Qin Junhao, Wang Xi, Ying Jidong, Lin Chuxia
College of Natural Resources and Environment, South China Agricultural University, Guangzhou 510642, China.
Key Laboratory of Agro-Environment in the Tropics, Ministry of Agriculture of China, Guangzhou 510642, China.
Toxics. 2022 Aug 9;10(8):462. doi: 10.3390/toxics10080462.
Biochar is a soil conditioner for enhancing plant growth and reducing plants' uptake of heavy metals. However, the protonation of biochar surfaces in acid soils can weaken the capacity of biochar to reduce the phytoavailability of soil-borne heavy metals over time. The aim of this study was to test this hypothesis by performing a plant-growth experiment with five harvest cycles to examine the durability of rice-straw biochar for the remediation of an acidic-mine-water-contaminated soil. The application of the biochar significantly reduced the phytoavailability of the heavy metals and inhibited the plant uptake of cationic heavy metals but not anionic Cr. The beneficial effects of the biochar were weakened with the increasing number of harvest cycles caused by the gradual protonation of the biochar surfaces, which resulted in the desorption of the adsorbed heavy metals. The weakening capacity of the biochar to reduce the heavy-metal uptake by the vegetable plants was more evident for Cu, Zn, and Pb compared to Ni and Cd. The experimental results generally confirmed the hypothesis. It was also observed that the bioaccessible amount of various metals in the edible portion of the vegetable was also reduced as a result of the biochar application.
生物炭是一种土壤改良剂，可促进植物生长并减少植物对重金属的吸收。然而，随着时间的推移，酸性土壤中生物炭表面的质子化会削弱生物炭降低土壤中重金属植物有效性的能力。本研究的目的是通过进行一个包含五个收获周期的植物生长实验来验证这一假设，以检验稻草生物炭修复酸性矿井水污染土壤的耐久性。生物炭的施用显著降低了重金属的植物有效性，并抑制了植物对阳离子重金属的吸收，但对阴离子铬没有抑制作用。由于生物炭表面逐渐质子化，导致吸附的重金属解吸，随着收获周期数的增加，生物炭的有益效果减弱。与镍和镉相比，生物炭降低蔬菜植物对铜、锌和铅重金属吸收的能力减弱更为明显。实验结果总体上证实了这一假设。还观察到，由于施用生物炭，蔬菜可食用部分中各种金属的生物可利用量也减少了。
