Fig. 1. (a) Carbon-13 cross polarization (CP) nuclear magnetic resonance (NMR) spectra of HF-treated soil (control soil). (b)–(f) Carbon-13 CP NMR spectra of HF-treated soil spiked with: (b) benzoic acid, (c) benzophenone, (d) naphthalene, (e) phenanthrene, and (f) palmitic acid. (g)–(k) Difference spectra generated by subtracting spectrum (a) from spectra (b)–(f), respectively; these difference spectra represent sorbed (g) benzoic acid, (h) benzophenone, (i) naphthalene, (j) phenanthrene, and (k) palmitic acid. (l)–(p) Carbon-13 CP NMR spectra of neat ¹³C-labeled compounds: (l) benzoic acid, (m) benzophenone, (n) naphthalene, (o) phenanthrene, and (p) palmitic acid. Spinning sidebands are marked with an asterisk (*).