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Metals In Western Water Supplies | Earth Wise

October 29, 2021 By EarthWise Leave a Comment

A new study published by the University of Colorado Boulder looked at the problem of rivers being contaminated by acid rock drainage. Rocks that include sulfide-based minerals, such as pyrite, oxidize when exposed to air and water. The resulting chemical reaction produces sulfuric acid which, when present in water, dissolves metals like lead, cadmium, and zinc. The recent study found that rare earth elements are also leached out of rock by this process.

Rock drainage occurs naturally throughout the western United States, but historic mines that disturbed large amounts of rocks and soil have dramatically increased this process and have led to growing downstream water pollution. Upwards of forty percent of the headwaters of major rivers in the West are contaminated by some form of acid mine or rock drainage.

The warming climate has brought longer summers and less snow in winters. Longer, lower stream flows make it easier for metals to leach into watersheds and concentrate the metals that would otherwise be diluted by snowmelt.

Rare earth elements are essential components of many high-tech devices such as computers, hard drives, and cell phones. There is not a long history of studying the hazards they might represent when they enter the environment.

The study looked at the Snake River watershed in Colorado and found that increasing amounts of rare earth elements are entering Colorado water supplies. Concentrations of rare earth elements are not ordinarily monitored and there are no water quality standards set for them.

According to the researchers, once rare earth elements get into water, they tend to stay there. Traditional treatment processes don’t remove them. It is a growing problem that needs to be addressed.

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Rare earth elements and old mines spell trouble for Western water supplies

Photo, posted October 27, 2007, courtesy of Dion Gillard via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Ocean Acidification And Mass Extinction

November 26, 2019 By EarthWise Leave a Comment

Since the industrial revolution, the concentration of carbon dioxide in the atmosphere has increased due to the burning of fossil fuels and land use changes. The ocean absorbs about 30% of the CO2 that is released in the atmosphere. As the levels of atmospheric CO2 increase, so do the levels in the ocean.

When CO2 is absorbed by the ocean, a series of chemical reactions occur, resulting in seawater becoming more acidic. Ocean acidification threatens calcifying organisms, such as clams and corals, as well as other marine animals, like fish. When these organisms are at risk, the entire marine ecosystem may also be at risk.

In fact, according to research recently published in the journal Proceedings of the National Academy of Sciences, fossil evidence from 66 million years ago has revealed that ocean acidification can cause the mass extinction of marine life. Researchers analyzed seashells in sediment laid down shortly after a giant meteorite hit earth. This strike wiped out the dinosaurs and 75% of marine species. Chemical analysis of the shells revealed a sharp drop in the PH of the ocean over hundreds of years after the meteorite strike. The meteorite impact vaporized rocks, causing carbonic acid and sulphuric acid to rain down, acidifying the ocean. The strike also resulted in mass die-off of plants on land, increasing atmospheric CO2.

Researchers found that the pH dropped by 0.25 pH units in the 100 to 1,000 years after the meteorite strike. Alarmingly, scientists expect the pH of the ocean to drop by 0.4 pH units by 2100 if our carbon emissions continue as projected.

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Ocean acidification can cause mass extinctions, fossils reveal

Photo, posted March 16, 2017, courtesy of Zachary Martin via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Emissions-Free Cement

October 29, 2019 By EarthWise Leave a Comment

The production of cement – which is the world’s leading construction material – is a major source of greenhouse gas emissions, accounting for about 8% of global man-made emissions.

Cement production produces carbon dioxide in two ways: from a key chemical process and from burning fuel to produce the cement. The process of making “clinker” – the key constituent of cement – emits the largest amount of CO2. Raw materials, mainly limestone and clay – are fed into huge kilns and heated to over 2,500 degrees Fahrenheit, requiring lots of fossil fuel. This calcination process splits the material into calcium oxide and CO2. The so-called clinker is then mixed with gypsum and limestone to produce cement.

A team of researchers at MIT has come up with a new way of manufacturing cement that greatly reduces the carbon emissions. The new process makes use of an electrolyzer, where a battery is hooked up to two electrodes in water producing oxygen at one electrode and hydrogen at the other. The oxygen-evolving electrode produces acid and the hydrogen-evolving electrode produces a base. In the new process, pulverized limestone is dissolved in the acid at one electrode and calcium hydroxide precipitates out as a solid at the other.

High-purity carbon dioxide is released at the acid electrode, but it can be easily captured for further use such as the production of liquid fuels or even in carbonated beverages and dry ice. The new approach could eliminate the use of fossil fuels in the heating process, substituting electricity generated from renewable sources.

The process looks to be scalable and represents a possible approach to greatly reducing one of the perhaps lesser known but nevertheless very significant sources of greenhouse gas emissions.

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New approach suggests path to emissions-free cement

Photo, posted March 26, 2014, courtesy of Michael Coghlan via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.