Category Archives: soils

Hemp to the Rescue

We’ve heard of many plants that have phytoremediative qualities, that is, the properties that can absorb and neutralize toxic substances in soils.   For all the versatility of hemp, I hadn’t thought of it as possessing that ability until I read recent post on Roads and Kingdoms entitled Hemp and Change.  The crux of the story is one of pollution and the potential for Hemp as one of those plants that can aid in cleaning up our dirty messes.

The Italian town Taranto in Puglia, which like many areas had a rich agricultural and gastronomic history, specifically cheeses and other dairy products.  A large steel plant was constructed nearby in the 1960s, which was led to degradation of air and soil that led to conditions where animals were no longer fit for consumption.  There are also indications that the residents have and continue to suffer from ill effects of the plant.

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:: image via Roads & Kingdoms

The issue is that the plant serves as the major source of jobs, so it’s a double-edged sword where residents are both in need of the economic benefit but suffer from the ill effects.  The plant owners were later charged with a number of crimes for the health and environmental issues, but beyond the legal culpability, there still remains the need for a viable clean-up of the sites, which is often too expensive and long term.

Thus phytoremediation provides a viable strategy for clean up of the toxic sites, with the potential to restore Taranto back to it’s agricultural glory.  A group called CanaPuglia and their founder Claudio Natile, who describes hemp and its use as a continuation of an Italian tradition.

“Hemp was a major Italian agricultural crop for hundreds of years. In the 1950s, the country was the second-largest hemp producer in the world after the Soviet Union. Italian hemp seeds provided some of the most resistant fibers, which were turned into clothing. However, with industrialization and the advent of synthetic fibers such as nylon, hemp started to disappear.”

They’ve planted 300 hectares of low THC hemp, which is also harvested to make a range of products, further providing economic vitality and helping to pay for the cleanup.  In this case, the toxicity doesn’t persist in the fibers, so it can be used, however there could be toxicity in the seeds so the hemp is not sold for food consumption.  The article doesn’t get too far into how hemp is working for pollution reduction, but offered a few links to explore.

According to the Huffington Post, in addition to hemp being a low-input and easy to grow plant, it “…was used at Chernobyl to harmlessly extract toxins and pollutants from the soil and groundwater. Hemp actually absorbs CO2 while it grows through natural photosynthesis, making it carbon-negative from the get-go.”

Commercial hemp, Darlingford, Manitoba, Canada.
Commercial hemp, Darlingford, Manitoba, Canada.

:: image via Huffington Post

The use a variety of plants for phytoremediation of toxic sites, including Brassicas, corn, tobacco, sunflowers and trees, to name a few, all are viable methods to uptake and capture pollutants.   The site explains that Phytoremediation is a process that takes advantage of the fact that green plants can extract and concentrate certain elements within their ecosystem. For example, some plants can grow in metal-laden soils, extract certain metals through their root systems, and accumulate them in their tissues without being damaged. In this way, pollutants are either removed from the soil and groundwater or rendered harmless.

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:: image via McGraw Hill – Botany Global Issues Map

The use of hemp is explained in a bit more detail “In 1998, Phytotech, along with Consolidated Growers and Processors (CGP) and the Ukraine’s Institute of Bast Crops, planted industrial hemp, Cannabis sp., for the purpose of removing contaminants near the Chernobyl site.”  The uptake of pollutants at Chernobyl included cesium and strontium, which was bio-accumlated in root structures at high concentrations.  While some toxins are broken down in soil and plants, high-grade elements like radioactive waste are pulled from soils into plants, so there is obviously the issue of proper and safe removal of this biomass after this process has taken place.

One interesting link on the larger concept is from the United Nations Enviornment Programme, a site called “Phytoremediation: An Environmentally Sound Technology for Pollution Prevention, Control and Remediation. ” which does offer a primer on the topic.  Contrasting it with traditional remediation, the site explains: “Remediation of contaminated sites using conventional practices, such as ‘pump-and-treat’ and ‘dig-and-dump’ techniques, is often expensive, has limited potential, and is usually only applicable to small areas. Additionally, these conventional approaches to remediation often make the soil infertile and unsuitable for agriculture and other uses by destroying the microenvironment. Hence there is the need to develop and apply alternative, environmentally sound technologies (ESTs), taking into account the probable end use of the site once it has been remediated.”

The process happens in multiple ways, but essentially has two methods – the first is breaking down and degrading organic pollutants; the second is to trap  metals or non-organics so they cannot move to other animals or areas.  The roots are the main source of phytoremediation, being in contact with pollutants directly through the extensive below-grade surface area.  When areas of contamination are deeper, trees are often used where their more extensive rooting systems can go further down than herbacous plants and shrubs.   There are also cases where water can be pumped from below grade and then treated on the surface using plants.

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:: image via Intech

As the above graphic shows, there are many methods at work with the phytoremediation process, many of which are working on the ‘soil-root’ interface.  There are a number of compounds released by the plants, “root exudates” that activate microorganisms that can extract, stablilize, degrade and stimulate toxics.  This changes the bioavaiability of the toxins through, as the UNEP site states “changes in soil characteristcs, release of organic substances, changes in chemical composition, and /or increase in plant-assisted microbial activity.”

There are over 30,000 sites in the US that require hazardous waste treatment, and many more worldwide.  While many plants that are viable for phytoremediation are available, many of these cannot be used for consumption because of issues with possible contamination. Hemp is perhaps one to consider as the fiber used can still be processed into useful, saleable products,  that could potentially fund the cleanup as well.  As marijuana legality relaxes somewhat, it may be more possible to use this plant to make our world a cleaner place.

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Get Shaking

One thing of note in Seattle is that it is a city of varied topography, and that this obviously guided the evolution of where settlement occurred, while creating districts and landmark areas (many ending with ‘Hill’).  An interesting post related to this topographic urbanism is the seismic stability of my new city.  From the Seattle Times, ‘When Seattle shakes from quakes, it’s going to slide, too’ provides a good snapshot of the impact of an earthquake on hillsides and the buildings dotting them.

University of Washington researchers performed a study which used simulation on a ‘fault rupture’ that transects the City of Seattle to see the impact.  The results are summarized in the caption from the Seattle Times:

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The issue is not just the damage, but the impact of these slides, as lead researcher Kate Allstadt mentions, in addition to “…widespread damage to buildings and infrastructure caused by the quake itself, landslides would compound the city’s problems and slow its recovery.”

This is a common issue in many cities on the West Coast, and a history of seismic activity coupled with slides is prevalent throughout the region:

The Puget Sound-area landscape is pocked with scars from slides triggered by ground shaking, but the worst of them occurred long before cities existed here. The last quake on the Seattle Fault, about 1,100 years ago, shook the ground so hard that entire hillsides slumped into Lake Washington, carrying intact swaths of forest with them.

A recent earthquake in 2001, for instance, set off over 100 landslides, according to the article.  This continuing threat of instability has interesting dimensions, particularly based on how much moisture is present, as dry soils yield far less damaging slides, at least in the models.  Unfotunately, many of the areas that would be impacted aren’t shown on current landslide risk maps, including West Seattle, Beacon Hill and Mount Baker.  A map shows the major risk areas.

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While it’s obvious why this matters, in terms of health and safety, most earthquake specific action focuses around the.  As mentioned in the Seattle Times article. “According to one scenario, a magnitude 6.7 quake on the Seattle Fault could kill 1,600 people and cause $33 billion in damage. That analysis glossed over the damage caused by landslides, but in major quakes, collapsing hillsides can cause as much — or more — destruction than the shaking itself, Allstadt pointed out.”

This additional cost and issues with access and cleanup mean serious study should be conducted related to how to deal with existing development in these areas, and what this means long-term for these areas of the city essentially waiting for the right event to collapse.

Another interesting article from The Atlantic Cities: “Seattle’s Hilly Neighborhoods Could Slide Into the Water During the Next Earthquake” delves into similar terrain looking at the UW study in more detail in areas of .  Writer John Metcalf looks at the smaller micro-impacts that the study (for instance see below), and the distinctions of the dry vs. wet scenarios.  The context is important, as in the case below, the impacts to major transportation routes in large landslide events could hinder response to areas of the City, in addition to the immediate damage.

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The summary is, that we need to be aware and prepared – as a region, but also in specific areas we know are going to be impacted and those that are key elements of the response infrastructure system.  We don’t know when, but it could be sooner than we think.  As mentioned in the Atlantic Cities article:

That’s why it’s crucial to start prepping, says Allstadt – finding out what microregions are especially vulnerable, planning rapid responses in and out of these zones, predicting what sewerage and electric infrastructure could be knocked out, educating home-buyers on the risks of living on uncertain slopes. “It could be now or a couple thousand years,” she says. “We just don’t know.”