María Teresa Barral Silva

Effects of lyophilization on human amniotic membrane

Purpose:  This study aimed to evaluate the effects of lyophilization and cryopreservation on human amniotic membrane (HAM) in terms of histological characteristics and growth factor levels.

Assessment of municipal solid waste compost quality using standardized methods before preparation of plant growth media

The quality of compost and its suitability for agricultural application depend upon physical and chemical parameters such as water-holding capacity, porosity, pH, electrical conductivity, C/N ratio, available nutrients and the absence of toxic substances. In the present study a complete characterization of an industrial municipal solid waste compost (MSWC) based on standardized European methods (CEN) for soil improvers and growing media was obtained, and compared with the quality of other Spanish composted biowaste and conventional substrates such as peat and pine bark. The MSWC was obtained from the main composting plant in Galicia (Spain), which processes organic waste that has been separated at origin and collected from more than 100 000 inhabitants. The MSWC presented a lower C/N ratio (15) than peat (84) and composted pine bark (CPB) (211), but had a similar ratio to other marketed MSWC. The nutrients and heavy metals were extracted using different recommended solvents (water, CaCl2 + diethylen triamin pentaacetic acid, and aqua regia). The nutrient concentrations of composted urban waste or manure were much higher than those of peat, CPB or pine bark. On the basis of the results of the plant tolerance test, the MSWC could be employed directly as a soil improver, but would need to be diluted with other low-salt components such as peat or CPB before being used as a growing media.

Availability and fractionation of Cu, Pb and Zn in an acid soil from Galicia (NW Spain) amended with municipal solid waste compost

The potential availability and chemical fractionation of trace elements in soil after compost addition was studied in a laboratory incubation. An acid agricultural soil, developed on biotitic schists, was amended with two rates of a municipal solid waste compost (3% and 6% weight) or lime (2.5 g CaCO3 kg-1, calculated to raise soil pH to values close to those of the compost-amended soil), and incubated in the laboratory for five months. Compost addition increased the availability of Cu, Pb and Zn (measured in DTPA extract) with respect to the control, whereas lime reduced it. Compost amendment increased soil total Cu, Pb and Zn concentrations, and their chemical distribution, assessed by means of the BCR (Bureau Communautaire de Reference) fractionation scheme, was different for each element. Compost addition increased Pb in the reducible (iron oxide-bound) fraction, Cu in the organic and iron oxide fractions, and Zn in the soluble and reducible fractions. Lime did not change the fractionation or total concentrations of the metals analysed. The most problematic element in the compost-amended soil from an environmental point of view is Zn, because it was found in highly mobile forms, while for Cu and Pb this risk is low.