Comments on the Reported Unusual Progression of Petroleum Hydrocarbon Distribution Patterns During Environmental Weathering.

The article discusses the field studies on the unusual progression of petroleum degradation in the subsurface environment under the absence of oxygen by the U.S. Geological Survey (USGS). Researches determined that for the C₁₀ petroleum fraction, degradation under methanogenic conditions uses up the longer chain normal alkenes, n-alkylcyclohexanes, and n-alkylbenzenes before the shorter homolog based on the results of the two field studies. In addition, the second discussion discussed the cummulative changes in the chemical composition of petroleum products that resulted from physical and biochemical weathering in subsurface environment.