Physical and Chemical Matrix Effects in Soil Carbon Quantification Using Laser-Induced Breakdown Spectroscopy

Abstract

Advanced field methods of carbon (C) analysis should now be capable of providing repetitive, sequential measurements for the evaluation of spatial and temporal variation at a scale that was previously unfeasible. Some spectroscopy techniques, such as laser-induced breakdown spectroscopy (LIBS), have portable features that may potentially lead to clean and rapid alternative approaches for this purpose. The goal of this study was to quantify the C content of soils with different textures and with high iron and aluminum concentrations using LIBS. LIBS emission spectra from soil pellets were captured, and the C content was estimated (emission line of C (I) at 193.03 nm) after spectral offset and aluminum spectral interference correction. This technique is highly portable and could be ideal for providing the soil C content in a heterogeneous experiment. Dry combustion was used as a reference method, and for calibration a conventional linear model was evaluated based on soil textural classes. The correlation between reference and LIBS values showed r = 0.86 for medium-textured soils and r = 0.93 for fine-textured soils. The data showed that better correlation and lower error (14%) values were found for the fine-textured LIBS model. The limit of detection (LOD) was found to be 0.32% for medium-textured soils and 0.13% for finetextured soils. The results indicated that LIBS quantification can be affected by the texture and chemical composition of soil. Signal treatment was shown to be very important for mitigation of these interferences and to improve quantification.

A critical review of recent progress in analytical laser-induced breakdown spectroscopy

“…For example, soils are often rich in Fe and Al, and thus spectral interference from these elements can prevent the use of intense carbon spectral lines at 247.86 nm and at 193.03 nm, especially in low-resolution portable LIBS systems. These problems require the use of spectrum correction or advanced calibration models [153]. Nevertheless, one outcome of related LIBS research is the realization that the conventional methods typically used in agrochemical practice (e.g.…”

Signal enhancement in collinear double-pulse laser-induced breakdown spectroscopy applied to different soils

“…The LIBS technique has been applied successfully to soils for assessing their elemental composition, classification, presence of contaminants, etc [27,31,[34][35][36][37][38][39]. LIBS is a quick and environmentally clean technique, and does not require the use of reagents for sample preparation, thus has great potential for application to soils.…”

Utilização de métodos espectroscópicos para avaliação de ácidos húmicos extraídos de solos de diferentes sistemas produtivos de pastagens

“…Após um período de 10 anos da instalação da vegetação do tipo Brachiaria, no lugar da vegetação nativa, o estoque de MOS foi reposto acumulando consequentemente grandes quantidades de carbono (REZENDE et al, 1999;SEGNINI, 2007 , 1998;CERRI et al, 2004;SEGNINI et al, 2014).…”

“…Estudos mostram que pastagens bem manejadas são capazes de estocar carbono presente na atmosfera no solo (CERRI et al, 2004;SEGNINI et al, 2014). Porém, o que falta é entender a dinâmica desse carbono que foi acumulado no solo.…”

“…O teor de carbono no solo inteiro, foi menor em todos os manejos e mata nativa, indicando que em profundidades maiores, ocorre pouco acúmulo de carbono (SEGNINI et al, 2014 (SENESI et al, 1991;MILORI et al, 2002).…”