Investigation of unstabilized polyvinyl chloride (PVC) for use as a long-term UV dosimeter: preliminary results

A new chemical UV dosimeter with a larger dose-capacity than the existing chemical dosimeters has been investigated for long-term UV measurements. Unstabilized Polyvinyl chloride (PVC), cast in 40 μm thick film, has been found to respond to at least 745 SED (Standard Erythema Dose = 100 J/m2) of erythemal solar UV radiation. This is equivalent to about two to three summer weeks of exposure in subtropical sites. The UV-induced changes in the PVC dosimeter were quantified using a Fourier Transform Infrared (FTIR) spectrophotometer and the decrease in the absorption intensity of the 1064 cm-1 peak was employed to quantify these changes. Dose response curves have been established by relating the decrease in the PVC dosimeter's absorption intensity at 1064 cm-1 to the corresponding erythemal UV exposure. The spectral response of the dosimeter was measured and found to be comparable to the erythema action spectrum. Some other optical characteristics of the dosimeter, such as the dose-rate dependency and the angular response were analysed. The dosimeter was found to have the potential to measure long periods of exposure to solar UV radiation as well as exposures to artificial UV

Alternative methods for the reduction of evaporation: practical exercises for the science classroom

Across the world, freshwater is valued as the most critically important natural resource, as it is required to sustain the cycle of life. Evaporation is one of the primary environmental processes that can reduce the amount of quality water available for use in industrial, agricultural and household applications. The effect of evaporation becomes intensified especially during conditions of drought, particularly in traditionally arid and semi-arid regions, such as those seen in a number of countries over the past 10 years. In order to safeguard against the influence of droughts and to save water from being lost to the evaporative process, numerous water saving mechanisms have been developed and tested over the past century. Two of the most successful and widely used mechanisms have included floating hard covers and chemical film monolayers. This paper describes a laboratory based project developed for senior high school and first year university classes, which has been designed to introduce students to the concepts of evaporation, evaporation modelling and water loss mitigation. Specifically, these ideas are delivered by simulating the large-scale deployment of both monolayers and floating hard covers on a small water tank under numerous user defined atmospheric and hydrodynamic conditions, including varying surface wind speeds and underwater bubble plumes set to changing flow rates

Annual measurement of solar UVB at a reef site using a polyphenylene oxide dosimeter

Numerous investigations detailed over the last thirty years have highlighted how solar UV (290-400 nm) can have a detrimental effect on coral health. It has also been postulated that coral bleaching is caused by a synergistic process between high water temperatures and increases in UV. As a consequence of its influence upon coral ecosystems, UV radiation must be monitored in underwater locations using an appropriate 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 adequately manage its impact. The high energy UVB waveband (290-320 nm) is believed to have the greatest negative influence on coral stress. This report details the employment of a simple, easily deployable UVB measuring dosimeter system based on polyphenylene oxide (PPO) at a coral reef location near Hervey Bay (25°17 S, 152°52′ E) over the interval of one year. Continual deployment of the PPO dosimeters measured a clear inverse correlation between tide level and UVB penetration, with the highest coral UVB exposures measured during the months of winter and spring (coinciding with typically lower tidal conditions during this time). This suggests that the UVB incident on Queensland coral reefs may not be strictly dependent on solar zenith angle (the Sun’s position in the sky), which is generally the primary factor in determining the extent of terrestrial UVB exposures. Further, this may mean that photo-damage incident on corals could be exacerbated in traditionally cooler months if current global warming trends continue

Dosimeter based on 8-Methoxypsoralen for UVA exposures over extended periods

A miniaturized UVA dosimeter based on 8-methoxypsoralen (8-MOP) has been developed and characterized for the evaluation of UVA (320 - 400 nm) exposures over extended periods longer than one day. Current research indicates that UVA is a contributing factor in non-melanoma skin cancers and the associated financial cost of damage caused by UVA is significant. Dosimetry is a technique that is commonly employed to measure UV exposures to an object or subject. Miniaturized dosimeters using polyphenylene oxide (PPO) have previously been used to measure received erythemal UV (UVery) exposures. A new miniaturized dosimeter using 8-MOP as the photoactive material has been characterized and a technique developed for the calibration of UVA exposures. Using Mylar as a UVB filter the spectral response showed 8-MOP to react only to wavelengths between 320 - 400 nm. The measured cosine response has an error of less than 13.8% for angles between 0° and 60°. Seasonal dose response tests conducted, indicate that these UVA dosimeters are able to measure exposures < 4.6 kJ/m2. These results have shown that a dosimeter constructed from 8-MOP in conjunction with a Mylar filter can measure UVA exposures over extended periods longer than one day

Investigation of correlation of broadband UVA reflection to broadband visible reflection for a variety of surfaces in the built environment

UVA radiation (320-400 nm) exposure is linked to detrimental health effects, including DNA damage, eye damage and impacts on immune suppression. Occupational exposure to UVA radiation could increase the risk of developing such health effects, through increased exposure from reflective surfaces. A range of surfaces have been investigated for broadband (from spectral) UVA and visible reflectance, from horizontal, inclined and vertical orientations. A selection of this data has been presented graphically. Non-metallic and coated metallic surfaces were shown to have low UVA broadband reflectance (<0.20) compared to some metallic surfaces UVA broadband reflectance (0.1-0.5). Uncoated metallic surfaces can use UVA reflectance as a function of visible reflectance, however non-coated metallic surfaces have no similar function. The metallic surface type data were used to correlate UVA broadband reflectance to visible broadband reflectance and a model developed to express UVA broadband as a function of visible reflectance. The model for zinc aluminium coated steel is a linear regression, with UVA reflectance ranging from 0.09 to 0.46 and visible reflectance ranging from 0.05 to 0.57, with an R2 of 0.95. The reflective coefficients used to create the model were produced on a solar zenith angle (SZA) range of 18°- 70.5°. The model was tested on a different dataset with a SZA range of 5.7°- 62.9° on clear days and was shown to have reasonable results with an RMSE of 0.049 for prediction of UVA reflectance from visible reflectance allowing prediction of the UVA reflectance from the visible reflectance for this surface type

Long-term UV dosimeter based on polyvinyl chloride for plant damage effective UV exposure measurements

Research on the influence of ultraviolet radiation (UV) on terrestrial plants and on its link with other influencing environmental factors requires information on UV exposures, both for a horizontal plane and specific portions of a plant, above and under the canopy. In this research, one set of UV dosimeters based on unstabilized polyvinyl chloride (PVC) were employed to measure the unweighted UVB (UVB) and the biologically effective UV radiation for plant damage (UVBEplant) incident on the leaves of a plant for a month, without having to change the dosimeters. The exposures were compared to the cumulative exposure concurrently measured with six sets of unstabilized polyphenylene oxide (PPO) dosimeters that required changing every four to six days. The difference in exposures between the two types of dosimeters was on average within 11%. The PVC dosimeter is the first reported polymer film dosimeter with a useable range of a month for measuring the plant damaging UV and the UVB exposures to specific parts of a plant. The exposure period of a month for the PVC dosimeter is an extension by a factor of four over the useable range of dosimeters previously reported in the literature for evaluation of the exposure of plants to UV radiation

An Inexpensive High-Temporal Resolution Electronic Sun Journal for Monitoring Personal Day to Day Sun Exposure Patterns

Exposure to natural sunlight, specifically solar ultraviolet radiation contributes to lifetime risks of skin cancer, eye disease and diseases associated with vitamin D insufficiency. Improved knowledge of personal sun exposure patterns can inform public health policy; and help target high risk population groups. Subsequently, an extensive number of studies have been conducted to measure personal solar ultraviolet exposure in a variety of settings. Many of these studies however use digital or paper-based journals (self-reported volunteer recall), or employ cost prohibitive electronic ultraviolet dosimeters (that limit the size of sample populations), to estimate periods of exposure. A cost effective personal electronic sun journal built from readily available infrared photodiodes is presented in this research. The electronic sun journal can be used to complement traditional ultraviolet dosimeters that measure total biologically effective exposure by providing a time stamped sun exposure record. The electronic sun journal can be easily attached to clothing and data logged to personal devices (including fitness monitors or smartphones). The electronic sun journal improves upon self-reported exposure recording and is a cost effective high temporal resolution option for monitoring personal sun exposure behavior in large population studies

Measured UV Exposures of Ironman, Sprint and Olympic-Distance Triathlon Competitors

Triathletes present an extreme case of modelled behaviour in outdoor sport that favours enhanced exposure to solar ultraviolet radiation. This research presents personal solar ultraviolet exposures, measured using all-weather polysulphone film dosimeters, to triathletes during the distinct swimming, cycling and running stages of competitive Sprint, Olympic and Ironman events conducted within Australia and New Zealand. Measurements of exposure are made for each triathlon stage using film dosimeters fixed at a single site to the headwear of competing triathletes. Exposures are expressed relative to the local ambient and as absolute calibrated erythemally effective values across a total of eight triathlon courses (two Ironman, one half Ironman, one Olympic-distance, and four Sprint events). Competitor exposure results during training are also presented. Exposures range from between 0.2 to 6.8 SED/h (SED: standard erythema dose) depending upon the time of year, the local time of each event and cloud conditions. Cycle stage exposures can exceed 20 SED and represent the highest exposure fraction of any triathlon (average = 32%). The next highest stage exposure occurred during the swim (average = 28%), followed by the run (average = 26%). During an Ironman, personal competitor exposures exceed 30 SED, making triathlon a sporting discipline with potentially the highest personal ultraviolet exposure risk

Comparison of GOME-2 UVA satellite data to ground-based spectroradiometer measurements at a subtropical site

The ultraviolet A (UVA) (315–400 nm) daily exposures and maximum daily irradiances from the Global Ozone Monitoring Experiment (GOME)-2 satellite have been compared over three years to the corresponding data from a ground-based spectroradiometer for a subtropical Southern Hemisphere site. This is one of the first such comparisons for the GOME-2 UVA waveband in the Southern Hemisphere. For the UVA daily exposures and the maximum daily irradiances, the comparisons were undertaken for all sky conditions and for cloud-free conditions. Under cloud-free conditions the R 2 of the fit regression line for the comparisons was 0.93 for the exposures and the irradiances. The influence of cloud reduced the R 2 values to 0.86 and 0.70 for the daily exposures and maximum irradiances, respectively. The relative root-mean-square error (rRMSE), mean absolute bias error (MABE), and mean bias error (MBE) for the maximum daily UVA irradiances on the cloud-free days were 0.08, 6.59 ± 7.32%, and −1.04 ± 9.83%, respectively. Similarly, for the daily UVA exposures on the cloud-free days, the rRMSE, MABE, and MBE were 0.10, 5.19 ± 6.42%, and −0.79 ± 8.24%, respectively. For the all-sky conditions, the corresponding values were 0.20, 15.23 ± 14.90%, and −0.79 ± 8.24% for the maximum daily irradiances and 0.19, 14.17 ± 14.56%, and −4.63 ± 20.60% for the daily exposures. In all studies of the influence of UVA on human health, this can complement ground-based measurements that provide the higher temporal and spatial resolution available only at a limited number of surface monitoring sites

Solar blue light radiation enhancement during mid to low solar elevation periods under cloud affected skies

Solar blue-violet wavelengths (380 nm - 455 nm) are at the high energy end of the visible spectrum, referred to as ‘high energy visible’ (HEV). Both chronic and acute exposure to these wavelengths have been often highlighted as causes of concern with respect to ocular health. The sun is the source of HEV which reaches the Earth’s surface either directly or after scattering by the atmosphere and clouds. This research has investigated the effect of clouds on HEV for low solar elevation (solar zenith angles between 60° and 80°), simulating time periods when potential ocular exposure in global populations are high during the early morning and late afternoon. The enhancement of ‘bluing’ of the sky due to the influence of clouds was found to increase significantly with the amount of cloud. A method is presented for calculating HEV irradiance from the more commonly measured global solar radiation (300 – 3,000 nm) for all cases when clouds do and do not obscure the sun. The method, when applied to global solar radiation data correlates well with measured HEV within the solar zenith angle range 60° and 80° (R2 = 0.94, MBE = -1.63%, MABE = 10.3% and RMSE = 14.6%). The technique can be used to develop repeatable HEV hazard evaluations for human ocular health applications