Tag Archives: TCE

Willows to the Rescue?

This week John and George sacrificed the usual Friday field work in order to work on our upcoming on-line native plants class to be in play as school starts.  Related to that, I’ve been fretting my second Florida outdoor interest—or let’s say nervous preoccupation—groundwater contamination.  The native plants connection is that millions of landscapers and homeowners who could use native plants with minimal chemical demands, instead spew mind-boggling (perhaps literally) herbicides, fungicides, and insecticides all over the ground, to percolate into the ground-water, which we later call tapwater.  (No, they do not get everything out.)

Salix caroliniana in flower by John Bradford.

Salix caroliniana in flower by John Bradford.

The situation is substantial and worsening, and in my humble opinion is under-publicized.  Somebody ought to start a blog (or a consumer revolution).  It is a joy to see an occasional piece in the PB Post and other Florida papers on this topic.  Yet hardly anybody cares, and a fine chemically tended lawn is a sign of responsibility and solid social status.  Just ask the HOA.  Okay, this paragraph could fill a book.  And such books exist, recently “What’s Gotten Into Us” by McKay Jenkins (2011).

Environmental author Steven Lerner—who has his own books on toxic stinkholes with depressing Florida examples—took a special interest in Tellevast, Florida near Sarasota.  The problems there are not pesticides, but rather defense industry wastes and spills, especially the chlorinated organic solvent called TCE (trichloroethylene) as well as beryllium and varied additional organic solvents.  Chlorinated organics turn up often on lists of carcinogens, for instance, the insecticide DDT, the herbicide 2,4-D, and dioxin.  They are the main rascals in Rachel Carson’s Silent Spring.

TCE is one of the worst U. S. groundwater contaminants.  (The likewise chlorinated herbicide Atrazine is a rival.)   TCE causes mutations and apparently cancers.  It deteriorates into even-more-carcinogenic vinyl chloride.  Sources of TCE pollution include defense-industry factories and aviation facilities.  My first known exposure was in Dayton, Ohio where TCE and additional solvents from Wright Patterson Airbase had visited the local groundwater.  The city erected air-strippers, which are water ventilation towers to transform water pollution to air pollution.

The citizens of Tellevast reportedly suffer disproportionately from cancers and medical troubles ascribed to TCE and other contaminants in the water beneath their feet.  The defense contractor Lockheed Martin owns the facility and is on the hooks for dealing with it.

Well, that’s all nasty, scary, debated, and politicized.  But this is a native plants blog, so, how ‘bout it?   Right!  This all brings us to the Willow Family, the Salicaceae.  The main Florida members of this family are poplars, cottonwoods, and a few willows.  The species in our local area and native to Tellevast is Carolina Willow (Salix caroliniana).

Willow leaves by JB

Willow leaves by JB

How do you oust chlorinated organic chemicals from groundwater without merely redistributing the poison?  There are several approaches but no silver bullet.  The approach of interest in our botanical blog is using poplars and willows for “bioremediation,” to disarm, alter, remove, and sequester the poisons.  It is all experimental, and truly promising at least under controlled conditions.  Poplars and willows are diverse, worldwide, resistant to toxins, easy to propagate, fast-growing, potentially deep-rooted, and able to suck up a lot of water.  They do nuke chlorinated organic pollutants.

Researchers are looking into the comparative efficacy of different species and hybrids.  The cast of species is important because different species flourish in different regions.  One size does not fit all. Poplars outshine willows, yet our own Carolina willow has made the defense team.

Trees detoxify water in multiple ways.  For starters, our green helpers suck up the polluted water through their roots and then alter and imprison the evil molecules in woody tissues.

More remarkable tools in the tree toolbox are enzymes called dehalogenases (dee-HAL-oh-jen-ase) able to clip chlorines off of organic molecules.  That’s almost magic, and to make more useful proteins there’s genetic engineering.  There are already GMO poplars engineered for various growth characteristics, so enzyme enhancement is no huge stretch. In fact, one poplar hybrid is already bioengineered specifically to degrade TCE and other organics.  And get this:  the gene engineered into the trees is a human gene, producing an enzyme to metabolize the carcinogenic molecules.

Risks include the possibility of sequestered toxins re-escaping from products made later from the trees.  Would you want to mulch your veggie garden with their chips?   Surprise chemical breakdown byproducts could emerge, and maybe even ecological misbehavior by the bionic trees.

Similarly armed with dehalogenase enzymes are bacteria, and they are partners in the clean-up and are targets for genetic engineering, which is occurring relevant to TCE.  Bacteria are easier and faster to engineer, incubate, and establish than trees.

Time to wrap this up.  In short, our groundwater is full of bad stuff.  Some of it comes from landscape and turf products where a shift to native species and less lawn would diminish the uckies. Most Florida shallow groundwater and some deep groundwater carries more contaminants than we’d like to know…or drink…even after “purification.”  The solvent TCE is a chlorinated organic goblin.  Tellevast floats 6 feet above TCE-laced water.   We’re not quite ready to plant the town with GMO willows.  But there’s hope for green remediation down the road.  So what the heck, we can load the groundwater up with carcinogens today and let our mutated great-grandchildren plant magic willows.



For an early in-depth look at the Tellevast situation:

For about bioremediation and TCE:


Posted by on July 13, 2014 in Carolina Willows


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