XRF surveys for three mining waste sites

X-ray fluorescence (XRF) technology is being used increasingly at numerous hazardous waste sites to screen soil and waste for concentrations of metals deposited over relatively large areas. A portable XRF unit allows the sampling team to collect real-time data in minimal time. Use of this technology however, should be limited to site screening. Also, appropriate caution should be applied to data interpretation and evaluation. This paper discusses XRF screening at three mining waste sites: Galena, Kansas; Annapolis, Missouri; and Midvale, Utah. XRF screening was conducted with field portable units in conjunction with laboratory confirmation sampling. Soil moisture, organic content, soil/sediment grain-size distribution, and the concentration of the chosen standard affect XRF screening concentration results. Thus, XRF screening alone may provide inaccurate concentrations of metals at a site. Drying, or at the very least, sieving and compacting earth materials prior to XRF measurement should improve the accuracy and precision of assaying metal concentrations in soil via XRF field methods. Based on the three case studies presented, proper use of field XRF requires developing site-specific contaminant-concentration models. A site-specific model is required to provide field results associated with a simple, first degree transformation function providing concentration results approaching actual values.