太湖北部沉积物不同形态磷提取液中有机质的特征

Characteristics of Organic Matter in Different Extractions of Phosphorus Forms in Sediments in North Part of Taihu Lake

综合应用高效体积排阻色谱、三维荧光光谱、红外光谱及元素分析等方法,研究了太湖北部3个湖区表层（0～10 cm）沉积物不同形态磷提取液中有机质的特征,并探讨了有机质与磷之间的关系.结果发现,沉积物中总磷的含量与其上覆水体的营养水平相一致;有机C/N、C/P比值在8.5～11.9和188.5～256.6之间,表明沉积物中有机质以湖泊内源自生为主,受陆源输入的影响很小.不同磷形态提取液中有机质的相对分子质量分布和三维荧光光谱存在很大差异,但不同沉积物之间的差别并不显著.3种提取液中有机质的相对分子质量顺序依次为：HCl〉NaOH〉NaHCO3,其重均相对分子质量（Mw）和数均相对分子质量（Mn）分别在4983～5873和3642～5065、3628～4198和2334～2616、3282～3512和2249～2380之间,可能反映了不同提取液中有机磷的组成及其生物活性的不同.沉积物提取液中有机质的三维荧光光谱均以类富里酸荧光峰A（Ex/Em=230～260nm/360～470 nm）或C（Ex/Em=290～320 nm/390～460 nm）为主,NaHCO3和HCl提取液中还分别发现了类蛋白荧光峰B（Ex/Em=275～280 nm/340～360 nm）和D（Ex/Em=225 nm/330～350 nm）及类腐殖酸荧光峰E（Ex/Em=360～375 nm/460～470 nm）.这些荧光光谱特征不仅揭示了不同提取液中有机质组成的差异,而且可能表明了太湖沉积物中有机质的降解受到再悬浮作用的强烈影响.此外,沉积物胡敏酸红外光谱中1059～1082 cm-1的吸收谱带也可能反映了磷酸盐的存在.

The characteristics of organic matter in different extractions of phosphorus forms in the surface sediments （0-10 cm） from throe different regions of north part of Taihu Lake were investigated using the combination of high-performance size-exclusion chromatography （HPSEC）, three-dimensional excitation/emission matrix （3DEEM） fluorescence spectroscopy, fourier transform infrared spectroscopy （FTIR） and elemental analysis, and the relationship between organic matter and phosphorus was also discussed. The results show that the concentrations of total phosphorus in sediments coincide with the corresponding trophic level of overlying water. The atomic ratios of C/N （8.5- 11.9） and C/P （188.5-256.6） indicate that organic matter in these sediments originated mainly from a lacustrine authigenic source, with minor terrestrial contribution. The molecular weight distribution and fluorescence spectroscopy of organic matter varied with different extractions, whereas the differences were not significant between sampling sites. The rank order of the molecular weight of organic matter in three kinds of extractions was ： HC1 〉 NaOH 〉 NaHCO3, with Mw and M, ranging from 4 983 to 5 873 and 3 642 to 5 065, 3 628 to 4 198 and 2 334 to 2 616, 3 282 to 3 512 and 2 249 to 2 380, respectively. These properties may suggest the composition of organic phosphorus and its bioavailability differs in different extractions. The fulvic acid-like （Ex/Em = 230-260 nm/360-470 nm of peak A or Ex/E. = 290-320 nm/390- 450 nm of peak C） fluorophore was predominant in these extractions, while protein-like （Ex/E. = 275-280 nm/340-360 nm of peak B and Ex/ Em= 225 nm/330-350 nm of peak D） and humic acid-like （ Ex/Em = 350-375 nm/460-470 nm of peak E） fluorophoros were observed in NaHCO3 and HCl extractions individually. Possibly indicates that the differences in the composition of organic matter and its decomposition in the sediment from Taihu Lake are subjected to resuspension. Moreover, the absorption of sedimentary humic acid from 1 059 to 1 082 cm-1 in the FTIR suggests that orthophosphate occurred in humic matrix.