Environmental Science & Engineering - www.esemag.com - September 2002
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Radium-226 monitoring for new metal mining effluent regulations

By Blake Barber & Steven Simpson,
Becquerel Laboratories

The MMER (Metal Mining Effluent Regulations) were published in the Canada Gazette, Part II this past June and will be fully in force December 6th, 2002. These new regulations (which replace MMLER) now apply to all metal mines in Canada, including pre-1977 mines. The intent is to monitor the effluent released by mines for parameters that have a potential negative environmental impact.

There is still debate amongst various groups about what should or should not be included and what limits are acceptable; however, after six years of extensive consultation the regulation has been set. Along with establishing an Environmental Effects Monitoring (EEM) program as set out by Environment Canada, testing for individual parameters must occur at specified intervals. The parameters tested include the radioactive isotope radium-226, pH, Total Suspended Solids, acute lethality testing, and the deleterious substances arsenic, copper, lead, zinc, and nickel.

Radium-226 requirements and methods Radioactivity in effluent is monitored in the form of radium-226, a daughter of uranium. Authorized limits for radium- 226 have been set as 0.37 Becquerels (Bq)/L for the maximum monthly mean concentration, 0.74Bq/L for the maximum concentration in a composite sample and 1.11Bq/L for the maximum concentration in a grab sample.

According to the regulation, sampling for radium-226 (on unfiltered and undiluted effluent) must occur weekly, at least initially. Section 13.2 states that "...the owner or operator of a mine, other than an uranium mine, may reduce the frequency of testing for Radium-226 ...to not less than once in each calendar quarter if that substance's concentration in the effluent is less than 0.037Bq/L in ten consecutive tests".

Therefore, after a comprehensive ten week screening period, effluent samples need only be analyzed quarterly if the level of radium-226 continues to fall below 10% of the monthly mean concentration value.

Although many environmental laboratories can provide metals analysis, few can fulfill the radium-226 requirements set out in the regulations. The guidance document published by Environment Canada for the sampling and analysis of metal mining effluents states that laboratories must demonstrate clearly their ability to work within a performancebased system. That is, results will be accepted only from a laboratory that is ISO 17025 (formerly ISO Guide 25) accredited by the Standards Council of Canada (SCC) for the determination of radium-226 in liquid samples.

There are generally three techniques to determine radium-226. Gamma spectrometry, the simplest and least expensive, cannot practically achieve the minimum 0.01Bq/L detection limit. Although radon emanation, a second method, does achieve the necessary detection limit, the analysis time is too long for this project. The best technique is co-precipitation with barium sulfate followed by alpha-spectrometry. This can provide the regulatory detection limit within an acceptable time frame. However, the SCC lists only two laboratories that are certified for this method, Saskatchewan Research Council in Saskatoon, SK and Becquerel Laboratories in Mississauga, ON.

Handling the surge With expansion of its peak capacity by Becquerel, the two labs should have sufficient capacity to process the anticipated sample volume. However, the short-term demand for radium-226 analyses is expected to be unusually high, and delays are likely if all the mines decide to wait until the regulations are enforced in December. This scenario would result in many hundreds of samples per week and the ensuing analysis logjam could delay results and force mines to continue weekly sampling long past the minimum ten weeks.

The economical approach Mine operators will want to reduce their Radium-226 sampling to quarterly. In order to do this, mines need approval from the governing agencies after completion of the mandatory ten consecutive week screening period. Because there is little time remaining before the December enforcement, it is recommended that monitoring programs start as early as possible to avoid additional weekly testing while waiting for approval.

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