Fighting Lead: Urban Remediation
I want to use a sustainable, solution-oriented, & critical approach to look at the serious and widespread problem of lead contamination.
First, we need to understand how lead functions in order to properly assess solutions to remediate the ground water & soil.
History
Lead (pB) is a carbon element with the highest atomic number (82) of any non-radioactive element. It is a neurotoxin, mainly damaging the brain and nervous system, but has also been linked to blood disorders as it accumulates inside the body. It has been extracted and used for thousands of years, by many different peoples for many different things, some of which include writing and drawing materials, currency, and the Roman aqueduct system, as it was one of the first easily smelted metals. Ancient botanists and physicians also remarked on its harmful effects to the mind. But it isn’t until the Industrial Revolution that lead production rates rise higher than these uses of antiquity.
By 1900, the US becomes a world leader in lead extraction, shifting from Britain. In this way, American Industry is inextricably tied to unearthing lead, and would find ways to monetize it quickly. The demand was manufactured mostly for plumbing, painting, and leaded gasoline which was invented in 1921. Between 1921 and the late 70′s-80′s when lead becomes outlawed in various substances, there is a massive pouring of lead into urban areas. This came with advertising & PR campaigns claiming lead was a safe & effective material for use in anything from car batteries and paint to gasoline. It became a commonplace material.
With this, we must center our attention on the working class people who labored for General Motors, Dupont, Sherwin Williams & others who exposed themselves daily through elevated levels in the air, and through skin, eye, and mouth contact. Cumulatively, what this has resulted in is elevated lead levels in urban soil, water, air, and of course elevated blood lead levels in animals & people who either worked with or consumed these lead filled products. Many lead lawsuits are still pending with these companies.
Urban gardening for food justice is a movement that must recognize this history in order to address the proper methodologies for remediation.
The first problem is that now that lead has been introduced to cities, it does not disappear, dissolve, or biodegrade. It is a heavy metal that sits inactive in the soil and water until it finds something to bind to, and we don’t want it to be in our bones & blood or in our produce.
If your first thought is “well let’s find a way to remove it” this is a compelling strategy and the first one I’ll discuss.
Phytoremediation
I’ve been using lead as a prime example because it is one of the most common and extreme contaminants in urban areas, however, as mentioned in my last blog post about How To Get Your Soil Tested, there are a plethora of contaminants which are not conducive to growing organic food. When using the phytoremediation method, it is important to know which of these chemicals needs to be removed as it changes the appropriate plants & removal methods. Here is a handy chart:
image credit Urban Omnibus
As you can see the methods vary slightly depending on how to best combat the contaminant. Lead can be removed slowly through phytoextraction, which is seasonal planting that ends in the harvest of the entire plant & hazardous waste disposal. Duckweed, sunflowers, and alpine pennycrass are suggested here, however a thorough resource for learning which plants to use for phytoextraction can be found here.
Biosolid Remediation
Another really effective and central way to attack lead in urban areas is biosolid remediation, or phytostabilzation as listed in the chart. This takes a chemical approach to remediation by adding copious amounts of material high in phosphorous, iron, manganese, and other organic matter in compost, manure, and mulch to the soil. When the lead comes into contact with this material, it binds to it, rendering it inactive. This binding process means that the lead available to enter our bloodstream through contact drops dramatically following remediation. Seeing that most cities cannot use expensive extraction methods to deal with lead, biosolid remediation is a cheap, effective way to render lead inactive, as well as promote a thick healthy layer of topsoil for proper soil development.
I might push biosolid remediation a step further and call for an overhaul of urban waste management procedure.
Imagine if the city was composting all of its organic material & then using that organic matter to remediate the soil, sustainably rendering lead (and other contaminant) exposure a problem of the past? It is absolutely possible, and effectively deals with two urban specific problems at the same time.
Barrier Remediation
In tandem with biosolid remediation is the barrier remediation method. This is where a barrier is created between the contaminated soil & the ground cover mulch as well as the raised beds for planting. The reason why a barrier is important is twofold. One, if you are planting anything with deep roots, you are not going to want them reaching into contaminated soil, you want to contain them to your rich compost beds. Secondly, ground water is just as contaminated as the soil. When the ground water swells, lead contaminated water rises up from underneath. The barrier method allows you to make sure contaminated ground water stays contained, further protecting your plants and animals as well as your own health!
All of these remediation methods are important to the future of urban soil development.
A combination of these methods, depending on intended use of the site, are most effective at minimizing exposure.
These techniques have been implemented in NYC, Baltimore, Chicago, and other cities in favor of ending this history of environmental destruction. Remember to always get your soil tested before digging into city dirt, and if you find out you have a contamination, do not fret! We have the knowledge and the tools to begin healing the earth, we just have to be empowered to act on them.