Light absorption, organic matter

Natural substances (dissolved organic matter, DOM) also contribute to light absorption, and a, is used to account for light attenuation by DOM in natural water. Total light absorption in a natural water follows the relation in Equation (5) ... 

Vostokov SV, Lisitsyn BE, Konovalov BV, Soloviev DM, Gagarin VI (2002) Mesoscale variability of chlorophyll a concentration, particulate organic matter content and spectral index of light absorption by phytoplankton in the upper layer of northeastern part of the Black Sea. In Zatsepin AG, Flint MV (eds) Multi-disciplinary investigations of the northeastern part of the Black Sea. Nauka, Moscow, p 235 (in Russian)... 

Various review articles [1-14] and textbook chapters [15,16] have dealt with the description and assessment of both direct and indirect phototransformations in the aquatic environment in the last 25 years. A major aspect of these studies was identification of the various reactive transients that are formed in sunlit natural waters, and to estimate or calculate their concentrations and their second-order reaction rate constants with contaminants in order to assess indirect phototransformation rates under environmental conditions. In this study, we maintain this reactive transient approach, outlining the main pathways of formation after absorption of light by natural organic matter. We also present a survey of studies addressing organic-matter-induced phototransformations of organic contaminants conducted during the last decade. This survey shows the importance of indirect phototransformations in the aquatic environment and illustrates how the transients responsible for such reactions may be identified. 

It is likely that most if not all of the observed binding of copper to organic matter results from complexation to fulvic or humic acids. Newport River water has a pronounced yellowish-brown color and shows continuously increasing light absorption with decreasing wave length (13) consistent with the presence of... 

Harmful substances may be present in water in either undissolved or dissolved form. Some organic compounds in water can absorb the UV light in a wavelength range of 254-280 nm. Just as turbidity detection is used to measure the total solids content, UV absorption detection at a wavelength of 254 nm can be employed to measure the total content of dissolved organic matter. The typical absorbance values at 254 nm for some important types of waters are listed in Table 1. 

Scheme 1. Conceptual model for direct and indirect photoreactions in heterogeneous systems. Symbols P represents the photoreactive halocarbon in solution, R-P represents halocarbon sorbed in reactive components of the sorbent, and U-P represents the halocarbon sorbed in unreactive components of the sorbent. Sorbents are sediments, natural organic matter, or biota. The types of reaction are direct with light absorption by P and indirect with light absorption...

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