颗粒吸收系数T-R法测定中光程放大系数的研究

A New Approach to Correct for Pathlength Amplification in Measurements of Particulate Spectral Absorption by the Quantitative Filter Technique

由颗粒散射作用引起的光程放大效应是影响水体中颗粒吸收系数测量准确性的关键因素.本文采用T-R测定方法(Transmittance-Reflectance method)和将比色皿置于积分球内的测定方法,测量6种样品的颗粒在滤膜上、悬浮液中的光学密度,计算光程放大系数β,利用传统拟合方法获得较为稳定的光程放大系数(β-1=0.507+0.636×ODf).测量结果同时表明,光程放大系数具有波长依存特性,呈现滞后效应;本文提出新的引入波长(λ)、滤膜上颗粒光学密度(ODf)2个参数的二元非线性拟合方法,得到β-1(λ)=(0.135+0.225×ODf(λ))×λ0.203,该方法实现了对光程放大效应更为精确的校正.

A new method is described that takes into account the hysteresis effect of pathlength amplification in measurements of particulate spectral absorption by the quantitative filter technique. Optical densities were measured on a variety of sample types,including phytoplankton cultures and pool waters. Optical densities of particles on glass-fiber filters ODI were obtained by using T-R （Transmittance-Reflectance） method and those of particles in suspension ODf were obtained by placing samples inside an integrating sphere. A univariate function for pathlength amplification factor β was thus derived, i. e. β^-1 = 0. 507 ＋ 0. 636 × ODf, which appeared consistently applicable to a variety of samples compared with previously published T method based formulae. However. the results also showed that β varied with wavelength, so called hysteresis effect. We therefore attempted to use a bivariate function of β, i. e. β^-1 （λ） = （0. 135 ＋0. 225 × ODf （λ） × λ^0.203. OD SMS predicted by the bivariate function fitted better with the measured OD SMS than that by the univariate function.