The PMA2104 detector gives an accurate measurement of the biologically weighted ultraviolet radiation from sunlight, also called sunburning UV radiation (SUV). Its spectral response follows closely the erythema action spectrum [1]. Spectral response is given in Figure1.
The PMA2104 measures UVB penetration into fresh or salt water. Measurements taken with the PMA2104 are comparable to those made by submersible spectroradiometers. The damaging effects of UV-B in the marine environment has been shown for phytoplankton [2], algae, and fish [3].
The detector is waterproofed, and can be safely submerged up to 100 meters. The detector's housing is rugged and easy to handle in a harsh environment. Two #10-32 taped holes on the bottom of the detector housing allow for attachment of lowering cables or handles to the detector so its position can be established and maintained. The weight of the detector is sufficient for easy submersion.
The biologic effectiveness of the UV radiation can be measured in terms of effective irradiance in radiometric units, for example [µW/cm
2]. It is often related to the sensitivity of the human skin to sunburn and expressed in Minimal Erythemal Doses per Hour [MED/Hr]. One MED/Hr is the effective irradiance capable of causing minimum redness (erythema) in an average number 2 skin. Based on a study [4], the relationship between MED/Hr and radiometric units was determined to be:1 [MED/Hr] = 5.833 [µW/cm
2]The integrated effective dose can be expressed in [mJoules/cm
2] or MED. It takes 1/2 hour to accumulate 1 MED when the subject is exposed to an irradiance of 2 MED/Hr.Sea level solar radiation under 3mm total ozone column, clear sky:
overhead sun: approx. 0.32 W/m2 (5.5 MED/Hr)
30° SZA: approx. 0.25 W/m2 (4.3 MED/Hr)
60° SZA: approx. 0.05 W/m2 (0.9 MED/Hr)
