An alternative approach to absorption measurements of aquatic particles retained on filters
An alternative approach to absorption measurements of aquatic particles retained on filters
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DOI：
10.4319/lo.1995.40.8.1358
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发表时间：
1995-12
影响因子：
4.5
通讯作者：
S. Tassan;G. Ferrari
中科院分区：
文献类型：
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作者：
S. Tassan;G. Ferrari
我们修改的程序用于吸收测量的水生颗粒保留在玻璃纤维过滤器，扩展程序的应用范围，以“情况2”沃茨与高悬浮泥沙含量，并允许浮游植物色素吸收的情况下，标准的溶剂提取方法是无效的测定。第一个结果是通过结合光透射和光反射测量（后者通过使用市售的双光束分光光度计的积分球附件成为可能），以消除样品后向散射引起的测量吸收的杂散贡献。第二个结果是通过用NaClO溶液漂白样品获得的，该方法即使对于水溶性色素（例如，藻胆素的重要类别）和耐溶剂的绿藻也被证明是令人满意的。该过程还允许颗粒悬浮液脱色，因此用于评价将过滤器保留样品吸光度转换为等效颗粒悬浮液值的经验表达式。这两个功能的修改程序已得到积极的测试，通过耐溶剂浮游植物物种和无机悬浮沉积物样品进行测量。对玻璃纤维过滤器中颗粒的光透射测量（Yentsch 1962）便于确定主要由天然浮游植物以及有机和无机碎屑组成的颗粒悬浮液的光吸收光谱（Gordon和Morel 1983）。该程序有两个基本的优点：颗粒可以集中，使仪器的准确性要求，可以满足无论发生在原位的高稀释，并提供信息的细胞在体内的吸收。数据分析中的主要问题是由于滤光片的多次散射导致光透射的大幅度改变，这导致高估了颗粒相对于悬浮状态的吸收（Butler 1962）。已经导出了几个经验表达式，用于将过滤器保留的颗粒（为了方便起见，在下文中也称为“样品”）的吸收转换为颗粒悬浮液的等效吸收。Cleveland和Weidemann（1993）对这一问题进行了综述。Kishino等人（1984年，1985年）提出了一种程序，根据甲醇提取色素前后的测量结果，区分浮游植物色素的吸收和碎屑的吸收。尽管对该方法的有效性仍存在一些疑问（Bricaud和Stramski，1990年），而且其有效性范围显示出一些局限性（对某些藻类物种影响很小或没有影响），但溶剂萃取法通常用于鉴定天然浮游植物种群中的色素吸收。目前的做法是尽量减少远期的损失，
We made modifications to the procedure used for absorption measurements of aquatic particles retained on glass-fiber filters that extend the procedure’s application range to “case 2” waters with high suspended sediment content and allow the determination of phytoplankton pigment absorption in situations where the standard solvent extraction method is not effective. The first result was achieved by combining light-transmission and light-reflection measurements (the latter made possible by the use of a commercially available integrating-sphere attachment for the dual-beam spectrophotometer) so as to remove the spurious contribution to the measured absorption caused by sample backscattering. The second result was obtained by bleaching the sample with a NaClO solution-a method that proved satisfactory even with water-soluble pigments (e.g. the important class of the phycobilins) and solvent-resistant Chlorophyceae. This process also allows for depigmentation of the particle suspension, and thus it was used to evaluate the empirical expression for converting the filter-retained sample absorbance to the equivalent particle suspension value. Both features of the modified procedure have been positively tested through measurements carried out on solvent-resistant phytoplankton species and on samples of inorganic suspended sediment. Light-transmission measurements on particles retained in glass-fiber filters (Yentsch 1962) are convenient for determining the light absorption spectrum of particle suspensions consisting mainly of natural phytoplankton and organic and inorganic detritus (Gordon and Morel 1983). The procedure has two basic advantages: particles can be concentrated so that instrumental accuracy requirements can be met regardless of the high dilution occurring in situ, and information is provided on the absorption of the cells in vivo. The main problem in data analysis arises from the large modification of light transmission due to multiple scattering by the filter, which results in an overestimate of particle absorption relative to suspension state (Butler 1962). Several empirical expressions have been derived for converting the absorption of filter-retained particles (for convenience also referred to as “sample” in the following) to the equivalent absorption of particle suspension. A review on this subject is given by Cleveland and Weidemann ( 199 3). Kishino et al. (1984, 1985) proposed a procedure for discriminating absorption by phytoplankton pigments from absorption by detritus based on measurements performed before and after pigment extraction by methanol. Although some doubts remain about the effectiveness of the procedure (Bricaud and Stramski 1990) and its validity range shows some limitations (little or no effect on some algal species), solvent extraction is the method generally used to identify pigment absorption in natural phytoplankton populations. It is current practice to minimize the loss of forward