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Net neutralisation potential (NNP)

Acid-base accounting (ABA), also called static testing, calculates a net neutralisation potential (NNP) representing the ability of a body of rock to produce acid rock drainage or to consume free acid and neutralise it. Methods for determining the NNP have been proposed by multiple research groups and some have been selected by government organisations to be part of mine development reporting requirements. The method required in a particular jurisdiction varies and this information should be obtained from the relevant government organisations. ALS offers a wide range of methods for ABA estimation, including: Sobek, Modified Sobek, Siderite correction, Modified Neutralisation Potential from MEND, and EN 15875 methods.

Condutividade, pH e neutralização

ABA methods available

ALS provides a variety of methods to suit the requirements of various jurisdictions.
The table below outlines the parameters included in each of our ABA packages.

ABA packages:
Net Neutralisation Potential (NNP)
Maximum Potential Acidity (MPA)
Neutralisation Potential (NP) & Fizz
Ratio (NP : MPA)
Neutralisation Potential (EN 15875 NP)
Acid Potential (EN 15875 AP)
Maximum Acid Potential (EN 15875 AP Max) √**
Neutralisation Potential Ratio (EN 15875 NPR)
Net Neutralisation Potential (EN 15875 NNP)
Paste pH
Sulphate by ICP
HCl-leachable Sulphate
Total Sulphate (Carbonate Leach)
Sulphide (calculated)
Sulphide (analysed) √** √** √** √**
Total Sulphur √**
Inorganic Carbon (CO2)
Inorganic Carbon (calculated)
Organic Carbon
Total Carbon
*meets EU regulations
** optional parameter, use A after the package name to indicate the optional extra analysis.



ALS Acid Base Accounting Technical Note

04 JUL 2022

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ALS Mine Site Lab Services web