A MODULATED LAMP SYSTEM FOR SOLAR UV‐B (280‐320 nm). SUPPLEMENTATION STUDIES IN THE FIELD

Abstract

Precise control and modulation of fluorescent sunlamps are necessary for ecologically valid simulation of solar UV‐B (280‐320 nm) radiation enhancement which would correspond to ozone reduction. A control system is described which allows lamp emittance to be modulated over a large dynamic range (50:1), permits stable lamp operation and starting at low temperatures, and provides a sensitive feedback loop to compensate for both atmospheric conditions, such as cloud cover, as well as changes in radiant emittance from the lamps resulting from factors such as temperature and lamp age.

The effect of u.v.‐B radiation on u.v.‐absorbing secondary metabolites in birch seedlings grown under simulated forest soil conditions

“…Filters were replaced regularly after 60 h. The seedlings exposed to u.v.-treatment received 5-5-6-0 kJ m~^ d"^ of additional biologically effective u.v.-B radiation as measured by a Macam SR9910 spectroradiometer (Macam Photometries Ltd. Livingston, UK). This was equivalent to an action of 1 at 300 nm, according to the 'generalized plant damage spectrum' of Caldwell et al (1983). This represents an equivalent of the dose that would be received under conditions of 25 % ozone depletion under a clear sky on a summer solstice day in Finland.…”

Variation of the enhanced biologically damaging solar UV due to clouds

“…A function that is available in the literature for each of the action spectra for generalized plant damage, 18 plant damage 12 and DNA damage 19 has been employed to calculate these action spectra. For the other action spectra, linear interpolation between the data points available in the literature has been employed.…”

An automatically operated system for simulating global change temperature and ultraviolet B radiation increases: application to the study of aquatic ecosystem responses in mesocosm experiments

“…Their system modulated lamp intensities between five UVB levels to study the effects of UVBR on marine planktonic organisms. Plant ecophysiologists have developed closed loop regulation systems to control UV lamps (Caldwell et al 1983;McLeod 1997) in order to obtain a constant elevation of natural incident UVBR that reproduces irradiance fluctuations closely. We developed an intermediate setup adapting the systems described by plant ecophysiologists to marine in situ constraints.…”

“…Two methodologies can be applied: supplementing a fixed irradiance value or supplementing a fixed percentage of ambient irradiance (Belzile et al 2006). This last methodology, originally developed by plant ecophysiologists (Caldwell et al 1983), is a more relevant method for simulating the predicted UVBR increases (Diaz et al 2003(Diaz et al , 2006.…”