Fig. 2. Effect of geologic substrate on fire-catalyzed Cr(VI) formation in soil.
Average reactive Cr(VI) concentrations (µg kg−1) within (a). rhyolite-, (b). mélange-, and (c). serpentinite-derived soil profiles (0−16 cm) that were not burned (gray circles; rhyolite, n = 3; mélange, n = 7; serpentinite, n = 3) or fire-affected (colored diamonds; rhyolite, n = 4, purple; mélange, n = 9, green; serpentinite, n = 7, orange). Note that the x-axis bounds differ by panel. Points are reactive Cr(VI) concentrations for each soil core based on triplicate measurements (error bars represent standard error). Concentrations below the detection limit are plotted as half the detection limit (6 µg kg-1). Solid and dashed lines represent the mean (based on n soil cores) and standard error of the means, respectively.