How much solar UV reflected from environment?

How much solar UV is reflected from objects in the environment? I know snow has very high UV reflectivity, and can be probematic for skiers and mountain climbers. But what about other common objects/materials, like:

-liquid water


-beach sand


-the sky

OK, the last one isn’t a material per se, but the basic question in all of these cases is this: if I’m completely shielded from direct sun exposure by a tiny parasol, how much UV exposure am I getting via reflections from the above list of items?

90% Snow
75% Aluminum Roof
22% White Concrete
15% Vegetation
15% Bare Soil
7% Wood Shingle
4% Black Asphalt
2% Water

From here. Not a great reference, since it’s data for a quiz rather than a research paper, but it’s from NASA so it’s probably accurate.

That’s a complex question. The reflectivity varies not only from one type of, say, plant to another, but it also varies with wavelength* and with angle of incidence and polarization. The best you’re going to do is general works. Here’s one:

Here’s one on UV reflectance of leaves:

*“Ultraviolet” is a term for a broad range of wavelengths, running from about 100 nm to 400 nm. People divide it up into three broad ranges, UV A (about 315-400 nm. These are the rays that get through the ozone and cause tanning. Most of it gets through glass and plastic, too), UV B (280-315 nm; These rays cause tanning, too, but are blocked by transparent glass and plastics, unless you work at it); and UV C (100-280 nm; These rays can cause skin cancer and other damage. The DNA absorption peak at 260 nm is what’s targeted by germicidal lamps Fortunately, this range is blocked by atmospheric ozone, so if you want these rays you need to use a special source, like a mercury lamp or xenon lamp)