Decomposition of lipids in soils: Free and esterified fatty acids, alcohols and ketones

Abstract

Because lipids are important to the properties of soils and the composition of sedimentary organic matter, the rates of decomposition of selected lipids in soils were determined. The rates of decomposition of total lipid extracts from plant materials and of carbohydrates showed marked differences that were dependent on the biological activity of the soils. In biologically-active soils, such as a rendzina or a brunic luvisol, pure lipids were readily degraded, regardless of their functional groups and chain length. An exception was montanic acid ( nC-28), which was refractory in all soils studied. In acid soils, such as a glossic luvisol or a dystric histosol, both chain length and functional groups affected the rate of decomposition of lipids, e.g. after 4 weeks at 28 C, the ratio of decomposition of oleic acid to, stearic acid was as high as 5. The same effect was found when 3-octadecanone (C-18 ketone) was compared to myristone (C-27 ketone). In most soils, the rate of decomposition of free and esterified stearic acid was similar, implying preliminary enzymatic hydrolysis of both the waxes and the fats.