Document ID: chunk:federal_register_of_legislation:F2013C00288:reg:6:p2
Version: federal_register_of_legislation:F2013C00288
Segment Type: reg
Provision Reference: reg 6 (pt 2/3)
Character Range: 777904–781759

content may have physical detrimental effects on a soil, compromising its agronomic and structural attributes, for example, increasing potential for corrosion of below-ground structures.

The same 1:5 soilwater suspension for pH determination may be used for measuring the electrical conductivity but to avoid contamination, electrical conductivity should be analysed first.

    6.3.2         Principle
The electrical conductivity is measured on the aqueous extract of a 1:5 soilwater suspension and recorded in dS/m at 25°C.

6.4              Cation exchange capacity and exchangeable cations

    6.4.1         Scope and application
Methods in the following table measure the cation exchange capacity (CEC) of major exchangeable cations/'bases' (Ca2+, Mg2+, Na+ and K+) of near-neutral and alkaline soils.

Soil type               pH   Extractant          Salt content*                                           Method **         Comments

Non-calcareous          7.0  1M                  EC< 0.3 dS/m                                            15B1              No pre-treatment for soluble salts
&                            ammonium chloride
non-gypsiferous soils                            EC> 0.3 dS/m                                            15B2              Pre-treatment: soluble salts are removed using aqueous ethanol and aqueous glycerol.

                                                                                                                           Adjustment: corrected for soluble Na+ when NaCl is the dominant soluble salt.
                                                 * Based on EC determined on a 1:5 soilwater extract.   15B3

                                                                                                         ** Soil Chemical
                                                                                                         Methods

Limitation: These methods are designed to assess the ion-exchange characteristics of soils for land surveys or soil fertility studies, not contaminated soil; they should only be used with natural soils or background samples to give supporting information about the extent of contamination. In other samples the methods are qualitative and the results will be indicators only. Soils heavily contaminated with soluble metals may saturate an extractant's exchangeable sites and may not, by itself, provide a true indication of the soil's exchangeable capacity.

US EPA Method 9081 (US EPA SW-846) can be used on most soils (calcareous and non-calcareous) to measure the total amount of displaced ions from exchangeable sites in soil, compared with the summation of individual ions to express the soil's CEC.

    6.4.2         Principle
The soil is shaken with an appropriate extractant under certain conditions to exchange cations in the soil with the chosen extracting ions. The processed extract is then analysed for exchangeable cations including Na+, K+, Ca2+ and Mg2+, or total CEC.

6.5              Water-soluble chloride

    6.5.1         Scope and application
This method measures water-soluble chloride in soil water extracts (1:5 soilwater) (Rayment & Higginson 1992, p.2425).

    6.5.2         Principle
Chloride in soil is extracted in deionised water and the chloride concentration determined by colorimetric analysis or potentiometric titration.

    6.5.3         Interferences
Water-soluble colour in the soil may mask the colour change at the endpoint of the titration. If this occurs, the colour can be removed by adding an aluminium hydroxide suspension (APHA Method 4500-Cl). Alternatively, chloride in the water extract can be determined using an ion-selective electrode or ion-chromatography.

6.6              Organic carbon

    6.6.1         Scope and application
This determination (Rayment & Higginson 1992, p. 29),