Total absorption spectra

At any wavelength, the aquatic medium has a total absorption coefficient, which is the sum of the absorption coefficients of all the light-absorbing components, at that wavelength. The variation of this total absorption coefficient with wavelength is the absorption spectrum of the medium as a whole. For any given water body, the total absorption coefficient at each wavelength is obtained by adding together the known

Fig. 3.12 Total absorption spectra of various natural waters in southeastern Australia (Kirk, 1981a and unpublished data). (a) Lake George, NSW. (b) Lake Burley Griffin, ACT. (c) Burrinjuck Dam, NSW. (d) Lake King, Victoria. (e) Jervis Bay, NSW. Waters a, b and c are inland, d is estuarine, e is marine (Tasman Sea). Chlorophyll and turbidity data for waters a-d are given in the legends to Figs. 3.6 and 3.8. The Jervis Bay water (e) contained 0.2mg phytoplankton chlorophyll a m~3 and was optically intermediate between Jerlov oceanic water types I and III.

Fig. 3.12 Total absorption spectra of various natural waters in southeastern Australia (Kirk, 1981a and unpublished data). (a) Lake George, NSW. (b) Lake Burley Griffin, ACT. (c) Burrinjuck Dam, NSW. (d) Lake King, Victoria. (e) Jervis Bay, NSW. Waters a, b and c are inland, d is estuarine, e is marine (Tasman Sea). Chlorophyll and turbidity data for waters a-d are given in the legends to Figs. 3.6 and 3.8. The Jervis Bay water (e) contained 0.2mg phytoplankton chlorophyll a m~3 and was optically intermediate between Jerlov oceanic water types I and III.

absorption coefficient of pure water at that wavelength and the absorption coefficients due to dissolved and particulate colour, determined as described above. Figure 3.12 shows the total absorption spectra of five Australian waters, three inland, one estuarine and one marine. To give an approximate indication of how the total absorption spectrum might be made up, Fig. 3.13 shows, for an idealized, rather productive, ocean water, the individual absorption spectra of dissolved colour (gilvin), phytoplankton and detritus at plausible levels, and of water itself, together with the total absorption spectrum of the water due to all four components together.

Wavelength (nm)

Fig. 3.13 Total absorption spectrum of an idealized, productive (1mg chlorophyll a m~3) oceanic water, together with spectra of the individual absorbing components.

Wavelength (nm)

Fig. 3.13 Total absorption spectrum of an idealized, productive (1mg chlorophyll a m~3) oceanic water, together with spectra of the individual absorbing components.

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