Photochemical reduction of hexavalent chromium, Cr(VI), by iron and dissolved organic matter (DOM) was previously investigated (1). We recently developed a new reliable analysis of Cr(VI) with a direct isotope dilution (DID) quantification approach (2) using ion chromatography tandem mass spectrometry (IC-MS/MS). The technique allows to compensate for any loss of Cr(VI) occurring between collection and analysis time that can affect sample integrity and introduce possible biases in measured concentrations. The DID method achieved trace level analysis with an MDL of 2 ng/L. Surface and ground water samples were collected from the Ontario Ring of Fire area and had total organic carbon levels between 8 and 80 mg/L. Preservation with ammonium hydroxide was needed for all ground water samples as majority of the samples had pH&lt;6, under which conditions Cr(VI) is not stable. Principal component analysis was used to better understand the simultaneous influence of dissolved organic matter, pH and total iron content on stability of Cr(VI).

Influence of dissolved organic matter on the stability of trace level hexavalent chromium in surface and ground water samples

253rd National Meeting (2017)

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