Underwater deployment of the polyphenylene oxide dosimeter combined with a neutral density filter to measure long-term solar UVB exposures

Numerous studies have conclusively shown how solar ultraviolet radiation (UV) (290-400 nm) has a negative impact upon underwater ecosystems. As a consequence of this, UV must be accurately evaluated in aquatic locations by employing a non-invasive measurement technique in order to better understand the damage it causes on both a macro and micro scale and provide solutions on how to manage its impact over both short and long time scales. Specifically, the UVB (290-320 nm) has the highest potential for causing stress to marine organisms. This manuscript details the deployment of a cost-effective and easily useable UVB detection dosimeter based on polyphenylene oxide (PPO) combined with a neutral density filter (NDF) derived from polyethylene. A long-term calibration regime performed over an extensive solar zenith angle range (SZA) in summer at a semi-tropical location showed that the PPO dosimeter used in conjunction with a polyethylene NDF could measure UVB exposures underwater up to 125 h in daylight (11-12 days approximately) before reaching near total saturation, providing an exposure limit as much as seven times greater that what was previously achievable with PPO dosimeters deployed without an NDF and approximately 42 times larger than those measured previously with polysulphone dosimeters.