The Benefits of Salad Greens as Solutions to Soil Contamination

When old factories, gas stations and other types of industrial locations that use a lot of petroleum or gasoline get torn down to be repurposed for new uses, work must be done on the land to ensure it is not still a “brownfield” when the new owners take over. In many cases, this type of land can be soaked or contaminated with oil. While redeveloping these types of properties for new uses, be they commercial or residential, is a noble goal, it can be prohibitively expensive to treat the land and perform remediation.

As such, researchers are constantly looking for new, alternative methods of treating these petroleum-damaged lands without needing to break the bank quite as much. And at Rice University in Texas, a team of engineers may have figured out a unique way of not just cleaning land that’s been contaminated by heavy oils, but also making it fertile again.

This type of process is extremely important for maintaining and remediating natural spaces and areas that will be used for new development. While the oil spills that get the most news attention are the large tanker spills that occur at sea, the truth is that 98 percent of all oil spills happen on land. While they tend to come in smaller sizes, they are significantly more frequent—the United States sees more than 25,000 spills a year reported to its Environmental Protection Agency alone.

The work at Rice University

The two engineers who led the Rice University study were Dr. Kyriacos Zygourakis and Dr. Pedro Alvarez. Their study focused on improving methods of removing petroleum contaminants from affected soils through a process called pyrolysis. This is a technique that involves heating up the soil while preventing oxygen from getting inside of it, which prevents the damage that can be done to fertile soil when burning hydrocarbons create large increases in temperature.

The team collected soil samples from Hearne, Texas that had been contaminated with a heavy crude into a kiln to see at which temperature oil would most efficiently be eliminated, and how long that process would take. They found that heating the samples at 420 degrees Celsius (788 F) for 15 minutes would eliminate 99.9 percent of total petroleum hydrocarbons and another 94.5 percent of polycyclic aromatic hydrocarbons, resulting in the same level of pollutants found in uncontaminated soils.

This method isn’t exactly new or groundbreaking, but what was unique about the test was that researchers then grew Simpson black-seeded lettuce (for which petroleum is highly toxic) on several soils: the original clean soil, some contaminated soil and some soils that had been heated and pyrolysed. The plants in the treated soils were a little bit slower to sprout up at the start, but after 21 days the plants grown in pyrolysed soil with water or fertilizer had the same germination rate and weight as the plants that were grown in the clean, uncontaminated soil. This meant that not only had researches succeeded in cleaning the soil they pyrolysed, but also managed to make it fertile again to allow for the growth of even a highly sensitive form of plant.

Research is still being performed on these soil remediation processes, but it’s always fascinating to see what researchers come up with, and the role plant life can play in these research methods! Soil Advocates can help provide more information about this, connect with us at admin@soiladvocates.ca or 289-221-0164.

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About the Author:

Dr. Leanne J Philip, BSc. (Hon.); MSc.; PhD. is the Managing Director & Chief Scientist of Soil Advocates Inc. She studied at the University of Guelph as an undergraduate (Plant Biology, Environmental Management and Urban Horticulture) and as a graduate student (Plant & Soil Interactions). She has a keen interest in soil sciences, which lead her to the University of British Columbia in Vancouver for doctoral studies in soil carbon sequestration and movement within British Columbia’s clear-cut soils. Further work in soil sciences in Europe and Canada reinforced Dr. Philip’s belief that soil processes and mechanisms belowground drive aboveground aesthetics and plant interactions. While active in both research, mentorship and teaching, most recently Dr. Philip has been working in applied soil sciences in industry and community outreach. Dr. Philip is a native of southern Ontario and is a strong advocate for scientific literacy within her community and responsible environmental stewardship.

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