Measurement of attenuation coefficients in natural water columns

Light scattering and light absorption by particulates and humic substances in natural waters can significantly affect the photoreaction rates of chemicals in aquatic systems. These scattering and absorption processes are quantitatively described by the use of an empirical parameter, the diffuse attenuation coefficient, K. We have tested actinometric and radiometric methods for measuring the diffuse attenuation coefficient K which can be used to calculate the depth averaged rate constant ( k pavg ) in a specific water body. The two methods were found to give excellent agreement. We found the method using a chemical actinometer system to be the most practical and convenient for use in field studies, but that more studies in other water systems and with other test cheimcals are needed to more rigorously test the method. We calculated k pavg equal to 0.33 ±0.17d −1 for carbazole in a 1‐m test pond.