Abstract: | Samples of humic substances were obtained from a waterworks at Fuhrberg, Germany. The material had a bimodal molecular size distribution with 40% of the total carbon in the 50,000–100,000-D (nominal molecular weight, NMW, in daltons) size fraction and 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 13C 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. |