A geochemical study of long-chain n-aldehydes in Washington coastal sediments

A series of n-aldehydes, C₂₀ to C₃₂, with strong even-to-odd carbon preference was identified in the mixture of solvent extractable lipids isolated from various Washington coastal sediments. A limited survey of the lipid composition of surface waxes of foliage and cuticular waxes of pollen from several major plant species indigenous to the Pacific Northwest revealed that similar series of n-aldehydes are intrinsic to regional vegetation. Debris from such plants, discharged at the mouth of the Columbia River, represents a “preformed” source of the n-aldehyde series accumulating in sediments from the Washington coastal region. Although the evidence suggests n-aldehydes are largely introduced erosionally to this region as a chemical component of land-derived debris and are not formed in situ in the coastal sediments, further study is warranted to establish the postdepositional stability of this series of compounds relative to other lipids of higher plantwax origin. Despite but few literature reports of the occurrence of these geochemicals, long-chain n-aldehydes are very likely common in many sediments from environments that receive an input of detrital organic matter from higher plants.