Magneto-electrical fusion enhancement of LIBS signals: a case of Al and Fe emission lines' characteristic analysis in soil

Soil is a vital resource for human survival. In particular, aluminum (Al) and iron (Fe) metal elements in soil play significant roles in stabilizing soil organic matter. Therefore, the rapid and effective detection of Al and Fe elements in soil is imperative. Compared with conventional elemental detection techniques, laser-induced breakdown spectroscopy (LIBS) has emerged as a pivotal method for soil detection because of the advantages of simultaneous detection of multiple elements, rapidity and environmental friendliness. However, the LIBS signal of trace metal elements remains to be enhanced due to some influencing factors like the soil matrix effect. Hence, this study introduces a magneto-electrical fusion soil LIBS signal enhancement device, through an investigation into the impacts of magnetic field strength, energization, and magneto-electric fusion on the LIBS signals of Al and Fe in soil. Examining the single-factor effects of magnetic field strength and energization on soil LIBS signals, enhancements were observed in the spectral intensity (SI), signal to background ratio (SBR), plasma electronic temperature (PET), and plasma electronic density (PED) for soil Al and Fe elements compared to those observed with the unenhanced LIBS technique. According to the results of two-factor analysis of variance (ANOVA), the cost of the study and the safety of use, the appropriate magnetic field strength and energizing voltage were selected, respectively, to be 110 mT and 12 V. The magneto-electrical fusion LIBS signal enhancement device was designed based on the above results of the study in terms of operational reliability, ease of operation, safety and economy. It mainly included a base module, a support module and an enhancement module. For the designed device performance, validation was carried out in terms of parameters and applications, respectively. For parameter validation, the fusion enhancement device realized the enhancement of soil LIBS signals in 4 different areas. For application validation, the soils originating from 4 different regions were subjected to discriminant analysis. Comparative analysis with the original LIBS technique revealed significant enhancement in the performance of the soil origin discrimination model facilitated by the fusion enhancement device. This study provides support for the development of efficient techniques and equipment for soil element detection in farmland, as well as a theoretical basis for high-quality agricultural production.