INVESTIGADORES
ZAGARESE Horacio Ernesto
artículos
Título:
Calculation of spectral weighting functions for the solar photobleaching of chromophoric dissolved organic matter in temperate lakes
Autor/es:
CHRISTOFER OSBURN,; HORACIO ZAGARESE; DONALD MORRIS,; BRUCE HARGRAVES,; WALTER CRAVERO,
Revista:
LIMNOLOGY AND OCEANOGRAPHY
Referencias:
Año: 2001 vol. 46 p. 1455 - 1467
ISSN:
0024-3590
Resumen:
The effect of solar radiation on the dissolved absorption coefficient (aCDOM[l]), which reflects the concentrationof chromophoric dissolved organic matter (CDOM), was investigated in several lakes near Bariloche, Argentinaand in northeastern Pennsylvania, USA. Samples of 0.2 mm filtered lake water were exposed in quartz tubes todifferent portions of the solar spectrum using optical cutoff filters to remove parts of the ultraviolet (UV) region ofthe solar spectrum. Changes in the spectral absorption in these samples and the absorbed incident energy were usedto calculate spectral weighting functions (SWFs) for the photobleaching (PB) of CDOM. PB was measured as theloss of aCDOM(l) (the aCDOM[l] was averaged from 280 to 500 nm) per unit absorbed energy. CDOM from humicand clear lakes, as well as from a Sphagnum bog and an algal culture, was used in the experiments covering a widerange of carbon sources. We used an iterative, nonlinear optimization method to fit the measured results to a simpleexponential function in order to generate each SWF. Comparing individual SWFs calculated for various CDOMsources, we computed a summary SWF from the experiments using epilimnial CDOM from our study lakes. Oursummary SWF was able to explain 80–90% of the observed variance in our exposure experiments, and we wereable to predict PB results obtained for other Argentine lakes (mean error 14.5%). Finally, we calculated that theeffect of UV-B radiation on PB was small (,20% of total decrease in the absorption coefficient) compared to UVAand blue light radiation. This suggested that increased UV-B radiation due to stratospheric ozone depletion wouldnot greatly increase the photobleaching of whole water column CDOM in Patagonian lakes (,10%).