Why sanding back is a bad idea

One project I was sort of interested but never really had time to tackle was the quantitative analysis of the metal content of paint. The following is a depth profile of a paint chip from our home renovations last year. As time progresses, the back ground gives way to the signal from the surface layer, and the next two coats of paint beneath.


Figuring out how to standardize is a royal pain, but a qualitative glance at the measurement shows that the various highly toxic metals have much higher concentrations in the older paint layers than the most recent layer. This is why health professionals recommend that home renovators simply paint over old paint, instead of sanding it. Sanding the paint off releases all these goodies into the air, where they can be breathed, eaten, or otherwise ingested.

Our house was built in the early 70’s. I don’t know how many times it was painted since then, but even without rigorous standardization, it is obvious that paint has become a whole lot less toxic over the lifetime of the building.

Lounge of the Field Lemming

I have accepted a job with an exploration company, and will be flying out on Thursday for three weeks in the Northern Territory. I’ve approached a couple of guest bloggers for that period, but don’t hold your breath.

The short story is that I started applying for industry jobs when the university kept delaying my transition from contract to permanent work. When I asked my PhD supervisor (who has been in exploration since I graduated) if he’s write me a reference, he asked me to come work for him. So that is what I’m doing.

I’m not sure how much presenting the long story about deciding between the relative merits of the two offers would add, so I won’t.

Where on (Google) Earth #18

Sagan has no blog, so I'll post 18. Next one is somebody else, though. No hints. Please also list the order in which the various features cross-cut.

Where on (Google) Earth? #17

This one might look a bit intimidating at first, but applying geologic principles instead of pattern recognition should make it easier than it appears.


A world geologic map might help too.

If former winners could give the public a 24 hour head start, that would be great. As always, an explanation of the method used and the geology featured is a welcome bonus. And everyone is welcome to talk to each other in comments to get on the right track.

Original Where on (Google) Earth series here.

Homeland Security bans reality

Today, the Department of Homeland Security is expected to announce a total ban on the use of, possession of, or residence in reality. Following on their prohibition of liquids in air travel and chemicals in chemistry sets, this ban is designed to ensure that the dangerous, unpredictable universe does not fall into the wrong hands.

Says DHS spokesman Norman Tonguesgroove, “In today’s modern world, there is really no valid reason for private citizens to inhabit reality. There are a variety of safer, more sensible alternatives freely or commercially available to the American public. We expect this prohibition to only impact on those radical realists who cling to outmoded ideals.”

The spokesman was quick to add that, where valid research purposes necessitated its use, university and government labs could be licensed to use reality under carefully controlled conditions. All relevant staff would require security clearance before any such work could proceed.

The department downplayed any suggestions that this new regulation was overly broad. “The federal government is expressly charged with providing for a common defense, so there are no constitutional or jurisdictional issues. Reality is simply too hazardous and erratic, even here on Earth. And the rest of the universe is downright lethal,” Tonguesgroove stated. “The only responsible course of action is to simply bar people from interacting with it.” The spokesman also assured key interest groups that their rights to fictional guns, speech, religion, and abortions would not be infringed.

The department expects only minor objection to this plan, as most ideological, religious, and political leaders have only tenuous connections to reality anyway. If anything, they find it more inconvenient than does the department.

This announcement will be made simultaneously on the DHS website and the Second Life Secret Police command center. There will be no physical press conference.

SPOILERS for Where on (Google) Earth #16

The original post is here.

If you are still working on it, stop reading now.

I recommend going to Ron's site, and having a go yourself before reading the spoilers.

If you know geology, it is actually fairly easy to deduce where the answer has to be.

Go ahead. Have a look.

I will talk you guys through the process below.

My first gut feeling was the Tarim Basin, but before running off to Asia, I decided to look at the pic analytically.

Ron's fatal mistake was adding the oblique view. While this looks mostly like a gimmick, it gave crucial information- namely the presence of snow-capped mountains to the East of the view area.

Also, there are no folded strata visible. Finally, the mountain looks like an eroded volcano. The obvious place to look for arid volcanic landscapes with higher mountains to the East is the Atacama desert. So, I started around 24 deg south, and worked my way up the coast into southern Peru, where the shore starts getting much less arid.

I had no joy, but I was confident in my reasoning, so I came back down along the dividing range, and look what I found...



22^o54'S 67^o13' West

I have no idea what the groundwater eroding ash canyons are called, but the meandering thing is a river.

Where on (Google)Earth #15?

Brian has kindly offerend to share the joy of his "Where on Google Earth?" series, so I figured I would step up to the plate. This entrant is dedicated to billabongs*:


Veterans of the series will note that I added a scale bar. I did so for three reasons:
1. It is good practice.
2. It will hopefully level the playing field for mortals against GoogleEarth gods like Ron, who can asertain the scale through diabolical means.
3. It might even help the educational value of these pictures, by giving people a feel for the size of the features shown.

* Known to Americans as ox-bow lakes

Carbon sequestration in mine tailings

Attention Grist and Wikipedia readers:

Please see this comment on the linking of this post from those websites (update Jan 2 2008).

We had a cool talk on Friday about carbon sequestration in mine tailings.

First, the background:
For the past couple billion years, the primary planetary thermostat is generally thought to have been the carbonate-silicate geochemical cycle. Weathering processes remove CO₂ from the atmosphere with the following reaction (using diopside as an example mineral): CaMgSi₂O₆ + 2CO₂ -> CaMg(CO₃)₂ + 2 SiO₂. subduction and continental metamorphism reverse the reaction: CaMg(CO₃)₂ + 2 SiO₂ -> CaMgSi₂O₆ + 2CO₂. This works for all calcium and magnesium silicates, not just diopside. The metamorphic part is assumed to proceed at a constant rate. The weathering part is dependent on temperature and p CO₂. So when CO₂ and temperature are high, the reaction proceeds faster. As CO₂ is removed from the atmosphere, the planet cools, and the reaction slows down. Without human interference, this cycle is expected to correct the current anthropogenic CO₂ increase in about 0.1 Ma.

Now, the observation:
Scientists studying mine tailings in abandoned asbestos mines in Canada found that the tailings (which are primarily serpentine: Mg₃Si₂O₅(OH)₄) were covered in white crusts- various hydrated magnesium carbonate species. Detailed study ensued.

The details (which I’m skipping since it’s after midnight and I’m only up because the baby is) are in themselves pretty awesome, as they show how the scientists sourced the carbon and investigated the relative importance of biotic and abiotic processes in reacting the tailings. Their conclusions are that in the 20 years since the mines closed, the tailings had sequestered as much CO₂ as the mining operations originally produced, making the mines carbon-neutral. Even better, the potential sequestration capacity of the unreacted serpentine in the tailings was substantially higher. Now they are trying to figure out how to accelerate the process, in the hopes that all mantle or mafic cumulate-based mines can sink carbon as a byproduct of production. In true lab style, they’ve evidently got labs full of tailings-packed tupperware reacting at all sorts of temperature, pH, and fluid activities.

We don’t currently mine enough nickel, chromite, or asbestos for this to be a stand-alone solution for all emissions, but in theory it could sequester up to about 0.1 Gt of carbon per year- substantially more than is used to operate the mines.

I love this kind of science, for several reasons. Firstly, it is one of those things that is bleeding obvious once observed, but still quite unexpected. If mine tailings weren’t reactive, we wouldn’t have mine pollution issues. So how could hundreds of millions of tons of powdered mafics fail to react with the atmosphere?

Secondly, it makes absolutists’ brains explode. Just when the left wing fruitcake faction of environmentalists thought that bird-killing windmills and nuclear power plants were the worst thing to come out of global warming, along comes this new discovery: What we really need to do to save the planet is to dig up more asbestos, nickel, and chromium.

More info:
The UBC mineral carbonation group
AGU abstract
American Mineralogist abstract (full article available for fee)