不同波段下黄海中二甲基硫光氧化动力学研究

采集黄海表层海水样品,在模拟太阳光照射条件下研究二甲基硫(DMS)在UVB(280、295和305nm)、UVA(320、345和395nm)和可见光(435和495nm)8个不同波段下的光化学氧化动力学行为,并探讨其对二甲亚砜(DMSO)生成的贡献率.研究结果表明,DMS光氧化过程均符合一级反应动力学方程,在UVB、UVA和可见光波段的光氧化速率常数分别为2.71~5.52、2.23~4.09和1.5~2.65d^-1.同一样品UVB波段下DMS的氧化速率明显大于UVA和可见光波段下的速率,且在280nm下最大.随着光照时间的增长,海水样品中DMS浓度与有色溶解有机物(CDOM)的光谱吸收系数(α(355))表现出明显的负相关性,表明CDOM吸光特性对DMS的光氧化过程有明显影响.此外,8个不同波段下DMS光氧化向DMSO的转化率在20.0%-31.9%范围之间,其中在280nm下达到最大值.

Photochemical kinetics of seawater dimethylsulfide in the Yellow Sea under different wavelengths

The surface seawater samples in the Yellow Sea were collected to study the photochemical oxidation behaviors of dimethylsulfide (DMS) under UVB (280, 295 and 305nm) UVA (320, 345 and 395nm) and visible lights (435 and 495nm) in simulated sunlight conditions. The production ratios of dimethylsulfoxide (DMSO) were also discussed. The results indicated that the photooxidation reaction of DMS exhibited first-order reaction kinetic behavior equation, and the rate constants under UVB, UVA and visible lights were 2.71~5.52, 2.23~4.09 and 1.55~2.65d^-1, respectively. In the same sample, the photooxidation rates of DMS under UVB were higher than those under UVA and visible lights, with the maximum rate at 280nm. The negative correlations were found between DMS concentrations and the spectral absorption coefficients (α(355)) of chromophoric dissolved organic matter (CDOM) under the 8 different wavelengths, suggesting that light absorption characteristics of CDOM might significantly affect the photochemical behaviors of DMS. In addition, the transfer ratios of DMS photooxidation into DMSO ranged from 20.0% to 31.9% under the 8 different wavelengths, with the maximum at 280nm.