Purpose: Eighteen soils were sampled in the Lake Aydat catchment in order to analyse free fatty acid (FA) content; FAs are considered to be among the most amenable biomarkers to mobilisation by runoff waters. The majority of the study area has soil cover consisting of grasslands or forest since the 2nd World War, although some covers having changed more recently. Material and methods: The soil studied all developed on volcanic rocks (andisols). The bulk organic matter (OM) content of the samples was characterized by Rock-Eval (RE) pyrolysis. The FAs were determined by gas chromatography-mass spectrometry (GC-MS) analysis of isolated and derivatized (methylation and trimethylsilylation) FA fractions. Results and discussion: Few low molecular weight compounds (LMW; i.e.