Protecting communities from toxic mine waste

Imagine an abandoned mine site, surrounded by dead trees and dotted with dark, red ponds with no signs of aquatic life. This is the result of mine waste left in the environment that gets weathered by water and air. With exposure to the elements over time, the waste produces toxic substances such as arsenic and lead.

“It is a major environmental problem facing the mining industry in Canada and worldwide,” said Aria Zhang, who studied a method for covering mine tailings as part of her Master’s degree at the University of Waterloo. “Once these toxins are released, it’s difficult to control. It pollutes the soil and seeps into lakes and groundwater. It can threaten people’s drinking water supply, agricultural production, and the ecosystem.”

Under the supervision of professors David Blowes and Carol Ptacek, and hydrogeochemist Jeff Bain, Zhang assessed the effectiveness of a cover of layers of soil, sand, and gravel placed over mine waste near Timmins, Ontario in 2008.

The cover was intended to inhibit the chemical reaction that produces toxins and prevent them from leaching into the environment. However, there were concerns within the remediation industry about how effective covers would be in containing toxins from the waste — which was deposited on this site between 1968 and 1972.

At old mine sites, metals like lead, arsenic, and copper have precipitated into unstable solids,” said Zhang. “It’s similar to limescale buildup in a kettle if there is hard water. They are sensitive to chemical changes, which means they could dissolve again under a cover and potentially get released into the environment.”

Using experimental techniques at the Canadian Light Source at the University of Saskatchewan and the Advanced Photon Source at Argonne National Laboratory in Illinois, Zhang and colleagues determined the remediation approach had been successful. They found that the cover did not destabilize toxic minerals at the site and was preventing more toxins from developing. Their findings were recently published in Applied Geochemistry.

Read more on Canadian Light Source website

Grape pomace, a waste of viticulture, is effective for nematode pest control on crops

Researchers from Universidad de Castilla la Mancha, Universidad Autónoma de Madrid and the Institute of Agricultural Sciences – CSIC proved the potential of wine production residues as biopesticides in agriculture, thus reducing the waste management problem and contributing to a circular economy. Their work shows that recycled biochar from grape pomace is effective to reduce the parasitic nematode infection of tomato plants in pots. Biochar characterization by synchrotron light infrared spectroscopy was performed at MIRAS beamline of the ALBA Synchrotron.

Cerdanyola del Vallès, 22nd November 2023 The large amount of grape waste generated after wine production can be transformed into a valuable product such as biochar, a form of charcoal. A new published study shows that biochar soil amendments can help to control the infection of a group of plant parasitic nematodes: the root-knot nematodes.

Nematodes are a big group of invertebrates also known as roundworms. They are among the most widespread pests and can be found in almost every crop worldwide, causing annual global agriculture losses of approximately $125 billion. In particular, root-knot nematodes parasite plants penetrating the roots and inducing knots or galls. The plant becomes their host and will nourish them until life cycle completion.

Root-knot nematode infection is difficult to eradicate and usually requires the use of toxic nematicides that are banned in most countries. In this sense, the research team, formed by scientists from the Universidad de Castilla la Mancha (UCLM), Universidad Autónoma de Madrid (UAM) and the Institute of Agricultural Sciences (ICA-CSIC), proposes the use of biochar as an environmentally friendly and economic alternative.

To run the studies, tomato plants were infected withMeloidogyne javanica, a root-knot nematode, and grown in hydroponic system over a clay sandy substrate mixed with different proportions of biochar. After several days of post-inoculation, nematode infection progression was analysedThe infective and reproductive traits of a Meloidogyne javanica population in tomato were significantly reduced (egg masses and eggs per plant) for the biochar pyrolyzed at 350ºC.

In parallel, researchers performed a complete characterization of biochar after a thermal treatment (pyrolysis at 350ºC and 700ºC) by determining their elemental composition and analysing the particulate structure. To do so they use, among other techniques, infrared spectroscopy at MIRAS beamline of ALBA. The analysis with synchrotron light enabled scientist to visualize the large changes in the biomolecular composition of biochar, occurring during grape pomace pyrolysis.

Read more on ALBA website

Mine tailings dumped into the sea analysed with synchrotron light

The case of Portmán Bay, at the Spanish Mediterranean coast, is one of the most extreme cases in Europe causing great impact on the marine ecosystem by disposal of mine tailings.

For more than 40 years, 60 million tonnes of mine waste were dumped directly into the sea, resulting from the open pit mining that took place in Sierra Minera in Cartagena. As a consequence, the Bay was literally filled with metal-rich artificial soil. Since 2014, a research group from the University of Barcelona (UB) has been studying Portmán Bay. Now, they have analysed samples of these sediments at ALBA because with synchrotron light they can obtain unprecedented information about the heavy metals contamination, such as arsenic.

Very few people know about Portmán Bay, where took place one of the most extreme cases of coastal ecological impact by mine activity in Europe. Figures speak for itself: the mining company Peñarroya dumped more than 60 million tonnes of mine waste into the sea through a 2km-long pipeline located at the west part of the bay. Over the years, the bay became totally filled with a mountain of artificial sediment. The shoreline moved 600m seaward and the trace of the pollution reached 12km out to sea.

>Read more on the ALBA website

Image: Miquel Canals putting sample supports, which were specifically designed and printed with 3D technology at ALBA, at the CLAESS beamline to be analysed with synchrotron light; with Carlo Marini, beamline scientist and Andrea Baza, PhD student from UB.