Abstract
Advanced field methods of carbon (C) analysis should now be capable of providing repetitive, se- quential measurements for the evaluation of spatial and temporal variation at a scale that was previously unfeasible. Some spectroscopy techniques, such as laser-induced breakdown spectros- copy (LIBS), have portable features that may potentially lead to clean and rapid alternative ap- proaches for this purpose. The goal of this study was to quantify the C content of soils with differ- ent 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 fine- textured 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. * Corresponding author.
Highlights
Increased greenhouse gas (GHG) concentrations in the atmosphere and consequent global warming are of great concern to a large part of the world’s population
Considering the spectral resolution of 0.1 nm, it is expected that the C emission line at 193.03 nm is affected spectral interference from Al lines: Al (II) at 193.04 nm, and Al (I) at 193.16 and 193.58 nm [15]
This low correlation is attributed to Al interference, since the C emission line at 193.03 nm suffers from subtle interference from Al lines
Summary
Increased greenhouse gas (GHG) concentrations in the atmosphere and consequent global warming are of great concern to a large part of the world’s population. Actions to reduce GHG emissions and increase mitigation are expected from governments and those involved in agriculture, which is recognized as one of the major sources of these gases. A variety of techniques is used to estimate soil organic matter, and soil C content [1]-[3] Wet combustion methods, such as Walkley-Black titration, are routinely used in most soil laboratories, mainly because they can be performed with simple instrumentation. These techniques are time-consuming and have certain limitations; they produce toxic residues and the results are not reliable. Automated methods tend to be more expensive due to the initial purchase of the instrument, plus the cost of reagents and materials for analysis
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