Know your Germaniums!

I'm having a hard time thinking today so let's stick with a subject that I know backwards and forwards: Germanium Isotopes.

Joke’s on you! There’s hardly anything to know about germanium isotopes.

YET.

In addition to working on my Master’s Project with the silica and germanium in the North Pacific, I’m also partly working on a project to measure germanium isotopes. If you mention germanium isotopes to an Isotope Geochemist, take special note of the worried look in their eyes and congratulate yourself on stumping a very smart person. My advisor and I are pretty much developing the technique for measuring these little guys in seawater. Why, you ask? Why give a shit about an element with such a ridiculous name? Well, I’ll tell you.

Germanium is #32 on the periodic table of elements. It’s a metalloid meaning that its behavior exists somewhere between a metal and non-metal. The most abundant isotope of germanium is Ge74 with 32 protons, 32 neutrons. Other isotopes of interest are Ge70, Ge72, Ge73, and Ge74. There are also some weird radioactive species of germanium floating around, but I don’t worry much about those guys. These are the four isotopes that I measure when I use a mass spectrometer (which I don’t like using very much [see “Mass Spectrometry Blows”]).

We’ve talked a little bit before about fractionation. Isotopic fractionation means that something (evaporation, precipitation, biology, whatever) has fucked with the natural abundance of isotopes in your sample. In the case of oxygen, fractionation happens during evaporation and precipitation. The fatty Fatterton isotopes get left behind in the seawater during evaporation and they are the first to drop out of the clouds when it rains.

Biology does an amazing amount of fractionation. It’s a lot easier to move around light isotopes than it is to move around heavy isotopes. This might not seem like a big deal to you and me, I mean come on! What’s a few atomic mass units? But when you are a single celled critter, that shit adds up. Carbon, oxygen, sulfur, and iron are all things that biology needs, and since life is inherently lazy it will to the least amount of work to get what it wants.

Problems that arise when one attempts to measure germanium isotopes:

1.) The mass difference between the lightest (70) and heaviest (74) species of germanium is not much compared to the overall weight of germanium: 4 mass units out of 74, which is only about 5%.

2.) There isn’t much germanium in seawater. My advisor and I have developed a way to concentrate ~ 99% of the germanium in a 20L seawater sample into about 40 mL. If I told you how we do it, I’d have to kill you.

3.) You have to have a top of the line Mass Spectrometer. Expensive and fussy.

4.) You have to be able to convert your germanium concentrate to a gas and input the gas into the Bitchy Mass Spectrometer at a perfectly constant rate. Sounds easy, but this shit is sensitive. We’re talkin’ isotopes, people.

So that’s where we’re at. We’ve got our germanium concentrate. We’ve got friends with mass specs, we just need to fine tune the procedure a little bit and voila! Germanium Isotopes! The Big Butt here is “But will this information be useful?” I don’t know, probably not. Useful or not though, it's still uncharted isotope territory that should be explored by someone and that someone is me!

Dishonorable Discharge

The class I teach is learning all about rivers, floods, and groundwater this week. This subject is important to learn about, especially for folks living in Los Angeles. I don’t know if you’ve ever noticed, but it doesn’t exactly rain all that much in LA, which is good because people turn into Road Retards as soon as the pavement is wet. But it’s also bad in that we have a population of 14 million that is sustained on imported water.

As anybody who has seen Chinatown should know, Angelinos are big, fat, greedy water thieves. Back in early part of the century the LADWP and specifically chief engineer William Mulholland planned a fantastically devious way to reroute water from up north in order to provide water to the booming population in LA. People affiliated with the DWP started buying up land in the area of Owens Valley (see map) and before you know it, the LADWP owned a shit-load of land with precious precious water on it.

^ Area of Water Stealing ^

There are now two aqueducts that pilfer water from up North. The original built in 1913 runs about 220 miles and the other, completed in 1970 runs 137 miles.

^ Crazy-ass Aqueducts ^

You gotta hand it to Mulholland for being ballsy enough to make this insane plan a reality. Had I grown up in or around OwensValley AND been subjected to the vast wind storms created by the drying of the lake bed AND thereby developed severe respiratory problems because of all the particulates in the air AND had my family’s farm get fucked out of their water rights, then I would absolutely despise the man and probably all Angelinos. OwensValley is now as dry as a bone. Recently Mayor Villaraigosa made a big to-doo about rerouting water back into the OwensValley. You can read all about it here:

http://www.npr.org/templates/story/story.php?storyId=6590362.

As most things Mayors do, this flashy production is merely a matter of publicity and won’t really do much to restore OwensValley to what it was at the turn of the century.

But our story gets better! Not only do we jack water from Northern California, we also reroute water from the Colorado River (see below). LA gets about half its water from the LA Aqueduct system and about 40% from the Colorado River and State Water Project, um, projects. Only about 10% of the water we use comes from groundwater and surface runoff.

By rerouting water for our own consumption, we’ve now fucked over Baja Mexico for their part of the Colorado River. Where there used to be lush estuaries and wetlands are now desiccant.

Fascinating stuff, huh? Who knew that water could be so scandalous.

So the next time you are taking a shower or drinking a cool glass from the tap (god forbid!) or participating in a wet tee-shirt contest, be mindful of where your water has come from. It has been on a long an arduous journey and deserves your respect.


Figure references:
CO Aqueduct: (Colorado River Aqueduct © 2004 Matthew Trump
LA Aqueduct: http://www.ladwp.com/ladwp/cms/ladwp004409.jsp
OwensValley: Owens Valley © 2004 Matthew Trump

Mass Spectrometry blows

Mass Spectrometers are big, expensive machines that rarely work properly. I have yet to encounter an Isotope Geochemist who likes working with them. If you own a mass spectrometer, chances are good that you spend the bulk of your budget getting the damn thing fixed only to have it poop out on you at a critical time. They’re fussy bitches. For instance, one that we have here at USC requires that you NOT walk around it as it is measuring for fear of screwing up the sample intake. It’s like a $750,000 baby.

So how do these stupid pieces of crap work? Well, I’ll do the best I can to explain the principles of Mass Spectrometry. Some of it will be hand-wavy because I’m not so keen on it myself, but you’ll get the gist. As always, we’ll begin at the beginning and explain the principles that make this instrument necessary.

Think back to the 4th grade when you learned about the atom. The basic components of an atom are protons, neutrons, and electrons. We define an element by its number of protons, but elements can and do have isotopes. An isotope is an atom with the same number of protons, but a different number of neutrons. For example: we’ve got Hydrogen (number 1 on the periodic table of the elements) which has two isotopes – Deuterium and Tritium. The most abundant of the three is plain, ole’ Hydrogen with one proton and one electron. Just an itty-bitty bit of all the Hydrogen we know and love is Deuterium (about 0.002%). Deuterium has one proton, one neutron, and one electron. Tritium has one proton and two neutrons and is radioactive with a half live of about 12 years.

Atoms can have LOTS of isotopes. Most of them are extremely unstable and only exist in the lab. Below is the famous “Chart of the Nuclides”. You’ve got the number of neutrons on the x-axis and the number of protons on the y-axis. The blue line is showing you a one-to-one relationship (protons = neutrons). You can see that the cluster of stable isotopes falls below this line. That’s because it’s really really hard for heavy atoms to be stable. Once you start pilling on the neutrons, you’re atom wants to break apart.

Since isotopes of the same element have a different number of neutrons, they have different masses. A Mass Spectrometer will let you separate out your isotopes according to those mass differences. Why all the bother, you ask? See “Science Lesson #2: Wally Broeker” for more info on why you would want to know the isotopic composition of something in the first place. Little critters tend to take up the lighter isotope of an element first, be it Sulfur, Carbon, Iron, Oxygen, Silica, etc. This is called fractionation. It’s only by looking at the isotopes of something (like sediments, or pyrite, or shells, or seawater) that you’ll see how much fractionation has been going on. From there you can infer what the biology has been up to.

To illustrate what a Mass Spectrometer actually does, imagine yourself running on a track. Or walking (lazy-pants!). You and a friend are walking along with you on the inside of the track and your friend on the outside. The track is an oval, so once you two reach the turn your friend has to walk faster to keep up with you. If she doesn’t walk faster she'll fall behind because you are a mean friend and won’t wait for her. In principle, this is what happens in a Mass Spectrometer.

Looking at the picture above, our atoms start out all together in the front part of the Mass Spectrometer (1). Let’s skip describing this part because the front end of our Mass Spec can get complicated depending on what kind of instrument you’re using. Our isotopes are spit out and head down what’s called a “Flight Tube” (2). At this point, a big magnet built into the Mass Spec pushes our isotopes around depending on their weight. This has nothing to do with the charge on the atom because our atoms have been stripped of their electrons (ionized). The heavier isotopes are going to take a different trajectory than our lighter isotopes (3). Little detector “cups” record how many atoms came down that path (4). At the end, you know how many isotopes came into each cup and from there you can calculate the abundancies of each isotope in your sample.

So there you have it: the principles behind Mass Spectrometry. A simple premises that is gummed up by complicated machinery. If I was smart I’d quit this grad student shit and get a job as a Mass Spec mechanic because as long as their will be Mass Specs, there will be broken Mass Specs.

Trig? Oh NO! Metry.

Let's learn some Math today.

You’re thinking: Boooo! Math blows! Show me your tits!

I’ll admit that most of Math is tedious and frustrating, but some subjects within the realm of Math can actually be useful. Like Trigonometry.

I didn’t appreciate Trigonometry when I was learning it, but looking back on it now I have very fond memories of my days in Trig class. My friendship with Sine and Cosine and Tangent has stood…uuuhh, standed? withstood (?) the test of time. I remember this one time that Cosine got so black-out drunk and threw up in my car! I’ll warn you, folks, do NOT give that function Tequila. Good times.

This might be a stroll down memory lane for some of you, and for others it may seem like I’m taking you down a poorly lit back ally where you are going to get stabbed for your shoes. Don’t worry. If anyone stabs you and steals your shoes it’s going to be me. You have nothing to fear from Math. In fact, Math might help you in this situation because god knows I’ll turn on you at the drop of a hat.

We’ll begin by looking at our friend, the triangle. A right triangle always has one 90º angle and two acute angles (angles less than 90º). Right triangles are where we get all of our Trigonometric constituents from, like sine, cosine, and tangent. Other types of triangles are:

Equilateral: all angles equal 60 º, all sides the same length
Isosceles: two sides are the same length, 2 angles are equal
Obtuse: one angle is bigger than 90º
Acute: all angles are smaller than 90º

Back to the right triangle. So we’ve got one angle of 90º (indicated by that boxy thingy in the corner) and two others that are less than 90º. Let’s define one of those angles as theta (the “O” looking thing with the line through the middle). Let’s also give each side a name: Stalin, Churchill, and Roosevelt. You get to brush up on your history today too! sin θ = opposite / hypotenuse = Churchill / Roosevelt
cosin θ = adjacent / hypotenuse = Stalin / Roosevelt
tangent θ = sin θ / cosin θ = opposite / adjacent = Churchill / Stalin

If we take these functions and flip around what’s on top (the numerator) and what’s on bottom (the denominator) we can define 3 more functions: secant, cosecant and cotangent

secant θ = upside-down cosine = hypotenuse / adjacent = Roosevelt / Stalin
cosecant θ = upside-down sine = Roosevelt / Churchill
cotangent θ = upside-down tangent = Stalin / Roosevelt

From here, Trigonometry takes the ball and runs with it. You get into identities, Pythagorean theorems, Reduction Formulas, Double-Angle Formulas, Power-Reducing Formulas, and so much more. It’s hard to appreciate that such a vast subject can be built on such simple principles. Drink it in folks, it's a profound concept. Trigonometry is my friend, and it can be your friend too!

Mommy, why does it rain?

Good Question. Why does it rain? The answer isn’t obvious. Let’s talk a little bit about the fabulousness of water vapor.

It’s a stone cold fact that warmer air can hold more water than cooler air. Hence, the favorite complaint of Bingo loving, cookie baking, grandmothers everywhere “It’s not the heat, it’s the humidity!” The relationship between water vapor content (which can be quantified via vapor pressure) and temperature looks like this:

It’s not linear, it's exponential. Air with properties above the line are called “supersaturated”. Air with properties below the line are called “undersaturated”. This can lead to something interesting when you mix them. Say you’ve got two parcels of air with different properties. One parcel, A, has a lower temperature and water vapor content and the other parcel, B, is warmer and has a higher water vapor content. (see below) Now bring those parcels into contact, they mix and the mixing line looks like this:
Uh oh! Our mixing line lives in the supersaturated zone, so put your galoshes on because you’re getting rained on, buddy.

Another reason why we get rain is because air cools as it rises. When it cools it’s less capable of holding moisture so all the water gets dumped out. This happens in places with topographic highs like mountains. You’ll always have a rainy side of your mountain and a dry side because of this very mechanism.

Keeping with today’s theme of simple questions with not-so-simple answers: why does air cool when it rises? Let’s back up and think about US, as humans, scurrying around on the surface of our plant. We don’t think about it much, but we’re under a lot of pressure because of all that gas in the atmosphere on top of us. Gas does have mass (rhyme!), and when you’ve got miles and miles of it piled up from the Earth’s surface out into the far reaches of space, it can add some serious poundage to your daily life. Right now you are being subjected to 14.7 pounds per square inch of atmospheric pressure. Right. Now. And. Now. Still Now. It’s always there, homes. Nothing you can do about it.

Gas, however, can do something about it. As gas moves up into the atmosphere, it moves into regions of lower pressure. It can relax finally, and stretch out. It expands and when it does that it cools.

Maybe the opposite case will cement this idea in your mind: when you pump up your bike tire, what happens? The tire warms up a little because you are compressing the air inside it. This process is called adiabatic heating or cooling. Whenever a gas expands, it cools. Whenever it compresses, it warms up.

So the next time some asshole tells you that it’s raining because God is crying, tell him about vapor pressure, mixing lines, and adiabatic cooling. If this angers and confuses your Redneck friend, just follow whatever you say with “America Rules!” and you’ll be safe.

Die, Die, Diatoms My Darling

I have this fantasy that biologists and geologists all actually hate one another. This is so NOT the case, but wouldn’t it be hilarious if there was this deep-seeded hatred amongst the two science tribes? We could have knife fights á la “Beat It”, but instead of knifes it would be broken Erlenmeyer flasks. We could sabotage each others experiments. “DNA sequencing? How about ‘Bunsen Burner explosion in the face!’” Take that, nerd.

However funny this may be, I have to do some biology for my work as an oceanographer. The bulk of ocean chemistry depends on what is going on in the biological realm, so I have to keep track of a few species of sea-faring critters. The three I am most familiar with are Diatoms, Coccolithophores, and Forams. Today we’ll look at the wonderful world of the Diatom.

Diatoms are the guys I like the best because they are the main players in the Silica cycle. They are phytoplankton (plants) that have a siliceous shell encasing them called a frustule or test. The ones I deal with live in the photic zone, which tends to be the upper 100m of water depending on how murky your water is. Diatoms can grow CRAZY fast. The majority of the time they multiply vegetativly meaning that one diatom will break into two smaller diatoms. Individuals have the ability to make a new shell in 10-20 minutes! They’re big fans of regions with high nutrients like upwelling zones and the Southern Ocean. Wherever and whenever there is a high concentration of nutrients in the water, diatoms will hit hard and fast. They’ll zoom in and use up all the nutrients, creating what is referred to as a “bloom”, and then die off quickly when the nutrient supply has been drained.

It’s not totally obvious why a plant would want to grow a siliceous frustule. There are a few theories to explain why this might happen:

1.) To serve as a UV filter. UV light is super bad for you when you are a tiny phytoplankton.
2.) To act as armor to protect them from other critters that graze on them (this is probably the most likely explanation).
3.) To act as ballast so they can float up and down in the water column.
4.) Because they want to, motherfucker.

The majority (70-80%) of the silica that diatoms take up to make their frustules gets recycled in the surface waters. Some of it makes its way down into the seafloor where it gets deposited. People like me go out and collect seafloor sediments in interesting locations in order to find out how much silica has made it to the seafloor and what (if any) implications that may have to the water chemistry in the region.


Diatoms are one of the few living creatures that are ok in my book. Make a diatom YOUR friend today!

References:
http://www.reef.edu.au/asp_pages/secb.asp?FormNo=7
Douglas (2006) Biogenic Sediments: Carbonate and Silica
Photo credit: Dr. Neil Sullivan, University of Southern Calif.

Malibu (Iso)STASY

Isostasy is a fun word to say. Isooostaaasy. Isotasy. Isostasy. Try it, you’ll like it.

Isostasy is a fancy word for something we are all familiar with. It is the kissing cousin of buoyancy. It is invoked to explain how we get so many different elevations around the globe.

Think of an iceberg. We all know that what we see above the water is a small percent of the total volume of ice. Let’s say we see 25% of the iceberg above the water. What happens as that iceberg melts? You loose ice, yes. The iceberg gets smaller, yes. But do you see any more than 25% of the iceberg above the water? No. You maintain the ratio of what is above the water to what is below the water even though the total volume of ice is less.

Now take this iceberg analogy and apply it to the Lithosphere.

SIDE NOTE! We talked the other day about what’s going on inside the Earth (see: The tale of Alfred Wegener) and defined the Core, Mantle, and Crust. I should clarify that the difference between what is considered “Crust” and what is considered “Mantle” is a compositional difference. When you hear “Lithosphere” and “Asthenosphere” you are now distinguishing between a phase difference. Lithosphere is solid, Asthenosphere is viscous. You can have chunks of Mantle rocks in the Lithosphere, just as long as those chunks are solid. Everybody cool? Ok, moving on…

Say a mountain is our iceberg. A solid hunk floating around in the viscous Asthenosphere. We can make this mountain smaller by erosion. Erosion breaks down the rocks that comprise our mountain and carries the sediment away via streams, rivers, or wind. Our mountain getting smaller is kinda like our iceberg melting. Just like the iceberg, as our mountain gets smaller, we maintain the ratio of exposed crust to the “root” below it. This can work in the opposite fashion. Say we have a convergent plate boundary where two continental plates are colliding (like the Himalayas) and neither plate wants to subduct beneath the other. The crust has nowhere to go but up. This is how we end up with the tallest mountains in the world. But now you know from the principles of isostasy, those big-ass mountains are supported by a HUGE-ass root underneath. That’s a lot of rocks, folks!

Isostasy can lead to something interesting which is called Isostatic Rebound. Imagine that you are the continental crust during a glacial. You’re grumpy because big, heavy ice sheets have collected on top of you. You are a little depressed and kinda cold. That’s a lot of fucking ice on your back, but wait! Here comes an interglacial. Ahhh, finally. The ice is melting. All that weight is lifted. You stretch out, you bounce back. The continental crust rebounds when all that ice goes away. This happens in places like the Baltic Sea and around Hudson Bay. Scandinavia is uplifting as we speak because of this very process.

So that’s isostasy. Not the most exciting topic in the world, but important to understand none-the-less. The next time you’re in a pool, demonstrate Isostatic Rebound to your friends by holding a beach ball underwater and then letting go so that it pops them in the face. “Isostatic rebound theory, bitch!”