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The National Agricultural Library is one of four national libraries of the United States, with locations in Beltsville, Maryland and Washington, D.C. It houses one of the world's largest and most accessible agricultural information collections and serves as the nexus for a national network of state land-grant and U.S. Department of Agriculture field libraries. In fiscal year 2011 (Oct 2010 through Sept 2011) NAL delivered more than 100 million direct customer service transactions.

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Journal Article

Journal Article

Underwater ultraviolet radiation: development of spectral models for northern high latitude lakes  [1997]

Laurion, I.; Vincent, W.F.; Lean, D.R.S.;

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The penetration of solar ultraviolet radiation (UVR) and photosynthetically available radiation (PAR) was measured in a range of subarctic lakes in the forest-tundra zone of northern Quebec. The diffuse attenuation coefficients for PAR (KdPAR) were highly correlated (r2 = 0.78) with dissolved organic carbon (DOC) concentration and only weakly correlated with suspended particulate material as measured by chlorophyll a (r2 = 0.48) or beam transmittance (r2 = 0.29). Colored dissolved organic matter (CDOM) was also largely responsible for the between-lake differences in spectral attenuation of UVR. The diffuse attenuation coefficient for UVR (Kd) was a nonlinear function of wavelength (lambda) and was accurately described by the model Kd (lambda) = Kd440 exp(-S [lambda-440]). The slope coefficient S was relatively constant among lakes (mean = 0.0151 nm-1, CV = 7%), whereas Kd440 was a linear function of several CDOM-related variables and best estimated by CDOM fluorescence (r2 = 0.98). Numerical analysis of spectra for high (subarctic) and low (Arctic) DOC lakes showed that the evaluation of the model parameters Kd440 and S was insensitive to the bandpass characteristics (2-8 nm) of different underwater radiometers. The Kd (lambda) model was then used to develop a nondimensional index of relative spectral composition (RI) to characterize different water masses as a function of dissolved organic matter (DOC and CDOM fluorescence). Below about 4 mg DOC L-1 there
is a sharp nonlinear rise in this index with decreasing DOC. These results show that CDOM controls the spectral composition of underwater UVR in northern high-latitude lakes and that the UVR/PAR balance in many of these waters is sensitive to minor changes in CDOM content.
From the journal
Photochemistry and photobiology
ISSN : 0031-8655

Bibliographic information

Language:
English
Type:
Journal Article
In AGRIS since:
2013
Volume:
65
Issue:
1
Start Page:
107
End Page:
114
All titles:
"Underwater ultraviolet radiation: development of spectral models for northern high latitude lakes"@eng
Other:
"Includes references"
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Bibliographic information

Language:
English
Type:
Journal Article
In AGRIS since:
2013
Volume:
65
Issue:
1
Start Page:
107
End Page:
114
All titles:
"Underwater ultraviolet radiation: development of spectral models for northern high latitude lakes"@eng
Other:
"Includes references"