河流沉积物中有机磷提取剂(NaOH-EDTA)提取比例与机制研究

选择海河流域高磷污染河流滏阳新河沉积物为研究对象,利用液相31P核磁共振(31P-NMR)技术优化了沉积物中有机磷提取剂NaOH和EDTA的配比,探讨了提取剂对总磷(TP)、有机磷(P o)及金属离子的提取机制.结果表明,不同配比的NaOH和EDTA提取液提取同一沉积物,所提取的TP和P o的量差异较大,但P o的提取量均高于NaOH单独提取,主要原因为EDTA与Fe、Al等离子的结合促进了无机磷(P i)和P o的释放;TP在1.00 mol·L-1NaOH+75 mmol·L-1EDTA配比的提取液中获得最大提取量,为3.88 mg·g-1,P o在0.25 mol·L-1NaOH+50 mmol·L-1EDTA配比的提取液中提取量最大,为0.24mg·g-1;相同浓度NaOH提取液中金属离子Fe、Mn、Ca、Mg、Al提取量随EDTA浓度增大呈升高趋势,主要是通过螯合作用、金属离子与OH-形成化合物实现.其中,Fe、Mn、Ca提取浓度与提取液pH呈显著负相关(P<0.01),说明其与OH-形成沉淀化合物;Al离子由于既可以与OH-生成可溶性的偏铝酸盐又可以被EDTA螯合形成可溶性络合物,因此其浓度随提取液pH升高呈指数增长趋势(P<0.01);NaOH与EDTA混合提取剂核磁共振图谱优于NaOH提取液,在本研究中均可以检测到膦酸盐、正磷酸盐、磷酸单酯、磷脂、DNA和焦磷酸盐.综合考虑:对北方河流富含Fe和Al的河流沉积物,0.25mol·L-1NaOH与50 mmol·L-1EDTA可以作为理想的沉积物有机磷提取剂.

Characterization and Optimization of the NaOH-EDTA Extracts for Solution 31P-NMR Analysis of Organic Phosphorus in River Sediments

Optimization and mechanism of NaOH-EDTA extraction solutions were studied in phosphorus (P) pollution river sediments, which were Fe, Al-rich sediment, by solution ³¹P nuclear magnetic resonance spectroscopy (³¹P-NMR). Different proportions of NaOH and EDTA showed different extraction efficiency on total P (TP) and organic P (P_o) in the sediment. The concentration of P_o in NaOH+EDTA extract was higher than that in NaOH extract. The mechanism was that the TP and P_o were released under the conditions of EDTA chelating with Fe and Al. The concentration of TP and P_o were the highest in 1.00 mol·L^-1 NaOH+75 mmol·L^-1 EDTA extract and 0.25 mol·L^-1 NaOH+50 mmol·L^-1 EDTA extract, which were 3.88 mg·g^-1 and 0.24 mg·g^-1, respectively. The extractions of Fe, Mn, Ca, Mg, Al were increasing as the EDTA increased under the same NaOH concentration. Extraction efficiency of Fe, Mn, Ca showed negative correlation with the pH of the extracting solution (P<0.01). Exponential relationship was found between the extraction of Al and the pH of the extraction solution (P<0.01) because of the AlO₂^- and EDTA-Al complex. The quality of spectra of NaOH-EDTA extract was better than that of NaOH extract. Six P species were detected in different extractions, including phosphonates, orthophosphate, pyrophosphate, orthophosphate monoesters, phospholipids and deoxyribonucleic acids. Therefore, 0.25 mol·L^-1 NaOH+50 mmol·L^-1 EDTA was the optimization extraction solution for P_o analysis in Fe and Al-rich river sediment by ³¹P-NMR.