Science Friday: On this Tiny Sphere is All the World's Freshwater | Sunlight is a h2o Disinfectant | Megafires and Tree-rings
A few days ago, we wrote about a remarkable graphic released by the USGS, showing all the water on Earth—freshwater, saltwater, water vapor, water in plants and animals; all of it—rolled into a sphere.
That sphere was only 860 miles in diameter, fitting comfortably between Salt Lake City and Topeka, Kansas, on a map. It was striking, especially considering that the water available for humans use in our daily lives is only a very small fraction of that; the vast majority of the Earth’s water is saltwater, and most of the freshwater is tied up in glaciers.
How big would a sphere of just the freshwater available to humans be? Reader Jay Kimball of 8020Vision, his interest piqued, went ahead and made such a graphic.
That sphere—the sphere representing the freshwater available to humans—has a diameter of just 170 miles. Head to his blog to see the math.
- Sun, salt and lime sounds like the beginnings of a cocktail recipe, but for some, it could mean cleaner, life-sustaining water.
In many developing countries, the only source of water is contaminated with viruses and bacteria. In fact, the United Nations estimates that 1 in 6 people don't have access to enough fresh drinking water.
Pouring water into clear plastic bottles and placing them in the sun can kill disease causing organisms in about six hours. It's a simple and cheap method that's been around forever, and it helps. (Who says sun tea isn't safe?)
But there's a hitch – the water has to be clear enough for the sun's rays to penetrate – and much of the world's water supply is murky from the clay soils in riverbeds and lake bottoms that mix with the water. Enter the scientists.
"Basically, you need to be able to read a newspaper through it. That means it's clear enough for the UV radiation to penetrate and kill the pathogens. If you can't see through it, it just won't work," explains Joshua Pierce, associate professor of materials science and engineering at Michigan Tech.
Pierce and his colleagues discovered that by adding a little table salt to this murky water, they could get the particles of clay to stick together and settle to the bottom, making the water clear enough to purify using the solar disinfection method. They also found that the addition of salt works best for certain kinds of clay soils, namely bentonite, and not so well with others. But when they added a little bentonite along with salt to water that contained other types of clay soils, it worked just as well.
Pierce says the method works because bentonite clays have an electrostatic charge – which makes them attracted to the charged ions in the salt. When bentonite is mixed with other particles, they stick together, and the salt pulls everything out of the water.
- ScienceDaily (May 16, 2012) — Today's mega forest fires of the southwestern U.S. are truly unusual and exceptional in the long-term record, suggests a new study that examined hundreds of years of ancient tree ring and fire data from two distinct climate periods.
Researchers constructed and analyzed a statistical model that encompassed 1,500 years of climate and fire patterns to test, in part, whether today's dry, hot climate alone is causing the megafires that routinely destroy millions of acres of forest, according to study co-author and fire anthropologist Christopher I. Roos, Southern Methodist University, Dallas.
The researchers found that even when ancient climates varied from each other -- one hotter and drier and the other cooler and wetter -- the frequencies of year-to-year weather patterns that drive fire activity were similar.
The findings suggest that today's megafires, at least in the southwestern U.S., are atypical, according to Roos and co-author Thomas W. Swetnam, the University of Arizona. Furthermore, the findings implicate as the cause not only modern climate change, but also human activity over the last century, the researchers said.