The acid–base properties of high and low molecular weight organic acids in soil solutions of podzolic soils

The acid properties of the organic acids and identified low molecular weight (LMW) organic acids in soil solutions of podzolic soils were determined using proton affinity spectra, based on EMF titration data, and Gran titrations. The proton affinity spectra showed apparent p K a values of 2.6, 4.1, 5.4 and 6.7 for the dissolved organic material. The LMW organic acids had similar p K a values. The average specific buffer capacity as determined by Gran titrations was 8.8±0.5 μmol H +/mg DOC. The specific buffer capacity for the identified low molecular acids was 40±2 μmol H +/mg DOC.