Stable isotope fractionation
The fractionation of stable isotopes during the microbial degradation leads to an enrichment of heavier stable isotopes in the residual fraction of a pollutant. Thus, the isotope fractionation of carbon, hydrogen or other elements involved in the cleavage or formation of chemical bonds during the initial step of microbial transformation can be used as an indicator for the in situ biodegradation. Moreover, the degradation pathway and the degree of biodegradation can be determined by the extent of the isotope fractionation. Before application in the field, laboratory investigations are necessary to determine stable isotope fractionation by defined microbial cultures.