壤的重要性，在这种情况下，使用短序列分步计划来分离 Pb、Cd、Zn 和 Cu。估计了土壤 pH 值和有机质及其对这些金属再分配的影响。结果表明，与未处理的花盆相比，酸可溶金属减少，而与有机质结合的金属增加。有机质结合金属的增加主要是以减少酸可提取和 Fe/Mn 结合金属为代价。生物炭的最大应用增加了 Pb、Cd、Zn 和 Cu 的有机结合部分（分别为 62%、61%、34%和 61%），而 BB 则分别增加了 61%、49%、42%和 22%。同时，Fe/Mn 氧化物结合部分与锌和铜密切相关。就土壤有机质（SOM）和土壤 pH 值而言，作为降低目标金属风险的潜在工具，与酸可提取金属呈显著正相关，而与有机质结合金属呈负相关。主成分分析（PCA）表明，TCPL 可提取和 HMs 形态及其与 pH 值和 SOM 的总方差代表 89.7%，这证实了在 PB 和 BB 处理下 pH 值和 SOM 对降低研究金属风险的积极影响。这些金属的流动性和生物可利用性及其地球化学形态根据 pH 值、土壤有机质、生物炭类型和应用率而广泛变化。作为一种环保且经济实惠的材料，生物炭强调了其作为一种工具的重要性，该工具使土壤在短期内更适合安全种植，并具有长期可持续性。本研究证明，它降低了 HMs 的流动性，降低了其环境风险，有助于食品安全。它还证实，进行更多的控制实验，如盆栽实验，是一种严格有效的方法，可以评估不同类型的生物炭作为土壤改良剂的适宜性，通过控制这些矿物质的迁移来修复受 HMs 污染的土壤。
