Our previous research demonstrated natural organic matter mediation of carbonate mineral formation in lakes. To better understand this process, we characterized the content and speciation of dissolved organic matter in carbonate minerals formed in Pyramid Lake, Nevada. A 400 grams block of precipitated calcium carbonate from the Pyramid Lake shore was dissolved in 8 liters of 10% acetic acid. Particulate matter was removed by centrifugation and dissolved organic matter was fractionated into nine fractions by a combination of dialysis, resin, adsorption, and selective precipitations to remove inorganic constituents. Coprecipitated dissolved organic matter constituted 0.23% of the calcium carbonate by weight and was depleted in nitrogen and enriched in hydrophilic acids when compared with dissolved organic matter produced by autochthonous processes in lakes. Infrared spectra of the fractions indicated hydroxy-acids as the major structural group that likely forms insoluble complexes with precipitated calcium carbonate in Pyramid Lake.
Presented at the ASLO 2007 Sciences Meeting