Nitroaromatic compounds (NACs) are prominent soil/sediment contaminants and potent mutagens, which are commonly found in military training sites. Our previous studies suggest that K⁺/Ca²⁺ exchange on smectite clay surfaces influences sorption and hence mobility of NACs in soils. In this study, we measure sorption/desorption of representative NACs by smectite clays saturated with K⁺ and Ca²⁺ at different ratios, and correlate the magnitude of sorption with the fractions of cations associated with mineral surfaces as well as mineral configurations. The results will provide more clear clues to design environmentally safe protocol to manipulate the mobility and bioavailability of NACs, which could enhance the remediation efficacy of contaminated sites.