Sunday, November 28, 2010

Six Degrees of Separation: Smectite Style

Hello, my dearest little poblano peppers!

How are you today?  Where are you today?  You know, I clicked on something according to my research, there are twelve whole readers of you out there. TWELVE of you that lovingly indulge me with a subscription!  I thank our usual suspects, Dr. DoyleSoilduckGonferalinID, and Layla.  And you others aren't my mom or dad (well, two of you are, but you don't actually subscribe, LOVE YOU!), so... who are you? Please let me know, so instead of me talking about soils I encounter, we can talk about our soils.  For example, uno de mis amigos vive en un ultisol importante, y otro vive sobre de  roca y un poco suelo (his guest post here).

So please, will you comment and introduce yourself?  Or what you want to hear about next? Or a random thought? I'll pause and wait, to give you a moment to do that....
Waiting for you to comment gives me similar existential issues as those confronted by Grover and Telly Monster in "Waiting for Godot Elmo" by Sesame Street's Monsterpiece Theater. 

Moving on, I have this little "6 degrees of soil separation" game going on in my head all the time.  I believe you can link anything back to soil, just like Kevin Bacon.  So today I am going to relate annoying small toads to the chemical structure of smectite*. I know, it's magic!  Thank you ;-)

First of all, let us let us focus our attention on a gentle, young, unsuspecting Bufo valliceps toad.
Actually, he indeed suspects, see why below.
According to my research hubs, this toad is a Bufo Valliceps. I like to water my foundation, catch them, and gawk at them adoringly.  I pour water onto the side of my house and they all come jumping out from the crack between the foundation and the soil. 
You see, when it doesn't rain, my clay shrinks to provide these naifs space to cuddle in a nice, moist resting area. 
And when it doesn't rain, I water my foundation to get rid of the very same crack in which they reside (Does it help your foundation stability for reals? No idea).
You see, this toad and my humble abode are located upon a smectite clay. I'm obsessed Perhaps you have heard of this soil herehere and here.  Anyways, the crystal pattern for smectite involves adjacent planes, or sheets of oxygen (among other elements).  And adjacent oxygens don’t “bond” with each other very strongly compared to say, hydrogen bonding [the polarity of water: discuss].  This means that when precipitation (rain) percolates into the soil, fresh soil water molecules have an opportunity to get all up in between the tetrahedal layers, which pushes the layers apart and increases the soil volume(!!!).  Yes dude, the soil gets bigger, and in an annoyingly uneven way.  "Le sigh," says my house.

Imagine, the soil under your house is a smectitic, and whenever it rains, the clay under your house expands, and shrinks when it doesn't.  It is like building on ... some other slowly flowing (viscous) material.  Your walls may crack, your door jams stick.  Anyways, we water it in a futile? effort at keeping soil moisture nice and even at all times, which should supposedly preserve our foundation's integrity.  And this is where the toads come in again.

In conclusion, our 6 degrees of Kevin Bacon separation:

  1. I pour water onto the soil next to my house foundation so that it will expand to close the crack between the two.  Toads hop out of the crack, annoyed (and then I catch them!).  You see,
  2. Maintaining near constant soil moisture levels may preserve our foundation located on a smectite clay. 
  3. Smectites change volume depending on soil moisture, 
  4. Cuz their adjacent tetrahedral layers are only bonded by oxygen bonds and 
  5. Water is more electrostatically attracted to the oxygens in between the tetrahedral layers than the oxygens are to each other.  
  6. Once hydrated, the smectite clay mineral expands with the added molecules.
Ta da!  You too, can use your soil science expertise to mildly inconvenience small animals!

PS These smectitic soils are characterized by high base saturation, partially explained here and here.  

Smectite: A mineral found in great quantities in vertisols, which are known for their shrink swell capacity due to expanding 2:1 lattice clays (source).
Phyllosilicates: Silicates (atomic structures featuring silicon) that combine to form planar sheets.
P.S. They discovered phylosilicates on Mars.  

Thursday, November 4, 2010

ATX: Your poo promotes birdwatching. Indirectly.

Birdwatching at Hornsby Bend (Photo credit: Meredith O'Reilly)
Hornsby Bend, Austin’s premier birding location, is a biosolids recycling facility.  

Say what? Your beatific contribution to the sewer system via flushing toilet travels through pipes and goes to a wastewater treatment plant. After treatment, the biosolids (or, if you want to sound like a nerd, primary and secondary waste-activated sludges) go to Hornsby Bend, where they are manipulated again ultimately composted with yard trimmings collected from Austinites to make Dillo Dirt (Read page 3 of this doc for more details on how this is done.)  The liquid waste portion of the biosolids make outdoor ponds, whose waters irrigate onsite fields.  

The birds love Hornsby Bend.  They like the ponds, the drying basins, woods and fields:
The biodiversity is present both because of the nutrient rich biosolids treatment  processes used by the facility and because of the diversity of habitats at the site stretching along 3 miles of the Colorado River. (source)
We built it, so they came, enjoyed, and returned.  And now we can go watch them. Meredith at GreatStems wrote a very nice blog post on Honsby Bend's birdwatching and history.

If you haven’t had a chance to visit Hornsby Bend's neat avian-friendly ecosystem, you should fer reals go. 

Here are some visiting tips:

You can go by your lonesome or join the group activities as listed on The Dirt on Soil's calendar, which include:
  • A monthly bird survey every 2nd Saturday of the month @ 7am,
  • Birder led "field trips" every 3rd Saturday of the month, and
  • Eco-literacy day every 4th Saturday of the month @ 9am -1pm
    • 3 hours of outdoor volunteer work; 1 hour of ecological education
Also, Hornsby Bend is open daily to the public from sunrise to suneset.

The Saaaands are Alive with The Sound of Muuuuusic!

This post reminds me of that lovely Julie Andrews song, parodied here.

Dear Readers (How are you?),
I confess: I've been pretty biased against sand.  Hydrologically speaking (which is totally my paradigm), I consider it the boring soil texture of the three (sand, silt, clay).  Por ejemplo:
  • Water flows through it the easiest (of sand, silt and clay), meaning is has the highest hydraulic conductivity*, and 
  • it holds onto the fewest nutrients because of it's low cation exchange capacity* (I mention CEC here and here).  
  • Also, it's soil moisture curve* leaves much to be desired.  I mean look,

(image source, from an awesome looking lecture on soil water relationships in soil)

Just look at how quickly sand loses it's soil moisture when the water table drops (shown on the x-axis).  Yawn, right? Clay holds onto it's water!! Jeez.

But recently, I came to terms with the idea that maybe sand was more interesting than I thought.  A few weekends ago, we saw some familia in Corpus Christi, TX and went to Padre Island National Seashore (Click here for map). As in, we went to the beach, where you get to play in nothing but pure, boring, bland sand.  So you'd think I'd be bored out of my mind there, but lo, it was not true.

Mi familia y yo started digging in the sand of the intertidal zone, and did some learning (BTW,  sandcastles, sand-chairs, and drip mountains are totally learning.)

This is South Padre Island National Seashore's intertidal (IT) zone*.  The IT zone here would be everything in between the seaweed piles to the low tide waves.  An IT ecology lesson here.
Wanna know what we saw?  Aliens!  Just kidding: one long, skinny worm, tonsa things that looked like dark, stubby worms, a decapod (a ten-footed something-or-other, shrimp?), and something that looked like a "sand crab" to my untrained eye.  Kinda like everything on this marine science page (seriously, look at the cool pictures!).
This is a blood worm (genus Euzonus), which might be what I saw (Image credit).
So, in conclusion, the sand is alive!   These creatures have ecological importance as nutrient recyclers, just like our soil brethren.  For example, can you believe, and I quote:
Some worms called polychaetes [my note: this is a class of worms that inlcude the Euzonus genus] simply eat the sand whole and let their digestive systems clean it off. Out the back end, eventually, comes a trail of clean sand (source).
Blood worms function on the sandy beach much like the earth worms do on land — they ingest the sediments (sand for the blood worms) and digest the organic material found between the sand grains. This type of feeding is called deposit feeding and results in a type of "cleaning" of the sediments. (source
You mean they poo a trail of clean sand!?!? Awesome.  So, why are we thankful for tiny sand creatures?  They don't cause diseases and they clean up after our organic mess.  HUGS YOU, little sand creatures!!!

And to you, Sand: I'm sorry for thinking you were boring.  I love your interstitial fauna* and you are easier to wash off our hands than clay.  Thank you, too :-)

It turns out that sand is waaaaay more interesting than I thought.  Check out this book review blog post by Brian Romans on the book Sand by Michale Wellans.  This author also has a SAND BLOG on all things sand!  Now back to your regular programming...

Intertidal zone: The transitional coastal region located between high and low tide marks (source).
Hydraulic conductivity: "A measure of the capacity for a rock or soil to transmit water; generally has the units of feet/day or cm/sec (source)," or "The ease of movement of water through the soil relative to a potential gradient (source)." Think of a potential gradient as a difference in water table levels: water flows from high to low water table levels.
Cation Exchange Capacity: "a measure of the negative charge on soils (primarily on clays and organic matter). It is expressed as the quantity of cations (positive ions) that can be adsorbed by the soil (source)."
Soil moisture curve: a graph that shows the relationship between soil moisture content and pressure head (aka water table draw-down).
Interstitial fauna (meiofauna): the tiny animals that live in between the sand grains.  Also "loosely defined as animals capable of passing through a 0.5-mm mesh (source)"