An important goal of environmental chemistry is tracing the source and degradation of pollutants . Various methods have been employed for fingerprinting pools of environmental pollutants such as the bulk chemical composition of a spill , isotope ratios of the bulk chemical mixture , or isotope ratios of individual constituent compounds . Stable isotopes of carbon and hydrogen can be used as complimentary fingerprinting techniques for natural gas . Recently , the D/H ratio of hydrocarbons from the Deepwater Horizon oil spill was used to verify that their origin was likely from the Macondo well . Hydrogen isotope ratios have also been used as a measure of the relative amount of biodegradation that has occurred in oil reservoirs in China , and studies on pure cultures of n-alkane degrading organisms have shown a chain-length dependence on the amount of hydrogen isotope fractionation during degradation . Additional studies have also shown hydrogen isotope effects in the degradation of Methyl tert-butyl ether and Toluene that have been suggested to be useful in the evaluation of the level of degradation of these polluting compounds in the environment . In both cases the residual unreacted compounds became enriched in deuterium to a few tens of per mil , with variations exhibited between different organisms and degree of reaction completeness . These observations of heavy residual compounds have been applied to field observations of biodegradation reactions such as the removal of benzene and ethylbenzene , which imparted a D/H fractionation of 27 and 50 per mil , respectively . Additionally analysis of o-xylene in a polluted site showed high residual D/H ratios after biodegradation , consistent with activation of C-H bonds being a rate limiting step in this process Stable isotope ratios have found uses in various instances where the authenticity or origin of a chemical compound is called into question . Such situations include assessing the authenticity of food , wine and natural flavors ; drug screening in sports ( see doping ) ; pharmaceuticals ; illicit drugs ; and even helping identify human remains . In these cases it is often not sufficient to detect or quantify a certain compound , since the question is the origin of the compound . The strength of hydrogen isotope analysis in answering these questions is that in many cases the D/H ratio of a natural product is related to the natural water D/H values in the area where the product was formed ( see : Hydrologic cycle ) . Since D/H ratios vary significantly between different geographic areas , this can serve as a powerful tool in locating the original source of many different substance
Deepwater Horizon oil spill
Deepwater Horizon oil spill
Hydrogen isotope biogeochemistry