Assessment of the photosynthetically active incident radiation on outdoor photobioreactors using oxalic acid/uranyl sulfate chemical actinometer

A simple actinometric method was evaluated for measuring the photosynthetic ally active incident photon flux on outdoor photobioreactors. The method is based on uranyl sulfate catalyzed photodecomposition of oxalic acid in pre sence of light. The uranyl-oxalate chemical actinometer absorbs radiation o f wavelengths below 535 nm. In the present work, the photobioreactor wall m aterial did not transmit light energy of wavelengths below 350 nm and the e ffective absorptivity method was used to evaluate the photon flux between 3 50-535 nm. The standard solar spectrum of the American Society for Testing and Materials (ASTM) was employed for estimating the ratio between the phot osynthetically active radiation (400-700 nm) and the solar radiation in the 350-535 nm range. This ratio (2.21) was taken to be equal to the quotient between the photosynthetically active radiation (PAR) and the incident phot on flux on the photobioreactor's surface (for the solar radiation between 3 50-535 nm). PAR measurements with 4 pi spherical and 2 pi quantum sensors w ere used to validate the method.