We studied a) leaching of Ulex, Pinus and Eucalyptus ashes; b) leaching from the surface layer (0 - 5 cm) of 6 types of soil subjected to thermal shock at a range of temperatures equivalent to those reached in a wildfire (25-degrees-C to 700-degrees-C); and c) leaching of Ulex, Pinus and Eucalyptus ashes through a subsurface soil layer not subjected to thermal shock. Element release from plant ashes and heat-treated soils was highly dependent on the solubility of the principal chemical forms in which that element occurred. The monovalent cations Na and K, largely present as chlorides and carbonates, were mobilized much more rapidly than the divalent cations Ca and Mg, largely present as oxides and carbonates. Element release from heat-treated soil was also dependent on shock temperature. The monovalent cations were extensively mobilized following shocks at less than 380-degrees-C, and the divalent cations following higher-temperature shocks. These differences appear to be related to element volatilization and mineralization of organic matter. The subsurface soil not subjected to thermal shock showed a tendency to retain the elements released from plant ashes and from heat-treated surface soil. The subsurface layers may also release hydrogen ions and organic matter, as a result of cation exchange and dissolution processes respectively.
The wine industry generates a large amount of wastes, including grape marc and vinification lees. These substances can be used to produce enzymes or other food additives. Composting could be a successful strategy for the sustainable and complete recycling of grape marc. In this work, the mesophilic biodegradation of grape marc during 60 d under microaerobic conditions using several ratios of seeds, skin, and stem were studied. The presence of Penicillium spp. was detected at the beginning of the composting. Changes in chemical and biological parameters were evaluated. Biodegraded grape marc with stem showed the best organic matter properties (C/N ratio of 14 and N content of 37 g/kg) and a germination index of 155% for the growth of ray grass seeds. The results suggest that the biodegraded of grape marc could be used as fertilizer, especially for ray grass crops.
The arsenic bioavailability in the bed sediments from the Anllóns River (NW Spain) has been assessed by using several analytical approaches. A six-step sequential fractionation was compared to three general availability tests: the Toxicity Characteristic Leaching Procedure (TCLP) extraction, which estimates the leaching potential of As and its effect on the survival of microorganisms (Vibrio fischeri), an extraction with 1 M HCl extraction, which estimates the bioavailability to higher plants, and a physiologically based extraction test (PBET), which estimates the bioavailability to superior animals. Arsenic was found to be mainly associated to the least mobile fractions: bound to Fe-Al oxides and in the residual phase. Among the three single extractants considered, the PBET extracted the highest As concentrations (1-11% of the total As). The TCLP extracts showed toxicity to Vibrio fischeri whereas for the plants evaluated, aqueous extracts did not show adverse effects.
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