Three different sources of compost were tested in order to be added to the soil at a student organic farm; the first had high levels of eTPH and pesticides (including those which we just removed), the other two did not pass the eTPH or PAH test. eTPH (>1500 ppm) was found in the C6-C36 range and Connecticut DEEP environmental consultants will not allow this material to be put on the site for which it was being tested. Any relevant information towards an answer on this subject is appreciated.
We did some experiments on hydrocarbon degradation in soils (http://dx.doi.org/10.1080/01490451.2010.489922, http://dx.doi.org/10.1016/j.soilbio.2010.09.026) and found that they sooner or later depleted under aerobic conditions as a result of oxidation. Their reduction from, say, fatty acids to alkanes seems unlikely, so I would suspect a fossile source of residual TPHs in your study. We did not conduct studies on PAHs so far, but it also seems unlikely that they form from biogenic sources like lignin.
A good indication of their origin might be their n-alkane composition. Petroleum hydrocarbons typically contain both even- and odd-numbered C-chains, whereas biogenic fatty acids contain mostly even-numbered C-chains (due to their acetyl coenzyme A way of chain increment during biosynthesis).
Can you show us some GC chromatogram of your compost extract?
Thanks for the enlightening answers, both people who responded! Being a student and observer to this process, I do not have a GC chromatogram. However, it became obvious to the decision-making group that the soil needed replacing, and that a petroleum-source was likely. Thanks again!
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