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Abstract

  1. Top of page
  2. Abstract
  3. Introduction
  4. Materials and Methods
  5. Results and Discussion
  6. Conclusions
  7. Acknowledgements
  8. References

Ultraviolet (UV) reflection in the urban constructed environment is not well understood for topical issues such as measuring and modeling the received UV exposure due to that UV reflection for outdoor workers. Both predominantly specular and diffuse reflecting surface types have been identified and investigated for the erythemal UV reflection ratio variation due to solar zenith angle and orientation. This paper presents relationships between erythemal UV reflection ratios measured for non-horizontal and horizontal surfaces, with predominantly specular surface types indicating stronger relationships with solar zenith angles than diffuse reflecting surfaces types. Erythemal UV exposures caused by the same reflecting surface types at three inclinations are also investigated. Non-horizontal surfaces can increase erythemal UV exposures compared to erythemal UV exposures received from the same horizontal surface by factors of 1.07–1.46 for specific body sites and by 1.01–1.70 for averages of group body sites for zinc aluminium coated steel sheeting.


Introduction

  1. Top of page
  2. Abstract
  3. Introduction
  4. Materials and Methods
  5. Results and Discussion
  6. Conclusions
  7. Acknowledgements
  8. References

Outdoor workers within the construction environment have always been affected by potential hazards that the average indoor worker is exposed to only on occasion. Various studies have shown that most outdoor workers can be subjected to levels of ultraviolet (UV) radiation exposure greater than the recommended safe work guidelines [1-3] unless appropriate personal protection measures are employed [4]. It is common knowledge that UV radiation is both hazardous and beneficial to humans [5-8] and is therefore important to incorporate in any Occupational Health and Safety scheme [9, 10]. Documentation providing information pertaining to UV radiation reflection in a worker's environment, unfortunately, is generally restricted to advising workers to be aware of surroundings, including any reflective surfaces [9, 10]. Of this documentation neither includes quantitative information on the influence and effects these UV reflective surfaces have on outdoor workers, however [9] does list some natural surface reflection. UV reflection in the literature has previously been investigated as albedo[9, 11-19] with preliminary measurements provided on man-made surface UV reflection restricted to just a few studies [11-13, 15, 16, 18, 19]. Ocular studies show the importance of ground reflectance on ocular exposure [19-21] but do not pursue exposure measurements due to vertical surface reflection. Initial studies have been carried out on the reflective capacities of common outdoor workplace surfaces [22] and the effect vertical UV reflective surfaces have on workers' UV exposure [23]. In addition, the method in which UV radiation reflection is measured from urban surfaces including non-horizontal surfaces has been revised, in order for all surface orientation UV reflection to be comparable [24]. In this particular paper [13], the technique in which UV radiation reflection is measured in the urban environment has been revised, and recommends that the traditional method of measuring albedo (suitable for most natural surfaces) not be used for urban structures due to the highly directional and source dependent UV reflection that has been measured in both published [22, 24] and unpublished studies [25]. There is evidence to support the need for this method of UV reflection measurement even for natural surfaces [26] such as snow. This is due to the reason that many surfaces do not reflect diffusely, but as some combination of diffuse and specular reflection. Specular reflection is defined as the reflection of radiation at the surface boundary of the interface between two media of differing refractive indices. Specular reflectors are understood to follow Fresnel's law (and Snell's Law). Diffuse reflection is defined as the back scattered reflection (from molecules) of radiation that penetrates just beyond the interface of two media. Diffuse reflectors are understood to follow Lambert's law. In general, man-made surfaces are more likely to reflect in some combination of diffuse and specular. As this method is highly dependent on solar zenith angle (SZA), there is now a need to characterise this reflection according to both SZA and therefore season; so that this information can be applied practically in view of Occupational Health and Safety practices for outdoor and construction workers, and indeed, even the general population. Additionally, since urban structures are dominated almost equally by vertical and inclined surfaces as compared to horizontal surfaces, the directionality of the UV radiation reflection should also be characterized, for example: models that predict solar irradiances. If a surface is likely to be a dominantly specular reflector, there may be a predictable relationship between UV reflection from non-horizontal and horizontal surfaces. This paper aims to investigate variation of UV reflective capacity from surfaces that are horizontal and non-horizontal, and establish if relationships exist between them.

Materials and Methods

  1. Top of page
  2. Abstract
  3. Introduction
  4. Materials and Methods
  5. Results and Discussion
  6. Conclusions
  7. Acknowledgements
  8. References

Erythemal reflection irradiance ratio measurements

The erythemal reflection ratio was calculated as follows: spectral UV irradiances were measured with the sensor normal to the plane in question at a distance of 0.5 m, and spectral UV irradiances were measured with the sensor oriented normal to the solar position. This is a newly revised method to more accurately compare UV reflection from non-horizontal surfaces to horizontal surfaces [24] to account for specular reflection behaviour from man-made surfaces. For this study both spectral scans are weighted with the erythemal action spectrum [5], calibrated, then integrated before calculation of the ratio. The UV reflection measurements were carried out using a USB4000 Plug-and-Play Miniature fibre optic spectrometer (Ocean Optics, Inc.), from 300 to 400 nm in 0.2 nm steps. Below 300 nm the signal-to-noise ratio of the USB4000 does not allow a reasonable measure of the UV radiation received at the earth's surface from 290 to 300 nm (which consists of 0.01% of the total UV spectrum). Consequently the erythemal irradiance measurements from the USB4000 measure less than the expected erythemal UV irradiance (ca 27% of total erythemal UV irradiance). However, these data collected are intended as relative measurements and not empirical measurements, therefore the ratio of the incident and reflected erythemal irradiance measurements will have a similar approximate ratio to a measurement that does include the 290 to 300 nm range. The USB 4000 spectrometer was calibrated to a spectroradiometer (model DTM 300; Bentham Instruments, Reading, UK) located at the University of Southern Queensland (Toowoomba, Australia) with calibration traceable to the National Physical Laboratory, UK. This instrument is permanently mounted outdoors in a temperature stabilised, environmentally sealed box. The USB4000 calibration was on a clear day over the solar zenith angle range of 26° to 65° and the azimuth angle range of 73.6° to 286.5°. Multiple measurements made by both the USB4000 and Bentham over the SZA range specified taken at the same times, were compared and a variation factor between both instruments was calculated per increment step.

Two surface types were investigated, zinc aluminium coated trapezoidal shaped steel sheeting, and pale green paint coated trapezoidal shaped steel sheeting. The size of each sheet was 90 × 100 cm. Reflected irradiance measurements from each surface oriented at the horizontal, vertical and a 35° inclination were made in succession to allow correlation of the reflected irradiances at the similar solar zenith and azimuth angles. The sheets were oriented with the trapezoidal ridges aligned to geographic north. There were up to six measurements per orientation per hour, with each one followed by an irradiance measurement with the sensor normal to the position of the sun in the sky. Measurements were carried out over multiple days, years and seasons. A range of seasons were investigated to include a wide range of SZA data. Measurements for the zinc aluminium coated trapezoidal sheeting were taken on the following days during times of minimal cloud cover: 27 April 2009 (Autumn), 14 August (Winter) and 19 October 2010, 11 September 2011 (Spring) and 11 and 12 January 2012 (Summer). Ozone measurements ranged from 257 to 309 DU as provided by the U.S. National Aeronautics and Space Administration's Total Ozone Mapping Spectrometer [27]. The instantaneous erythemal reflection measurements were measured from surfaces as presented in Fig. 1, however, generally without the head forms present.

image

Figure 1. Equipment used to obtain comparative UV exposures for the inclined, horizontal and vertical surfaces.

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Erythemal UV exposure measurements

A series of simulated environments for workers were employed for working with or near inclined, horizontal and vertical UV reflective surfaces (Fig. 1) at the University of Southern Queensland (Toowoomba, Australia, 27.5°S, 151.9°E). Two surface types were explored, zinc aluminium coated trapezoidal shaped steel sheeting, and a pale green paint coated trapezoidal shaped steel sheeting. The zinc aluminium coated sheeting was investigated with the surfaces facing north in Autumn (3 and 4 March 2009 with ozone measured at 249 DU) and for an east and west orientation (changed from east facing to west facing at noon) in Autumn (17, 23 and 24 April 2009 with ozone measured at an average of 262 DU). The pale green coated sheeting was measured with the surfaces facing north on 28 and 29 April 2009 with ozone at 258 DU. Most days had minimal cloud cover for the majority of the time, with some sporadic cloud cover not exceeding 50% coverage (or 4 octa) of the sky. A life size manikin head form was aligned parallel to each surface at a distance of 50 cm and was employed in order to simulate a human near or on these surfaces. Attached to each head form were multiple polysulphone dosimeters for measurement of the erythemal exposures [25]. Dosimeters are a small easy to use device that responds to ultraviolet radiation exposure due to photochemical responses in polysulphone, changing the optical density and therefore absorbance properties of the material, which was measured using a spectrophotometer (UV-1601; Shimadzu & Co, Kyoto, Japan) with an error of ±0.004%. Each dosimeter is measured before and after exposure at 330 nm to obtain the relative change in optical density for each dosimeter. Polysulphone dosimeters have a variation in the dose response calculation of ca 10% for changes in absorbance up to 0.3 [28]. Dosimeters in this study did not exceed 0.3 absorbance, therefore for all relative UV exposure measurements ratios, each dosimeter had an error of 10%. The resulting error of the absorbance's measured per head form or per position which provide the erythemal UV exposure ratio is 20%.

Polysulphone dosimetry is an acceptable method to evaluate erythemal UV exposure, due to the spectral response that approximates the erythemal action spectrum [5, 29] provided that there is an appropriate calibration under the same atmospheric conditions [30]. There can be issues with dosimeters used on non-horizontal planes [31] however as the dosimeters are being used comparatively per position this is not considered critical. The dosimeters were calibrated to the scanning spectroradiometer described in the previous section located on a building rooftop nearby which records the global UV spectral irradiance every 10 min from 280 to 400 nm in 0.5 nm steps.

The dosimeters were placed in 13 positions on each head form, including top of the head, forehead, nose, chin, chest, cheeks, ears, shoulders, back of head and back of neck (Fig. 2). Dosimeters were replaced on the head forms every hour from 8 A.M. to 3 P.M. or 4 P.M. to obtain temporal variation in erythemal UV exposure during the day, with dosimeter calibrations carried out for each hour of exposure. Measurements were taken over multiple days due to the extra time required to set up and replace dosimeters for the temporal data.

image

Figure 2. Dosimeter positions on a head form for the measurement of the erythemal UV exposures.

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Results and Discussion

  1. Top of page
  2. Abstract
  3. Introduction
  4. Materials and Methods
  5. Results and Discussion
  6. Conclusions
  7. Acknowledgements
  8. References

Erythemal reflection irradiance ratio measurements

All the erythemal UV reflection ratios of irradiance data were categorised according to ten degree SZA intervals and the general spread of the data for the zinc aluminium sheet is presented in Fig. 3. The error bars are the standard deviation of the data in the respective SZA interval. This figure shows that the erythemal reflection ratio from this surface type from the vertical plane is dependent on SZA with increasing erythemal reflection correlated with increasing SZA. The best fits to these data were found with quadratic (R2 of 0.97) and exponential (R2 of 0.95) relationships with for Fig. 1 (vertical surface only) and R2 of 0.55 for all erythemal weighted reflection data values from a north facing vertical surface for zinc aluminium coated steel for a quadratic relationship [25]. R2 is the coefficient of determination and represents the percentage variance of the y-axis that is explained by the variation in the x-axis. It is interesting to note that while erythemal reflection from a horizontal surface has the appearance of a cubic relationship with SZA, this relationship is not supported and has an extremely low R2 (less than 0.3). The erythemal reflection from the inclined surface is similar to that from the horizontal surface with low correlation with SZA. Despite the low correlation of a predictable relationship with SZA, both the horizontal and vertical instantaneous erythemal reflection ratios show variation with SZA, which still indicates a predominantly specular reflecting surface due to the strongly dependent vertical reflection. A predominantly diffuse reflecting surface should show little to no correlation of reflection ratio with SZA or angle of incidence for any plane in question, which is clearly not demonstrated in Fig. 3.

image

Figure 3. Instantaneous erythemal UV reflection ratio for vertical, horizontal and inclined zinc aluminium coated trapezoidal steel according to solar zenith angle.

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With the 90° difference in angle of orientation between the horizontal and vertical surfaces, it was expected to find that a comparison between the two surface reflection ratios would have reciprocal reflection relationship with SZA, where high SZA values will result in erythemal reflection ratios from the vertical surface that might be observed from the horizontal surface at low SZA values. However, this does not appear to be the case as shown in Fig. 4a where the vertical instantaneous erythemal reflection ratio is plotted against the horizontal instantaneous erythemal reflection ratio for zinc aluminium trapezoidal sheeting. The erythemal reflection ratios are correlated according to measurement time and day. Analysis of the time and day grouping, shows that low SZA is mostly grouped in the lower left hand corner (white diamonds), mid-range SZA (light grey diamonds) is grouped mostly in the centre of the plot, and high SZA (dark grey diamonds) in the higher right hand corner. This does not suggest a reciprocal relationship at all, rather indicating that at higher SZA, both horizontal and vertical instantaneous erythemal reflection will be higher. Despite the lack of a reciprocal relationship, we do see a variable relationship, whereby at low SZA, the horizontal erythemal reflection ratio exceeds the vertical, and at large SZA, vice versa. The resulting linear relationship is modelled as y = 1.142− 0.141. It is interesting to note that for the pale green (paint coated) trapezoidal surface (Fig. 4b), there is almost erythemal reflection ratio parity at all SZA with a relationship of y = 1.0713x. This would be a strong indicator that the paint coated surface tends to reflect more diffusely than specularly compared to the zinc aluminium coated trapezoidal surface with less specific grouping in reflective capacity at various SZA.

image

Figure 4. (a) Instantaneous erythemal UV reflection ratio from a vertical plane relative to a horizontal plane, for zinc aluminium coated trapezoidal sheeting, according to solar zenith angle. White diamonds: 0–29°SZA, light grey diamonds: 30–49°SZA, dark grey diamonds: 50–70°SZA. (b) Instantaneous erythemal UV reflection ratio from a vertical plane relative to a horizontal plane, for pale green coated trapezoidal sheeting, according to solar zenith angle. White squares: 20–29°SZA, light grey squares: 30–49° SZA, dark grey squares: 50–70° SZA.

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In Fig. 5a the inclined instantaneous erythemal reflection ratio is plotted against the horizontal. Interestingly, the zinc aluminium coated surface also has a stronger linear relationship (as compared to the vertical versus horizontal), however with a 12.5% higher erythemal reflection ratio for the inclined surface to the horizontal surface as indicated by the line of best fit. The grouping of the SZA data indicates however there is less of a defined relationship than that observed with the vertical versus horizontal (Fig. 4a) with low, medium and high SZA overlapping significantly. In Fig. 5b there is a similar relationship for the pale green trapezoidal surface as compared to vertical versus horizontal (Fig. 4b) with a much stronger linear correlation, and the reflection ratios not strongly grouped by SZA. The inclined surface is positioned at a 35° angle each time and the strengthened relationship between the inclined and horizontal surfaces is likely due to this surface being closer to the perpendicular plane to the solar position. The angle of the inclined surface was chosen as it is a common elevation angle for roofs constructed in residential housing designs in Australia.

image

Figure 5. (a) Instantaneous erythemal UV reflection ratio from an inclined plane relative to a horizontal plane, for zinc aluminium coated trapezoidal sheeting, according to solar zenith angle. White diamonds: 0–29°SZA, light grey diamonds: 30–49° SZA, dark grey diamonds: 50–70° SZA. (b) Instantaneous erythemal UV reflection ratio from an inclined plane relative to a horizontal plane, for pale green coated trapezoidal sheeting, according to solar zenith angle. White squares: 20–29°SZA, light grey squares: 30–49° SZA, dark grey squares: 50–70° SZA.

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With the vertical to horizontal erythemal reflection ratios producing the largest variation observed, further investigation into the variation itself was conducted. Fig. 6 displays the variation between vertical to horizontal reflection ratios against SZA, and inclined to horizontal reflection ratios against SZA. Trend lines indicate that in variance between inclined and horizontal reflection ratios, inclined reflection ratios are generally higher than horizontal reflection ratios. For the variance between vertical reflection ratios and horizontal reflection ratios, it is apparent there is a cut-off SZA at which erythemal reflection ratios from vertical surfaces change from being less than horizontal erythemal reflection ratios to greater than horizontal erythemal reflection ratios. The plotted trend line provides an equation of y = 0.005x − 0.286, resulting in a cut off SZA of 55°. The significance of the cut-off SZA simply means that a vertical surface will reflect more due to position of the sun at large SZA. It also suggests that dominant specular reflection drives the variation between the erythemal reflection ratios of the vertical and horizontal surfaces. This is due to the angle of incidence and as pointed out by Heisler and Grant [14] the amount of reflection increases when approaching the near grazing incidence angles for certain surfaces and the basic geometrical difference between the surface orientations. However, it is unlikely that very large reflective ratio due to near grazing angles would be observed, since that would require very small SZA for vertical surface and a different sensor receiving position. At large SZA for a horizontal surface, it is also unlikely as atmospheric factors attenuate the UV irradiance.

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Figure 6. Difference between ratios of instantaneous erythemal reflection from vertical relative to horizontal (Δ) and inclined relative to horizontal (○) for north facing surfaces.

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Erythemal UV exposure measurements

Table 1 indicates the ratio of the UV exposures obtained on head form positions oriented with the axis through the centre of the form and the vertex parallel to each of the surface inclinations, as shown in Fig. 1. It can be observed in Fig. 1, that for the horizontal and inclined surfaces, the head form shades a portion of the reflective surface. This shaded area is less than one-third of the surface. The vertical surface rarely experienced shading, due to the SZA range investigated (maximum SZA observed was 70°). As a result it was expected that shading may adversely affect the UV exposure obtained at each site. However, a review of specific site positions and relative exposures given in Table 2 suggest otherwise. The three sites chosen are the forehead, the chin and the chest. For these three sites, the chin and the chest are most likely to have been shaded on all head forms. The chin, despite the likelihood of least shading occurring on the vertical head form (compared to horizontal and inclined in Fig. 2), actually receives the least amount of UV exposure. This suggests that the erythemal reflection from the zinc aluminium coated surface towards the horizontal head form was enough to exceed the erythemal UV reflection for the vertical head form and therefore received higher UV exposure. Whilst both head forms would have been exposed to ambient UV irradiance as well as reflected UV irradiance, it shows the reflection from the horizontal surface is still greater throughout the day. The dosimeter positioned on the chest also appears to experience this for part of the day around solar noon. However the vertical surface then appears to produce higher erythemal exposures on the head form at the larger SZA, with up to 40% higher exposures than the erythemal exposures received by the head form near the horizontal. This potentially could be due to the solar position reducing reflection from the horizontal surface with very large incident angles. There is quite a lot of fluctuation between the vertical and horizontal surface occurring for the erythemal exposure obtained at the forehead, however it is always higher for the vertical surface with a 23% increase compared to the horizontal. The effect of the inclined surface reflection compared to the horizontal surface reflection on erythemal exposures received on the head forms is extremely high, with sometimes twice as much exposure received on the forehead of the head form near the inclined surface. Overall, the inclined surface indicates an average of 38% more exposures received at the specific dosimeter sites near the reflective surface, as a result of the nearby reflective surface. Shading would have been similar for both head forms. Inclined surfaces have been previously shown to receive increased UV exposures compared to horizontal surface from incident UV irradiance [32-34]. The data presented here shows that for UV exposures dependent on reflected UV irradiance and not incident irradiance, the same is true.

Table 1. Comparison of the erythemal UV exposure ratios for head forms affected by horizontal, vertical and inclined UV reflective surfaces, categorised according to different dosimeter groupings
 8 A.M. to 9 A.M.9 A.M. to 10 A.M.10 A.M. to 11 A.M.11 A.M. to 12 P.M.12 P.M. to 1 P.M.1 P.M. to 2 P.M.2 P.M. to 3 P.M.3 P.M. to 4 P.M.Daily average
Zinc aluminium trapezoidal (north facing)
All features average
Inclined to horizontal1.241.311.271.501.301.131.201.28
Vertical to horizontal1.331.191.291.251.111.121.021.19
Face + chest + ears average
Inclined to horizontal1.361.391.501.691.461.131.291.40
Vertical to horizontal1.441.401.321.501.301.311.351.37
Facial features (only) average
Inclined to horizontal1.021.531.211.151.551.551.341.33
Vertical to horizontal1.191.170.731.000.871.031.111.01
Zinc aluminium trapezoidal (east and west facing)
All features average
Inclined to horizontal1.021.531.211.151.551.551.341.681.38
Vertical to horizontal1.191.331.111.141.251.511.651.641.35
Face + Chest + Ears average
Inclined to horizontal0.981.531.191.281.682.221.421.671.50
Vertical to horizontal1.161.421.221.721.522.272.391.871.70
Facial features (only) average
Inclined to horizontal1.031.581.130.921.712.161.391.731.46
Vertical to horizontal1.010.860.881.111.401.461.391.581.21
Pale green trapezoidal (north facing)
 All features average
Inclined to horizontal1.671.281.671.651.371.431.181.46
Vertical to horizontal2.131.342.052.101.921.781.561.84
Face + Chest + Ears average
Inclined to horizontal1.250.971.931.381.050.871.121.22
Vertical to horizontal2.091.242.061.631.391.401.601.63
 Facial features (only) average
Inclined to horizontal1.981.362.071.641.451.671.581.68
Vertical to horizontal2.681.822.371.872.142.572.632.30
Table 2. Comparison of the erythemal UV exposure ratios for head forms affected by horizontal, vertical and inclined UV reflective surfaces, for specific head form positions
 8 A.M. to 9 A.M.9 A.M. to 10 A.M.10 A.M. to 11 A.M.11 A.M. to 12 P.M.12 P.M. to 1 P.M.1 P.M. to 2 P.M.2 P.M. to 3 P.M.3 P.M. to 4 P.M.Daily average
Zinc aluminium trapezoidal (north facing)
Forehead
Inclined to horizontal1.171.292.032.001.630.991.121.46
Vertical to horizontal1.121.431.061.371.251.171.211.23
Chin
Inclined to horizontal1.421.201.701.551.350.991.151.34
Vertical to horizontal0.930.750.550.550.490.530.550.62
Chest
Inclined to horizontal1.181.361.541.431.31.251.341.34
Vertical to horizontal1.431.040.880.790.711.191.481.07

Looking at the average dosimeter values in Table 1, we see that the inclined to horizontal erythemal exposure ratio for the specific positions occurs similarly for both the north and east/west facing head form studies for the inclined to horizontal erythemal exposure ratio. The erythemal UV exposures received by a vertical surface compared to a horizontal surface range from 1.01 to 1.70 increases for all averaged (and different) site groupings. The erythemal UV exposures received by an inclined surface compared to a horizontal surface range from 1.28 to 1.50 increases for all averaged (and different) site groupings.

The erythemal UV reflection exposure measurements appear to be quite large considering the surrounding area is a grass surface, which has been shown in the literature to have a UV reflective ratio of up to 3.7% [11-16, 18, 19]. If the UV reflective surfaces used in this study were used in areas that contained higher surrounding and incidental UV reflective surfaces such as concrete, which ranges from 7% [14, 19] to 15.8% [16], it is likely that the UV exposures received could be increased further. The technique used here could also be easily used to assess other similar construction situations including tin smiths [3, 4]. The information reported here provides a preliminary report on the minimum effect of such vertical and non-horizontal inclined UV reflected surfaces that can be used to start anticipating changes in personal UV exposures obtained by construction workers despite the variability that is observed over time. It is anticipated that over further data collection, a range of reflection ratios for specific surface types will be compiled that can be used to estimate increases to personal UV exposure and should be disseminated to the public. This may encourage outdoor workers to take more control of their personal UV exposure. The effect of multiple UV reflective surfaces on personal exposure is also an important extension to this work, and will be considered in future studies on UV reflective surfaces and their impacts on UV exposures. Indeed, studies in which UV and even non-UV reflective factors are used to predict urban albedo with respect to the urban canyon rely on the assumption that all surfaces are perfect diffusers [35] which has been carried through from earlier studies [36, 37]. Future models for urban canyon and albedo modeling would need to consider adjusting this assumption given the results shown here in this study. Future studies in urban reflectance modeling may wish to analyse the variance of shortwave radiation reflection in order to improve their models.

Conclusions

  1. Top of page
  2. Abstract
  3. Introduction
  4. Materials and Methods
  5. Results and Discussion
  6. Conclusions
  7. Acknowledgements
  8. References

This paper has shown that the erythemal UV reflection ratios for vertical surfaces are SZA dependent for zinc aluminium coated metal sheeting, however there is much less predictability due to SZA for horizontal or inclined surfaces. Variation between the erythemal UV reflection ratios between non-horizontal and horizontal surfaces according to SZA indicates a potentially dominant specular reflecting surface for zinc aluminium trapezoidal sheeting. Lack of variation between the erythemal UV reflection ratios between non-horizontal and horizontal surfaces and low correlation with SZA indicates a dominantly diffuse reflecting surface for pale green trapezoidal sheeting. Knowledge of variation in reflection can be applied in other research and should be disseminated to the public and construction industry.

There is a relationship between instantaneous erythemal reflection ratios from non-horizontal surface to horizontal surfaces. If the reflective capacity of a horizontal surface type is known, it should be possible to predict the reflective capacity of a non-horizontal surface type given the reflective ratios are known. This study also indicates that erythemal UV reflective non-horizontal surfaces are able to increase the erythemal UV exposure received by a nearby person compared to a horizontal surface, with the average erythemal UV exposure ratio for both vertical and inclined surfaces compared to horizontal surfaces factors ranging from 1.07 to 1.46 for specific body sites and by 1.01–1.70 for averages of group body sites for zinc aluminium coated steel sheeting.

Acknowledgements

  1. Top of page
  2. Abstract
  3. Introduction
  4. Materials and Methods
  5. Results and Discussion
  6. Conclusions
  7. Acknowledgements
  8. References

This work has been supported by Oliver Kinder, Workshop Manager for Faculty of Sciences at the University of Southern Queensland, who created the structures to support the head forms and walls.

References

  1. Top of page
  2. Abstract
  3. Introduction
  4. Materials and Methods
  5. Results and Discussion
  6. Conclusions
  7. Acknowledgements
  8. References
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