Figure 3
Variance scatterplots of PCA results for Group 1 (ore, tailings, and Lost Lake sediments; top panel) and Group 2 (microbial mats/flocs; bottom panel), illustrating their utility as model-independent means of examining spectral variance. Each point represents one sample EXAFS spectrum in a coordinate space defined by the product of the first eigenvector (principal component, v1) and its sample-specific first eigenvalues (w1,i ) on the x-axis, plotted against the product of the second eigenvector (v2) and its sample-specific second eigenvalues (w2,i ) on the y-axis. Axes are dimensionless. Outlying samples have been labeled for reference