Compound-specific δD-δ13C analyses of n-alkanes extracted from terrestrial and aquatic plants

Stable hydrogen and carbon isotopic compositions of individual n-alkanes were determined for various terrestrial plants (33 samples including 27 species) and aquatic plants (six species) in natural environments from Japan and Thailand. In C3 plants, n-alkanes extracted from angiosperms have a deltaD value of -152+/-26parts per thousand (relative to Standard Mean Ocean Water [SMOW]) and delta(13)C value of -36.1+/-2.7parts per thousand (relative to Peedde Belemnite [PDB]), and those from gymnosperms have a deltaD value of -149+/-16parts per thousand and delta(13)C value of -31.6+/-1.7parts per thousand. Angiosperms have n-alkanes depleted in C-13 relative to gymnosperms. n-Alkanes from C4 plants have a deltaD value of - 171+/-12parts per thousand and delta(13)C value of -20.5+/-2.1parts per thousand, being a little depleted in D and much enriched in C-13 compared to C3 plants. n-Alkanes of CAM plants are a little depleted in D and vary widely in 813 C relative to those of C3 and C4 plants. In aquatic plants, n-alkanes from freshwater plants have a deltaD value of -187+/-16parts per thousand and delta(13)C value of -25.3+/-1.9parts per thousand, and those from seaweeds have a deltaD value of - 155+/-34parts per thousand and delta(13)C value of -22.8+/-1.0parts per thousand. All n-alkanes from various plant classes are more depleted in D and C-13 relative to environmental water and bulk tissue, respectively. In addition, the hydrogen and carbon isotopic fractionations during n-alkane synthesis are distinctive for these various plant classes. While C3 plants have smaller isotopic fractionations in both D and C-13 seaweed has larger isotopic fractionations. (C) 2003 Elsevier Science Ltd. All rights reserved.