Phytoremediation

When I write this article I usually base it on a plant or creature, or a natural system. Usually something that I’ve observed locally that piques my interest. The subject of this piece seems a little distant and theoretical but maybe it’s closest to home of all. On my mind right now, possibly quite literally it transpires, is phytoremediation, and more specifically, does it have any practical uses at our homes? 

We’d better start with what phytoremediation is: in short, it is using plants to clean up contamination in some way, be that in the soil, water or air by removing pollutants. 

Why does this matter? I happened to catch a radio interview with a very well respected scientist and it transpires that there is early research linking pollutants to certain degenerative brain diseases. Now, I don’t want to get too heavy, but it got me thinking about some amazing things that people are doing with plants to clean up pollutants, like the project called Wild Park in Brighton that was brought to my attention recently, which filters and cleans road runoff to protect a precious chalk aquifer that runs below the city of Brighton. I wondered if there are any, admittedly, less grand, applications of phytoremediation that could apply to the everyday person at their house and garden?

As it happens, there are a few things that we can do to help ourselves at home. In old gardens like those that many of us have, there can be contaminants in the soil from old lead-based paint, maybe near a shed or the house or from bonfires that have had goodness knows what put on them, hopefully nothing too toxic, but even treated timbers leave a legacy of potentially harmful compounds in the soil. Then there's Creosote and tar residues from historic fence painting or those old sleepers that we might have used for veg planters. Creosote was banned for sale to the general public in 2003 due to the PAHs - polycyclic aromatic hydrocarbons - that it contains that are, well, not very nice. Other heavy metals (a term for metallic elements with relatively high density) leaked from batteries, paints or perhaps from the runoff from roads can lead to an accumulation in the soil of zinc, lead, and cadmium. 

There are some plants that will help to clean up soils and some of those aren’t half bad to look at! Sunflowers (Helianthus Annuus) have been found to be really good at reducing different PAH levels from soil and also they can accumulate a varied range of other contaminants - don’t put the seeds on your salad if you think that they are taking up contaminants though! Willows (Salix Spp.) are great too, their root systems have been shown to remediate diesel fuel polluted sites. Also mustard greens otherwise known as Indian mustard (Brassica juncea) is a top performer at phytoremediation and has been shown to remove three times more Cadmium than any other plant as well as being very effective with other heavy metals in the soil. And if you happen to have had a collapsed nuclear reactor in your garden you’re in luck because mustard greens cleaned up the Cesium-137 radioactive waste from Chernobyl! 

We can do a little inside the house too. Older houses can have higher indoor pollutants from woodburner smoke, pollutants from high VOC (Volatile Organic Compounds) paints and mold from damp. New houses aren’t exempt from this though, that new carpet smell may not actually be doing great things in your home. The 1989 The NASA Clean Air Study tested three house plants (spider plants, peace lilies and snake plants) in sealed chambers and showed that they could help remove harmful compounds such as benzene, formaldehyde, and trichloroethylene from the air. Before we get too excited though, they are part of the package rather than the answer to the problem. Better to have good clean air ventilation and try to remove the causes of the pollution in the first place!

It’s good to know that we have some agency to remediate to some degree the pollutants in and around our homes and another reason to love and revel in the wonder of plants all the more!

Andy. 

Photo by Justin Simmonds on Unsplash