Tag Archives: phytoremediation

Phytoremediation with lupin and arsenic

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Is anyone else reminded of Arsène Lupin? (More about Lupin later in this posing)

An August 24, 2021 news item on ScienceDaily describes research on soils and phytoremediation (decontamination by plants),

Pollution of soils with highly toxic arsenic is a worldwide problem generating substantial risks to human health and the environment.

In Canada, over 7000 sites contaminated with metals such as arsenic are considered ‘highly concerning’ by the government, with some past and recent mining operations and wood preservative facilities having left their mark on the environment by increasing soil arsenic levels by up to 1000 times the maximum regulatory health limits.

One way in which arsenic contaminated soils could be rejuvenated is to exploit natural mechanisms which have evolved in certain plants for contamination tolerance.

“The legume crop white lupin (L. albus) is one such arsenic tolerant plant species being studied as for sustainable remediation,” explains Adrien Frémont, lead author of the study and a doctoral student in biological sciences at the Université de Montréal. “The mechanism behind arsenic tolerance in white lupin is thought to be the release of plant chemicals directly into soil by roots, but the nature of these compounds is unknown and hard to study due to the complexity of these belowground interactions.”

Caption: The legume crop white lupin (L. albus) is one such arsenic tolerant plant species being studied as for sustainable remediation. Credit: UMONTREAL

An August 24, 2021 University of Montreal (Université de Montréal) news release (also on EurekAlert), which originated the news item, describes the work in more detail,

Root chemicals an undiscovered country

To study this, the team developed nylon pouches which could be placed close to roots in soil to capture exuded molecules without damaging the root system. The complex mix of molecules collected from these pouches were analysed using advanced (metabolomic) chemical profiling to identify the compounds capable of binding metals produced by the Lupin plants in response to high concentrations of arsenic. Some of these metal-binding molecules, phytochelatins, are known to be used internally by plants to deal with metal stress but have never before been captured as exuded into polluted soils.

“We’re really excited to see how matching new root-soil sampling approaches with advanced metabolomic profiling can yield such unexpected discoveries”, notes Frémont. “We know that plants can drastically change soil properties and can transform or immobilise soil pollution, but the chemistry underlying how they achieve this, and in particular the makeup and function of root-exuded compounds, is still very much an undiscovered country.”
 

Plant roots directly altering polluted soils

The next steps of the research are to branch out into more detailed analysis of the precise chemical reactions taking place at the root-soil interface, including exploration of different plant species, interactions with microorganisms and the challenge of diverse soil pollution.

As Dr. Nicholas Brereton, University of Montreal and the study’s senior author, mentions: “It can be a real challenge to research the complex interactions going on belowground between plants and soil, but these findings are rewarding in telling us that natural mechanisms have evolved in plants to deal with this type of pollution. Although we’re still only just beginning to scratch below the surface of how these plant root strategies work, as we learn more, we can potentially utilise these natural processes to improve soil health and help to alleviate some of the most persistent anthropogenic damage to our environment.”

Here’s a link to and a citation for the paper,

Phytochelatin and coumarin enrichment in root exudates of arsenic-treated white lupin by Adrien Frémont, Eszter Sas, Mathieu Sarrazin, Emmanuel Gonzalez, Jacques Brisson, Frédéric Emmanuel Pitre, Nicholas James Beresford Brereton. Plant Cell & Environment DOI: https://doi.org/10.1111/pce.14163 First published: 15 August 2021

This paper is behind a paywall.

For anyone interested in phytoremediation, I have a March 30, 2012 posting about it and there’s this Wikipedia entry. Depending on the circumstances, you might also consider phytoremediation as a form of phyto-mining, i.e., using plants to recover metals from mine tailings (see my March 5, 2013 posting).

Arsène Lupin

There are two of them (the first and the latest ones) being mentioned here; but there are many versions of Arsène Lupin in manga, anime, movies, etc.

The first fictional Arsène Lupin was created in 1905 by Maurice Leblanc. Here’s a description (on the Normandie tourisme website) of the first Lupin in an article about the latest Lupin, a series streamed on Netflix.

…

Maurice Leblanc was born in Rouen in 1864. Fascinated by legends of witches, Celts, Romans and the Vikings growing up, Leblanc would go on to develop a deep knowledge of and love for the region around Rouen, known as the Pays de Caux. After working in a factory in Rouen by day, writing only in his spare time, Leblanc eventually left his home town to study in Paris, where he then started working as a journalist for several publications including Le Figaro. Fate then struck, as publisher Pierre Lafitte launched the magazine Je sais tout and commissioned Leblanc to write a series of new crime stories where the hero would be a sort of French anti-Sherlock Holmes.

Who was the original Lupin? Not unlike Lupin in the TV series, the Arsène Lupin of the books was a thief, a master of disguise, a rascal but never a killer, a hit with the ladies and a righter of wrongs who takes from the rich, a French Robin Hood if you like. He takes on a multitude of personas in the books, constantly changing his looks and his name – examples include Prince Paul Sernine, Raoul d’Andrésy, Horace Velmont and Don Luis Perenna. In the [Lupin] series [2021], this is echoed by Assane’s alter-egos Paul Sernine, Luis Perenna and Salvatore813, as well as his choice of name for his son, Raoul. Yet superman Lupin, both in the books and on screen, always manages to triumph somehow over his enemies, even when all seems lost, through bending the rules, outsmarting the police and sheer self-belief.

You can find out more about the latest Lupin in its IMDb entry,

Inspired by the adventures of Arsène Lupin, gentleman thief Assane Diop sets out to avenge his father for an injustice inflicted by a wealthy family.

The television series starring Omar Sy was a huge hit in France and has been seen worldwide.

Let them (Rice University scientists) show you how to restore oil-soaked soil

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I did not want to cash in (so to speak) on someone else’s fun headline so I played with it. Hre is the original head, which was likely written by either David Ruth or Mike Williams at Rice University (Texas, US), “Lettuce show you how to restore oil-soaked soil.”

A February 1, 2019 news item on ScienceDaily on the science behind lettuce and oil-soaked soil,

Rice University engineers have figured out how soil contaminated by heavy oil can not only be cleaned but made fertile again.

How do they know it works? They grew lettuce.

Rice engineers Kyriacos Zygourakis and Pedro Alvarez and their colleagues have fine-tuned their method to remove petroleum contaminants from soil through the age-old process of pyrolysis. The technique gently heats soil while keeping oxygen out, which avoids the damage usually done to fertile soil when burning hydrocarbons cause temperature spikes.

…

Lettuce growing in once oil-contaminated soil revived by a process developed by Rice University engineers. The Rice team determined that pyrolyzing oil-soaked soil for 15 minutes at 420 degrees Celsius is sufficient to eliminate contaminants while preserving the soil’s fertility. The lettuce plants shown here, in treated and fertilized soil, showed robust growth over 14 days. Photo by Wen Song

A February 1, 2019 Rice University news release (also on EurekAlert), which originated the news item, explains more about the work,

While large-volume marine spills get most of the attention, 98 percent of oil spills occur on land, Alvarez points out, with more than 25,000 spills a year reported to the Environmental Protection Agency. That makes the need for cost-effective remediation clear, he said.

“We saw an opportunity to convert a liability, contaminated soil, into a commodity, fertile soil,” Alvarez said.

The key to retaining fertility is to preserve the soil’s essential clays, Zygourakis said. “Clays retain water, and if you raise the temperature too high, you basically destroy them,” he said. “If you exceed 500 degrees Celsius (900 degrees Fahrenheit), dehydration is irreversible.

The researchers put soil samples from Hearne, Texas, contaminated in the lab with heavy crude, into a kiln to see what temperature best eliminated the most oil, and how long it took.

Their results showed heating samples in the rotating drum at 420 C (788 F) for 15 minutes eliminated 99.9 percent of total petroleum hydrocarbons (TPH) and 94.5 percent of polycyclic aromatic hydrocarbons (PAH), leaving the treated soils with roughly the same pollutant levels found in natural, uncontaminated soil.

The paper appears in the American Chemical Society journal Environmental Science and Technology. It follows several papers by the same group that detailed the mechanism by which pyrolysis removes contaminants and turns some of the unwanted hydrocarbons into char, while leaving behind soil almost as fertile as the original. “While heating soil to clean it isn’t a new process,” Zygourakis said, “we’ve proved we can do it quickly in a continuous reactor to remove TPH, and we’ve learned how to optimize the pyrolysis conditions to maximize contaminant removal while minimizing soil damage and loss of fertility.

“We also learned we can do it with less energy than other methods, and we have detoxified the soil so that we can safely put it back,” he said.

Heating the soil to about 420 C represents the sweet spot for treatment, Zygourakis said. Heating it to 470 C (878 F) did a marginally better job in removing contaminants, but used more energy and, more importantly, decreased the soil’s fertility to the degree that it could not be reused.

“Between 200 and 300 C (392-572 F), the light volatile compounds evaporate,” he said. “When you get to 350 to 400 C (662-752 F), you start breaking first the heteroatom bonds, and then carbon-carbon and carbon-hydrogen bonds triggering a sequence of radical reactions that convert heavier hydrocarbons to stable, low-reactivity char.”

The true test of the pilot program came when the researchers grew Simpson black-seeded lettuce, a variety for which petroleum is highly toxic, on the original clean soil, some contaminated soil and several pyrolyzed soils. While plants in the treated soils were a bit slower to start, they found that after 21 days, plants grown in pyrolyzed soil with fertilizer or simply water showed the same germination rates and had the same weight as those grown in clean soil.

“We knew we had a process that effectively cleans up oil-contaminated soil and restores its fertility,” Zygourakis said. “But, had we truly detoxified the soil?”

To answer this final question, the Rice team turned to Bhagavatula Moorthy, a professor of neonatology at Baylor College of Medicine, who studies the effects of airborne contaminants on neonatal development. Moorthy and his lab found that extracts taken from oil-contaminated soils were toxic to human lung cells, while exposing the same cell lines to extracts from treated soils had no adverse effects. The study eased concerns that pyrolyzed soil could release airborne dust particles laced with highly toxic pollutants like PAHs.

”One important lesson we learned is that different treatment objectives for regulatory compliance, detoxification and soil-fertility restoration need not be mutually exclusive and can be simultaneously achieved,” Alvarez said.

Here’s a link to and a citation for the paper,

Pilot-Scale Pyrolytic Remediation of Crude-Oil-Contaminated Soil in a Continuously-Fed Reactor: Treatment Intensity Trade-Offs by Wen Song, Julia E. Vidonish, Roopa Kamath, Pingfeng Yu, Chun Chu, Bhagavatula Moorthy, Baoyu Gao, Kyriacos Zygourakis, and Pedro J. J. Alvarez. Environ. Sci. Technol., 2019, 53 (4), pp 2045–2053 DOI: 10.1021/acs.est.8b05825 Publication Date (Web): January 25, 2019

Copyright © 2019 American Chemical Society

This paper is behind a paywall.

Cleaning up disasters with Hokusai’s blue and cellulose nanofibers to clean up contaminated soil and water in Fukushima

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The Great Wave off Kanagawa (Under a wave off Kanagawa”), also known as The Great Wave or simply The Wave, by Katsushika Hokusai – Metropolitan Museum of Art, online database: entry 45434, Public Domain, https://commons.wikimedia.org/w/index.php?curid=2798407

I thought it might be a good idea to embed a copy of Hokusai’s Great Wave and the blue these scientists in Japan have used as their inspiration. (By the way, it seems these scientists collaborated with Mildred Dresselhaus who died at the age of 86, a few months after their paper was published. In honour of he and before the latest, here’s my Feb. 23, 2017 posting about the ‘Queen of Carbon’.)

Now onto more current news, from an Oct. 13, 2017 news item on Nanowerk (Note: A link has been removed),

By combining the same Prussian blue pigment used in the works of popular Edo-period artist Hokusai and cellulose nanofiber, a raw material of paper, a University of Tokyo research team succeeded in synthesizing compound nanoparticles, comprising organic and inorganic substances (Scientific Reports, “Cellulose nanofiber backboned Prussian blue nanoparticles as powerful adsorbents for the selective elimination of radioactive cesium”). This new class of organic/inorganic composite nanoparticles is able to selectively adsorb, or collect on the surface, radioactive cesium.

The team subsequently developed sponges from these nanoparticles that proved highly effective in decontaminating the water and soil in Fukushima Prefecture exposed to radioactivity following the nuclear accident there in March 2011.

I think these are the actual sponges not an artist’s impression,

Decontamination sponge spawned from current study
Cellulose nanofiber-Prussian blue compounds are permanently anchored in spongiform chambers (cells) in this decontamination sponge. It can thus be used as a powerful adsorbent for selectively eliminating radioactive cesium. © 2017 Sakata & Mori Laboratory.

An Oct. 13, 2017 University of Tokyo press release, which originated the news item, provides more detail about the sponges and the difficulties of remediating radioactive air and soil,

Removing radioactive materials such as cesium-134 and -137 from contaminated seawater or soil is not an easy job. First of all, a huge amount of similar substances with competing functions has to be removed from the area, an extremely difficult task. Prussian blue (ferric hexacyanoferrate) has a jungle gym-like colloidal structure, and the size of its single cubic orifice, or opening, is a near-perfect match to the size of cesium ions; therefore, it is prescribed as medication for patients exposed to radiation for selectively adsorbing cesium. However, as Prussian blue is highly attracted to water, recovering it becomes highly difficult once it is dissolved into the environment; for this reason, its use in the field for decontamination has been limited.

Taking a hint from the Prussian blue in Hokusai’s woodblock prints not losing their color even when getting wet from rain, the team led by Professor Ichiro Sakata and Project Professor Bunshi Fugetsu at the University of Tokyo’s Nanotechnology Innovation Research Unit at the Policy Alternatives Research Institute, and Project Researcher Adavan Kiliyankil Vipin at the Graduate School of Engineering developed an insoluble nanoparticle obtained from combining cellulose and Prussian blue—Hokusai had in fact formed a chemical bond in his handling of Prussian blue and paper (cellulose).

The scientists created this cellulose-Prussian blue combined nanoparticle by first preparing cellulose nanofibers using a process called TEMPO oxidization and securing ferric ions (III) onto them, then introduced a certain amount of hexacyanoferrate, which adhered to Prussian blue nanoparticles with a diameter ranging from 5–10 nanometers. The nanoparticles obtained in this way were highly resistant to water, and moreover, were capable of adsorbing 139 mg of radioactive cesium ion per gram.

Field studies on soil decontamination in Fukushima have been underway since last year. A highly effective approach has been to sow and allow plant seeds to germinate inside the sponge made from the nanoparticles, then getting the plants’ roots to take up cesium ions from the soil to the sponge. Water can significantly shorten decontamination times compared to soil, which usually requires extracting cesium from it with a solvent.

It has been more than six years since the radioactive fallout from a series of accidents at the Fukushima Daiichi nuclear power plant following the giant earthquake and tsunami in northeastern Japan. Decontamination with the cellulose nanofiber-Prussian blue compound can lead to new solutions for contamination in disaster-stricken areas.

“I was pondering about how Prussian blue immediately gets dissolved in water when I happened upon a Hokusai woodblock print, and how the indigo color remained firmly set in the paper, without bleeding, even after all these years,” reflects Fugetsu. He continues, “That revelation provided a clue for a solution.”

“The amount of research on cesium decontamination increased after the Chernobyl nuclear power plant accident, but a lot of the studies were limited to being academic and insufficient for practical application in Fukushima,” says Vipin. He adds, “Our research offers practical applications and has high potential for decontamination on an industrial scale not only in Fukushima but also in other cesium-contaminated areas.”

Here’s a link to and a citation for the paper,

Cellulose nanofiber backboned Prussian blue nanoparticles as powerful adsorbents for the selective elimination of radioactive cesium by Adavan Kiliyankil Vipin, Bunshi Fugetsu, Ichiro Sakata, Akira Isogai, Morinobu Endo, Mingda Li, & Mildred S. Dresselhaus. Scientific Reports 6, Article number: 37009 (2016) doi:10.1038/srep37009 Published online: 15 November 2016

This is open access.

Nanoremediation to be combined with bioremediation for soil decontamination

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There’s a very interesting proposal to combine nanoremediation with bioremediatiion (also known as, phytoremediation) techniques to decontaminate soil. From a June 10, 2016 news item on Nanowerk,

The Basque Institute of Agricultural Research and Development Neiker-Tecnalia is currently exploring a strategy to remedy soils contaminated by organic compounds containing chlorine (organochlorine compounds). The innovative process consists of combining the application of zero-iron nanoparticles with bioremediation techniques. The companies Ekotek and Dinam, the UPV/EHU-University of the Basque Country and Gaiker-IK4 are also participating in this project known as NANOBIOR.

A June 10, 2016 Elhuyar Fundazioa news release, which originated the news item, provides more detail about the proposed integration of the two techniques,

Soils affected by organochlorine compounds are very difficult to decontaminate. Among these organochlorine compounds feature some insecticides mainly used to control insect pests, such as DDT, aldrin, dieldrin, endosulfan, hexachlorocyclohexane, toxaphene, chlordecone, mirex, etc. It is a well-known fact that the use of many of these insecticides is currently banned owing to their environmental impact and the risk they pose for human health.

To degrade organochlorine compounds (organic compounds whose molecules contain chlorine atoms) present in the soil, the organisations participating in the project are proposing a strategy based on the application, initially, of zero-iron nanoparticles [also known as nano zero valent iron] that help to eliminate the chlorine atoms in these compounds. Once these atoms have been eliminated, the bioremediation is carried out (a process in which microorganisms, fungi, plants or enzymes derived from them are used to restore an environment altered by contaminants to its natural state).

The bioremediation process being developed by Neiker-Tecnalia comprises two main strategies: biostimulation and bioaugmentation. The first consists of stimulating the bacteria already present in the soil by adding nutrients, humidity, oxygen, etc. Bioaugmentation is based on applying bacteria with the desired degrading capability to the soil. As part of this process, Neiker-Tecnalia collects samples of soils contaminated by organochlorine compounds and in the laboratory isolates the species of bacteria that display a greater capacity for degrading these contaminants. Once the most interesting strains have been isolated, the quantity of these bacteria are then augmented in the laboratory and the soil needing to be decontaminated is then inoculated with them.

Bank of effective strains to combat organochlorines

The first step for Neiker-Tecnalia is to identify bacterial species capable of degrading organochlorine compounds in order to have available a bank of species of interest for use in bioremediation. This bank will be gathering strains collected in the Basque Country and will allow bacteria that can be used as a decontaminating element of soils to be made available.

The combining of the application of zero-iron nanoparticles and bioremediation constitutes a significant step forward in the matter of soil decontamination; it offers the added advantage of potentially being able to apply them in situ. So this methodology, which is currently in the exploratory phase, could replace other processes such as the excavation of contaminated soils so that they can be contained and/or treated. What is more, the combination of the two techniques makes it possible to reduce the decontamination times, which would take much longer if bioremediation is used on its own.

There is a NANOBIOR webpage here.

For the curious I have two 2012 posts that provide some very nice explanations by Joe Martin, then a Master’s student in the University of Michigan’s Public Health program,: Phyto and nano soil remediation (part 1: phyto/plant) and Phyto and nano soil remediation (part 2: nano).

Nickel-eating plant in the Philippines

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For anyone interested in phytoremediation and/or phytomining, this news from the Philippines is quite exciting (from a May 9, 2014 news release on EurekAlert, Note: A link has been removed, (also on ScienceDaily),

Scientists from the University of the Philippines, Los Baños (UPLB) have discovered a new plant species with an unusual lifestyle — it eats nickel for a living — accumulating up to 18,000 ppm of the metal in its leaves without itself being poisoned, says Professor Edwino Fernando, lead author of the report. Such an amount is a hundred to a thousand times higher than in most other plants. The study was published in the open access journal PhytoKeys.

The new species is called Rinorea niccolifera, reflecting its ability to absorb nickel in very high amounts. Nickel hyperaccumulation is such a rare phenomenon with only about 0.5–1% of plant species native to nickel-rich soils having been recorded to exhibit the ability. Throughout the world, only about 450 species are known with this unusual trait, which is still a small proportion of the estimated 300,000 species of vascular plants.

A May 9, 2014 Penfold Publishers news release, which originated the items elsewhere, provides more details and an image of the nickel-eating plant,

The new species, according to Dr Marilyn Quimado, one of the lead scientists of the research team, was discovered on the western part of Luzon Island in the Philippines, an area known for soils rich in heavy metals.

“Hyperacccumulator plants have great potentials for the development of green technologies, for example, ‘phytoremediation’ and ‘phytomining'”, explains Dr Augustine Doronila of the School of Chemistry, University of Melbourne, who is also co-author of the report.

Phytoremediation refers to the use of hyperacccumulator plants to remove heavy metals in contaminated soils. Phytomining, on the other hand, is the use of hyperacccumulator plants to grow and harvest in order to recover commercially valuable metals in plant shoots from metal-rich sites. [emphasis mine]

In a previous piece about phytomining and in contrast to this news release, I suggested that phytoremediation could also function as phytomining (an idea I found elsewhere), my March 5, 2013 posting. There are also a November 22, 2012 posting and a Sept. 26, 2012 posting on the topic of phyto-mining (anyone keen to read everything here on this topic, may want to search the term both with and without hyphens).

Here is the nickel-eating plant,

Caption: This photo shows the newly described metal-eating plant, Rinorea niccolifera. Credit: Dr. Edwino S. Fernando Usage Restrictions: CC-BY 4.0

Caption: This photo shows the newly described metal-eating plant, Rinorea niccolifera.
Credit: Dr. Edwino S. Fernando
Usage Restrictions: CC-BY 4.0

Here’s a link to and a citation for the paper,

Rinorea niccolifera (Violaceae), a new, nickel-hyperaccumulating species from Luzon Island, Philippines by Edwino Fernando, Marilyn Quimado, and Augustine Doronila. PhytoKeys 37: 1–13. doi: 10.3897/phytokeys.37.7136

This paper is open access.

In a burst of curiosity I checked out the University of Philippines website and found some research bearing similarity to today’s (May 9, 2014) piece although in this case the metal being discussed is gold and the researchers are investigating the possibility of using bacteria to produce gold nanoparticles. From an April 16, 2014 article written by Miguel Victor T. Durian for the university’s Horizon magazine,

A pioneering nanotechnology study conducted by scientists at the UPLB National Institute of Molecular Biology and Biotechnology (BIOTECH) is exploring the potentials of plantgrowth- promoting bacteria (PGPB) in the biosynthesis of nanogold.

Dr. Lilia M. Fernando, Dr. Florinia E. Merca, and Dr. Erlinda S. Paterno are looking at how nanogold could be produced in large quantities using PGPB as this could bring down medical diagnostic and treatment costs especially against a dreaded disease – cancer.

…

“Our study primarily aimed to find a less expensive source of gold through the biosynthesis of the element by microorganisms.” Dr. Fernando explained. “Gold costs around 200 to 300 US dollars (or about Php9,000 to Php14,000), …,” Ms. Fernando added.

Furthermore, PGPB is abundantly available in the soils of the Philippines. In fact, the researchers carried out their collection of PGPB in Tarlac and Bohol. Moreover, cultivation of PGPB does not require any special incubation procedures in order to maintain its nano-size because it can survive at room temperature. This makes the cultivation of PGPB easier and less expensive compared to other microorganisms.

I look forward to hearing more about these projects as they develop.

Phytoremediation, clearing pollutants from industrial lands, could also be called phyto-mining

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The University of Edinburgh (along with the Universities of Warwick and Birmingham, Newcastle University and Cranfield University) according to its Mar. 4, 2013 news release on EurekAlert is involved in a phytoremediation project,

Common garden plants are to be used to clean polluted land, with the extracted poisons being used to produce car parts and aid medical research.

Scientists will use plants such as alyssum, pteridaceae and a type of mustard called sinapi to soak up metals from land previously occupied by factories, mines and landfill sites.

Dangerous levels of metals such as arsenic and platinum, which can lurk in the ground and can cause harm to people and animals, will be extracted using a natural process known as phytoremediation.

A Mar. 4, 2013 news item on the BBC News Edinburgh, Fife and East Scotland site offers more details about the project and the technology,

A team of researchers from the Universities of Edinburgh, Warwick, Birmingham, Newcastle and Cranfield has developed a way of extracting the chemicals through a process called phytoremediation, and are testing its effectiveness.

Once the plants have drawn contaminated material out of the soil, they will be harvested and processed in a bio-refinery.

…

A specially designed bacteria will be added to the waste to transform the toxic metal ions into metallic nanoparticles.

The team said these tiny particles could then be used to develop cancer treatments, and could also be used to make catalytic converters for cars.

Dr Louise Horsfall, of Edinburgh’s University’s school of biological sciences, said: “Land is a finite resource. As the world’s population grows along with the associated demand for food and shelter, we believe that it is worth decontaminating land to unlock vast areas for better food security and housing.

“I hope to use synthetic biology to enable bacteria to produce high value nanoparticles and thereby help make land decontamination financially viable.”

The research team said the land where phytoremediation was used would also be cleared of chemicals, meaning it could be reused for new building projects.

In my Sept. 28, 2012 posting I featured an international collaboration between universities in the UK, US, Canada, and New Zealand in a ‘phyto-mining’ project bearing some resemblance to this newly announced project. In that project, announced in Fall 2012, scientists were studying how they might remove platinum for reuse from plants near the tailings of mines.

I do have one other posting about phytoremediation. I featured a previously published piece by Joe Martin in a two-part series on the topic plant (phyto) and nano soil remediation. The March 30, 2012 posting is part one, which focuses on the role of plants in soil remediation.

Phyto and nano soil remediation (part 1: phyto/plant)

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One of my parent’s neighbours was a lifelong vegetarian and organic gardener. The neighbour, a Dutchman,  had been born on the island of Curaçao, around 1900, and was gardening organically by the 1940’s at the latest. He had wonderful soil and an extraordinary rose garden in the front yard and vegetables in the back, along with his compost heap. After he died in the 1980’s, his granddaughter sold the property to a couple who immediately removed the roses to be replaced with grass in the front and laid a good quantity of cement in the backyard. Those philistines sold the soil and, I imagine, the roses too.

Myself, I’m not not a gardener but I have a strong appreciation for the necessity of good soil so, I’m pleased to repost a couple of pieces on soil remediation written by Joe Martin for the Mind the Science Gap (MTSG) blog. First here’s a little bit about the MTSG blog project and about Joe Martin.

I wrote about the MTSG blog in my Jan. 12, 2012 posting, which focussed on this University of Michigan project designed by Dr. Andrew Maynard for Masters students in the university’s Public Health program. Very briefly here’s a description of Andrews and the program from the About page,

Mind the Science Gap is a science blog with a difference.  For ten weeks between January and April 2012, Masters of Public Health students from the University of Michigan will each be posting weekly articles as they learn how to translate complex science into something a broad audience can understand and appreciate.

Each week, ten students will take a recent scientific publication or emerging area of scientific interest, and write a post on it that is aimed at a non expert and non technical audience.  As the ten weeks progress, they will be encouraged to develop their own area of focus and their own style.

…

About the Instructor.  Andrew Maynard is Director of the University of Michigan Risk Science Center, and a Professor of Environmental Health Sciences in the School of Public Health.  He writes a regular blog on emerging technologies and societal implications at 2020science.org.

As for Joe Martin,

I am a second year MPH student in Environmental Quality and Health, and after graduation from this program, I will pursue a Ph.D. in soil science.  My interests lie in soil science and chemistry, human health and how they interact, especially in regards to agricultural practice and productivity.

Here’s a picture,

Joe Martin, Masters of Public Health program, University of Michigan, MTSG blog

Joe gave an excellent description of nano soil remediation but I felt it would be remiss to not include the first part on phyto soil remediation. Here’s his Feb. 3, 2012 posting about plants and soil remediation:

Pictured: The Transcendent Reality of Life and the Universe.

Plants are awesome. It’s from them that we get most of our food. It’s from plants that many of our medicines originated, (such as Willow and aspirin). We raise the skeletons of our homes and furnish their interiors with trees. Most of our cloth is woven from plant fiber, (a statement I feel comfortable making based solely on the sheer weight of denim consumed each year in this country.) And although there is an entire world of water plants, all of the plants I listed above are grown in the soil*. How the individual soil particles cling to each other, how they hold water and nutrients, and how the soil provides shelter for the various macro and micro-organisms is as important to the growth of plants as sunlight.

But no matter how proliferative, no matter how adaptive plants are, there are still spaces inaccessible to them. A clear example would be the Saharan dunes or a frozen tundra plain. However, many of places where plants can’t survive are created by human activity. The exhaust of smelters provides one example – waste or escaped zinc, copper, cadmium, and lead infiltrate downwind soils and often exterminate many or most of the natural plants. Normal treatment options for remediating metal contaminated soils are expensive, and can actually create hazards to human health. This is because, like some persistent organic pollutants (the infamous dioxin is a great example), the natural removal of metals from soils often proceeds very slowly, if it proceeds at all. For this reason, remediation of metal soil often involves scraping the contaminated portion off and depositing it in a hazardous waste landfill. In cases of old or extensive pollution, the amount of soil can exceed thousands of cubic feet. In this process, contaminated dust can easily be stirred up, priming it to be inhaled by either the workers present or any local populations.

But it can be cousins of the evicted shrubs and grass which offer us the best option to undo the heavy metal pollution. In a process called phytoremediation, specific plants are deliberately seeded over the contaminated areas. These plants have been specifically chosen for the tendency to uptake the metals in question. (In some cases, this process is also used for persistent organic pollutants, like 2,3,7,8-TCDD, infamously known as dioxin.) These plants are allowed to grow and develop their root systems, but are also selectively mowed to remove the pollutant laden leaves and stems, and ultimately remove the contaminant from the soil system. Once the pollution level has descended to a sufficiently low level, the field may be left fallow. Otherwise, the remediating plants can be removed and the ground reseeded with natural plants or returned to agricultural, commercial, or residential use.

When it is applicable, phytoremediation offers a significant advantage over either restricted access, (a common strategy which amounts to placing a fence around the contaminated site and keeping people out), or soil removal. While the polluted grass clippings much still be treated as hazardous waste, the volume and mass of the hazardous material is greatly reduced. Throughout the process, the remediating plants also serve to fix the soil in place, reducing or preventing runoff and free-blowing dust. Instead of bulldozers and many dump trucks, the equipment needed is reduced to a mower which captures grass or plant clippings and a single dump truck haul each growing season. Finally, the site does not need to be reinforced with topsoil from some other region to return it to useable space. These last few advantages can also greatly reduce the cost of remediation.

The major disadvantages of phytoremediation are time and complexity. Scraping the soil can be done in a few months or less, depending on the size of the area to be remediated. Phytoremediation takes multiple growing seasons, and if the land is a prime space for development this may be unacceptable. Phytoremediation requires different plants for different pollutants or mixtures of pollutants. I chose the copper, zinc, lead, and cadmium mixture earlier in the article because in a study from 2005, (Herrero et al, 2005), they specifically attempted to measure the ability of rapeseed and sunflower to extract these metals from an artificially contaminated soil. The unfortunate reality is that each contaminant will have to be studied in such a way, meticulously pairing pollutants (or mixture of them) with a plant. Each of the selected plants must also be able to grow in the soil to be remediated. Regardless of type of contamination, a North American prairie grass is unlikely to grow well in a Brazilian tropical soil. For these reasons, phytoremediation plans must be individually built for each site. This is costly both in dollars and man hours. Furthermore, there is always the problem that some pollutants don’t respond well to phytoremediation. While copper, zinc, and cadmium have all been found to respond quite well to phytoremediation, lead does not appear to be. In the Herraro et al study, the plants accumulated lead, but did so in the roots. Unless the roots were dug up, this would not effectively remove the lead from the soil system. Unfortunately, lead is one of the most common heavy metal pollutants, at least in the U.S., a legacy of our former love for leaded gasoline and paint.

Despite these disadvantages, phytoremediation presents a unique opportunity to remove many pollutants. It is by far the least environmentally destructive, and in many cases may be the cheapest method of remediation. I am happy to see that it appears to be receiving funding and is being actively researched and developed, (for those who don’t pursue the reference, the Herraro article came from The International Journal of Phytoremediation.) In recent times, we’ve been hit with messages about expanding hydrofracking and the Gulf Oil spill, but perhaps I can send you into this weekend with a little positivity about our environmental future. The aggregated techniques and methods which can be termed “phytoremediation” have the potential to do much good at a lower cost than many other remediation techniques. That sounds like a win-win situation to me.

* I am aware that many of these crops can be grown aero- or hydroponically. While these systems do provide many foodstuffs, they are not near the level of soil grown crops, and can be comparatively very expensive. I chose not to discuss them because, well, I aspire to be a soil scientist.

1.) Herreo E, Lopez-Gonzalvez A, Ruiz M, Lucas Garcia J, and Barbas C. Uptake and Distribution of Zinc, Cadmium, Lead, and Copper in Brassica napus vr. oleifera and Helianthus annus Grown in Contaminated Soils. 2005. The International Journal of Phytoremediation. Vol. 5, pp. 153-167.

A note on photos: Any photos I use will be CC licensed. These particular photos are provided by Matthew Saunders (banana flower) and KPC (rapeseed) under an attribution, no commercial, no derivation license.  I originally attempted to link to the source in the caption, but wordpress won’t let me for some reason. Until I work that out, the image home can be found under the artist’s names a few sentences earlier. I believe this honors the license and gives proper credit, but if I’ve committed some faux pas, (which would not be a surprise), don’t hesitate to comment and correct me. And thanks to those who have done so in previous posts, its one of the best ways to learn.

Part 2: nano soil remediation follows.

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