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.

A Breath of Fresh Air

If you like fresh air, you're probably a big fan of the Clean Air Act and its amendments. While the air in many places is far from ideal, prior to federal legislation it was downright deadly in American cities. A clear gray sky on a summer's day in Philadelphia is a little off-putting, but it beats a smothering fog in the valleys outside Pittsburgh. After the deadly Donora smog in 1948 killed 20 and sickened thousands of others. Federal investigators were asked to come in, and determined that air pollution was in fact the killer, among other factors.

Donora smog, 1948 (Smithsonian)

The government prefers to take baby steps when implementing positive change, rather than jumping in feet first, and tackling air pollution is no exception. The first step came in 1955 with the Air Pollution Control Act, which provided funding for research and led to the Clean Air Act of 1963 and Air Quality Act of 1967. These provided the first air quality monitoring.

Pittsburgh in the 1940s (Citylab)

The Clean Air Act of 1970 was a major step forward. It developed limits on pollution and expanded federal enforcement powers. Among the controls included were auto emissions. States were mandated to implement plans to reduce pollution.
The Amendments of 1990 aimed to reduce air pollution linked to acid rain and ozone depletion.
Looking at a picture of the summer sky over Los Angeles, it might be hard to believe the Clean Air Act is working. However, the number of ugly sky days is lower than prior to enactment. Air quality monitors in California frequently show poor quality, and geography is partly to blame. Ocean breezes carry pollution as far as the mountains, where it gets stuck and sometimes builds up for days.

Los Angeles skyline (LAist)

Acid rain has been reduced as a result on the 1990 amendments. pH testing has shown freshwater pH levels in many areas have risen closer to neutral 7. Pure water is neutral, but in nature, water is rarely pure. Pristine rain is slightly acidic because of carbon dioxide in the atmosphere forming carbonic acid. However, the lowered pH in rivers and lakes nationwide was far lower than caused by carbonic acid. Targets of the 1990 amendments were nitrogen oxides (NOx) and sulfur dioxide (SO2). Emissions have been greatly reduced over the last 30 years, and ecosystems are continuing to slowly recover.

Visuals of higher pH meaning less acidic water samples
(National Atmospheric Deposition Program)

Information this week comes the EPA (Clean Air Act overview), Smithsonian Magazine (Donora), and more EPA (acid rain). For a great visual on showing higher pH and lower NOx and SO2, check out the National Atmospheric Deposition Program.

EPA: https://www.epa.gov/clean-air-act-overview/evolution-clean-air-act
Smithsonian: https://www.smithsonianmag.com/history/deadly-donora-smog-1948-spurred-environmental-protection-have-we-forgotten-lesson-180970533/
EPA: https://www.epa.gov/airmarkets/acid-rain-program
nm1 LAist: https://laist.com/2018/10/30/why_las_smog_has_been_extra_smoggy.php
nm2 Citylab: https://www.citylab.com/design/2012/06/what-pittsburgh-looked-when-it-decided-it-had-pollution-problem/2185/
nm3 Smithsonian
nm4 National Atmospheric Deposition Program http://nadp.slh.wisc.edu/data/animaps.aspx

Dead Zones

This week we’re taking a look at a problematic summer tradition: hypoxic dead zones. These are marine or aquatic areas that don’t have enough oxygen to support life. The most famous is probably the dead zone in the Gulf of Mexico. Let’s look at dead zones, how they form, and what you can do to help prevent them.

The most common cause of dead zones is excessive nutrient runoff. Nutrients in this case are nitrogen and phosphorus, nutrients from plants. The main source of this nutrient runoff is agriculture, but it can also come from detergents, animal waste, and untreated sewage.

Gulf of Mexico dead zone (Digital Journal)

The nutrient overload leads to a sudden population boom in the local algae community. It seems paradoxical that algae, which produces oxygen, leads to an area without oxygen. First, when a large mat of algae covers the water’s surface it prevents oxygenation at the water/air interface. Then, when the algae dies and decomposes, that is where the oxygen disappears to. Mobile critters like fish can move to more oxygenated areas to survive, but something that can’t move or is very slow like a starfish or sea urchin will suffocate unless the situation clears up.

How a dead zone forms (Gulf Hypoxia)

Sometimes the algae bloom is of a type that produces toxins. Sometimes the toxins cause fish kills. Shellfish can absorb the toxins through filter feeding and pass them on to predators and people. Algae toxins can even threaten public drinking water.

A closer look at an algae bloom (NOAA)

How can you help? Trying to stop non-point pollution seems hopeless, but if everyone ups their game a little bit it adds up and makes a difference. Simple steps you can take at home include limiting the amount of fertilizer you use for your lawn and garden, cleaning up after your pup, and washing your car in the grass rather than the driveway or street. Reducing fertilizer use reduces the amount of excess nitrogen and phosphorus washing into the storm drain and out to sea. If you’re already doing that, buy organic produce which doesn’t use any fertilizer or pesticide. Picking up your dog poop keeps the nitrogen and phosphorus from that source out of the system as well. Washing your car in the yard lets the phosphorus in the detergent soak into the yard rather than washing into the storm drain. Every little bit helps.

This week's information comes from the EPA.