Micro-organisms in soil can volatilize inorganic As salts to gaseous arsines, moving it from a geological setting into a biological one. Measurements of arsine are difficult to record. Cryotraps can be used to condense arsine, but the required cooling makes them unsuitable for field research.
Andrew Meharg and colleagues, University of Aberdeen, UK, have developed and validated a trap that captures different species of arsine at ambient temperature. The gases are adsorbed onto silica gel impregnated with silver nitrate. The arsine gas samples can be stored for months at ambient temperature.
In field tests, arsines release from soil was shown to correlate with the quantity of As and, to a greater extent than expected, the concentration of organic matter (OM) in the soil. Areas with high OM and low As, i.e., paddy fields contaminated with 11.3 ppm arsenic, showed the highest arsine emission levels—up to 240 mg per hectare per year. Areas with higher As contamination, up to 1,300 ppm, but less OM, only showed trace amounts of arsine.
- Field Fluxes and Speciation of Arsines Emanating from Soils
A. Mestrot, J. Feldmann, E. M. Krupp, M. S. Hossain, G. Roman-Ross, A. A. Meharg,
Environ. Sci. Technol. 2011.