ABSTRACT
Compositional changes in dissolved natural organic matter (NOM) following the injection of reclaimed water at the Bolivar aquifer storage and recovery (ASR) site were followed using a combination of Apparent Molecular Weight (AMW), separation using XAD-8 and XAD-4 resins and solid state 13C cross polarization with magic angle spinning (CP/MAS) Nuclear Magnetic Resonance (NMR) spectroscopy. Interaction of the organic matter with the biofilm and matrix resulted in a reduction in DOC from near 20 mg L−1 to near 10 mg L−1. A reduction in AMW was also measured. Chemical and NMR evidence suggest that both decomposition and adsorption are the major mechanisms for removal of dissolved organic carbon (DOC) with the hydrophilic DOC rapidly lost near the point of injection. Sorption of DOC occurs less extensively as the water passes through the aquifer with the higher AMW and more acid hydrophobic materials being preferentially sorbed. ASR therefore results in the reduction in content of DOC as well as in its complexity. The remaining DOC appears very similar in chemistry to the natural organic matter found in surface and ground waters.
