Metal(loid)organic compounds in geothermal gases and waters

Volatile metal(loid)organic species of geogenic and anthropogenic origin are analyzed by low temperature gas chromatography coupled on-line with plasma mass spectrometry (LTGC/ICP–MS) with detection limits in the higher pg-range (per m3 gas). In respect to the determination of aqueous samples, this instrumental technique is combined with sample derivatization by the hydride generation technique. Volatile species of As, Sb, Se and I could be detected in gases over hot springs in British Columbia (Canada). Methylated species of Hg, Ge, As, Sb and Te were also determined in concentrations in the ng/kg- to low μg/kg-range in geothermal waters from Ruapehu, Waimangu, Waiotapu and Tokaanu (North Island, New Zealand); up to 1% of the total dissolved metal(loid)s are found in methylated forms. Volatile metal(loid)organic species of geogenic origin are compared with those emanating from anthropogenic sources (waste and sewage gases, river and harbor sediments). Possible formation mechanisms for these compounds are discussed.