Variability in photobleaching yields and their related impacts on optical conditions in subtropical lakes.
Changes in the concentration and spectral absorption of chromophoric dissolved organic matter (CDOM) may strongly condition the optical properties of tropical and subtropical water bodies. We examined the spatial distribution of CDOM-related absorption, spectral slope and vertical attenuation of solar radiation in two shallow lakes in the Esteros del Iberá wetland system. In situ measurements were made to examine spatial variations in photobleaching yields in natural lake conditions. The results showed that "fresh" allochthonous CDOM is more susceptible to phototransformations than either "aged" allochthonous organic matter or autochthonous sources, if the distances from sources are considered as proxies for residence time. Based on measured changes in absorption spectral slope in relation to solar ultraviolet irradiance, a model was developed which used CDOM as a non-conservative tracer of water masses. Spatial changes in CDOM absorption within the lake were then used to compare photo related transformations to those associated with conservative mixing.
Loiselle
Steven A
SA
Environmental Spectroscopy Lab, Dipt. Farmico Chimico Tecnologico, CSGI, University of Siena, via Aldo Moro 1, 53100 Siena, Italy. loiselle@unisi.it
Bracchini
Luca
L
Cózar
Andres
A
Dattilo
Arduino M
AM
Tognazzi
Antonio
A
Rossi
Claudio
C
D000042:Absorption; D017753:Ecosystem; D004784:Environmental Monitoring; D005618:Fresh Water; D009930:Organic Chemicals / Q000737:chemistry* / Q000528:radiation effects; D038761:Photobleaching; D010782:Photolysis; D012993:Solar Energy; D013472:Sunlight; D053833:Wetlands
D009930:Organic Chemicals