Characterization of organic contamination of groundwater in a mining area, Globe, Arizona

Abstract

Organic contamination is associated with inorganic contamination in a plume resulting from acidic mine drainage water in an area of copper mining, Globe, Arizona. The level of dissolved organic carbon (DOC) is low, but is eight times the 0.5 mgC/l background. The source is probably organic reagents used in mineral processing. DOC fractionation using XAD-8 resin sorption chromatography gave a hydrophobic acid fraction (humic substances) of 1.0 mgC/l, and the hydrophobic neutral fraction was also anomalous, being as high as 49% of DOC. The fractionation data matched that for a waste-solution lake, believed to be a source of the aquifer contamination. Loss of DOC is occurring downgradient in the aquifer, based on comparison of DOC/chloride ratios. Loss occurs as the pH increases to over 4 or 5. Sorption onto metal precipitates being formed, particularly of the hydrophilic fraction, may be occurring.