3.2.4 Ammonium oxalate extracted Fe, Si, and Al e
The Fe, Si, and Al extracted by acid ammonium oxalate is an estimate of short-range-order minerals (Parfitt, 1989). Ammonium oxalate removes nanocrystalline inorganic forms and organic-complexed Fe and Al. The values are generally is quite uniform throughout the profile (Figure 8). The values on Anak Krakatau and Panjang are small, but the values observed in Sebesi are relatively higher and can be considered as having some andic property (mean Alo + ½ Feo = 5.9%, std. dev = 1.95). There is a trend of increasing oxalate extractable ions from Anak Krakatau, Rakata, Panjang, and Sebesi: Feo (0.44, 0.63, 0.64, 1.02%) and Alo (0.81,0.89,1.00,5.36%).