光衰减系数与悬浮颗粒物浓度的关系

The Relationship Between Attenuation Coefficient and Concentration of Suspended Particles

海水中光合作用有效光强(PAR)的变化受多种因素影响,其中分布在海水中的悬浮颗粒物是造成PAR在水中衰减的重要因素之一,尤其是在风与潮混合作用较强的近海。已有的研究表明:PAR在水中是呈指数衰减的,并且在悬浮物颗粒物分布比较稳定时,光衰减系数k与悬浮物体积浓度线性相关。在生态模型中,往往需要利用k获得水下光强,而衰减系数k很难直接通过观测得到,因此本文目的就是建立衰减系数与悬浮颗粒物体积浓度的关系,后者可通过观测得到。经过对2个航次与2个定点观测数据的处理,得到了PAR衰减系数分别与所有粒径悬浮物颗粒物总体积浓度以及3种粒级(黏土、粉砂、细砂)悬浮物体积浓度之间的线性关系式,并且发现相对于细砂,较小粒径的黏土、粉砂的浓度能更好的表征PAR的衰减特性。

The optical properties of oceanic water are closely related to the evolution of the ecosystem, for example, the primary production level is largely controlled by the transparency of seawater. The distribu- tion of under-water light intensity （photosynthetically available radiation mostly） in the coastal sea is in- fluenced by many factors, which include not only the absorption and scattering of clear seawater and dis- solved matter, but also the attenuation caused by the suspended particles, especially in coastal sea where highly variable turbidity dominates. The previous researches have already showed that the light decays ex- ponentially with depth in water, and a linear relationship was found between attenuation coefficient （K） and volume concentration of suspended particles （Pk） while cumulative slope of suspended particles distri- bution is nearly constant （slope^3.0-＋-0. 3）. In some ecosystem models, K is needed to estimate the in- tensity of under-water light, but it cannot be observed directly. Then the main goal of the present paper is to determine the relationship between K and the volume concentration of suspended particles measured in situ. Regression analysis reveals that linear relationship exists between the attenuation coefficient （K） and total volume concentration of suspended particles （Pk）. Other relationships are also revealed between at- tenuation coefficient （K） and the volume concentrations of 3 kinds of suspended particles classified with the diameter. It＇s concluded that the suspended particles with small size play more role on the attenuation of PAR.