Department of Chemical Engineering, Queen's University, Kingston, ON, K7L 2N9, Canada.
Chemistry-School of Science and Technology, University of New England, Armidale, NSW, 2351, Australia.
Environ Pollut. 2023 Jun 15;327:121610. doi: 10.1016/j.envpol.2023.121610. Epub 2023 Apr 8.
Soil organic matter (SOM) plays a key role in environmental chemistry of macro and micro nutrients as well as heavy metal (loids). In this research, a modified sequential extraction scheme was used to isolate labile and recalcitrant SOM from organic rich soils after 18 months of ageing with antimony. Humic substances were extracted with a mixture of 0.5 M sodium hydroxide +0.1 M sodium pyrophosphate solution from soils. Then soils deprived of humic substances were sequentially subjected to extraction with glycerol, citric acid, pre-treated with acid and extracted with boiling alkali mixture. The humic acids (HA) and fulvic acids (FA) of isolated SOM fractions were separated and HAs been characterized using FTIR, 1H NMR, and UV-VIS. Acid-alkali treatment of the most recalcitrant SOM fraction (A1-ROM) led to the extraction of sparingly soluble, highly aromatic compound with considerable amounts of N (44% of the extractable N), possibly due to the breakdown of bounds between aromatic rings and amine functional groups. Nevertheless, the highest content of C and TOC was associated with the glycerol extractable SOM. Substantial amounts of Fe and Al were extracted with glycerol, resulting in a dramatic rise of Sb in SOM extracts. The largest increase (60%) in Sb concentrations was observed after the removal of Fe with citric acid. The humic substances (HS) were responsible for 63% of extractable Sb, whereas even after exhaustive alkali extractions 22% of the total Sb remained in the residual humin fraction. Within the HS fraction, 95% of antimony was associated with the low molecular weight FAs. Antimony concentrations in organic fractions correlated significantly with TOC and N contents, possibly due to the role of amine functional groups in Sb complexation. The results of this research highlight the importance of Fe-Al-SOM bridging and humin fraction in sequestration of Sb in recalcitrant SOM pools.
土壤有机质（SOM）在宏量和微量营养元素以及重金属（loid）的环境化学中起着关键作用。在这项研究中，使用改良的连续提取方案，从经过 18 个月老化处理的富含有机物的土壤中分离出易变和难分解的 SOM。腐殖物质用 0.5 M 氢氧化钠+0.1 M 焦磷酸钠溶液从土壤中提取。然后，用甘油、柠檬酸、酸预处理和煮沸的碱混合物依次提取去除腐殖质的土壤。从分离的 SOM 部分中分离出腐殖酸（HA）和富里酸（FA），并用 FTIR、1H NMR 和 UV-VIS 对其进行了表征。对最顽固的 SOM 部分（A1-ROM）进行酸碱处理，导致提取出疏水性、高度芳香性的化合物，其中含有相当数量的 N（可提取 N 的 44%），可能是由于芳环和胺官能团之间的键断裂。尽管如此，甘油可提取 SOM 与 C 和 TOC 的含量最高。大量的 Fe 和 Al 与甘油一起被提取，导致 SOM 提取物中 Sb 的含量急剧上升。用柠檬酸去除 Fe 后，Sb 浓度增加最大（60%）。腐殖物质（HS）负责提取 Sb 的 63%，而即使经过彻底的碱提取，仍有 22%的总 Sb 残留在残余腐殖质部分。在 HS 部分中，95%的 Sb 与低分子量的 FA 有关。有机部分中的 Sb 浓度与 TOC 和 N 含量显著相关，这可能是由于胺官能团在 Sb 络合中的作用。这项研究的结果强调了 Fe-Al-SOM 桥接和腐殖质部分在难分解 SOM 库中 Sb 固定中的重要性。
