Measuring metal contamination on-site

Environmental scientists from Macquarie University have developed what they claim is an accurate, rapid and inexpensive method for assessing metal-contaminated sites. Published in the journal Environmental Pollution, their method uses a combination of portable X-ray fluorescence technology (pXRF) with conventional laboratory analysis to measure the extent and distribution of metal contamination at a site.

“Metal-contaminated sites are often haphazard when it comes to the distribution of metal contaminants, making it problematic for investigators when they are limited by the costs associated with analysing a large number of samples in the lab,” explained Marek Rouillon, lead author on the study. “As such, investigators are expected to attempt to characterise contaminated sites with a limited number of laboratory measurements to save on costs.

“On the other hand, when investigators are free to take a large number of measurements to determine the contamination at a site, they gain a greater understanding of the extent and distribution of the contamination, therefore lowering the risk of site misclassification.”

As a result, Rouillon and his colleagues wanted to develop a way to measure more samples using a rapid on-site measurement method that produced results in an accurate and more cost-effective manner than current techniques allowed. “To achieve this,” Rouillon said, “we decided to integrate the advantages of in situ pXRF — an inexpensive measurement method that can be done on-site, allowing investigators to collect real-time data — with the more thorough laboratory analysis technique of ICP-MS.”

The researchers successfully demonstrated that 20-second in situ pXRF measurements can be corrected to align with a small subset of ICP-MS data, allowing for the accurate, rapid and inexpensive high-resolution characterisation of metal-contaminated sites. They wrote that their increased sampling led to several benefits, “including more representative site characterisation, higher soil-metal mapping resolution, reduced uncertainty around the site mean, and reduced sampling uncertainty”.

“Measuring contaminants in real time using in situ pXRF enables efficient, on-site decision-making for further sampling, without the need to return to the site,” said Professor Mark Taylor, a co-author on the study. “This is an incredibly useful way to go about testing for metal contamination at a site.”

“Our in situ pXRF/ICP-MS method not only generates superior site assessment information for more confident decision-making, but is less expensive when compared to the current standard practice of merely sampling and off-site laboratory measurements,” added Rouillon.