Fig. 3. Fourier transform infrared spectra of hexadexyltrimethyl ammonium (HDTMA)-sorbed/mixed soils. HDTMAC represents hexadecyltrimethyl ammonium chloride (a), AS represents alluvial soil (b), AS–HDTMA sorbed (c), AS–HDTMA mixed (d), VS represents volcanic soil (e), VS-HDTMA sorbed (f), and VS–HDTMA mixed (g).