Instituto Nacional de Investigación y Desarrollo Pesquero, (INIDEP), Argentina

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Signatura:10318.
Aut. Analit.: Kirk,-J.T.O.; Hargreaves,-B.R.; Morris,-D.P.; Coffin,-R.B.; David,-B.; Frederickson,-D.; Karentz,-D.; Lean,-D.R.S.; Lesser,-M.P.-et.-al.
Tít. Analit.: Measurements of UV-B radiation in two freshwater lakes: An instrument intercomparison.
Título: Impact of UV B Radiation on pelagic freshwater ecosystems.
Serie: Eegeb. Limnol. Adv. Limnol. 43. 71-99
P.imprenta: 1994. 71-99
Descriptores: radiometers-; ultraviolet-radiation; spectral-analysis; wave-length; light-attenuation; optical-classification; absorption-coefficient; vertical-profiles; bacteria-; USA,-Pennsylvania,-Giles-L.; USA,-Pennsylvania,-Lacawac-L.
Resumen: Instruments and biological dosimeters were used to measure solar spectral irradiance in two lakes, one clear and the other moderately coloured, with emphasis on the ozone-sensitive UV-B wavelengths. An atmospheric model provided an approximate standard against which were compared commercial instruments from Biospherical Instruments, Inc., International Light, Inc., LI-COR Inc., and Optronic Laboratories, Inc. Comparisons of irradiance in air, and irradiance and attenuation coefficients at several depths, revealed differences in spectral resolution, accuracy, sensitivity to low light energy, and convenience in generating depth-specific profiles. Broadband instruments trade off resolution for simplicity and, in some cases, greater sensitivity, but are subject to errors when the solar spectrum is modified by sun angle, atmospheric column ozone, and the inherent optical properties of the water. For UV-B measurement in lakes, an ideal instrument should have a narrow bandwidth, sensitive and temperature-stable light detector and wavelength filter/selector with high rejection of stray light, well-characterized cosine response and immersion coefficients in both air and water, and an integral sensor for precise measurement of depth. None of the instruments tested matched the ideal, but each had useful characteristics as well as limitations that in some cases could be minimized by coupling their use with an atmospheric model. Analysis of results from bacterial and phage dosimeters; using a new "biological attenuation coefficient", K*, yielded values corresponding to instrument-derived attenuation coefficients in the range of 320-340 nm, suggesting that UV-B and UV-A irradiance contributed to the damaging effects of sunlight. Aseveral-fold reduction in mortality by Mylar super( registered )-screening of dosimeters argues for a significant effect of UV-B light. Bacteria (DNA repair-defective) were consistently more susceptible to light than were phage under matched conditions.

     


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