Phase 2 site investigations are commissioned when a Phase 1 desk study identifies a credible pollutant linkage between a potential source and a receptor. Soil metals analysis is one of the most common components of a Phase 2 investigation, and the quality of the results depends as much on how samples are collected as on what happens in the laboratory.

Which metals are typically screened

The standard screen for a UK brownfield or mixed-use development site covers the metals most commonly associated with industrial land use: arsenic, cadmium, chromium (total), copper, lead, mercury, nickel, selenium, and zinc. For sites with specific historical uses, additional analytes may be relevant. Former petrol stations typically require petroleum hydrocarbon and BTEX screening alongside metals. Former tanneries may require chromium speciation to distinguish between trivalent and hexavalent forms. We discuss the site history with clients before finalising the analytical scope.

Sampling strategy and sample handling

The sampling strategy should be agreed with the environmental consultant or geotechnical engineer before fieldwork begins. For a standard grid-based investigation, we recommend collecting samples at 0.5m depth intervals from each trial pit or borehole, with additional samples from any visually anomalous material. Samples should be placed in clean, sealed containers and kept at 4 degrees C during transit. Avoid using galvanised containers or tools that could contaminate samples for zinc or cadmium analysis.

How results are interpreted

Results are reported as total extractable metals concentrations in mg/kg dry weight, and compared against the relevant UK Soil Guideline Values (SGVs) published by the Environment Agency. SGVs are land-use specific: the threshold for residential use with home-grown produce is more stringent than for commercial or industrial use. Where concentrations exceed an SGV, the report flags this clearly and notes the relevant land use scenario. Interpretation of exceedances in the context of a risk assessment is the responsibility of the environmental consultant, not the laboratory.

Turnaround and reporting

Standard turnaround for soil metals by ICP-OES is five working days from sample receipt. Expedited two-day turnaround is available at an additional charge of £55 per submission. Reports include the analytical results table, the method reference (BS EN ISO 11885 for ICP-OES), the uncertainty of measurement, and a comparison table against the relevant SGVs. We can provide results in a format compatible with most risk assessment software on request.

If you are planning a Phase 2 investigation and want to discuss the analytical scope before fieldwork begins, a scoping call is free and takes around twenty minutes. Get in touch with us to arrange one.