Leaf-wax n-alkanes 2 H/ 1 H ratios are widely used as a proxy in climate reconstruction. Although the broad nature of the relationship between n-alkanes δ 2 H values and climate is appreciated, the quantitative details of the proxy remain elusive. To examine these details under natural environmental conditions, we studied a riparian broadleaf angiosperm species, Populus angustifolia, growing on water with a constant δ 2 H value and monitored the δ 2 H values of leaf-wax n-alkanes and of stem, leaf, stream, and atmospheric waters throughout the entire growing season. Here we found the δ 2 H values of leaf-wax n-alkanes recorded only a 2-wk period during leaf flush and did not vary for the 19 weeks thereafter when leaves remained active. We found δ 2 H values of leaf-wax n-alkanes of P. angustifolia record conditions earlier in the season rather than fully integrating the entire growing season. Using these data, we modeled precipitation δ 2 H values during the time of wax synthesis. We observed that the isotope ratios of this precipitation generally were 2 H-enriched compared with mean annual precipitation. This model provides a mechanistic basis of the often-observed 2 H-enrichment from the expected fractionation values in studies of broadleaf angiosperm leaf-wax δ 2 H. In addition, these findings may have implications for the spatial and temporal uses of n-alkane δ 2 H values in paleoapplications; when both plant community and growth form are known, this study allows the isolation of the precipitation dynamics of individual periods of the growing season.biomarkers | compound-specific isotope analysis | geographic information system | isoscape | stable isotopes S table isotopes serve as tracers and integrators of both environmental and physiological signals within plant materials. Terrestrial plant leaf waxes (i.e., n-alkanes, n-acids, and others) and their isotope ratios have attracted much interest as a higher plant-specific biomarker for paleoclimate reconstruction (1), because these compounds are easily identified and isolated from a variety of geologic materials and are relatively robust to geologic alteration (2). The environmental information recorded in hydrogen isotope ratios of leaf waxes have become a prevalent proxy to reconstruct ancient climates (3-5), mountain building events (6, 7), and floral transitions (8). However, critical questions related to the interpretation of ancient higher plant biomarkers remain unanswered, especially with respect to the extent of the leaf life cycle recorded by this proxy.Environmental and climate transect studies have shown that δ 2 H values of higher plant n-alkanes and environmental waters are correlated (9, 10), but temporal observations of δ 2 H values of n-alkanes have produced conflicting data on the nature of this relationship (11-15) that require clarification to elucidate how δ 2 H values of ancient n-alkanes can be interpreted. To reconcile these issues and to provide the critical constraints for climate reconstructions using δ 2 H values of n-alkanes, car...

Identification and evaluation of long‐term markers is crucial in prolonging the detection window for anabolic steroid abuse in sport. Recently, sulfoconjugated epiandrosterone was identified as a potential long‐term marker for the abuse of certain endogenous anabolic agents, including testosterone, which continues to be widely used as a performance enhancing agent in sport. To evaluate the applicability of epiandrosterone sulfate as a marker for testosterone use, administration studies were conducted with multiple modes of testosterone administration – transdermal, intramuscular, and subcutaneous. A modified sample preparation method was used to collect both glucuronidated and sulfoconjugated analytes of interest. Carbon isotope ratio measurements from the administration studies are presented here. Epiandrosterone was less effective than the conventionally used target compounds for detection of the low dose application (transdermal gel). With intramuscular administration, epiandrosterone was more diagnostic than with transdermal administration, but it did not prolong the detection window more than the conventional target compounds. With subcutaneous administration, the doses administered to the subjects were varied and the effect on the epiandrosterone values was dependent on the magnitude of the dose administered. Epiandrosterone does not appear to be a useful marker in the detection of low dose testosterone administration. It is responsive to higher dose administration, but it does not provide an extension of the detection window relative to conventional target compounds.