Saturday, July 26, 2008

Wall Street Journal on Light Pollution

The WSJ has an article on light pollution:

Light pollution has tripled since 1970, according to Italian astronomer Fabio Falchi.

Not mentioned in the article is the billions of dollars this light represents in wasted energy costs in the U.S. Every business should be aware that some large percentage of their lighting bill goes out without making a cent for them if they aren't using fully shielded lights. Using those clich├ęd acorns to light your lot? You are losing some 70% of your electric bill for lighting straight into the sky and into the pained, scrunched, unhappy eyes of the customers who can't see beyond your lights, who can't see into otherwise well-lit areas in your lot because of the glare from the acorns.

Thursday, July 24, 2008

Granite counters: the claim of radiation risk


The New York Times has a surprising article today about the radiation risks of granite counters.

Granite is an intrusive rock--slowly cooled from magma several kilometers below the surface, the rock grows large crystals from the hundred-thousand to million year cooling period. It is also chemically more "continental"; that is, more quartz, more "felsic" minerals, as opposed to the "mafic" minerals that contain much olivine and pyroxene, two minerals rich in iron and magnesium. True granite is a chemically specific intrusive, and much of what is called granite isn't, but a cousin of it. Roughly you can say to expect quartz, feldspar (of some type, there are several), and a sheet silicate like mica or biotite.

Despite the popular image of the Earth's crust riding on an ocean of molten magma, there is little liquid under our feet. While it's hot, there is enough pressure to keep things solid. Occasionally something will upset that balance and allow the rock to melt, whether by bringing hot material up to a lower pressure (like at the mid-ocean ridges) or by adding a special ingredient to make it melt (like water released by ocean sediments subducting under a continent). Melting is complicated and rarely complete, and some minerals melt at a lower temperature than others, leaving behind and chemically changing what sort of rock it is. Granite is like this. It melts at a lower temperature than basaltic materials. It often contains more water. And it brings with it certain compatible elements including uranium and thorium. This is why granites are more radioactive than most rocks. They can contain 10-20x more uranium and thorium than the solid left behind. Some of the more exotic "granites" are pegmatites--the extremely large crystal remnants of the last little bits of liquid at the end of solidification--and they contain the highest amounts of these elements.

But is this a hazard? Granites I've encountered have rates ranging from nothing to about 10x background. This isn't that much. Time spent at cruising altitude is about 40x background at 500ft. It certainly wouldn't be worth the fuss of ripping up a kitchen, unless it was proven to be the source of elevated radon levels. After reading the literature about naturally occurring radon sources, I have difficulty assigning the radon to just a small granite piece. Any soil or rock within 4 gas-diffusion-days of the basement or slab can be a source of radon for a home, and the total amount of uranium in that quantity is going to exceed the amount in the countertop (especially the part of the countertop that is within radon's half-life time of the surface). If you covered your walls in granite it might be different.

Wednesday, July 09, 2008

Walker Lake, Nevada

Will we have the political fortitude to solve the problem of a oversubscribed watershed before all native fish die in the second largest natural lake fully in Nevada?

The cost of mitigating the health issues of a completely dry lake bed must be more expensive than a few water rights purchases, yes?

Tuesday, July 01, 2008

elements in glass

Ever wondered about the elemental composition of the differently colored versions of glass? Or what exactly does "crystal" glass contain that regular glass doesn't? Have a geochemist bring back last night's empties to the lab. To first order, be careful with the fancy-ware. More iron means more color. And if you need white, try some zinc oxide.

Trace elemental analysis of a big night out
P.S. Of course this is just about these particular elements, and doesn't count the bulk silicon, oxygen, sodium and such.