X-RAY FLUORESCENCE RELIABILITY FOR DETECTING SOIL CONTAMINANTS IN COMMUNITIES

Mining activities have released an enormous amount of heavy metals (HM) into the environment. Unfortunately, soils serve as a sink, and due to potential exposure, HM carcinogenicity and toxicity, this poses a major threat to human health. Communities living in the vicinity of legacy and active resource extraction sites need to know about their environmental quality. However, barriers exist that may prevent knowledge transfer and environmental monitoring efforts; these include environmental injustices, information disparities, and the costs associated with soil analyses. X-ray fluorescence (XRF) is a rapid, lower-cost tool that can be used for soil contamination screening, but for what elements and to what degree can we be confident in the results? To address this information and access issue, this study compared XRF elemental soil concentrations to the “gold standard”, inductively coupled plasma mass spectrometry (ICP-MS). Soil samples were obtained from yards and gardens from three counties in Arizona, USA and public areas in Troy, New York, USA. The agreement between the methods was determined by t-test, interclass coefficients, Bland-Altman plot, and a two-way ANOVA. The XRF concentrations for Iron (Fe), Nickel (Ni), Chromium (Cr), and Potassium (K) were significantly different in Arizona from the ICP-MS, indicating its lack of XRF reliability. On the contrary, XRF had a poor relationship with ICP-MS for Vanadium (V), Iron, Chromium, and Aluminum (Al) in New York. It corroborated ICP-MS concentrations for Arsenic (As), Lead (Pb), Copper (Cu), Zinc (Zn), and Manganese (Mn) in Arizona and New York. Nickel was the only element that had a strong correlation between the two methods in New York but not in Arizona, while Barium (Ba) and Calcium (Ca) results showed a strong correlation between the two detection methods in Arizona. Furthermore, the anthropogenic activities were tested by pollution load index (PLI), enrichment factor (EF), and geo-accumulation index (Igeo) toward the validated elements. In this work, we successfully validated the XRF for the following elements: As, Pb, Cu, Zn, Ca, Ba and Mn. The results indicate that XRF is an affordable and on-site technique to examine soil pollutants and can help local communities and farmers near resource extraction sites and industrial activities.