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Using Trees to Clean Up Pollution: M. Cristina Negri

Can plants clean up nuclear waste, solve the energy crisis, remediate contaminated land and water, and curb critically high levels of greenhouse gas emissions?


Agronomist, soil scientist, and self-described “doctor of the earth,” M. Cristina Negri presented her innovative research on using plants to counteract environmental pollution at the 2011 Chicago Humanities Festival.



Ground contamination is difficult to deal with because pollutants disperse finely into soil, seeping into every nook and cranny of the dirt. Contaminants such as heavy metals bond with clay and organic matter in a way that makes extraction extremely time- and energy-consuming.


The conventional way to “clean” contaminated earth is to dig up all the soil the contaminants have touched and cover it in more dirt, sequestering it far below ground and away from sources of fresh water. If the dirt cannot be buried away then the only other thing to do is block off the land from human usage, rendering large blocks of earth completely unproductive for decades.


Negri researches how plants can draw pollutants—like how they draw minerals and nutrients—out of soil and water in a process called phytoremediation.


“Plants take up things or elements or contaminants or nutrients from the soil so why not use it for [clean up]? The beauty of it is it’s totally green.”


Negri’s work has taken her to many dangerously polluted industrial and disaster sites. She speaks about her experience at Chernobyl and hopes for a solution to the nuclear contamination at Fukushima.


“I went to Chernobyl in ‘96, so 10 years after the explosion. What struck me was the depression among people. How people really had no hopes and had no idea they were in control of their lives and it was a very unsettling feeling …. it’s basically a place that has been abandoned and left in place - crystallized in time.”



Highlights include

  • 00:36 - Negri’s background

  • 06:02 - How Negri became interested in phytoremediation

  • 10:15 - Specific challenges in land contamination

  • 17:18 - An elegant solution

  • 18:32 - Applications for phytoremediation in Chicago

  • 23:08 - Using phytoremediation in conjunction with biofuels and reducing water pollution

  • 30:29 - Using plants to work with radioactive pollution

  • 31:50 - Problems in Chernobyl

  • 32:59 - Negri’s work in Chernobyl

  • 38:33 - Possibilities in using phytoremediation to aid with the radioactive cleanup in Fukushima

Destructive human activity has rendered countless acres of land toxic and unusable. However, different ways of thinking about natural processes gives hope to the future of environmental policy. Negri talks about her vision for cleaning up the polluted the Chicago River through combining urban planning and phytoremediation in a project to create public oases along the banks. Negri’s compelling story of using nature to heal nature is a brilliantly simple and elegant solution to a complex problem. What other environmental issues might be solved with this kind of thinking?

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