Laser-Induced Breakdown Spectroscopy for Simultaneous Quantitative Analysis of Multi-Elements in Soil
YU Ke-qiang, ZHAO Yan-ru, LIU Fei, HE Yong*
College of Biosystems Engineering and Food Science, Zhejiang University, Key Laboratory of Equipment and Informatization in Environment Controlled Agriculture, Ministry of Agriculture, Hangzhou 310058, China
Abstract：Abundance or deficiency of soil elements is an expression of soil fertility. Rapid detection of elements in soil is a key point of front information acquirement tools in precision agriculture, and it also provides a theoretical basis for pollution prevention of soil heavy metal and sustainable development of agriculture. This research focused on using laser-induced breakdown spectroscopy LIBS) technique combined with calibration curve and chemometrics method to conduct the simultaneous quantitative analysis of multi-elements (Al, Fe, Mg, Ca, Na and K) in soil. First of all, five certified reference materials (CRM) of soil numbered GBW07446，GBW07447，GBW07454，GBW07455，GBW07456 were ablated by a laboratorial LIBS setup in air. 50 LIBS spectra of each type of soil were averaged to reduce the error in experiment process. By integrating the acquired LIBS emission spectra and atomic spectra database from national institute of standards and technology (NIST), analytical spectral lines and corresponding spectral regions were identified. Then, calibration curves of the intensity of a peak and integrated intensity of a peak or several peaks (peak area) coupling with the element content s were fitted. The results indicated that the linear relation from the calibration curves fitted by peak areas and element contents were superior to the calibration curves fitted using intensity of a peak and element contents (except the Fe). Meanwhile, partial least-squares regression (PLSR) was employed to build the quantitative model by using the selected spectral regions and corresponding element contents, which offered a promising result with relatively high RP and showed more advantages than the calibration curve method. The approach revealed that LIBS technology combined with chemometrics methods displayed a bight prospect in the field of spectrochemical analysis. The achievements of the research not only provide a guide for detecting soil nutrient spatial distribution and precision fertilization technique, but also lay a theoretical foundation for developing the portable LIBS detector used in the field.
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