Fourier transform infrared (FT-IR) spectrometry.

Plants have a large capacity to transfer water and associated contaminants from soil to atmosphere. We measured the transfer rate for a range of constituents of gasoline that vary in volatility, solubility, and octanol/water partition coefficient. We tested benzene, toluene, ethyl benzene, meta-xylene, 1,2,4-trimethyl benzene, cyclohexene, n-pentane, ethyl ether, n-propyl ether, and t-butyl methyl ether. Aliphatic hydrocarbon constituents of gasoline were either not water soluble to sufficiently high concentration for study or they are too volatile to handle conveniently (e.g., butane). An extractive Fourier Transform Infrared Spectrometer was used to measure concentrations in the gas phase above plants which had their root system immersed in water containing the contaminant. Deuterated water was used as a monitor for transpiration rate. The relative rate of transfer for different compounds was reasonably consistent with the work of Briggs, et al. [1], which relates their movement in plants to the log of their octanol/water partition coefficient (log Kow). For the ethers it appeared that they moved more rapidly than expected based on log Kow.