Effect of laser wavelength on soil carbon measurements using laser-induced breakdown spectroscopy

We investigate the effect of laser wavelength on laser-induced breakdown spectroscopy (LIBS) on the measurement of carbon in agricultural soils. Two laser wavelengths, 1064 nm and 532 nm, were used to determine soil carbon concentration. No chemical pretreatment, grinding, or pelletization was performed on soil samples to simulate in-field conditions. A multivariate calibration model with outlier filtering and optimized parameters in partial least squared regression (PLSR) was established and validated. The calibration model estimated carbon content in soils with an average prediction error of 4.7% at a laser wavelength of 1064 nm and 2.7% at 532 nm. The limit of detection (LOD) range for 532 nm was 0.34-0.5 w/w%, approximately half of the LOD range for 1064 nm laser wavelength. The improvement in prediction error and LOD of LIBS measurements is attributed to the increase in plasma density achieved at 532 nm.

Automated summary

This study investigates the influence of laser wavelength on the measurement of carbon in agricultural soils using laser-induced breakdown spectroscopy (LIBS). It was found that a 532 nm laser wavelength achieved more accurate prediction of carbon content compared to a 1064 nm wavelength. Additionally, the limit of detection was lower for the 532 nm wavelength compared to the 1064 nm wavelength.