The effects of natural organic matter on the speciation and transport of Cu(II) in groundwater

Abstract

Potentiometric titrations were performed on bulk natural organic matter (NOM) water samples from five different sources. Complexometric titrations with Cu(II) were performed on two different NOM water fractions of Orange County Water District (OCWD) groundwater (0.5K filter retentate water and XAD-8 humic extraction water), which had been subdivided into molecular weight (MW) fractions. Column experiments, conducted at pH 6.2, I = 10 mIVI, and T = 23°C, were performed to investigate: 1) the movement of NOM through a sandy aquifer; 2) the movement of Cu(II) through a sandy aquifer; 3) and the movement of Cu(II) through a sandy aquifer with NOM present. Titrations indicated that OCWD NOM has a high charge density (~ 20 meq g⁻¹ C, pH 3 - 8) and significant affinity for copper 6 meq g⁻¹ C at pH 6.2). The column experiments suggested that the movement of copper through a silica-packed column was only slightly facilitated with NOM present in the aqueous phase.