Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, 430072, China; Graduate School of the Chinese Academy of Sciences, Beijing, 100039, China.
Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, 430072, China.
Water Res. 2016 Oct 15;103:352-361. doi: 10.1016/j.watres.2016.07.058. Epub 2016 Jul 26.
Accurate identification of phosphorus (P) forms is crucially important for understanding the geochemical cycle of P; however, until now the role of ferrous iron P (Fe(II)-P) buried in sediments has been completely ignored in nearly all sequential extraction procedures developed. Using sediment cores sampled from Donghu Lake in Wuhan, China, this study explored a modified version of widely used sequential P extraction method (SEDEX; Ruttenberg, 1992) in which Fe(II)-P was identified as an independent fraction. Based on the high selectivity of the extractant (0.2% 2,2'-bipyridine+0.1 M KCl) and the dissolution equilibrium of P, procedures for extracting Fe(II)-P were optimized using a 1:100 solid:liquid ratio and extraction at 50 ± 1 °C for 24 h. The sedimentary P extracted was divided into five fractions: loosely-bound P, Fe(II)-P, CDB-P, Ca-P and O-P. Fe(II)-P was the predominant fraction in fresh sediments in Donghu Lake, accounting for 15.7-49.9% of TP, with a mean of 31.6%. The mean values of Ca-P, O-P, CDB-P and loosely-bound P were 28.4%, 22.7%, 17.1% and 4.3%, respectively. Combined with component analysis of extracts and recovery experiments of standard reference minerals (vivianite, Fe3(PO4)2·8H2O) in natural sediments, extraction of Fe(II)-P with 0.2% 2,2-bipridine and 0.1 M KCl was robust, with a good recovery rate (88.7-100.6%) and little of the Ca-P dissolved. It is possible to use this innovative SEDEX not only to distinguish the contribution of different P matrices in fresh sediments, but also to investigate the transformation of sedimentary P under different redox conditions. Therefore, greater focus on Fe(II)-P is necessary, because it is a major sink for the geochemical process of sedimentary P.
准确识别磷（P）形态对于理解 P 的地球化学循环至关重要；然而，到目前为止，几乎所有开发的连续提取程序都完全忽略了埋藏在沉积物中的亚铁磷（Fe(II)-P）的作用。本研究使用取自中国武汉东湖的沉积物岩芯，探索了广泛使用的连续 P 提取方法（SEDEX；Ruttenberg，1992）的一种改良版本，其中 Fe(II)-P 被确定为一个独立的分数。基于萃取剂（0.2％2,2'-联吡啶+0.1 M KCl）的高选择性和 P 的溶解平衡，通过 1:100 的固液比和 50±1°C 下提取 24 h 来优化 Fe(II)-P 的提取程序。提取的沉积物 P 被分为五个分数：松散结合的 P、Fe(II)-P、CDB-P、Ca-P 和 O-P。Fe(II)-P 是东湖新鲜沉积物中的主要分数，占总磷（TP）的 15.7-49.9％，平均值为 31.6％。Ca-P、O-P、CDB-P 和松散结合的 P 的平均值分别为 28.4％、22.7％、17.1％和 4.3％。结合提取物的成分分析和天然沉积物中标准参考矿物（蓝铁矿，Fe3(PO4)2·8H2O）的回收实验，用 0.2％2,2-联吡啶和 0.1 M KCl 提取 Fe(II)-P 是可靠的，回收率良好（88.7-100.6％），且溶解的 Ca-P 很少。这种创新的 SEDEX 不仅可以用来区分新鲜沉积物中不同 P 基质的贡献，还可以研究不同氧化还原条件下沉积物 P 的转化。因此，有必要更加关注 Fe(II)-P，因为它是沉积物 P 地球化学过程的主要汇。
