I Scream, You Scream, We All Scream for Isoprene

Plants are well known for absorbing carbon dioxide from the atmosphere and replacing it with oxygen as part of the photosynthesis process. But that’s not the only thing they put into the air. Trees emit tons of a chemical known as isoprene every year, mostly during summer months. It’s surprising to learn that plants contribute to air pollution. 

An abundance of isoprene can lead to formation of greater amounts of ozone by combining with nitrogen in the form of NO and NO2. Ozone in higher levels of the atmosphere is good because it blocks harmful UV rays from the sun, but at our level it’s a major pollutant.  

The current theory is that plants produce isoprene as a method of heat resistance. Like water vapor and oxygen, it is emitted through the pores in a plant’s leaf. Not every plant produces isoprene, but the biggest producers in the US are oaks and poplars.  

Shenandoah National Park (NPS)

Isoprene is what gives the Blue Ridge Mountains their blue appearance. The chemical haze scatters blue light, which makes the mountains appear blue from a distance. It also gives the Smoky Mountains their smoky appearance. 

Great Smoky Mountains (NPS)

We learn such shocking things about nature. I had no idea before today that plants are polluting the air with volatile organic compounds, which when man-made seem to be about the worst thing under the sun. Yet here they are, also giving some of our national parks their distinguishing features and even namesakes. 

Information comes from National Center for Biotechnology Information and Department of Energy Office of Science.

Weird and Wonderful Water

Water is the stuff of life. We can't live without it, and neither can the rest of the food chain. The search for extraterrestrial life hinges on whether or not a planet or moon contains liquid water, but that assumes that any life off Earth is the same as Earth-based life. This week we'll take a look about what makes water so special and how it keeps all of us alive.

Water, the most abundant substance on Earth.
Unless air is more abundant.

Water is unique among all chemicals (yes, it's a chemical) because it is the only one found in solid, liquid, and gas states naturally on Earth. While ice and water vapor aren't basic requirements for life, they are key components of the water cycle. Water stored as snow and ice in the mountains is slowly released during the dry summers in the American west, meaning a steady flow in rivers throughout the year. Clouds made of water vapor transport precipitation over long distances. On top of that, ice and steam make modern life more convenient- think food storage and electricity generation.

Winter snow waiting for the spring melt, March 2016

Typically, solids are more dense than liquids, which in turn are more dense than gases. Water flips this around, as ice is less dense than liquid water. If you freeze a container of water, you'll notice that the ice fills more of the container than the water did. This is why your frozen pipes burst in winter. The expansion of water as it freezes is a visual of the density decreasing. Because ice is less dense than water, it floats. Because ice floats, it forms on the surface of lakes and other bodies. This allows aquatic life to survive. If water froze from the bottom up, everything would either freeze in place, or eventually be exposed on the surface.

Molecular structure of liquid water and ice (Mountain Empire CC)

Water has adhesive and cohesive properties. Water molecules stick to each other (cohesion) and other substances (adhesion). Adhesion causes capillary action. This is the movement that is responsible for plants being able to absorb water in the ground through their roots, up the stem, and to the highest leaves. Cohesion also contributes to surface tension. Water molecules on the surface are more tightly packed and can resist pressure from outside forces. This allows objects to float. Water striders can stand on the surface because of surface tension.

Water strider striding water (National Wildlife Federation)

Water has a high specific heat. Specific heat is the amount of energy needed to raise the temperature of a gram of water by one degree Celsius. Because it takes a lot of energy (1 calorie per gram) to heat water, it takes a lot of heat to boil water. Ocean life appreciates not being boiled. Water also holds onto heat it absorbs and releases it slowly, moderating Earth's temperature and making the seasonal changes gradual.

Water dissolves more substances than any other. The polar structure of the water molecule. The positive hydrogen end will attract negative ions, while the negative oxygen ends attract positive ions. Water's solvency is important for plants and animals to absorb nutrients, and for animals to flush waste from their bodies. Nonpolar substances like fats do not dissolve. That's where the saying "Oil and water don't mix" comes from. Less dense fats will float on top of water, and with some skill they can be separated.

Next time you take a drink, raise a glass in appreciation of water. Without it, your drink wouldn't be here and neither would you. This week's information comes from USGS and Mountain Empire Community College.