Herbicides and Stormwater Ponds, Urban Greening or Urban Poison?

With a number of comments, emails and questions submitted about stormwater ponds and toxins, I thought a few clarifying comments would be appropriate.

Aquatic Herbicides

The discussion over Roundup's safety and use is a no-winner for either side.  You have one side who is going to continue spraying a poison into surface waters because they feel the herbicide is safe.  Then you have the other view, one that a poison is a poison and that all herbicides should be avoided.

Science can be argued and research pointed to that supports both sides.  My personal belief, after suffering from so many health issues is that any man made chemical that is not necessary to live with should be avoided, especially those used for convenience sake, such as herbicides or pesticides.  Remember the whole Agent Orange fiasco?

However the interesting questions about last blog post were more focused on the questions of whether plants remove pollutants and toxins from stormwater or do nutirents such as phosphorous and nitrogen, and heavy metals participate out into the pond soils?

Other issues raised included topics such as the logistics of plants growing in ponds and relative littoral zone availability for root contact and full plant growth.

I thought I'd post some interesting links about these topics and let the readers decide as to how they want to view the issues.  Letting others decide for themselves is so much easier than trying to convince people to believe one way or another way.

It's like the Roundup salesman who used to visit the tree farm where I worked while attending law school.  He'd swear that the glyphosate based herbicide was so safe for humans that people could drink the undilluted concentrate straight and it'd never hurt anyone.  But no mater how hard he argued, I'd never drink the herbicide.  Today my cardiologist tells me to avoid all foods or substances that have a 'phos' term in the ingredients because of potential liver and kidney damage.  Once you damage those organs your life is pretty well tied to dialysis or transplant surgery.

Yes I personally think applying herbicides in stormwater ponds is a terrible action to take when considering long term health, safety and welfare of the urban core's inhabitants.

But with respect to plants and their ability to clean water, below are a couple interesting links and thoughts to consider.

Consideration One - no room on the pond's edge (too steep a slope) to plant plants.  True.  But this argument is quite old and there has been so much research completed on extending littoral zone areas with the use of floating wetlands or managed aquatic plant systems that the 'lack of space' argument is pretty much a non-issue.  One can scratch their head about how to add more plants to a pond or one can create floating islands of aquatic plants.  

Consideration Two - do the soils or do the plants that clean stormwater?  Again there is considerable research published showing both soils and plants remove nitrogen and phosphorous from stormwater and surface water.  The decades of research and work about cleaning Lake Apopka conducted by UF's Dr. Reddy using constructed wetlands shows both soils and plants are important in removing pollutants.

Other research specifically points to the use of aquatic plants for removing pollutants from water.

Even several of the universities here in Florida have conducted research into plants and their ability to clean stormwater, including removing nutrients and pollutants.  Dr. Mark Clark of the University of Florida has completed a floating wetland and nutrient removal study as well as researchers with the University of Central Florida, including Dr. Chopra and others. 

In fact, many studies point to the successful ability to employ floating plant systems in efforts to clean stormwater. 

NASA uses aquatic plants to clean sewage!

Studies have also been conducted showing the capabilities of plants to not only remove nutrients but to also remove metals and other toxins from surface waters.

Aquatic vegetation is used across the world to clean sewage, removing nutrients, bacteria and metals.

Another interesting plant-based stormwater cleansing project is the Egret Marsh Algae Scrubber here in Florida, where algae is grown in stormwater then harvested, removing both nitrogen and phosphorous from effluent and runoff before entering the intracoastal waterway.

But not only here in Florida, there are other states - such as Michigan - where aquatic plants are considered important for cleaning stormwater.

Since both soils and plants have been shown to be effective in cleaning stormwater the question the becomes, 'why not employ both?'

You can make your own decision.  You can decide what technical arguments you wish to use to defend your present practice - whatever it may be.

For me it is easy.  Use lots of plants to clean storm runoff before the pollutants reach aquatic life and begin the bio-accumulation process, like in the example of mercury we are so familiar with. 

But really the BIG question is not about whether to use plants to clean water or not.

The real question is what to do with the plants in the pond, regardless of what they are there for, once they have reached maturity.  Do you kill the plants with a herbicide and leave them in the pond or do you remove the biomass from the water system through mechanical harvesting?  This is the real question - the one many maintenance managers want to avoid discussing.

I am strongly biased against aquatic herbicide use.

When the aquatic plants absorb pollutants, be they nutrients or metals, then once the plants reach maturity they should be harvested and removed from the pond as done in some of the research projects referred to here.

Killing mature aquatic plants that have sequestered toxins and allowing the pollutants to re-enter the water column just doesn't make sense to me.

But that is my strong opinion.  I will never be convinced aquatic poisons are safe.

Even though the Roundup salesman man have convinced himself to drink the glyphosate containing concentrate, I never would.  Come on!  Drink a poison?  I have trouble keeping my body alive consuming healthy foods and lots of clean water!

And though there are many standard policy manuals (mostly written by herbicide companies for end users use) that recommend the safety of herbicide use in the urban core, I never would condone application of aquatic herbicides into urban stormwater systems.

Yet I also know I will never convince those in charge of pond maintenance to stop using herbicides to kill cattails.

But when I see the dead plants I can't help but think of the herbicide use decision maker sitting in his swivel chairs at his desk in an air conditioned office, happy they don't have to deal with the probably more difficult chore of figuring out how to harvest cattail biomass, removing sequestered nutrients and toxins from the stormwater.

It is so much easier to just kill the cattails and let them fall back into the pond.

And statistically, chances are the diluted poisons will never affect anyone in their family or anyone they know in their lifetime.

But somewhere, sometime the herbicide or a derivative of the herbicide, or a once sequestered toxin will be re-released into the water supply.  And an innocent child coming in contact with the water will develop a cancer and die.  Though we will never know what caused our nine month old granddaughter, Heidi's brain tumor and death, Tallahassee's water supply had received critical reports of certain toxins.

And I suspect that somewhere in the life cycle of stormwater and herbicide use, another child will come in contact with a once sequestered toxin and suffer unnecessarily.  All while the maintenance manager issues another purchase order for Roundup.

I think life's meaning is really found somewhere in our purposed intent of how we treat and care for the earth.  Please don't tell me herbicides are safe to use.