Hou Zheng-Wei, Li Jian-Hong, Li Cai-Sheng, Zhang Jing-Min, Lin Qing-Huo, Zhao Qing-Jie, Wu Zhi-Peng, Wang Yu
College of Tropical Crops, Hainan University, Haikou 570228, China.
Rubber Research Institute, Chinese Academy of Tropical Agricultural Sciences, Haikou 571101, China.
Huan Jing Ke Xue. 2023 Aug 8;44(8):4497-4506. doi: 10.13227/j.hjkx.202208042.
The effects of coconut fiber biochar (CFB) and nitrate-modified coconut fiber biochar (NCFB) on the passivation of exogenous lead (Pb) in paddy soils and their underlying mechanisms were investigated using soil incubation experiments combined with spectroscopic techniques such as scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), synchrotron radiation X-ray fluorescence (SRXRF), and Fourier transform infrared absorption spectroscopy (FTIR). The effects of NCFB and CFB on the passivation of exogenous lead (Pb) in paddy soils and its underlying mechanisms were investigated. Compared with that of CFB, the inner wall of NCFB honeycomb pores was rougher, and the amount of alcohol-phenol-ether functional groups containing the C-O structure and the amount of carboxyl groups containing the C[FY=,1]O/O[FY=,1]C-O structure on the surface of CFB was significantly decreased after nitric acid modification. Compared with that in the control (without biochar) paddy soil after 150 d of incubation, the EDTA-extracted Pb content in the paddy soil with CFB and NCFB was reduced by 39.7% and 105.4%, respectively. The carbonate-bound and Fe-Mn oxide-bound Pb contents were significantly lower, and the organic-bound and residue Pb contents were significantly higher in the NCFB-added soil. The SRXRF scans showed that the exogenous Pb was enriched in the microregions of CFB particles rich in Ca and Cu elements and relatively less so in the microregions of soil aggregates rich in the Fe, Mn, and Ti elements. In addition, the characteristic peaks of carboxylates (1384 cm) in A-CFB and A-NCFB were significantly enhanced in the incubation experiment in the presence of exogenous Pb compared to A-CFB and A-NCFB in the absence of exogenous Pb. The addition of CFB or NCFB was more effective in passivating exogenous Pb in paddy soils and promoted the gradual transformation of Pb from unstable to more stable forms in paddy soils to achieve the effect of passivating Pb. The greater amount of carboxyl functional groups in NCFB participated in the passivation of exogenous Pb, which made NCFB more effective than CFB in passivating Pb. NCFB was more effective than CFB in passivating exogenous Pb in paddy soils due to its rougher inner walls of honeycomb pores and abundant carboxyl functional groups. In tropical areas such as Hainan, coconut fiber biochar and its modification can be considered as an environmentally friendly candidate method for the remediation of soil Pb contamination.
采用土壤培养实验结合扫描电子显微镜（SEM）、X射线光电子能谱（XPS）、同步辐射X射线荧光光谱（SRXRF）和傅里叶变换红外吸收光谱（FTIR）等光谱技术，研究了椰纤维生物炭（CFB）和硝酸盐改性椰纤维生物炭（NCFB）对水稻土中外源铅（Pb）的钝化效果及其潜在机制。研究了NCFB和CFB对水稻土中外源铅（Pb）的钝化效果及其潜在机制。与CFB相比，NCFB蜂窝孔内壁更粗糙，硝酸改性后CFB表面含C—O结构的醇—酚—醚官能团数量以及含C=O/O—C—O结构的羧基数量显著减少。培养150 d后，与对照（不添加生物炭）水稻土相比，添加CFB和NCFB的水稻土中EDTA提取态Pb含量分别降低了39.7%和105.4%。添加NCFB的土壤中，碳酸盐结合态和铁锰氧化物结合态Pb含量显著降低，有机结合态和残渣态Pb含量显著升高。SRXRF扫描结果表明，外源Pb在富含Ca和Cu元素的CFB颗粒微区富集，而在富含Fe、Mn和Ti元素的土壤团聚体微区富集相对较少。此外，在有外源Pb存在的培养实验中，A-CFB和A-NCFB中羧酸盐（1384 cm）的特征峰相比无外源Pb时的A-CFB和A-NCFB显著增强。添加CFB或NCFB对水稻土中外源Pb的钝化效果更佳，促进了水稻土中Pb从不稳定形态向更稳定形态的逐步转化，从而实现对Pb的钝化效果。NCFB中较多的羧基官能团参与了外源Pb的钝化，使得NCFB在钝化Pb方面比CFB更有效。由于NCFB蜂窝孔内壁更粗糙且羧基官能团丰富，其在钝化水稻土中外源Pb方面比CFB更有效。在海南等热带地区，椰纤维生物炭及其改性材料可被视为修复土壤Pb污染的一种环保备选方法。
