Water Analysis Via Portable X-Ray Fluorescence (PXRF) Spectrometry.

Water quality is a growing concern worldwide. Often, surface waters become polluted via inadvertent spills or accidents. Recent examples of such in the United States include the Gold King Mine spill of metal-laden sludge into the Animas River of Colorado/New Mexico, and the water crisis in Flint, Michigan where the city’s drinking water supply was polluted with lead. To date, there is not a quick, field portable means of assessing various elements in solution. Standard laboratory analysis of water is often accomplished by inductively coupled plasma atomic emission spectroscopy (ICP-AES), but while accurate, such equipment is not easily field portable. In this project, portable X-ray fluorescence (PXRF) spectrometry was used to rapidly assess elemental concentrations in hundreds of water samples. First, 256 water samples from 10 different countries were assessed for salinity. PXRF and ICP-AES elemental data as well as data from a Traceable digital conductivity meter were compared. Using piecewise linear regression, results showed that PXRF can successfully predict water electrical conductivity (EC) via quantifying Cl in water samples (validation R² and RMSE of 0.77 and 0.95 log µS cm^-1, respectively). Next, 390 leachate samples from mine tailings in South Africa were subjected to PXRF and ICP-AES elemental analysis. Results showed wide ranges in elemental concentration and detectability. Some correlations between the datasets were strong, while others suffered from spectral overlaps in the PXRF data. Correlations were generally stronger as elemental concentration increased. Working with the PXRF instrument manufacturer, it may be possible to develop a “water mode” to more specifically enhance the scanning of low density matrices such as water. Summarily, the PXRF provides reasonable elemental detection in water samples which shows potential application where rapid, on-site analysis is required.