ALAS Model

This paper describes the Anthropogenic Lead ArchaeoStratigraphy (ALAS) Model of Hurst used to estimate the year a leaded gasoline was released into the environment (2002, Environ. Geosci., v. 9, no. 2, 43-50; Lead Isotopes as Age-Sensitive, Genetic Markers in Hydrocarbons).

Hurst-Schmidt MDD Model

The Middle Distillate Degradation Model utilizes the ratio of nC17 (heptadecane) to pristane to estimate the age of fuels, such as diesel, jet-A, and heating oil, following their release into the environment. The model is a modification of the Christensen – Larsen technique developed in 1993. The Hurst – Schmidt paper also discusses the limitations of the method and evaluates factors that may compromise resultant age estimates (Environ. Geosci., 2005, v. 12, no. 3, 177-192).