Document ID: chunk:federal_register_of_legislation:F2013C00288:reg:4:p4
Version: federal_register_of_legislation:F2013C00288
Segment Type: reg
Provision Reference: reg 4 (pt 4/12)
Character Range: 747769–750689

of air-drying temperature on analyte modification is not completely understood but in some cases it seems to change the bioavailability or extractability of the analyte. The impact of air-drying on analysis may be more pronounced in certain soil types and in sediments. Therefore, air-drying is only applicable to some methods of soil analysis.

Soils for most metals and some other inorganic analytes can be air-dried, and then sieved. However, the procedure described below is not applicable to analysis of volatile constituents—including volatile metallics such as metallic mercury, methyl mercury or tetraethyl lead—or where analytical methods specifically forbid such preparation (e.g. certain leaching tests). Samples for volatile metallics should be homogenised and sub-sampled in the field-moist state.

Note: Grinding samples will increase surface area and may give higher results.

4.2.4.1         Sample drying
Dry at least 25% by weight or 200 g of the sample, whichever is the smaller, by spreading the soil on a shallow tray of a suitable non-contaminating material, such as plastic or stainless steel. If necessary, break up large clods with a spatula to speed up the drying process. Allow the soils to dry in the air (at <40°C), ideally with the trays placed in a clean air chamber, or a non-contaminating oven at 40 ± 3°C. The relative humidity should be less than 70% to achieve drying within a reasonable time. The sample is dry when the loss in mass of the soil is not greater than 5% per 24 hours (AS 4479.1-1997).

     4.2.4.2         Grinding of dry sample
Note: Grinding increases the surface area and can give higher results.

Grinding is not recommended for analysing 'available' metal contaminants, as it can release natural metals inside the soil particles that are not normally available.

Where necessary, crush the dry sample in a mortar and pestle of appropriate material (glass, agate or porcelain) or other suitable grinding apparatus to achieve a particle size appropriate to the analysis. Mix the sample as thoroughly as possible.

Take care to avoid contamination during the grinding process, and clean equipment between each sample to prevent cross-contamination. See below. To evaluate decontamination efficiency, the final wash solution should be sampled and analysed (Barth & Mason 1984); one final wash sample per process batch or 1 in every 10 samples ground, whichever is the smaller. Alternatively, treat a well-characterised control soil sample similarly. If there is significant carry-over due to the grinding process, the results from that process batch may have to be rejected.

WARNING: Grinding of soils can produce fine dust particles that may present a health hazard if inhaled. Sample grinding, and subsequent handling, should be performed in accordance with work health and safety requirements.

4.2.4.3         Sieving
Unless impracticable or not recommended for