Low-tech soil testing

“What’s one portable way to measure how polluted our soil is?”

Portable X-ray fluorescence spectrometry, or pXRF, is one the most widely accepted instrumental methods for soil analysis that has become a key technique for field geochemical analyses especially in mining and environmental applications. It is also one of the oldest, with the first commercial

spectrometer

built in 1948. X-ray fluorescence is an analytical technique to determine the elemental composition of a sample by illuminating it with an X-ray beam. When exposed to X-rays, each element re-emits varying X-ray wavelengths, which are used to identify the elements present in a sample.¹
        Due to its portability, pXRF provides nearly real-time data to support in-field decision making for exploration, mining, site remediation or waste management fieldwork. Moreover, this technique is a cost-saving alternative to laboratory soil-testing techniques such as ICP-OES, ICP-MS or AAS.² In waste management and remediation applications, pXRF is used to identify the composition of unknown waste and verify waste-loads before disposal or treatment. When used in soil-testing, pXRF is used to determine soil composition but is often paired with laboratory data analysis to validate field-results to generate the most accurate overall results.
        In South Africa, pXRF was used extensively to analyze the former Edendale lead mine located in Mamelodi, at the outskirts of Pretoria, to detect heavy metals soil pollution. The analysis yielded similar results to the laboratory-performed analyses obtained by the ICP-OES, demonstrating that pXRF is a useful tool for soil analysis and soil pollution assessment, especially in countries where economic resources are limited to routinely perform expensive lab studies.³

Image source: Portable X-ray fluorescence instrument with tapered absorption collar. Accessed February 27th 2022. https://patents.google.com/patent/US7671350B2/en?q=Portable+X-ray+fluorescence&oq=Portable+X-ray+fluorescence