Maria Teresa Hernandez

Soil microbial activity after restoration of a semiarid soil by organic amendments

Unsuitable agricultural practices together with adverse environmental conditions have led to degradation of soil in many Mediterranean areas. One method for recovering degraded soils in semiarid regions, is to add organic matter in order to improve soil characteristics, thereby enhancing biogeochemical nutrient cycles. In this study, the effect of adding the organic fraction of urban wastes (both fresh and composted) on different carbon fractions and on microbiological and biochemical parameters (microbial biomass C, basal respiration and different enzymatic activities) of a degraded soil of SE Spain has been assessed in a 2 year experiment. Three months after the addition of the organic material, spontaneous plant growth occurred and the plant cover lasted until the end of the experiment. Organic soil amendment initially increased the levels of soil organic matter, microbial biomass, basal respiration and some enzyme activities related to the C and N cycles These values decreased but always remained higher than those of the unamended soil. The results indicate that the addition of urban organic waste is beneficial for recovering degraded soils, the microbial activity of which clearly increases with amendment. The incorporation of compost seemed to have a greater positive effect on the soil characteristics studied than the incorporation of fresh organic matter.

Effects of biosolarization as methyl bromide alternative for Meloidogyne incognita control on quality of soil under pepper

The Adenosine triphosphate (ATP) content, dehydrogenase, phosphatase, urease, and β-glucosidase activity decreased after manure amendment plus solarization (biosolarization), but they recovered after cropping, reaching levels higher than or similar to those before the biosolarization. However, these biochemical parameters decreased and did not recover with time in the methyl bromide (MeBr) treatment. Potential negative soil effects were assayed by measuring, ecotoxicity (Vibrio fisheri luminescence), germination index, electrical conductivity, and heavy metals content. Biosolarization did not negatively affect these parameters, while MeBr application irreversibly decreased the germination index and ecotoxicity. Higher-quality pepper production (extra and first class) were observed with biosolarization but not with MeBr, but no differences were found for pepper yield. Biosolarization gave a Meloidogyne incognita (M. incognita) incidence similar to that of MeBr application.

Impact of organic soil amendments on phytochemicals and microbial quality of rocket leaves (Eruca sativa).

The effect of soil amendments prepared from organic wastes (sewage sludge and urban solid waste) at two concentrations (45 t ha(-1) as D1 and 135 t ha(-1) as D2) was evaluated on phytochemicals and microbial quality of rocket, a highly valuable vegetable. The addition of sewage sludge to the soil increased rocket yield 5.5 times compared to control and urban solid waste. Organic amendments increased the water content and the maturity stage of the leaves, which contributed to a reduction in the content of total and individual glucosinolates as well as flavonols and anthocyanins. However, higher content of vitamin C was observed after cultivation with sewage sludge at D2 compared to control leaves (204.6 and 177.4 mg 100 g(-1) of fw, respectively). This study shows that sewage sludge at optimum doses can be considered a suitable amendment because of increased crop yield without detrimental effects on phytochemicals, including vitamin C content, when the leaves reached the commercial maturity stage.

Influence of CeO2 content on the electrical properties of Y2O3TZP ceramics

Abstract Yttria-tetragonal zirconia (Yue5f8TZP) ceramics with 1.7–3.0 mol% Y 2 O 3 , alloyed with variable amount of CeO 2 (2 to 12 mol% CeO 2 ) have been prepared by hydroxide coprecipitation method. ac impedance complex plane analysis and ionic conductivity domain measurements were performed. Preliminary ageing experiments in water vapour were also carried out. The total conductivity does not suffer any change when CeO 2 is incorporated and the grain boundary effect is partially avoided by the incorporation of CeO 2 to the tetragonal structure. The ageing effect is also improved when that oxide is incorporated at concentrations higher than 4 mol%.

Y(Er)-doped tetragonal zirconia polycrystalline solid electrolyte: Part 3 Electrical properties

The electrical conductivity of fully dense bodies of polycrystalline tetragonal zirconia (TZP) in the composition range 2 to 3 mol % Y2O3 (Er2O3) was measured. Throughout this work, a.c. impedance complex plane analysis was used. From this method grain-interior and grain-boundary conductivity contributions were obtained separately. Plots of conductivity against reciprocal temperature of both contributions were evaluated. An electrode-electrolyte interphase conductivity contribution was detected and considered. The influence of impurities, and ageing behaviour was also studied. The activation, migration and association energies were estimated and discussed on the basis of up-to-date theoretical and structural information.

Indexes of humification grade in manures

Abstract Cation exchange capacity of manures has been found well correlationed with different parameters which define their humification grade. The CEC C h and CEC/Ch ratios appear as suitable values to understand the humification state in these manures.

Evaluation of ionic transport number of CeO2 doped Y-TZP and PSZ ceramics with alumina additions

Abstract Different zirconia-based composite materials, one TZP (3Ce-TZP) and two PSZ (1Ce-PSZ and 2Ce-PSZ) with 10 wt% Al 2 O 3 additions, were studied with respect to electrical transport properties. Ionic transport number determinations and ac conductivity results as a function of oxygen partial pressure and temperature indicated that these compositions are ionic conductors within a large range of working conditions. The TZP composition exhibited the largest ionic conductivity and pure ionic behavior in air, from 800° to 1100°C. In PSZ materials the presence of significant amounts of cubic phase and/or the presence of some monoclinic phase may be responsible for the observed low ionic transport numbers.

Prokaryotic communities and potential pathogens in sewage sludge: Response to wastewaster origin, loading rate and treatment technology

Sewage sludge features high nitrogen and phosphorous contents encouraging its use as a biosolid in agriculture, but it bears potential chemical and microbiological risks. To tease apart the relative contribution of main factors determining the sludge chemical and microbial features, we analysed 28 treatment plants differing in the wastewater origin (municipal residues, agro-food or chemical industries), organic loading rate and treatment technology (extended aeration, activated sludge or activated sludge followed by anaerobic digestion). We found that the treatment technology and the organic loading rate are main determinants of the sludge chemical properties, including its organic load, nutrient and metal contents, and override the effect of the wastewater origin. Sludge bacterial and archaeal community structure and diversity, characterized through massive sequencing of the 16S rRNA gene, were also mostly determined by the treatment technology partly through shifts in the sludge nutrient load. The same factor conditioned the relative abundance of sequenced bacteria most closely related to potential pathogens, but not that of cultivable Escherichia coli or Salmonella spp. We did not find an effect of the geographic location of the plant on any of the variables at the regional scale of our study. Operational parameters appear as major determinants of the sludge chemical and microbial properties, irrespective of the source of wastewaters, thus leaving a broad management window for improving the agronomic value of sewage sludge.