Determining optical absorption of colored dissolved organic matter in seawater with a liquid capillary waveguide
Determining optical absorption of colored dissolved organic matter in seawater with a liquid capillary waveguide
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DOI：
10.4319/lo.1999.44.4.1142
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发表时间：
1999-06-01
影响因子：
4.5
通讯作者：
Phinney, D
中科院分区：
文献类型：
--
作者：
D'Sa, EJ;Steward, RG;Phinney, D
用长光程毛细管波导测量了来自不同海洋和沿海沃茨的0.2 μ m过滤海水样品的光吸收光谱，并与三种不同的实验室波长计的结果进行了比较。0.5米长550 μ m（内径）的水波导仅使用120 μ l过滤海水。使其便于在流通池中使用或当样品体积受限时使用。光源光通过全内反射在毛细管波导内传播，因为波导壁相对于水性芯的折射率较低。有色溶解有机物（CDOM）在355 nm处的吸收系数和S，对数线性化的CDOM吸收光谱的斜率，测定所有样品。毛细管波导测量的CDOM的吸收光谱紧密匹配的CDOM浓度变化超过一个数量级，由光谱仪测量。用毛细管波导获得的吸收光谱与用标准波长计获得的吸收光谱之间的偏差随着总吸收的降低和波长的增加而增加，这大概是因为在毛细管波导中观察到的基线偏移更大。偏移是由于海水样品和淡水参考之间的折射率差异造成的。在适当的参考下，毛细管波导将非常适用于连续监测表层海水CDOM吸收。
Optical absorption spectra of 0.2-mu m filtered seawater samples originating from diverse oceanic and coastal waters were measured with a long pathlength capillary waveguide; results were compared with those of three different laboratory spectrophotometers. The 0.5-m-long 550-mu m (inside diameter) aqueous waveguide uses only 120 mu l of filtered seawater. making it convenient for use in flow-through cells or when sample volumes are restricted. Source light propagates inside the capillary waveguide by total internal reflection because of the lower refractive index of the waveguide walls with respect to the aqueous core. The absorption coefficient of colored dissolved organic matter (CDOM) at 355 nm and S, the slope of the log-linearized CDOM absorption spectra, were determined for all samples. The CDOM absorption spectra measured by the capillary waveguide closely matched that measured by spectrophotometers for CDOM concentrations varying over an order of magnitude. The deviations between the absorption spectra obtained with the capillary waveguide and those obtained with the standard spectrophotometers increased with decreasing total absorption and with increase in wavelength, presumably because of the greater baseline offsets observed in the capillary waveguide. The offsets are due to differences in refractive indices between the seawater samples and the freshwater reference. With a suitable reference, the capillary waveguide will be very useful for monitoring surface seawater CDOM absorption semicontinuously.