萃取剂对泥炭腐植酸性质和微量元素的影响

Influence of Extractant on Quality and Trace Elements Content of Peat Humic Acids

氢氧化钠(NaOH)和焦磷酸钠(Na4P2O7)是从陆相环境中分离腐植酸(HA)最常用的2种萃取剂。为了评价萃取剂对HA性质和微量元素的影响,采用3种不同溶液,即(a)0.5mol/LNaOH;(b)0.1mol/LNa4P2O7;(c)0.5mol/LNaOH+0.1mol/LNa4P2O7从5个泥炭藓泥炭样品中分离HA,并分析了萃取得到的HA的灰分含量、元素组成和主要原子比,以及傅立叶变换红外光谱(FT-IR)和发光光谱特征。此外,还用X射线荧光法测定泥炭样品和HA中的Br、Cu、Fe、Ni、Pb和Zn的含量。试验结果表明:用NaOH和NaOH+Na4P2O7萃取的HA在灰分、元素含量和光谱特征上十分相似,而Na4P2O7溶液通常降低了萃取率,似乎是影响了HA的本质,使之具有更加复合和芳香性的特征。与原泥炭样品比较,不论什么萃取剂萃取得到的HA,其Br、Cu和Ni含量均增加,而Fe、Pb和Zn含量减少。相比于其他的方法,用Na4P2O7萃取得到的HA含有更多Br、Cu、Ni和Zn,可能是因为HA的芳香性分子对这些元素显示出更大的亲和力。

Among several extractants used to isolate humic acids （HA） from terrestrial environments, sodium hydroxide （NaOH） and sodium pyrophosphate （Na4P207） are the most utilized. In order to evaluate the influence of these different extractant solutions on the HA quality and on their trace elements content, HA were isolated from five Sphagnum- peat samples using three different solutions： （a）0.5 mol/L NaOH; （b）0.1 mol/L Na4P207; （c）0.5 mol/L NaOH ＋ 0.1 mol/L Na4P207. The obtained HA have been analyzed with respect to ash content, elemental composition, main atomic ratios and characterized by FT-IR and total luminescence （TL） spectroscopies. In addition, both raw peat and HA have been analyzed using X-ray fluorescence in order to determine the Br, Cu, Fe, Ni, Pb and Zn contents. Results showed that HA extracted with NaOH and NaOH ＋Na4P207 are quite similar with respect to ash, elemental contents and spectroscopic characteristics, while Na4P207 solution, which in general reduces the extraction yield, seems to affect the nature of HA, featuring a more complex and aromatic character. With respect to the contents in the corresponding raw peat samples, the HA fractions were richer in Br, Cu and Ni, regardless of the extractant used, and poorer in Fe, Pb and Zn. Further, Br, Cu, Ni and Zn were more concentrated in the HA extracted with Na4P207 than in those extracted with NaOH and NaOH ＋Na4P2OT, probably because of the greater affinity of these elements for these more aromatic humic molecules