Tuesday, October 25, 2011

Why Pee is Cool - entry #6 - "Pee, Our Connection with the Earth's Metabolic Cycle"

Here, in the final PeePeePost, is where we bring all we have learned together and find out how the act of peeing unites us with our planet.

sciseekclaimtoken-4eab48c19bc77 Any form of life that we know of needs two basic things.  The first is matter, as life has to be made of something.  The second is energy, so life can do something with that matter (e.g., move around, reproduce, watch trailer park boys).  Most life on earth gets its energy from the sun.  All life on earth gets its matter from...from earth, duh!

As we learned in the last PeePost, the atoms in your body are no different from the atoms in rocks/oceans/air/etc.  Additionally, the composition of our bodies is close-ish to that of the earth's crust!!

Graph of abundances of chemical elements in the earths' upper continental crust.  We are made mostly of the really abundant stuff in the upper left (e.g., oxygen, carbon, hydrogen, etc.)

Because of those two facts, I like to think of any kind of earth life as little tiny earth particles--walking, talking, peeing, sometimes neighborly little chunks of the earth's crust.

Humans are earth particles.

These earth particles are constantly using earth's atoms, moving them around, changing them from one chemical to another.  This, with a lot of help from non-living things like evaporation and gravity, results in atoms moving all around the earth.  In this process, the atoms will spend time in all sorts of lifeforms, and they will even spend time in non-living things like rocks, the oceans, and our atmosphere.  The movement of a molecule or chemical element in this way is known as a biogeochemical cycle.  The most well-known biogeochemical cycle is probably the water cycle:

One thing this image doesn't capture is plants and animals changing water into oxygen and back again.

The water cycle is super-complicated, but basically involves water evaporating from the oceans, falling out of the atmosphere as rain, and letting gravity pull it back to the ocean through rivers and groundwater.  I like to think of this as the continents' way of taking showers.

The coolest thing about biogeochemical cycles like the water cycle is that WE participate in them!  Every time you pee you are putting yourself somewhere in that cycle.  So if you live in a place like California, where people drink water pretty directly from precipitation, when you pee the water goes via the waste-water treatment plant to lakes and streams and eventually into the ocean.  That looks like this:

So we know that water is in our pee, but what else is there?  In PeePee Posts 2, 3, and 5 we talked about nitrogen being in our pee.  The nitrogen cycle is really cool!  It starts with nitrogen atoms in the atmosphere in the form of N2.  Plants need nitrogen atoms to survive, but they can't use the abundant N2 from the air.  So, these awesome earth particles called nitrogen-fixing bacteria take electrons from chemicals like sugars, dump them into N2, throw in some protons and energy, and form the ammonium ion (NH4+).  Other organisms then change the ammonium ion into the nitrate ion (NO3-).

Now those things (NH4+ and NO3- ions), plants can use.  They take either ion and incorporate them into proteins and other parts of their body.  We then eat plants' bodies and pee their nitrogen back out as urea, which gets turned back into ammonium ions.  Eventually the nitrogen goes back into the atmosphere, completing the cycle.  Here is the nitrogen cycle.  Check us out!!  Peeing!!!  We're part of it!

Notice the big factory on the right.  In the early 1900s, we humans figured out how to turn N2 into NH4+, just like the nitrogen-fixing bacteria do!  This was a STUPENDOUS discovery!  Today this process accounts for 1-2% of all the worlds energy usage!!  Its use on such a gigantic scale has altered the nitrogen cycle in ways that could take centuries to calm back down to a steady state. (awesome article here)  What effects this will have on life on earth are not at all clear.  Scary!

Humans imitating plants in this fertilizer factory in Billingham, England.  Photo courtesy addictive picasso.

In PeePee Post 4 we learned that phosphorus is also in our pee.  The phosphorus cycle is cool because it is MEGA MEGA slow.  As opposed to the nitrogen and water cycles, which can move through the atmosphere, the phosphorus cycle moves through the earth!!!!

Here's how it happens.  Mountains containing phosphorus in the form of chemicals called phosphates are slowly eroded by rain and wind.  On the way down the mountain the phosphates are used by plants and animals in things like their DNA or bones.  The phosphorus atoms continue their slide down the mountain, eventually reaching the ocean where organisms use them some more.  However, eventually the phosphorus atoms fall all the way down to the bottom of the ocean!  You might be thinking that this pathway from mountains down to the bottom of oceans seems more like a one-way trip and less like a cycle.  So what completes the cycle?  Mountain formation!!!!  This brings the phosphorus from the bottom of the ocean back up onto land, and as you might imagine it takes a LONG TIME!  (awesome review here)

There we are, participating in the cycle by eating plants and other animals, and peeing out their phosphorus atoms.  Just as with the nitrogen cycle, we humans have discovered ways to drastically change the way this cycle works.  We do this by mining huge phosphate deposits for use as fertilizer.  There are enough phosphate deposits for us to keep doing this for a long time, but if we want to keep going like this eventually we are going to have to mine the bottoms of the ocean or wait for mountain formation to catch up.  As with many of our experiments on what earth systems can handle, the long-term consequences of our actions are unclear, but the preliminary data is enough to freak me out.

Anyway, check out this insanely huge phosphate mine in India.

Phosphate mine in Jhamar Kotra, India.  Apparently it is common in the mine to find fossils of the mega-ancient stromatolites that helped form this phosphate deposit.  Photo via Geology Rocks!

This mine is so big you can actually see it on google maps!

View Larger Map

It's not all doom and gloom though.  Even though I find it scary how significantly our industrial practices are affecting earth's biogeochemical cycles, I still think it is awesome that when we pee we are naturally participating in these cycles.  We participate in all sorts of other biogeochemical cycles when we pee (potassium, sulfur, etc).  All life on earth is connected via these cycles in one way or another.  Give that some thought next time you're peeing.  You are participating in the earth's metabolic system!

Related Posts:
PeePeePost #1: "Why Is Pee Yellow?" or "Rainbow of Urine"
PeePeePost #2: "Why Does Pee Smell?" or "Aroma of Life"
PeePeePost #3: "Explosive Urination" or "Gunpowder Comes from Pee!!!"
PeePeePost #4: "PeePee Portal to Phosphorus" or "What the Alchemists Did Right"
PeePeePost #5: "How Pee Unites You With Rocks"