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Although lipids are involved in diverse soil processes and affect various soil properties, the contribution of rhizodeposits and the root zone to lipid concentrations and distributions in soils is unknown. For the first time, we determined the concentrations of alkanoic acids, n-alkanes and n-alkenes in root zone leachates and roots of maize and potato using gas chromatography/mass spectrometry (GC/MS). In total, the lipid concentrations of leachates were 100 μg g−1 (maize) and 17 μg g−1 (potato). The saturated n-alkanoic acids, ranging from n-C14 to n-C28 and having the maximum at n-C22 (maize) and at n-C16 (potato), were more abundant than the other compounds. Maize leachates had more alkanes (20 μg g−1) than potato leachates (3.1 μg g−1), but the members of the homologues were nearly the same. Comparison of these distributions with data for roots, microorganisms and soil indicated that the lipids in the leachates from the root zone mainly originated from abrasion of fine roots, rhizodeposits and rhizosphere microorganisms. [ABSTRACT FROM PUBLISHER]

Abstract: The harmless removal of municipal solid waste (MSW) requires the biodegradation of organic matter to decrease the risk of gaseous emissions and leaching of contaminants. We studied the re-circulation of leachates from an aerobic treated MSW in a lysimeter and compared these results with a similar laboratory study using small-scale reactors. The reduction of total organic C and biological and chemical oxygen demands provided clear evidence for the biodegradation of organic matter in MSW after 12 months of leachate re-circulation. Curie-point pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) and pyrolysis-field ionization mass spectrometry (Py-FIMS) revealed that the biodegradation was more efficient in the large-scale lysimeter than in the laboratory reactors. Different from the laboratory experiments, carbohydrates and N-containing compounds were decomposed almost completely after 2 months. Furthermore, temperature-resolved Py-FIMS showed that leachate re-circulation led to a higher thermal stability of the residual, non-decomposed organic matter. In summary, the two analytical pyrolysis methods proved that the re-circulation of leachates through MSW promoted organic matter biodegradation and offers an improved aerobic waste treatment technology. [Copyright &y& Elsevier]

Biodegradation of organic matter is required to reduce the potential of municipal solid waste for producing gaseous emissions and leaching contaminants. Therefore, we studied leachates of an aerobic-treated waste from municipal solids and a sewage sludge mixture that were re-circulated to decrease the concentration of biodegradable organic matter in laboratory-scale reactors. After 12 months, the total organic C and biological and chemical oxygen demands were reduced, indicating the biodegradation of organic compounds in the leachates. Curie-point pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) and pyrolysis-field ionization mass spectrometry (Py-FIMS) revealed that phenols, alkylaromatic compounds, N-containing compounds and carbohydrates were the predominate compounds in the leachates and solid waste. Leachate re-circulation led to a higher thermal stability of the residual organic matter as indicated by temperature-resolved Py-FIMS. Admixture of sewage sludge to solid waste was less effective in removing organic compounds from the leachates. It resulted in drastic higher and more bio-resistant loads of organic matter in the leachates and revealed increased proportions of alkylaromatic compounds. The biodegradation of organic matter in leachates, re-circulated through municipal solid waste, offers the potential for improved aerobic waste treatments and should be investigated on a larger scale. [ABSTRACT FROM AUTHOR]