in Environment, Resources and Sustainability
Probing Heavy Metals with Light
Ingrid Pickering and Graham George use synchrotron-based X-ray absorption spectroscopy (XAS) to explore the molecular form and function of metals in the environment and in the body, and to find strategies to reduce or eliminate toxic effects.
Heavy metals such as mercury and arsenic are known to be toxic, yet many organisms have mechanisms to cope with these toxins, and some plants actively accumulate them. Ingrid Pickering, Canada Research Chair (CRC) in Molecular Environmental Science, uses XAS to study hyperaccumulators—plants that take up and store high amounts of metals from the environment.
One such plant is a purple-flowered milkvetch, or locoweed, which is common on the Great Plains. The plant accumulates toxic levels of selenium in its tissues. This affects the nervous systems of cattle that eat it, causing symptoms described as the “blind staggers.”
Understanding how locoweed handles such high levels of selenium could provide a strategy whereby plants are used to clean up contaminated water or soil.
Biological properties of a heavy element— such as whether it is toxic, benign or even beneficial—are largely controlled by the molecule that contains the metal.
Graham George, CRC in X-ray Absorption Spectroscopy, studies biochemical transformations of toxic elements in living tissues. He is currently working with molecules that include arsenic, selenium, mercury, and sulphur.
Such knowledge will aid the design of new, highly specific molecules that bind to the metal and carry it out of the body. This work has important applications in drug therapy, water treatment, and the remediation of contaminated industrial sites.
Finding the Antidote to Mass Poisoning
For nearly 70 years, it has been known that a lethal dose of arsenic cancels an equal, and otherwise lethal, dose of selenium.
George and Pickering have used synchrotron XAS to reveal the reason for this toxicological curiosity—why a detoxification molecule containing one selenium and one arsenic atom is formed in blood and excreted. Their research could have profound implications.
The contamination of well water by natural arsenic has resulted in the mass poisoning of nearly 100 million people in Bangladesh and the surrounding Ganges River delta.
Soil selenium levels in the area are also very low, and the scarce selenium that is ingested is leached from the body in the arsenicselenium molecule. Unlike arsenic, selenium is essential to human health, and symptoms of selenium deficiency can closely resemble those of arsenic poisoning.
George, Pickering and co-workers hypothesize that rather than arsenic poisoning, the Bangladeshi are actually suffering from selenium deficiency. The U of S team is now part of an international collaboration conducting a clinical trial of selenium supplementation in Bangladesh.
Maintaining Healthy Rivers
Toxicologist and CRC in Aquatic Ecosystem Health Diagnosis, Monique Dubé is working to ensure our rivers supply safe water for future generations.
She is a member of the Aquatic Toxicology Research Centre at the U of S, a $7-million initiative unique in Canada.
As water is the lifeblood of all organisms, rivers are the arteries of the earth. Dubé monitors and studies the effects of stressors such as sewage, industrial effluents, farm chemical runoff, and mining and pulp mill waste on our river systems and food webs. Her work will help policy makers address two basic questions: How much is too much? And what must we do about it?
Dubé’s research group has developed artificial stream systems to assess the toxic effects of waste mixtures on fish and river life. One project involves identifying contaminants from pulp and paper mills that cause reproductive problems in fish. Dubé is also working to transform lab studies to scales applicable in real ecosystems.
With support from the Saskatchewan government, she developed The Healthy River Ecosystem Assessment System (THREATS), software that identifies “hotspots” when changes have occurred in the quality of water in rivers and in the health of the plants and animals that live in them.
Under UNESCO, Dubé chairs an international group on the use of ecology and hydrology to resolve water-related issues in developing countries.
Engineering Environmentally Friendly Energy
Ajay Dalai, Canada Research Chair in Bio- Energy and Environmentally Friendly Chemical Processing, is developing more economical, renewable sources of energy and “greener” chemical processing methods.
The quest for clean energy has become the holy grail of environmental research.
Dalai’s group has successfully produced biodiesel from oilseeds and waste vegetable oils, with properties very similar to diesel fuel. While the replacement of petro-diesel is a longterm goal, in the immediate future biodiesel is an important fuel additive. Since it contains no sulphur or nitrogen, biofuel lowers emissions. The addition of one per cent of biodiesel also improves fuel lubricity—or slipperiness— up to 65 per cent, thereby greatly reducing engine wear.
Hydrogen has the potential to be the ultimate clean energy source—when burned, water is the only by-product. Dalai is developing methods of producing pure hydrogen from waste biomass, such as municipal solid wastes and wood chips. He and his U of S colleagues are converting glycerol, a by-product of biodiesel, to hydrogen. They are also developing catalysts to convert methanol and crude ethanol to hydrogen.
Dalai is also working to develop cleaner methods of processing heavy oil and gas, and value-added products from fuel oil by-products. He has been successful in oxidizing toxic sulphur compounds in natural gas, sewage and jet fuels, and capturing mercury from coal-fired power plant flue gases. Dalai is working with several industry and government partners to test and eventually commercialize this research.
Reclaiming the Oil Sands
A team of U of S scientists, led by U of S civil engineer Lee Barbour, is helping to transform more than 20,000 hectares of land disturbed by oil sands mining into sustainable ecosystems.
In partnership with Syncrude, and with funding from NSERC, the team has been researching how to store sufficient moisture for vegetation while minimizing the salts that are released when mountains of clay shale—or overburden— are removed to expose the oil sands.
Barbour and geological sciences professor Jim Hendry are working on research to reclaim other types of waste materials, such as sulphur and coke, from oil sands mining and refining. Composed almost entirely of carbon, coke is a fine-grained black sand that is the by-product of extracting crude oil from tar sand.
The team’s research results will help ensure sustainable boreal forest ecosystems are reestablished following oil sands development.