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Santiago de Compostela, Spain

Paradelo R.,Facultade de Farmacia | Moldes A.B.,Facultade de Ciencias | Prieto B.,Facultade de Farmacia | Sandu R.-G.,Facultade de Farmacia | Barral M.T.,Facultade de Farmacia
Compost Science and Utilization | Year: 2010

A combination of physical, chemical, spectroscopic and biochemical parameters, along with different plant assays, was used to assess the maturity and stability of nine finished composts obtained from several raw materials (biodegradable fraction of municipal solid waste, green waste, sewage sludge, manure, and grape marc), and by different procedures (aerobic and anaerobic processing, industrial-scale and laboratory scale). Measures of total, alkali-soluble and water-soluble organic matter, N forms, colour, absorbance, respiration, dehydrogenase activity, and phytotoxicity were performed. The selection of a single parameter for stability and maturity evaluation for all the composts was not possible. A significant positive correlation (P<0.01) was found between microbial respiration and dehydrogenase activity. Also, significant correlations were found between dehydrogenase activity and water-soluble C (P<0.05) and water-soluble N (P<0.05), which are presumably the main forms of energy used by microorganisms. Nevertheless, common maturity/stability indicators, such as the C/N ratio in the solid and the aqueous phase, were not related either to microbial activity or phytotoxicity. In fact, the results of the plant growth tests were not correlated • to any other parameter. A principal component analysis was performed to differentiate those parameters giving the maximum information about the status of each compost. A combination of a measure of humification and a measure of microbial activity or water-soluble organic carbon could be used to explain the differences in the stability of the composts, whereas for maturity evaluation plant tests are necessary. Source

Paradelo R.,Facultade de Farmacia | Villada A.,Facultade de Farmacia | Gonzalez D.,Facultade de Farmacia | Barral M.T.,Facultade de Farmacia
Fresenius Environmental Bulletin | Year: 2010

The phytotoxic effects of heavy metals and organic substances which can be often found in compost have been tested in the conditions commonly used for compost phytotoxicity assessment. A germination-elongation phytotoxicity test was carried out with aqueous solutions of Cu (5-50 mg L-1), Pb (5-100 mg L-1), Zn (5-100 mg L-1), acetic acid (50-300 mg L -1), propanoic acid (50-300 mg L-1), butyric acid (5-50 mg L-1), and etfianol (1-10 g L-1), and the results were compared to those of a second test in which a previous step of soaking of the seeds in die tested solutions was introduced. Three species were used: Hordeum vulgare L. (spring barley), Lolium multiflorum Lam. (Italian ryegrass) and Lepidium sativum L. (garden cress). Cress was the most sensitive species to all the substances used. The phytotoxic concentrations were found to be about 5 mg L-1 for Cu and Pb, 25 mg L-1 for Zn, 50-100 mg L -1 for die 3 organic acids, and 2 g L-1 for ethanol. The results also showed that the previous imbibition made the test more reproducible, and more sensitive since it rendered phytotoxic results at lower doses of heavy metals. Comparing me results to die usual concentrations of these substances in compost of various origins shows that organic compounds are more prone to be die cause of compost phytotoxicity in germination tests, rather man heavy metals. © by PSP Volume 19-No Sa. 2010. Source

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