Characterization of the Immersion Factor for a Series of In-Water Optical Radiometers

Photochem & Photobiology

2007

Solar ultraviolet radiation (UV) is known to have a significant effect upon the marine ecosystem. This has been documented by many previous studies using a variety of measurement methods in aquatic environments such as oceans, streams and lakes. Evidence gathered from these investigations has shown that UVB radiation (280–320 nm) can negatively affect numerous aquatic life forms, while UVA radiation (320–400 nm) can both damage and possibly even repair certain types of underwater life. Chemical dosimeters such as polysulphone have been tested to record underwater UV exposures and in turn quantify the relationship between water column depth and dissolved organic carbon levels to the distribution of biologically damaging UV underwater. However, these studies have only been able to intercept UV exposures over relatively short time intervals. This paper reports on the evaluation of a high exposure UV dosimeter for underwater use. The UV dosimeter was fabricated from poly 2,6‐dimethyl‐1,4‐phenylene oxide (PPO) film. This paper presents the dose response, cosine response, exposure additivity and watermarking effect relating to the PPO dosimeter as measured in a controlled underwater environment and will also detail the overnight dark reaction and UVA and visible radiation response of the PPO dosimeter, which can be used for error correction to improve the reliability of the UV data measured by the PPO dosimeters. These results show that this dosimeter has the potential for long‐term underwater UV exposure measurements.

Section: Methodsmentioning

confidence: 99%

Evaluation of a High Exposure Solar UV Dosimeter for Underwater Use

Photochem & Photobiology

2007

“…This is due to the discrepancies between the refractive indices for air and water at the collector interface. The methodology employed to calculate immersion factors for optical instrumentation has been detailed in previous studies [24,25,26] with the actual immersion factors for the EPP2000 spectrometer provided in [22].…”

Section: Ppo Dosimeter Calibration and Immersion Effect Correctionsmentioning

confidence: 99%

Applicability of the polyphenylene oxide film dosimeter to high UV exposures in aquatic environments

Journal of Photochemistry and Photobiology B: Biology

2009

Previous research has proven that the Poly (2,6-dimethyl-1, 4-phenylene oxide) (PPO) dosimeter is capable of receiving both in-air and underwater UV exposures that are significantly greater than those of the more commonly used polysulphone dosimeter, within a range of accuracy close to what would be expected of dosimetric measurements made in-air provided that the necessary calibrations are completed correctly by factoring in different atmospheric column ozone levels, SZA ranges, varying water turbidity and DOM levels. However, there is yet to be an investigation detailing the performance of the PPO dosimeter and its ability to measure UV in an actual field environment over an extended period of time. This research aims to bridge this gap in the knowledge by presenting a measurement campaign carried out in two real world aquatic environments and a simulated sea water environment using a batch of PPO dosimeters set at different depths and aligned to a range of different angles and geographical directions by means of attachment to a custom built dosimeter submersible float (DSF) unit over the space of a year at a sub-tropical location.Results obtained from this measurement campaign were used to compute a K d value for the sea water in each particular season. These K d values where found to be in close agreement to standalone K d values derived from results taken using a standard calibrated spectrometer in the same sea water.

“…This is due to the discrepancies between the refractive indices for air and water at the collector interface. The methodology employed to calculate these immersion factors was based upon the work of Zibordi [23], Hooker & Zibordi [24] and Zibordi et al [25].…”

Section: Immersion Effectmentioning

confidence: 99%

Field calibrations of a long-term UV dosimeter for aquatic UVB exposures

Journal of Photochemistry and Photobiology B: Biology

2008

Various methodologies using a wide range of measurement systems have been employed previously in order to determine the amount of UV that could be incident upon various aquatic organisms in a number of different aquatic locales. Broadband meters and spectroradiometers have been employed extensively to take underwater measurements. However, these measurement campaigns are limited by the fact that radiometric equipment requires a human controller, constant power supply and regular calibrations and corrections in order to function properly. Dosimetric measurements have also been made underwater using two distinct types of dosimeter.The first type based on a synthetic chemical, like polysulphone, and the second type based on a biological matter, such as a DNA sample. The studies made using biological dosimeters have displayed very good results, however the time and skill necessary to make these types of dosimeters can outweigh their usefulness. The chemical dosimeters are easier to make and have also provided useable data, but only for short periods of exposure, usually no more than a day. Previous research has shown that Poly (2,6-dimethyl-1, 4-phenylene oxide) (PPO) has excellent potential for use as a long -term underwater solar UVB dosimeter. However, there is no documented methodology on how to properly calibrate the PPO dosimeter for waterbased measurements and it has yet to be trialled in an outdoors marine environment, either real or simulated. This manuscript shows that calibrations obtained in air can not be transferred to calibrations made in water, calibrations made in one type of water can be employed for another type of water, but only within a certain range of spectral transmission and calibrations made at different depths in the same water type are interchangeable. It was also discovered that changing solar zenith angle had an effect upon calibration data. This research addressed these issues by formulating and 2 developing a calibration methodology required for accurate underwater long -term UVB measurements in the field using the PPO film dosimeter.3