Dr. Jorge S. Alvarado, Ph.D. | Science and technology for the preservation and restoration of the soils
Today I am going talk about a not so holistic matter: I am going to talk about: The responsibility of a scientist and attempting to use natural means that can be used within science, to places that have been contaminated.
Allow me to tell you a story: In the 50s and 60s the world was different and we had the Cold War paranoia; and the United States stored wheat and corn throughout the country, and to keep them healthy, they added pesticides.
Eventually the pesticides reached the soil, they percolated through the soil and have contaminated the aquifers in the United States. There are aquifers in many areas that are extremely deep (and that is a major problem), but everything in the Midwest of the United States has aquifers that are quite superficial and people drink water from those aquifers.
What is the problem? It has been discovered that the chemicals that were used to maintain this wheat, are carcinogenic; and that was discovered until the 70s. So, people are drinking water with carcinogenic products.
What do we have to do? First, we have to see how we can clean up, we have to see where is the contamination at. And there comes what we call characterization of an area that has been contaminated; and it is the most important thing we need. Why? Because depending on the characterization we will have differences in the cleaning method of that place.
So characterization has to be a dynamic process. We cannot just arrive and use traditional methodologies, but we have to use a method where there are geologists, chemists, biologists, computer technicians; where we can all engage with each other and look for the best solution.
We have to be economically responsible, so we have to do it faster, cheaper and better. If we can achieve these three objectives, we can make a characterization. As I say, it is important.
The principal pollutant that was used is called carbon tetrachloride. Carbon tetrachloride is a unique molecule in a way: It is 1 carbon with 4 chlorines. It turns out that each chlorine is electronegative and pulls carbon in the same way, making it extremely stable. So bacteria or any other chemical product does not destroy it. The belonging of carbon tetrachloride in the soil is a lot greater than any other chemical product, and has been there since the 60s.
This is the molecule, and what I want is for you to see how stable it is, because it is completely symmetrical.
What is the problem? This was used in farms, in silos, and something called Quonset huts (which are huge huts where wheat was stored).
Interesting what we have discovered, is that the use was not inappropriate, but a misuse. For example, in these Quonset huts, what we have found is that outside the doors is where the contamination is. We have created methods to detect contamination in parts per trillion.
So someone finished with their little pesticide bottle and did like this at the door, and that has created an incredible contamination. Remember: for it to be carcinogenic, the carbon tetrachloride has to be in concentrations of greater than 5 parts per billion (in other words, those are quite low concentrations). So, if someone did like this, that is more than enough to be above 5 parts per billion.
Allow me to show you how our places are. We still have the silos today (in some cases); in some cases the silos have been eliminated and what we have is simply an empty lot and the contamination is there. Generally the land is close to towns where people are again drinking contaminated water.
These two here below are instruments that we use to open up the soil without the need to cause waste, and they have sensors to monitor conductivity and other things; and then we can know what is in the soil, in the subsoil, without the need to open wells and have waste; so those are instruments that help us with that.
So what do we do? One of the technics of which I will be talking about is the creation of iron nano and micro-particles that have been used for the destruction of carbon tetrachloride but have never been able to completely destroy it. What we have created are these micro-particles that we have surrounded with an organic material, which in reality is a corn material. These particles are hydrophilic (it means they dissolve in water) and we can inject them directly in the subsoil.
So, the purpose is -we as chemists- to modify the environment to be able to make the chemical reactions happen. We introduce the micro-particles that have organic matter. What happens when we introduce them? There is bacteria in the soil; bacteria begins to eat the organic matter, is very happy: eats, eats, eats; it reproduces, reproduces, reproduces, and the conditions change. It changes from an oxygenated system to a non-oxygenated system: anaerobic.
When the system changes to an anaerobic system there is one thing called redox potential that makes a reaction happen or not. Then, we can change the redox potential to values that are less than 600 millivolts that makes the reaction occur. Thus, all this is a supposition before doing it. If that happens, then we can completely destroy the carbon tetrachloride, and the final product in reality would be iron 3, iron 3 is rust. So, we would leave the place without contamination and we would not create more contamination (as other methods use it).
First thing we did is: Does it work? Then, we chose a place (in this case it is a place in Kansas, United Stated, and called Centralia) and we did the characterization first. So, do you see the circuits? Those are the silos; the square little houses are what we call Quonset huts; and we found a place of contamination that can be seen there: the flow goes towards the Northeast, from the water that is there.
In other words, we knew very well how it is; and this place has the characterization that the water is not moving -it is like a pool-. We simply wanted to know to see if the process worked.
So we took the area that is to the west to make a pilot plan and see if this was going to work out. At the end we did a characterization a bit more detailed and we discovered there was an area that was a little bit more contaminated; we did not make a square but another shape, to cover the entire area.
From there we found that the contaminations where above the 2000 parts per billion (in some areas), so the place was highly polluted. We injected the small iron molecules and the first thing we find is (in almost every case) that the iron goes from the 2000 parts per billion to almost 0 in two weeks. So we can completely destroy the carbon tetrachloride in two weeks.
In this carbon tetrachloride we have a point that did not work out; interesting: in that point we did not inject iron; but it seems there is a physical effect that makes the tetrachloride move and cause that anomaly.
Interesting. The product has still worked for more than four years and has destroyed carbon tetrachloride that was at that point.
To tell you that it is true, the picture above gives us the chloroform concentrations (which is the first product of degradation) and the second product is the dichloromethane. Then, we can see the formation starting from 0, where the chloroform is formed, and immediately the dichloromethane begins to form. As the carbon tetrachloride disappears the chloroform is formed; the chloroform begins to disappear to form the dichloromethane.
The following product is very fast and we cannot monitor it; but what we can monitor is which is the iron formation. I am inserting iron 0. What happens with the iron? So we do various things:
One is, we measure the redox potential (what I said) and we see that the beginning of the system goes below values of -600, making the system start; afterwards there is a reaction of electron donor, and the reaction continues happening for up to four years because it is a chain reaction.
We monitor the oxygen, and we see that the oxygen goes from a higher point and decreases to obtain the anaerobic conditions; and iron (Fe) begins in 0 and rises dramatically to reach bigger values, meaning that the reaction is happening.
So, at the end we went from places where they were contaminated at 200 parts per billion, to 2016: we almost have no contamination. In various places we have 100% cleanliness, and there are a pair that have 8% of contamination, that are functioning and still getting cleaned.
So, a few conclusions of what I have told you: We have to think and be logical in the way in which you make you characterization, and that characterization will give you the method in order to clean.
I am not going to read this, but I want to show you a few more examples.
This is another example of cleaning that we have used: It is an irrigation system where we have used water in very small particles and have analyzed each particle to form wetlands. So, the water where it leaves the system and reaches the soil has been cleaned, by the size of the particle.
It turns out that there is an immigration, bird immigration, from the South (South America), it has a conical shape, they come from everywhere and come together exactly in Midwestern United States, and reopen in Canada.
It so happens that our programs are exactly where birds fly. The purpose was to form a wetland with the water that we had, so the birds could stop in their same immigration and continue onwards. It is a somewhat environmental way to make a cleaning system; and at the same time give the area a bit more environmental things (let’s say).
So, as there is how birds fly, this was the pilot system. When we measured and where sure that each one of the particles would reach the soil without contamination.
The one you see there (in the other one) is the final system. When you are looking at it, already a lot bigger and in serious application. And here a picture when we see the wetland, and in the middle a duckling (so you can see it is working).
Another project we have is the cleaning using trees as cleaning bombs. This is an area that has been contaminated; we make wells of different sizes, where we can plant a tree at different... 10 feet, 20 feet, even 50 feet.
So, each of the trees work as a bomb to remove contamination from the water, it passes it through its system, and throws it through its leaves. The water ends up clean and we have been able to have a clean system.
Here (as you can see) you see each one of the wells where each one of the trees come. We have used two varieties: one called poplar and the other one called sauce; Both natives to the are where we are working, we have not brought any foreign tree.
At the end (as you see), there is how we have made the wells to put each one of the trees; and we have managed to maintain and clean the contaminated areas with the Phytoremediation system.
This is the last one of our programs (I brought you a movie, but we are not going to see it). This place has been contaminated, and what were are doing at this moment is placing horizontal wells (instead of vertical) to extract the contaminants. So, there has been contamination as you see... in this picture you can see there is a people completely, around the contaminated. The pink areas are the areas where contamination exists and where it is at this moment.
One of the biggest problems that we have in a town like this, is that carbon tetrachloride is volatile and enters the soil, through the soil, in your house; so you are breathing carbon tetrachloride; and breathing is a lot more complicated than drinking it.
So, for all these houses what we have had to do are air cleaning systems (for each of the houses). In the United States we have a radon problem and we have radon house cleaning systems; and we use the system to clean carbon tetrachloride. So it is a commercial system and easy to implement.
In this case we have introduced a horizontal well and we can extract it; and we are in the cleaning process of this place. It is interesting, the system has close to 500 parts per billion of contamination; unfortunately the system cannot be applied any other way or with other techniques throughout the town. So that limits us in what we are going to do; and we are hoping the cleanse lasts from 10 and 20 years (unfortunately).
I want to thank the people who work with us; and if you have any questions (anytime), at your service.