Formation of Nonextractable Soil Residues: A Stable Isotope Approach

Stable carbon isotopic measurements were employed to characterize the transformation of a 13C-labeled polycyclic aromatic hydrocarbon (PAH), anthracene, in a closed soil bioreactor system. The 13C-label was used to calculate a carbon mass balance including mineralization and the formation of nonextractable soil-bound residues. Similar results were obtained from 13C-labeled carbon and 14C-labeled carbon mass balance calculations for separate batch experiments with labeled anthracene. In concentration ranges typical for real PAH-contaminated sites, the sensitivity of the 13C tracer method meets the requirements of classical radiotracer experiments. Therefore, our balancing method based on stable isotope-labeled chemicals may supplement or substitute radiotracer experiments under many circumstances. One major advantage of using stable isotope-labeled tracers is the possible application in transformation studies where the use of radioactive substances is of environmental concern. The transformation of 13C-lab...