Quartz is the most stable natural solid phase of silica. It weathers extremely slowly at the Earth's surface1, and often resists weathering even after all other silicate minerals have been degraded. However, there is ample evidence from both ancient and modern environments indicating enhanced dissolution and mobility of silica under conditions that cannot easily be explained by the inorganic controls of quartz solubility2. Increased solubility of quartz has been observed particularly in soils rich in organic material; however, no direct link between dissolved organic carbon and dissolved silica has been identified3. Here we present evidence for an increase in the solubility of quartz in a natural water brought about by dissolved organic compounds. These compounds were produced by the biodegradation of petroleum, and consist largely of a complex mixture of organic acids. We propose that silica is being complexed and mobilized by these organic acids in waters having close to neutral pH.
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