Radioactive tracer such as a cell or tissue, or as a flow tracer to track fluid flow. Radioactive tracers are also used to determine the location of fractures created by hydraulic fracturing in natural gas production. Radioactive tracers form the basis of a variety of imaging systems, such as, PET scans, SPECT scans and technetium scans. Radiocarbon dating uses the naturally occurring carbon-14 isotope as an isotopic label. Isotopes of a chemical element differ only in the mass number. For example, the isotopes of hydrogen can be written as H, H and H, with the mass number at top left. When the
Hydrogen isotope biogeochemistry samples with more precision. Hydrogen isotope applications quickly emerged in petroleum geochemistry by measuring oil, paleoclimatology by observing lipid biomarkers, and ecology by constructing trophic dynamics. Modern advances are currently underway in the clumped isotope composition of methane after development of the carbonate thermometer. Precise measurements are also enabling focus on microbial biosynthetic pathways involving hydrogen. Ecologists studying trophic levels are especially interested in compound specific measurements for construction of past diets and tracing predator-prey relationships. Highly advanced machines are now promising position specific hydrogen isotope analysis of biomolecules and natural gases. All isotopes of a chemical element contain the