Faculty of Science, University of South Bohemia, Branišovská 31, 370 05 České Budějovice, Czech Republic.
Water Res. 2013 Feb 1;47(2):547-57. doi: 10.1016/j.watres.2012.10.053. Epub 2012 Nov 21.
Correct identification of P forms together with their main Fe and Al binding partners in non-calcareous sediments is of crucial importance for evaluation of P cycling in water bodies. In this paper, we assess extraction methods frequently used for this purpose, i.e., a sequential five-step fractionation (water, bicarbonate buffered dithionite solution (BD), NaOH, HCl, nitric-perchloric acid), ascorbate extraction (pH ~7.5), and oxalate extraction (pH ~3), directly on a range of laboratory prepared Fe and Al minerals enriched with adsorbed P. Extraction selectivity and efficiency for particular P, Fe and Al forms were also verified by specific combinations of these extraction methods applied on freshwater sediment samples. In the sequential fractionation, BD was highly effective in dissolving both amorphous and crystalline Fe (hydr)oxides and the associated P, while neither FeS nor Al (hydr)oxides were dissolved. The following NaOH extraction effectively dissolved both amorphous and crystalline Al (hydr)oxides. The high solubilizing power of BD and NaOH to dissolve crystalline Fe and Al oxides that have only a small P-sorption ability prevents the use of resulting Fe/P and Al/P ratios as simple predictors of total P sorption capacity of sediments and soils. Ascorbate non-selectively extracted small proportions of FeS and amorphous Fe and Al (hydr)oxides, but significant amounts of adsorbed P, which hinders its use for the characterization of P forms in non-calcareous sediments. Similar nonselective characteristics were found for oxalate extractions. As oxalate extracts most of the adsorbed phosphate, it is not possible to use it unambiguously to determine specific Fe/P and Al/P ratios of active complexes. However, this method is convenient (and more selective than NaOH step in the sequential fractionation) for the determination of amorphous Al (hydr)oxides.
正确识别非钙质沉积物中的 P 形态及其主要的 Fe 和 Al 结合体对于评估水体中的 P 循环至关重要。在本文中，我们评估了常用于此目的的提取方法，即顺序五步分级提取（水、碳酸氢盐缓冲连二亚硫酸盐溶液 (BD)、NaOH、HCl、硝酸-高氯酸）、抗坏血酸提取（pH7.5）和草酸盐提取（pH3），直接应用于一系列用吸附态 P 富集的实验室制备的 Fe 和 Al 矿物。还通过应用于淡水沉积物样品的这些提取方法的特定组合验证了特定 P、Fe 和 Al 形态的提取选择性和效率。在顺序分级提取中，BD 高度有效地溶解了无定形和结晶态 Fe（氢）氧化物及其相关的 P，而 FeS 和 Al（氢）氧化物都没有溶解。随后的 NaOH 提取有效地溶解了无定形和结晶态 Al（氢）氧化物。BD 和 NaOH 溶解结晶态 Fe 和 Al 氧化物的高溶解能力，而这些氧化物的 P 吸附能力很小，这阻止了使用由此产生的 Fe/P 和 Al/P 比作为沉积物和土壤总 P 吸附能力的简单预测因子。抗坏血酸非选择性地提取了少量的 FeS 和无定形的 Fe 和 Al（氢）氧化物，但吸附态 P 的含量很大，这阻碍了其用于非钙质沉积物中 P 形态的特征描述。草酸盐提取也具有类似的非选择性特征。由于草酸盐提取了大部分吸附态磷酸盐，因此无法使用它来明确确定活性络合物的特定 Fe/P 和 Al/P 比。然而，对于确定无定形 Al（氢）氧化物，该方法很方便（并且比顺序分级提取中的 NaOH 步骤更具选择性）。
