07/1571 - Response to Information Request [As Published] · 142007.1571

Project 305-2325
February, 2006 , Page 4
hydrogen peroxide (H202). This is a quick, qualitative-assessment of the potential acidity

 

of the soil.

Reactivity to hydrochloric acid (HCI) was also assessed as a qualitative determination of
the neutralising carbonate content including calcium carbonate (shells) within the soil.
Reaction to Hydrogen Peroxide was also assessed as a qualitative determination of
oxidisable material. The results of these screening tests were used as an additional too!
in determining which soil samples should be further assessed by quantitative laboratory
testing.

The pH values ranged from 5.7 to 9.2 (Avg. 8.2) with pHrox ranging from 3.6 to 6.0 (Avg.
5.0), and the full results for the pH and pHrox tests are presented in Appendix D.

Where the measured pHr is <4, oxidation of the sulfides has probably occurred in the
past, indicating the presence of Actual Acid Sulfate Soils (AASS). A pHr > 4 but <5
indicates an acid soil where the cause of the acidity needs further investigation. The
PHrox test is used to indicate the presence of potential acid sulfate soils (PASS). If the
PHrox <3 and a significant reaction with hydrogen peroxide has occurred, then it strongly
indicates PASS and the more the pHrox drops below 3 the more positive the presence of
sulfides. The lower the final pHrox result and the greater the difference between pHrox
and pH, the more likely that PASS is present. |

4.3.1. Quantitative Tests

The second stage of laboratory testing was carried out on a selection of samples showing
the most severe potential acid sulphate readings, i.e. those showing low pH and large
change between the pHr and the pHrox readings. The second stage of laboratory testing
consisted of Chromium Reducible Sulfur (Scr) tests, and Titratable Actual Acidity (TAA)
tests.

The Scr test provides data on sulfuric acids, without influence from organic acids. The
TAA test is a measure of the soils existing acidity prior to oxidation of sulfidic material.

The results from the second stage quantitative ASS tests show negligible presence of
oxidisable sulphur (<0.01 %S). Full results of the testing are summarised below in Table
1, and test report sheet is included in Appendix D. :

 

# SOIL SURVEYS ENGINEERING

ae.