Remote sensing to monitor mining pollution

Remote sensing methods that could be used in future to monitor pollution from mining at less cost and to common standards across the EU were tested in six diverse sites across Europe by IST project MINEO.

Faced with increasing environmental pressure and regulatory controls due to surface and groundwater pollution, soil contamination, and terrain instability, the mining industry and decision makers need innovative and cost-effective tools for environmental data acquisition and processing that provide a sound basis for sustainable economic development of the sector.

MINEO’s answer was to develop the components of a future decision-making tool for use in environmental planning, and to disseminate knowledge and generate awareness of the role that can be played by earth observation data in this process. These decision-making tools and methods to exploit the data could potentially be used in future sustainable information systems that locate and monitor environmental risks.

Innovative earth observation techniques

Regularly updated information stored in databases related to mining environments is used to draw up Environmental Impact Assessments (EIAs) and Environmental Management Plans (EMPs). To collect this information innovative earth observation techniques developed by the 11-member MINEO consortium can be used. Hyperspectral imaging sensors that identify and map materials through spectroscopic remote sensing produce data that can characterise the chemical and/or mineralogical composition of the ground surface.

The primary advantages of this future space-borne imaging technique are the reduction in conventional, time consuming and expensive field sampling methods and its capability to gather repeat data, which assists in monitoring mining pollution.

“Today, only three commercially available sensors are able to meet these requirements [for mineral discrimination]: HyMap, from Australia, CASI from Canada and AISA from Finland,” explains coordinator Stéphane Chevrel of the Bureau de Recherches Géologiques et Minières, France. “All are airborne sensors, the reason why we used airborne data.”

Such earth observation data, when integrated into Geographic Information Systems (GIS) and combined with other data relevant to environmental concerns, is valuable in producing EIAs and EMPs of mining at local and regional scale. It can also be used in the production of pollution risk maps around mining areas.

A major project output was the development of a specific spectral database application, the MINEO Spectral Library. Fed with more than 1500 representative spectra, it is an extensive spectral library of contaminated or impacted areas from the six test sites. The application allows the management, comparison, and search and retrieval of spectra, according to spectral characteristics, type of surface feature or target investigated, location, climatic conditions, etc. These can be directly displayed in the image-processing software environment for immediate use in hyperspectral image processing for environmental impact mapping. The consortium also developed general guidelines for image processing procedures and algorithms for contamination and impacts.

Positive results from test sites

Six mining areas were chosen as test sites – Portugal, the UK, Germany, Austria, Finland and Greenland – reflecting Europe’s climatic, geographic and socio-economic environmental diversity. MINEO relied on the use of high quality airborne hyperspectral imaging spectrometer data. The main concern during the airborne survey was to acquire as much high quality data from the six test sites as time and weather would allow.

The results from the six test sites were very encouraging despite the very challenging and problematic abundance of vegetation that characterises the European landscape. Promising results were obtained in combining the maps with other relevant GIS information for modelling contamination, pollution risk, site rehabilitation or change detection.

The possible generic character of the procedures and algorithms used was examined, in particular through site cross-validation approaches, with a view to their applicability and reproducibility in Europe and other parts of the world. MINEO found that imaging spectroscopy can make an invaluable contribution to mapping mining-related contamination and/or impacts across a large variety of mining environments and in different climatic contexts.

This very innovative method needs further research before it can reach a real operational status. However, the MINEO project laid the groundwork for future projects involving imaging spectroscopy in environmental studies and sparked the interest of the international scientific community for mining-related remote sensing studies.

“The potential for these results is excellent for future very high spectral resolution satellite data, complemented by very high spatial resolution data,” explains Chevrel. “Project participants continue to use the skills developed over the course of the project. We are currently using Hyperion data [onboard NASA’s EO-1 experimental satellite] for testing and setting up new projects to continue developing applications.”

“The transposition of the MINEO concept to space-borne hyperspectral imagery will not be a problem since somebody will launch a spaceborne sensor that meets our requirements [for mineral discrimination]. This is unfortunately not planned in the short term,” concludes Chevrel.