On-site heavy metal testing and monitoring using monochromatic XRF methods

Field Sampling, Measurement and Sensor Technology
Oral Presentation

Prepared by Z. Chen, X. Zhang, T. Tongue
XOS, 15 Tech Valley Drive, East Greenbush, NY, 12061, United States


Contact Information: zchen@xos.com; 518-880-1500


ABSTRACT

On-site heavy metal testing can provide great value for environmental site characterization and remediation. In the past decade, handheld x-ray fluorescence (HHXRF) analyzers have been an essential tool for rapid screening of heavy metal soil contamination at brownfield sites. For lead contamination in soil from industrial and mining sites, HHXRF is a very effective method for on-site testing. However, measuring As, Hg and Cd prove to be ineffective due to the low detection threshold required by regulations for these elements. For example, samples for an As contaminated site often require off-site lab analysis because the analyzer cannot reach the required level of detection for regional and national regulations.
On-site real time monitoring of heavy metals in water discharges and waste water cleanup can also provide huge benefits for environmental applications. Currently, there is no reliable and effective method to monitor heavy metal contamination in real time for water discharge or water lagoon remediation. For example, coal-fired power plants often discharge water containing high levels of Se and As. Lack of online testing methods for Se and As makes the remediation more difficult and challenging.
An innovative monochromatic XRF technology has been developed at XOS in the past decade. The monochromatic excitation beam technique drastically reduces the background signal and yields unprecedented low limits of detection. The technology has already been commercialized in a portable multiple monochromatic beam energy dispersive XRF (HDXRF) analyzer for soil and solid waste, the first to achieve non-destructive on-site analysis of As, Hg, Cd, Cu, Ni, and other heavy metals in soil at a low single digit ppm level, and is the basis for a new ASTM standard test method, D8064-16. In this paper, both standard samples and field data will be presented, including an upstate NY case study of As contamination at the Geneva Foundry site, highlighting the substantial economics benefits of this new method.
This monochromatic excitation technology can also be applied to the wavelength dispersive XRF (WDXRF) method. A low power transportable monochromatic WDXRF system has been developed for low ppb level detection of a single metal such as, As, Se, or Pb in water. This novel approach is the first to demonstrate ppb low level detection can be done by a compact XRF system, and unlocks the potential of online testing of As, Se and Pb in water with no sample preparation or chemical reagents. In this paper, data for testing As, Se, and Pb at low ppb level will be discussed.