Effects of addition of bentonite on the hydrocarbon fraction of a podzol soil (A₁ Horizon)

Abstract

SUMMARY Lipids generally accumulate in surface horizons of soils deficient in clay minerals. Samples from a podzol (A1 horizon–no clay) were incubated with a supply of hetero‐ or homo‐ionic (Mg)‐bentonite for 4 months at 28 °C. A significant decrease of unbound lipids was observed. A detailed study of the mainly hydrocarbon fraction revealed that several processes were involved. A transfer of lipids, particularly hydrocarbons, occurred from the free to the bound phase. Consequently, reduced toxicity of these lipids towards soil microorganisms can be expected. The addition of clay resulted in a stimulation of oxidation processes, the extent of which varied with the exchangeable cations; heteroionic bentonite led to increased mineralization, whereas Mg‐bentonite promoted mild oxidation reactions. The increased microbial activity also produced short‐chain hydrocarbons; with Mg‐bentonite, unusual C21‐C35 n‐alkanes were detected. All of these microbial hydrocarbons were found in the bound phase.

Plant roots release phospholipid surfactants that modify the physical and chemical properties of soil

“…In microbiologically active soils, lipids are readily decomposed (Amblès et al, 1989). The drier soil samples required longer equilibration times, providing greater opportunity for microbial degradation to occur.…”

“…It is also possible that the lipid had a more direct effect on the microbial population. Amblès et al (1989) reported that some lipids are toxic to soil microflora, although their definition of a lipid was broad and included simple hydrocarbons. The phosphatidylcholine surfactant used in this study is very similar to the lipids universally found in plant, bacterial and fungal membranes and therefore, is unlikely to be particularly toxic to soil organisms.…”

Geochemical and ecological significance of soil lipids under Rhododendron ponticum stands

“…2a). The dominant long-chain ([C 27 ) alkanes with a strong odd-even predominance are usually ascribed to epicuticular waxes and protective layers on vascular plants and commonly observed in lipid extracts from terrestrial vegetation, including Ericaceae and topsoils (Salasoo 1987;Amblès et al 1989;Jambu et al 1991). A higher predominance of long-chain homologues was observed in the subsoil under Rhododendron (R1B, R2B and R3B).…”

“…Among the different SOM fractions, it is recognized that lipids play a key role in important biogeochemical soil processes, and also in the relationship between plants and their ecological environments (Amblès et al 1989;Farrimond and Flanagan 1996;Bull et al 2000;Quenea et al 2004;Jandl et al 2007). This is relevant for this study, since a frequent observation in temperate forests invaded by Rhododendron is the accumulation of plant litter on the soil surface.…”

Lipídios em sedimentos arqueológicos: resultados preliminares do sítio arqueológico Rio do Meio, Ilha de Santa Catarina (SC)

“…Com a contínua reciclagem do material proveniente de plantas (folhas, galhos e raízes), a matéria orgânica do solo é constantemente renovada, sendo freqüentemente encontradas as classes de lipídios que caracterizam resíduos de plantas, atividade bacteriana, microflora e microfauna (Goossens et al, 1986;Amblès et al, 1989Amblès et al, , 1993Amblès et al, , 1994Dinel et al, 1990;Jambu et al, 1991Jambu et al, , 1993Jambu et al, , 1995Hita et al, 1996;van Bergen et al, 1997van Bergen et al, , 1998Bull et al, , 2000aNierop, 1998). Embora a transiência seja uma característica marcante, os solos possuem mecanismos positivos à preservação da matéria orgânica, como a adsorção em diferentes frações (argila, ácidos húmicos e ácidos fúlvicos), e à formação de agregados (Guggenberger & Zech, 1999;Kaiser & Guggenberger, 2000;Bastos et al, 2005).…”