SUBSURFACE INTERACTIONS OF HUMIC SUBSTANCES WITH CU(II) IN SATURATED MEDIA

The interactions between natural organic matter (NOM) and Cu(II) durin g transport through saturated media were investigated with column expe riments. Six sources of NOM represented different humic fractions. SiO 2 and alpha-Al2O3 comprised the mineral surfaces. The experiments were conducted at pH 6.2 and 7.5. Total Cu(II) was measured by atomic abso rption spectroscopy; NOM was measured as UV absorbance at 254 nm. Resu lts showed variation in NOM breakthrough as a function of source. The presence of Cu(II) caused greater retardation of all NOM sources relat ive to the NOM-alone systems. The NOM effect on Cu(II) transport was m ixed, depending on the NOM source. At pH 7.5, NOM greatly facilitated Cu(II) transport. These mechanisms may influence NOM and Cu(II) transp ort in groundwater: (1) competition between NOM and the mineral surfac e for Cu(II) complexation, (2) formation of mixed ligand complexes, (3 ) complexation of Cu(II) by adsorbed NOM, and (4) Cu(II) bridging of N OM to mineral surfaces.