EnviroMail 140 Australia - Method EA027

ANC Corroboration by Chip Tray Incubation, as per the National ASS Guidance (2018)

slide under microscope
28 OCT 2022 ALS

ALS is excited to announce the development of an ANC Corroboration by Chip Tray Incubation method, designed to authenticate the Acid Base Accounting provided by Chromium Suite (EA033) and/or SPOCAS (EA029) analyses. This will translate into reduced environmental disturbance as well as significant cost savings in large land remediation projects since liming can be a costly and time intensive process.

Traditional Chromium Suite and SPOCAS analyses determine the Acid Neutralising Capacity (ANC) of the soil, however they cannot measure its effectiveness under field conditions. By simulating field conditions Chip tray Incubation can demonstrate the effectiveness of the ANC.

The current National Acid Sulfate Soils Guidance (NASSG, 2018) recommends that ANC as determined by Chromium Suite or SPOCAS analyses should only be included in Net Acidity and Liming Rate calculations if the ANC has been corroborated by chip tray incubation. An incubation period of ≥ 9 weeks is recommended to ensure the soil pH has stabilised (Creeper et al, 2012).

Chip Tray Incubation is suitable for samples that have yielded a positive ANC result in Chromium Suite (evidenced by pHKCl ≥ 6.5) or SPOCAS analysis (evidenced by pHox > 6.5).


To illustrate how corroborated ANC can save on liming cost, see the example below. The reduced net acidity and liming rate results outlined in green (including ANC) can only be applied if the ANC has been corroborated. Results outlined in red (excluding ANC) apply when the ANC has not been corroborated.

Method Analyte Units LOR Sample 1 Sample 2 Sample 3 Sample 4
EA033 Net Acidity (sulfur units) %S 0.02 <0.02 <0.02 <0.02 2.06
EA033 Net Acidity (acidity units) Mole H*/t 10 <10 <10 <10 1290
EA033 Limiting Rate kg CaCO3/t 1 <1 <1 <1 97
EA033 Net Acidity excluding ANC (sulfur units) %S 0.02 0.57 0.90 0.89 2.23
EA033 Net Acidity excluding ANC (acidity units) Mole H*/t 10 358 564 557 1390
EA033 Limiting Rate excluding ANC kg CaCO3/t 1 27 42 42 104


Moist soil (adjusted to near field capacity) is incubated aerobically at room temperature in chip trays for a period of 9 weeks. Soil moisture status is periodically monitored and adjusted if necessary to ensure that the moisture level remains at optimum level.

Nine week incubation 

At the conclusion of the 9-week incubation:

  • If the pHINC is ≥ 6.5, the ANC can be included in Net Acidity and Liming Rate calculations.
  • If the pHINC is < 6.5, ANC should not be included in Net Acidity and Liming Rate calculations. Results are reported in the following format:
Method Analyte Units LOR Sample 1 Sample 2 Sample 3 Sample 4 Sample 5
EA027 pH (INC) pH Unit 0.1 7.2 7.2 7.1 5.3 6.5
EA027 ANC Corroborated Yes Yes Yes No Yes

Sample Requirements

It is recommended that samples should be maintained frozen to minimize oxidation until Chip Tray Incubation can commence, to facilitate the most accurate results.

Hence, it is required to indicate on the Chain of Custody when Chromium Suite or SPOCAS is requested that additional volume has been provided specifically for EA027 (ANC Corroboration by Chip Tray Incubation) which may be required depending on the ANC results reported on the requested suites.

All samples from such work orders will then be maintained frozen until after the Chromium Suite (EA033) or SPOCAS (EA029) results have been released. 

The client can then select samples for Chip Tray Incubation. These will be “re-batched” and the 9-week Chip Tray Incubation will commence.



National Acid Sulfate Soil Guidance - Identification and Laboratory Methods Manual; Appendix B and C, pp 76-81 (2018)


Creeper N. et al

A simplified incubation method using chip trays as incubation vessels to identify sulphidic materials in acid sulphate soils (2012)


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