Kriging interpolation method for laser induced breakdown spectroscopy (LIBS) analysis of Zn in various soils

Abstract

Laser induced breakdown spectroscopy (LIBS) was used to determine Zn concentrations in various types of soils, and discarding and kriging interpolation methods were combined to enhance the accuracy and precision of the LIBS analysis. In order to determine Zn concentrations in 10 field soils, the discarding method was used for pre-treatment of LIBS data acquisition. A remarkable decrease of relative standard deviation was observed indicating a significant increase of pulse-to-pulse precision. Nine artificial soil sets containing different contents of sand, kaolin, and goethite were manufactured for the interpolation database, and they displayed differing LIBS broadband spectra due to their respective sample matrices. In addition, the calibration slope of each soil set varied significantly showing up to a 3.36-fold difference. We found that the matrix effect derived from sand, kaolin, and goethite contents can be determined by detecting major elements in soil (Si, Al, and Fe) from LIBS analysis without additional measurements. The kriging interpolation model was applied using the database obtained from the artificial soil sets. The concentration of Zn in field soils calculated from data treatment methods showed significantly accurate results when compared to ICP-OES analysis results. By minimizing factors affecting the LIBS result, heavy metal concentrations in various types of soils can be determined using a developed database without calibration.