Rapid analysis of ¹³C in plant‐wax n‐alkanes for reconstruction of terrestrial vegetation signals from aquatic sediments

Abstract

[1] Long-chain, odd-carbon-numbered C 25 to C 35 n-alkanes are characteristic components of epicuticular waxes produced by terrestrial higher plants. They are delivered to aquatic systems via eolian and fluvial transport and are preserved in underlying sediments. The isotopic compositions of these products can serve as records of past vegetation. We have developed a rapid method for stable carbon isotopic analyses of total plant-wax n-alkanes using a novel, moving-wire system coupled to an isotope-ratio mass spectrometer (MW-irMS). The n-alkane fractions are prepared from sediment samples by (1) saponification and extraction with organic solvents, (2) chromatographic separation using silica gel, (3) isolation of straightchain carbon skeletons using a zeolite molecular sieve, and (4) oxidation and removal of unsaturated hydrocarbons with RuO 4 . Short-chain n-alkanes of nonvascular plant origin (<C 25 ) are removed by evaporation on the moving wire. Test samples processed using this procedure yielded n-alkane fractions essentially free of interfering components. The d C values obtained by irmGC-MS. Isotopic variations in compound-class n-alkane fractions from a latitudinal transect of core-top sediments from the Southwest African margin (3°N-28°S) were congruent with those measured by compound-specific isotopic analyses of plant-wax n-alkanes. The amplitude of the variations was smaller, indicating contributions from non-plant-wax hydrocarbons, but the measurements revealed variations in carbon isotopic composition that are consistent with vegetation zones on the adjacent continent.

Glacial/interglacial changes in southern Africa: Compound‐specific δ13C land plant biomarker and pollen records from southeast Atlantic continental margin sediments

“…The Holocene lipid data, when interpreted in terms of leaf wax contributions of C 3 versus C 4 plants, broadly paralleled the present‐day distribution of C 3 and C 4 vegetation on the South African continent, when taken in conjunction with the observed westerly and northwesterly paths of aerosol plumes, including smoke from vegetation fires and dust from arid regions, as observed by satellite and field measurements. Our findings were in general accord with the data reported nearly synchronously by Schefuß et al [2003] for a survey of marine sediments in a similar area of the southeast Atlantic Ocean and those published by McDuffee et al [2004] when they introduced their new moving wire technique for isotope analysis.…”

Influences of Water and Sediment Quality and Hydrologic Processes on Mussels in the Clinch River

“…Organic compounds in bed sediment were mostly PAHs from coal and naturally occurring aliphatic compounds (Krstolic et al ., ) and showed no spatial trends. The aliphatic compounds were predominantly even numbered isomers indicating sources from plant‐based, naturally occurring compounds (McDuffee et al ., ; Samuels et al ., ; Eglinton and Hamilton, ). All samples had low concentrations of pyrene and other similar PAHs that are typically found in combustion products.…”

A Review of Ant Cuticular Hydrocarbons

“…Oddnumbered C 25 to C 35 n-alkanes typically dominate ant CHC profiles, as is almost universally the case in insects (Lockey 1988; references cited herein). Odd-numbered n-alkanes also are characteristic components of epicuticular waxes produced by terrestrial higher plants ( McDuffee et al 2004). In insects, the primary function of CHCs is to act as anti-desiccation and waterproofing compounds (Edney 1977), and their abundance is correlated with varying environmental conditions (Wagner et al 2001; …”