A unique, large release of ¹⁴CO₂ from an industrial source occurred near Oak Ridge, TN in summer 1999. This release resulted in a whole-ecosystem pulse label of ¹⁴C in the local forest. A gradient of labeling occurred; sites nearest the source experienced a pulse about three times that produced by atmospheric weapons testing. At four sites consisting of two soil types (an ultisol and an inceptisol) and two levels of ¹⁴C exposure in 1999 (enriched and near-background), replicated plots were established in fall 2000. Forest litter was manipulated on these plots through multi-year reciprocal transplants of enriched vs. near-background litter. The differently labeled root and surface litter sources were used to track the source and dynamics of physically and chemically isolated soil organic matter pools. Mineral soil samples (0-15 cm depth) were physically fractionated into unprotected and microaggregate-protected particulate organic matter (POM), microaggregate-protected silt- and clay-sized particles, and easily dispersed silt- and clay-sized particles not associated with microaggregates. Hydrolysis with 6N HCl was then used to separate hydrolyzable and acid-resistant organic matter in the silt- and clay-sized fractions. Radiocarbon analyses of soil carbon pools from enriched vs. near-background sites indicate substantial incorporation of new carbon derived from fine root sources into unprotected POM with some transfer into microaggregate-protected POM and mineral fractions. Acid hydrolysis of silt- and clay-sized particles clearly separated two fractions with different ¹⁴C signatures. Hydrolyzable carbon in all mineral fractions had ¹⁴C signatures that were similar to those of unprotected POM. Although the acid-resistant fractions contained far less radiocarbon, increasing ¹⁴C signatures over time demonstrate the presence of a highly dynamic component in the acid-resistant pools. Incorporation of radiocarbon from surface litter was negligible compared to root sources and was most obvious in the hydrolyzable fractions.