(ORDO NEWS) — One of the most serious environmental problems today is the cultivation of land contaminated with toxic elements from industrial activities, elements such as arsenic, antimony and tungsten.
But these same elements can be brought to the surface of the Earth by natural processes, such as the bubbling of hot springs.
Therefore, it is important to understand how the environment treated them before the appearance of man.
A site in Aberdeenshire, Scotland, famous for its early fossil life preserved by hot springs, shows us how this could have happened.
Some of the best preserved plant fossils in the world are found in Rhynie, west of Aberdeen, in deposits thought to have originated from the oldest terrestrial ecosystem in the world.
Exquisitely detailed plants, as well as spiders, insects, mushrooms and other living creatures, have been preserved there thanks to hot springs about 410 million years ago.
These are some of the earliest fossilized plants known, so they are important because they can tell us about plant evolution.
But these hot springs also contained elements that would be toxic to most life forms.
Our latest research shows how minerals deposited among plants extract toxic metals from spring water and limit their environmental impact.
The plants at Rainey were encased in the mineral silica, which is deposited around hot springs.
In tourist destinations like Iceland, New Zealand, and Yellowstone National Park in the US, bacteria in the water are involved in the formation of these silica deposits, and the same would be in Rainey.
In addition to silica, fossils contain certain minerals, including pyrite (iron sulfide, so-called fool’s gold), manganese oxides, and titanium oxides.
It was these minerals, produced by bacteria and other life forms, that absorbed the toxic metals.
Pyrite formed by bacteria absorbed arsenic from spring water. Manganese oxides, usually deposited by fungi, also absorbed arsenic.
Titanium oxides, which are formed, in particular, around decaying plant residues, absorbed tungsten and antimony.
Thus, between them, minerals formed as a result of biological activity are the main sources of toxicity. Rainey’s testimonies show how natural processes have helped clean up the environment since life first colonized the earth.
Our solutions to man-made environmental problems, such as pollution from industry and mining, typically involve a range of chemical treatments.
But an exciting “natural” approach is the microremediation technique, in which fungi concentrate and retain contaminants in their substance.
Fungi can be very resistant and adapt quickly to substances we consider toxic.
One strategy is to collect fungi that live on mining or industrial waste and are prone to control them, and then use the fungi to clean up waste in other problem areas.
Thus, mushrooms can be used to restore land contaminated with harmful metals.
Evolution is the key word here. The ecosystem (plants, animals, and their habitats, including minerals) is not “intent on” cleaning up toxic chemicals the way humans do.
However, life is more likely to thrive and reproduce in ecosystems that remove harmful substances.
Just as certain fungi may be chosen to help fight polluted land, evolution has favored species that have adapted to environmental changes in the geological past, as Rainey implies.
The deposits in this particular geological area were formed by hot springs, the waters of which retained plant cells.
But because the hot springs that formed the Rainey deposit were rich in arsenic, antimony and other trace elements, there is uncertainty about how representative these fossils might be of early plant communities.
Scientists might argue that the plants found at Rainey could be an adaptation to an environment that was chemically unusual.
There is no clear answer as to whether this was the case, but our observations do suggest that the ecosystem was capable of responding to water chemistry, so the existence of these plants was not necessarily abnormal.
Visitors to hot springs in New Zealand and Yellowstone today can see orange and yellow crusts containing harmful arsenic, antimony, and so on, as well as precious metals such as gold and silver, so the springs are of commercial interest.
Hot springs around the world also contain an element that until recently was largely ignored – lithium.
Spring water provides a renewable source of this element, which is now fundamental to batteries, especially in electric vehicles, which are needed to meet carbon emission targets.
Thus, hot springs can play more than one role in environmental cleansing.
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