水合三氯乙醛前体物的分子量分布和荧光特性

Molecular Weight Distribution and Fluorescence Characteristics of Precursor of Chloral Hydrate

运用超滤分离技术将水合三氯乙醛前体物含量最高的夏季水样中溶解性有机物分为四个部分,采用三维激发-发射矩阵荧光光谱对不同分子量有机物组分进行表征,并对20种氨基酸、牛血清白蛋白等模式化合物进行氯化试验,以找出水合三氯乙醛的主要前体物成分。结果表明MW<1 k Da的水合三氯乙醛生成势含量最高,为24.81μg/L,其次为10 k Da<MW<0.45μm(17.49μg/L)、3 k Da<MW<10 k Da(8.16μg/L)和1 k Da<MW<3 k Da(5.50μg/L),其中MW<1 k Da和10 k Da<MW<0.45μm两部分有机物占水合三氯乙醛前体物含量的75.55%。三维激发-发射矩阵荧光光谱结果表明水合三氯乙醛的主要前体物可能为类芳香性蛋白质和类微生物代谢产物等物质而非类富里酸和类腐殖酸。丙氨酸、天冬酰胺、天冬氨酸、半胱氨酸、组氨酸、苏氨酸、色氨酸、酪氨酸、牛血清白蛋白、鲱鱼精DNA等模式化合物是水合三氯乙醛主要前体物,其水合三氯乙醛生成量均大于30μg/mg C。

Dissolved organic matter （DOM ） from the representative summer sample with the highest chloral hydrate formation potential （CHFP）was fractionated by a series of ultrafiltration membranes into four groups based on molecular weight （MW）. Three-dimensional excitation and emission matrix （3D-EEM）fluorescence spectroscopy was employed to characterize different MW fractions. Ultimately,CH yields of model compounds including 20 amino acids （AAs）,bovine serum albumin （BSA）,etc. during chlorination were investigated,aiming to screen main CH precursors. The results indicate that the highest CHFP occurs in MW〈1 kDa fraction, with the value of 24. 81 μg/L,and the next are 10 kDa〈MW〈0. 45 μm （17. 49 μg/L）,1 kDa〈MW〈3 kDa （8. 16 μg/L）and 3 kDa〈MW〈10 kDa （5. 50 μg/L）fractions in sequence,in which the sum of MW〈1 kDa and 10 kDa〈MW〈0. 45 μm fractions accounts for 75. 55% of total CHFP. The characterization of different MW fractions by 3D-EEM fluorescence spectroscopy manifests that the primary CH precursors can be aromatic protein-like and soluble microbial by-product-like substances rather than fulvic acid-like and humic acid-like substances. Alanine,asparagine,aspartic acid,cysteine,histidine,threonine,tryptophan,tyrosine,BSA, herring sperm DNA,CH yields of which are higher than 30 μg/mg C,are the main precursors of CH.