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Fig. 2. (A) Calibration of laser-induced breakdown spectroscopy (LIBS) using data from the calibration set soils (r2 = 0.99, p < 0.001; n = 6). Quantitative data from the ratio, C/(Al + Si), of C line at 193 nm to the sum of the Al line at 199 nm and Si line at 212 nm. (B) Plot of the LIBS data from the verification set of the Colorado soils (r2 = 0.95, p < 0.001; n = 12; two points nearly coincident). Slopes of calibrations curves plotted each of 30 d were not significantly different.
