Scientists in Sweden just discovered a species of moss removes arsenic from water, taking the usefulness of plants up a few notches in my book. While it’s old news that plants turn carbon dioxide into oxygen, arsenic removal from a plant is really uncommon.

Swedish Floating Hook Moss Removes Arsenic

Researchers at Stockholm University have discovered that a type of moss known as “floating hook moss” (Warnstorfia fluitans) can eliminate arsenic from water. The removal process is not only effective but it is also very fast, transforming contaminated water to a safe drinking level in just one hour.

Here are the basic facts:

1. Floating hook moss removes arsenic from flowing water.
2. It does best when the water is low in other nutrients and flows more quickly.
3. The moss removes arsenic even when dead.
4. The arsenic bonds to the moss, keeping the arsenic out of the water more effectively.
5. The conditions where the moss is most effective are also similar to natural conditions.

How does moss remove arsenic?

Floating hook moss removes arsenic from water by binding arsenic to biomass tissue. It’s not the first plant known to do this, but scientists are excited by the potential discovery of a new phytofilter (plant filter).

When is moss most effective at removing arsenic?

Scientists found that the floating hook moss removed up to 82% of arsenic from the water in under 1 hour. The moss removed arsenic from the water most quickly when arsenic levels were lower and when other nutrients were not available. The floating hook moss removed arsenic in fast-flowing water more efficiently than in slow-flowing water.

Keep in mind: the scientists noted that the lower levels of arsenic are most similar to natural water sources, so the fact that moss removes arsenic better at low levels is not a problem. The scientists also said that nutrient concentrations of natural water is low. Essentially, the scientists found that the conditions where the moss removed arsenic most effectively are similar to natural conditions.

The scientists believe that moss removes arsenic from the water so quickly because it is able to absorb arsenic along much of its surface area, rather than through a traditional root system found in land-lubber plants.

Astonishingly, the moss removes arsenic from the water even when it is dead. That said, living moss was twice as efficient at removing arsenic compared to dead moss.

Can we use the moss to remove arsenic from water?

Finally, the scientists noted that arsenic bound firmly to the moss. That simply means that the arsenic was firmly connected to the moss and is not easily removed – an important feature if a plant is to be used as a filtration device!

We’re a ways away from using moss to remove arsenic in a commercial setting. However, this discovery puts the possibility of such technology on the table.

Let’s cover a few basic questions about arsenic, now that we know how moss removes arsenic from water.

What is arsenic?

Arsenic is pretty bad news. This element is a known carcinogen and can cause cramping, vomiting, and bloody diarrhea when ingested. Arsenic poisoning generally comes from drinking contaminated water. It is harmful to unborn children and there is no real cure aside from removing exposure to arsenic and treating symptoms.

How do we remove arsenic from water?

The United States regulates arsenic in drinking water. You cannot remove arsenic by boiling the water or disinfecting the water with a bleach such as chlorine. However, reverse osmosis, ultrafiltration, ion exchange, and distillation will remove arsenic.

Where does arsenic come from?

Arsenic is naturally occurring in the earth’s crust. Certain aquifers and groundwater sources have higher levels of arsenic, especially in the Western US and in Southeast Asia. Arsenic levels in the ground and water can be higher for a variety of reasons, including:

• Naturally elevated levels in wells, especially if you use a private well that is unregulated by the EPA.
• Smoking tobacco products that contain arsenic.
• Differing mineral compositions of the soil.
• Mining or hydraulic fracturing techniques that disturb aquifers or inject chemicals containing arsenic.
• Rice, apple juice, shellfish, and other foods that are susceptible to absorbing arsenic from the soil and water around them.
• Pesticides, especially those used for cotton and preserving wood, contained arsenic. Though this has been regulated for over 50 years, arsenic does not simply go away after pesticide use ceases.
• Copper smelting is a well-studied source of arsenic, especially in the air.

Before you get too worried about arsenic poisoning, keep in mind that arsenic poisoning in the US is relatively rare.

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You can find the original research article at: Andhi, A., et al., Phytofiltration of arsenic by aquatic moss (Warnstorfiafluitans), Environmental Pollution(2017), https://doi.org/10.1016/j.envpol.2017.11.038