Occurrence and distribution of monomethylalkanes in the freshwater wetland ecosystem of the Florida Everglades

• A series of mono-methylalkanes were identified in freshwater wetlands of the Everglades ecosystem.
• They are suggested to originate from various microbial sources including cyanobacteria.
• Diagenetic processing during early burial may control the abundance and molecular complexity of mono-methylalkanes.

A series of mono-methylalkanes (MMAs) with carbon numbers from C10 to C23 and C29 were detected in freshwater wetlands of the Everglades. A decrease in concentration and molecular complexity was observed in the order from periphyton and floc, to surface soil and deeper soil horizons. These compounds were present in varying amounts up to 27 μg gdw−1 in periphyton, 74 μg gdw−1 in floc, 1.8 μg gdw−1 in surface soil, <0.03 μg gdw−1 in deeper soils (12–15 cm). A total of 46 MMAs, including three iso and three anteiso-alkanes, were identified. Compound specific carbon isotopes values were determined for some dominant MMAs, and suggest that they originate from microbial sources, including cyanobacteria. Potential decarboxylation from fatty acids could also potentially contribute to the MMAs detected. Early diagenetic degradation was suggested to affect the accumulation of MMAs in soils and further studies are needed to address their applications as biomarkers.