Tag: immersion

Landfills: Dealing with the Smell (H2S)

Hydrogen Sulfide:
H2S

Diagram of the hydrogen sulfide system in a landfill.

Although it makes up less than 1% of the gases produced by landfills, hydrogen sulfide (H2S) is the major reason landfills smell as bad as they do. H2S is produced by decomposition in the landfill, and if it’s not captured it not only produces a terrible, rotten-egg smell, but also produces acid rain, and, in high enough concentrations, it can be harmful to your health (OSHA, 2005; Ohio Dept. Health, 2010).

Decomposition

A wall partially covered with drywall. Image via FEMA via Wikimedia Commons (Nauman, 2007).

Some hydrogen sulfide is produced when organic matter decays, but for big landfills like the one we visited, construction materials, especially gypsum wallboard (drywall), are probably the biggest source.

Gypsum is a calcium sulphate mineral, that’s made into sheets of drywall that are used cover the walls in most houses because it’s easy to work with and retards fire. The U.S. used 17 million tons of gypsum for drywall in 2010 according to the USGS’s Mineral Commodity Summary (USGS, 2011 (pdf)).

Gypsum:

CaSO4•2(H2O)

As you can see from the chemical formula, each gypsum molecule has two water molecules attached. In a fire, the heat required to evaporate the water keeps the temperature of the walls down to only 100 degrees Celcius until the water has evaporated out of the gypsum board.

A number of landfills have banned drywall because it produces so much hydrogen sulfide, but the one we visited still takes it. It’s big enough that they capture the landfill gasses, including the hydrogen sulfide, and then separate it from the other, more useful gasses, like methane, which can be burned to produce heat energy. H2S can also be burned, but they you end up contributing to acid rain.

H2S and Acid Rain

When hydrogen sulfide reacts with oxygen in the atmosphere it produces sulfur dioxide.

2 H2S (g) + 3 O2 (g) —-> 2 SO2 (g) + 2 H2O (g)

Sulfur dioxide, in turn, reacts with water droplets in clouds to create sulfuric acid.

SO2 (g) + H2O (g) —-> H2SO4 (aq)

Acid rain accelerates the dissolution of statues. (Image by Daniele Muscetta)

When those droplets eventually coalesce into raindrops, they will be what we call acid rain.

Acid rain damages ecosystems and dissolves statues. It used to be a major problem in the midwestern and eastern United States, but in 1995 the EPA started a cap and trade program for sulfur dioxide emissions (remember sulfur dioxide is produced by burning hydrogen sulfide) that has made a huge difference.

The head (top) of a well (vertical metal pipe) that captures the gas from inside the landfill.

Capturing H2S

Probably because of the EPA’s restrictions, the landfill company pipes all the gases it collects through scrubbers to extract the hydrogen sulfide. There are a few ways to capture H2S, they all involve running the gas through a tank of some sort of scavenging system that holds a chemical that will react with hydrogen sulfide and not the other landfill gases. At the landfill we visited the remaining landfill gas, which consisted of mostly methane, was used for its energy.

Cahokia Mounds

Students observe the physical and human geography of the Mississippi flood plain from the top of the main mound at Cahokia. An ox-bow lake can be seen to on the right side of the picture, and behind it is a glimpse of the Mississippi River with St. Louis in the distance.

Almost a thousand years ago, 20,000 people lived at a place called Cahokia. At the center of their city, was the largest artificial mound in North America. A large part of Cahokia’s success is surely its location: near the confluence of the Mississippi and Missouri Rivers — just across the Mississippi from modern-day St. Louis. Yet less than 400 years later (see timeline) the city was abandoned, and no one is quite sure what happened.

Our middle and high school took a trip out to Cahokia last month. It was during the same intercession between quarters when we visited the Laumeier Sculpture Park, the Da Vinci Exhibition, and did our brief biological survey of the campus.

The elevation of the main mound, sitting on the flat Mississippi flood plain, with the St. Louis skyline in the distance, was a great place to talk about the importance of physical geography in the location of cities (your biggest cities are always going to be on rivers, or the ocean or, often, both) and to reflect on how history repeats itself — a once thriving metropolis is nothing now but displaced piles of alluvium and mystery.


View Cahokia in a larger map

Cahokia is a World Heritage Site, and it has an excellent museum. I particularly liked the detail in their life-sized reconstruction of a section of the city.

Their website is also good. Apart from the timeline, mentioned above, they have a nice interactive map for details about each of the numerous mounds, and a long page about the archeology.

The site is pretty big, so you can spend a fair amount of time exploring. Fall, when the leaves have turned color, and the air has cooled a little, is an excellent time to visit.

Students explore the trails at Cahokia.

Laumeier Sculpture Park

At Laumeier Sculpture Park.

“It’s one of the places I’m most proud to bring people when they visit St. Louis,” commented (more or less) one of the other faculty on our field trip to the Laumeier Sculpture Park. My hope was that this trip, combined with our visit to the Leonardo Da Vinci Exhibition, would be a nice way to demonstrate that the distance between art and science isn’t so large after all.

I believe this sculpture is called, "Balance".

I required all of my students (physics and middle school science) to identify their favorite piece and sketch it. We’ll be covering forces, balance and mechanics in the coming quarter, making this part of the spark-the-imagination part of the lesson.

Also, detailed sketches are not easy. An accurate drawing requires a lot more careful observation than even taking a picture. By trying it themselves they’d get a much greater appreciation of Da Vinci.

The large pieces are quite impressive. The brightly painted metal tank combination at the top of this post just towers over everything. However, one of the neatest was carved out of one enormous piece of wood. It’s made to emulate the distinctive, ridged bark of the cottonwood tree. The artist accentuates the ridges and valleys quite elegantly, making a wonderfully warm and organic abstraction.

Looking up at the cottonwood tree sculpture.

There’s also an indoor museum (which was closed while we were there), and, apparently, pieces are added and taken away so the park is worth revisiting. The only problem is that you’re not allowed to climb on the sculptures. This is a quite understandable precaution to protect the pieces, but, as some of the students observed, the sculptures “invite” you into and onto them. It’s a stark contrast to the St. Louis City Muesum, which is designed specifically to be played on.

Becoming Da Vinci

Notes (by Natasha D.,"aged" and reflected) from our visit to the DaVinci Exhibit.

Working models of Leonardo Da Vinci’s devices, and video of his sketchbook, so inspired one student that she emulated Da Vinci’s style as she took her notes during our visit to the Da Vinci Machines Exhibition. While I’d asked them to bring their notebooks, I’d not said anything about taking notes (nor is there to be a quiz afterward) so it was very nice to see this student’s efforts. The exhibition is in St. Louis at the moment, until the end of the year.

Scan of a page of the Codex de Leicester by Leonardo DaVinci. (Image via Wikimedia Commons).
Flywheel using spherical weights. Constructed based on Leonardo da Vinci's drawings. Photo by Erik Möller via Wikimedia Commons.

What I liked most about the exhibit is that you can operate some of the reconstructions of flywheels, gears, pulleys, catapults, and other machines that came out of DaVinci’s notebooks.

Da Vinci did a lot with gears, inclined planes, pulleys and other combination of simple machines, so the exhibit is a nice introduction to mechanics in physics. The exhibition provides a teacher’s guide that’s useful in this regard.

It’s an excellent exhibition, especially if you spend some time playing with the machines.

Milking Goats

Learning how to milk goats.

Part of the afternoon chores at the Heifer Ranch was milking the goats. It was not something required of the students, but since our barn was located right next to the goats’ milking barn, a lot of them volunteered to try it out.

Carefully milking a goat.

Most used the somewhat dainty, one handed technique, and I’ll confess I was among that group, but a few students (see first image) really got into it.

A good producing goat (doe) can produce about 3 quarts per day (McNulty et al., 1997).

After milking, the goats’ teats are dipped in iodine solution (25 ppm recommended by McNulty et al., 1997) to kill any germs and prevent infection.

Sanitizing with iodine solution.

As for the green splotches on the backs of the goats. On our first morning at the Heifer Ranch we had walked past a paddock with about half a dozen goats. A student noticed the green and asked why. Fortunately, we had a guide to explain a little about the basics of animal husbandry – apparently, the marks indicate which goats are likely to be pregnant.

A Night in the Slums (simulated)

Uncomfortable sleeping arrangements of the (simulated) slum.

One of the highlights of the Heifer Ranch trip was the chance for students to spend a night in their global village. It’s really a set of villages, each simulating a life in an under-developed part of a different developing country.

The Thai village. Everyone wanted to end up in the Thai village.

The Guatemalan house is pretty nice; it keeps you out of the elements, you have actual beds, and running water. The Thai houses are actually pretty awesome. They stand on stilts next to the open fields, giving good air circulation and elegant views. They remind me a lot of some of the older houses from where I grew up. The refugee camp, on the other hand is pretty decrepit. The slums aren’t much better but at least have one house with a wooden floor, though the door was so broken it was pretty useless.

Our students were assigned villages at random, but varying numbers were placed in each village to replicate the population densities more accurately. One adult was assigned to each village. We were supposed to act as if we were incompetent (not hard I know), either as two-year-olds or senile elders.

I ended up in the high population slums.

A dragonfly sits on the hard ground in the slums.

On the positive side, I was not the only adult there. Mrs H., who had joined our group with her daughter for the week of activities at Heifer, was also assigned to the slums. On the negative side, she and the girls commandeered the one “posh” building that had an actual floor to sleep on. The boys and I had to sleep on the hard, stony ground.

It didn’t help that one of the boys was “pregnant”. One person in each group been given a water balloon in a sling and told to keep it with them, safe, until dinner, when they would “give birth”, at which point the others in the “family” could help take care of the “child”. A key objective was for the child to survive until morning.

The boys scouted all the houses in the village and scavenged a large piece of metal grating to sleep on. It was not great, but it was doable. Better, at least, than the concrete-hard, uneven ground.

Making dinner over an open fire in the simulated slum.

There was a lot more that happened on that night. None of the groups was given enough to be comfortable on their own. There was a lot of haggling, trading and even commando raids, but, in the end, they pulled together and made something of it.

The experience was quite useful, I think. Conditions were uncomfortable enough to register with the students, though a single night is not enough to really internalize all the challenges of urban slums where over one billion people spend their lives. But it does provide some very useful context for the poignant images of Jonas Bendiksen (Living in the Slums) and James Mollison (Where Children Sleep).

Image from the book, Where Children Sleep by James Mollison.

Fog on the Downs and Lake

Early morning.

The first few mornings at Heifer were cold. About five or six degrees Celcius (in the 40’s Fahrenheit) at sunrise. The large barn we slept in had been “converted” from housing horses to housing people. Apparently, horses prefer wide-open, drafty places.

But a warm sleeping bag goes a long way. And being forced to wake up just before the break of dawn does have certain advantages. I’m rarely up and about in time to capture the morning light. With the early morning fog drifting across the slopes and rising off the lake, those first few mornings were wonderful for photography.

Sunrise is usually the coldest time of day. After all, the Sun’s been down all night, and is only just about to start warming things up again. Cold air can’t hold as much moisture (water vapor) as warm air, so as the air cools down overnight the relative humidity gets higher and higher until it can’t hold any more – that’s called saturation humidity; 100% relative humidity. Then, when the air is saturated with water vapor, if it cools down just a little more, water droplets will start to form. The cooler it gets the more water is squeezed out of the air. Water vapor in the air is invisible, but the water droplets are what we see as fog. Clouds are big collections of water droplets too; clumps of fog in the sky.

Early morning fog drifts over the lake.

Tarantulas near the Global Village

Tarantula encountered on the path between the Zambia and Thailand (at the Heifer International Global Village).

We ran into this young tarantula on the path between the Zambian and Thai houses in Heifer International’s global village in Arkansas. We were taking the tour, and while this young fellow (probably male according to Zaq our guide) was not part of the regular schedule, we were lucky to find him. While tarantulas are venomous (mildly), and some have stinging hairs, their bites are about as painful as a bee sting (Warriner, 2011). But they are large, and, since most of us have a visceral fear of large arachnids, they’re pretty awesome to encounter (charismatic megafauna – is the term I like to use).

Zaq branished the wooden Spoon of Silence and shouted, "Hey. Take a look at this."

Tarantulas arrived in Arkansas about 8000 years ago (Warriner, 2011) at the height of the warmer, drier climate that followed the melting of the great North American glaciers about 10,000 years ago. The climate of Arkansas has gotten a bit wetter since then, but the spiders survive in isolated, drier upland areas (according to the Arkansas Tarantula Survey), like bits of grassland surrounded by forest. Pretty much like the grassy slope between the Thai and Zambian houses in the global village.

They can live to be 10-20 years old, which I think is pretty impressive for a spider.

Tarantulas usually just hang out at the mouth of their burrow and ambush anything that looks like prey to them. This includes insects and other spiders, but sometimes even lizards and very small mammals.

Identifying tarantula species is apparently difficult because their differences are usually quite subtle. The Arkansas chocolate tarantula (Aphonopelma hentzi), “is presumed to be Arkansas’ only tarantula species” (Barnes, 2002).

If you annoy them (with something like the Wooden Spoon of Silence) tarantulas will rear up and look menacing. Which is pretty awesome.

A slightly annoyed tarantula.