Extraction of metals from basalt by humic acids

Abstract

IN many studies, the activity of humic acid in weathering and other geological processes has been considered negligible. Only simple, low molecular weight organic acids are usually considered effective in mineral degradation¹. Those acids, however, frequently constitute only a minor fraction of the soil organic matter, particularly in semi-arid and arid areas. In Israel, fulvic acid/humic acid ratios in the organic matter of major soil types range, with one exception, from 1.5 to 6 (ref. 2). Humic acids are also well represented in the organic matter of many sediments^3,4. The effect of these high molecular weight compounds on mineral decomposition and metal dissolution is therefore of great interest in the earth sciences. The results presented here suggest that humic acids also may have a significant role in rock solubilisation and weathering, because of their capacity to extract considerable amounts of metals, particularly copper and zinc, from basalt rock.