Turf Battles and Plant Physics
Stuart Gaffin is a climate researcher at Columbia University and is a regular contributor with his blog “Exhausted Earth”. Reuters is not responsible for the content — the views are the author’s alone.
These fields are modern versions of the original “AstroTurf” installed inside the Houston Astrodome in the late 1960s, after it was found living turf grass would not survive there. Synthetic fields are becoming increasingly popular as outdoor recreational fields, usually replacing grass fields.
In cities they are also becoming popular as playground surfaces, instead of the old “asphalt jungle” pavements. Concerned individuals from many different quarters, including environmental scientists and park advocates, health researchers, parents and community groups, are raising many questions about the potential environmental and health consequences of unmitigated synthetic turf usage.
A good summary article can be found in the March 2008 issue of Environmental Health Perspectives . Among the main health concerns is the fact that a large component of the synthetic field is made of crumb rubber pellets derived from recycled vehicle tires.
Tires contain a number of known chemical toxins that prevent them from being placed even in landfills. Ground-up tire pellets are therefore even more worrisome as they tend to erode even faster and leach into groundwater. Parents are naturally concerned when they see their children in direct contact with the crumb on the fields, possibly ingesting it and bringing it home on their clothing and shoes.
To make matters worse, I and other scientists have recently been reporting how hot these playing surfaces are on summer days. A graph of synthetic turf temperatures I measured last summer, compared to a nearby grass field, is shown at the end of this blog. I often find that synthetic turf fields run 60° F hotter than grass fields on sunny afternoons, easily reaching temperatures of 140° F or more. This is close to the temperatures I have recorded on black ‘tar beach’ rooftops. So, when children play on synthetic turf fields in the summer heat, it may be like sending them to play on a rooftop surface.
Which brings me to the interesting science question: Since synthetic turf fields look like grass fields and have a similar dark-green color, how do grass fields and plants in general manage to avoid reaching such high temperatures and dying as a result?
The answer is evaporation of soil moisture through their leaves. Plants are nature’s “geniuses” when it comes to evaporating water to stay cool in the sunlight. They need sunlight for photosynthesis of course so they perfected mechanisms of evaporation to avoid burning up. So what can plants do for those burning hot tar beach roofs? The answer is “a lot” in the form of “green roofs”, which I’ll post about next time.
Graph showing surface temperatures over time: Ambient air temperature 78 F on July 3, 2007, at 1:00 p.m. The blue line, starting at just above 140 F, is the temperature for artificial turf and the lower green line, starting at 90F, is grass. Temperatures in Fahrenheit (vertical scale), time (30 minutes) (horizontal)