Effects of volatilization on the hydrogen isotope composition of selected n-alkanes

The hydrogen isotope composition of n-C-15 to n-C-32 n-alkanes was measured by GC-IRMS to investigate the behavior of H isotopes during evaporation. The H isotope fractionation of n-C-15 to n-C-19 ranged from -8.5 to -22.5 parts per thousand, demonstrating the preferential vaporization of the isotopically heavier organic compounds. The H isotope fractionation rates of n-C-16 to n-C-18 showed no obvious fluctuations with time (average rates were 1.1, 0.5 and 03 parts per thousand per day, respectively); this indicated that fractionation followed the Rayleigh model. Although less conclusive, the fractionation of H isotopes in n-C-19 also apparently followed the Rayleigh trend. Information on fractionation rates may be useful for identifying the dominant attenuation and degradation processes for organic substances in the environment. The results also highlight potential applications of isotope fractionation factors, which were determined by regression analysis, for investigations into the behavior of organic substances in the environment. (C) 2013 Elsevier B.V. All rights reserved.