The binding affinity of a hydrophobic singlet oxygen probe toward natural organic matter isolates was investigated. A linear phase-partitioning model was used to calculate partition coefficients and intramicellar concentrations of singlet oxygen several orders of magnitude larger than those reported by traditional singlet oxygen probes. From the obtained data, a kinetic model was developed to describe the microscopic environment experienced by hydrophobic compounds in natural water systems. Micellar radii and molecular weights were derived from the experimental data and evaluated. The data obtained provides additional support of a microheterogeneous environment within bulk natural solutions. The enhanced concentrations of photogenerated reactive intermediates within these microenvironments may improve understanding of hydrophobic pollutant degradation in the environment.