MEND Report 1.16.2a
July 1994

EXECUTIVE SUMMARY

Static prediction methods are becoming increasingly important to the mining industry worldwide as efforts are made to diminish the environmental impact of acidic rock drainage (ARD). At present ARD analytical methods are still in the developmental stages and no reference materials exist to enable laboratories to compare the accuracy and precision of their results. The aim of this project was to use the consensus approach in the determination of the net neutralization potential and thereby standardize the material, NBM-1 for a static prediction test.

The preparation of a standard reference material for ARD prediction technologies was undertaken at the request of Mr. Benoit Godin, Section Head, Environmental Contaminants Division, Environmental Protection, Yukon Division, Environment Canada and the Mine Environment Neutral Drainage (MEND) Committee by the Canadian Certified Reference Materials Project (CCRMP) at CANMET. This project is a follow on to CANMET job number 50977 in which the standard material was processed and the homogeneity assessed according to the protocols of CCRMP.

In this project fourteen laboratories were selected on the basis of their experience with ARD methods and previous participation in other CCRMP projects or, on the referral of the Coordinator of the Prediction and Monitoring MEND Committee. The participants were requested to follow the standard acid base accounting method for the determination of the net neutralization potential (NNP). The method, as written in reference 1, was supplied and a slight fizz test rating was specified for use.

Due to a bimodal distribution of the results, the mean of the NNP results is assigned provisional status. This value, 42.9 tonnes CaCO3/1000 tonnes, refers to the determination of NNP by the standard acid base accounting method (1) with a fizz test rating of slight. The current provisional value and its uncertainty limits are subject to change as more analytical information becomes available. Also, values obtained by varying numbers of laboratories are reported for the paste pH, fizz test rating and NNP by other methods.

It is recommended that further study be made of the acid base accounting method. Suggestions to improve the method are stated. It is also recommended that further work be performed on the standardization of NBM-1 for NNP by other methods, and, also, other standard materials with different NNP values be prepared. The standard material, NBM-1, can be used for the very necessary method development and as a control standard for acid base accounting analyses.

Last Modified: 2003-11-26		Important Notices

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