水体中溶解有机物的荧光光谱特性分析

Analysis the Spectral Characteristics of Dissolved Organic Matter in Water by Laser Induced Fluorescence

以355 nm激光为激发光源,在实验室中利用激光诱导荧光(LIF)方法对不同水体中溶解有机物(DOM)的荧光光谱进行了测量,并以最小二乘法-高斯拟合对水体荧光光谱进行了拟合,解卷积得出了水喇曼散射谱及DOM的荧光光谱.在改变激发光脉冲强度的条件下,以一定浓度腐殖酸溶液为测量样品分析了DOM的荧光饱和特性.结果表明,随着激发光功率密度的增加,水喇曼散射强度线性增加,而DOM的荧光强度随着激发光功率密度的增加先是线性增加,此时归一化荧光强度为一恒定值.当激发光功率密度大于55 mW/cm2时,荧光强度增加缓慢,归一化荧光强度则逐渐降低.研究发现,在有机物浓度较高时,出现了激发态分子间的单重态-单重态猝灭,并且在低浓度情况下,随着有机物浓度的增加,出现了有机物荧光峰值强度位置的红移并伴有波形的展宽.

In the experiment it was used as an excitation at 355 nm from a third harmonic Q-switched Nd ： YAG laser. The fluorescence spectrum of dissolved organic matter （DOM） in several type water samples in combination with laser induced fluorescence （LIF） measurements were measured in laboratory. The spectrum of water Raman scattering and fluorescence of DOM were separated from total luminescence spectroscopy of water with Gaussian fit of the least squares method,and a very high correlation coefficient excelled 0. 992 5 was obtained. The characteristics of fluorescence saturation of humic acid at 1 mg/L concentration were analyzed through change laser pulse power. The results show that the fluorescence intensity arrives maximum at 55 mW/cm^2 with rising laser pulse energy,the fluorescence intensity rapidly decrease and the stability of fluorescence intensity becomes to worse following the intensity of laser pulse energy farther increasing. The phenomenon of quenching of excited singlet states molecular at high concentrations has been found, and a gradual ＇red＇ shift of peak position of DOM appeared as well as a broadening of emission spectral band-shape at linear excitation condition with rising DOM concentrations.