FULVIC AND HUMIC ACIDS ISOLATED FROM GROUNDWATER - COMPOSITIONAL CHARACTERISTICS AND CATION BINDING

Samples of humic substances were obtained from a waterworks at Fuhrberg, Germany. The material had a bimodal molecular size distribution with approximately 40% of the total carbon in the 50,000-100,000-D (nominal molecular weight, NMW, in daltons) size fraction and approximately 50% of the carbon in the < 10,000-D (NMW) size fraction. The fulvic and humic acids isolated from the bulk humic substances were low in nitrogen content and had low H/C atomic ratios. Furthermore, the fulvic and humic acids had very similar elemental, spectral and copper binding characteristics. Over 70% of the carbon in both the fulvic and humic acids was present in aromatic or aliphatic groups, with C-13 NMR analyses indicating approximately even distribution among the two types. Competitive elemental binding studies indicated that Ca2+, Mg2+, Al3+ and Fe3+ do not effectively compete for copper binding sites on these compounds. In humic acids, these cations are predominantly bond by carboxylic groups.