Soil chemical and biochemical properties of a salt-marsh alluvial Spanish area after long-term reclamation

Marisma, one of the largest salt-marsh alluvial areas in SW Spain, has been reclaimed since 1970 by artificial drainage and amendment with phosphogypsum (PG) so as to reduce Na⁺ saturation. Within the reclaimed area, two 250- × 20-m plots were treated as follows: (1) amendment with 25 Mg/ha of PG every 2 to 3 years between 1979 and 2003 (plot PY); (2) like PY but PG treatment stopped after 1997 (plot DR). A contiguous virgin Marisma salt-marsh plot (MV), neither drained nor amended, was the control. In MV, soil microbial biomass C, most enzyme activities and total organic C content were much greater than in PY and DR soils, despite the salinity stress. The decrease in soil organic matter content in PY and DR soils was likely due to cotton-cropping practices, which favoured the organic C mineralisation and nutrients removal by crops. Microbial activity of MV soil, probably stimulated by the rhizodepositions of the natural vegetation, did not suffer from the osmotic effect due to the raising of soil solution ionic strength. Microbial quotient could be ranked as MV > PY > DR, whereas the metabolic quotient had an opposite trend. Thus, both quotients suggested that the interruption of PG amendment was not favouring microbial activity. Principal component analysis clearly identified the chemical and biochemical soil properties mostly affected by the reclamation and also indicated the longer PG amendment in PY plot. Stepwise discriminant analysis identified two physiologically different types of soil microflora, one less active present in the MV virgin soil and another more active present in the reclaimed PY and DR soils.     

Effects of dredging operations on sediment quality: contaminant mobilization in dredged sediments from the Port of Santos, SP, Brazil

Background, aim, and scope  

Contaminated sediments are a worldwide problem, and mobilization of contaminants is one of the most critical issues in environmental risk assessment insofar as dredging projects are concerned. The investigation of how toxic compounds are mobilized during dredging operations in the channel of the Port of Santos, Brazil, was conducted in an attempt to assess changes in the bioavailability and toxicity of these contaminants.     

A new sustainable formulated feed based on discards from food industries for rearing the sea urchin Paracentrotus lividus (Lmk)

During a 18‐week experiment in a sea‐based system, Paracentrotus lividus was fed with two formulations of a new sustainable feed whose main ingredients were food farming discards, mostly outermost lettuce leaves, in different percentage. Egg white was added as protein source and binder, and a little amount of commercial fish feed was added as lipid source. At the end of the experiment, a high survival rate (>80%) and an increase in test diameter (22%), total weight (130%), gonad weight (240%) and gonad index expressed as size‐adjusted gonad weight (288%) were recorded. Gonads achieved a good colour and high levels of essential and polyunsaturated fatty acids, hence representing a commercially valuable product. Comparing the two feed formulations, the one with the lower lettuce content (57% vs. 67%) led to the best product quality, in terms of gonad features (gonad index and colour) and content of essential fatty acids. In order to move towards a higher sustainability of the aquaculture sector, this study proposes a low‐cost feed, produced with cheap and sustainable ingredients such as food farming discards.     

Effect of pH on Structural Changes in Perch Hemoglobin that Can Alter Redox Stability and Heme Affinity

pH can be manipulated to alter the oxidative stability of fish-based foods during storage. X-ray diffraction was used to investigate the ability of reduced pH to cause structural changes in fish hemoglobins that lead to enhanced oxidative degradation. Decreasing pH from 8.0 to 6.3 and 5.7 created a large channel for solvent entry into the heme crevice of perch hemoglobin beta chains. The proton-induced opening of this channel occurred between site CD3 and the heme-6-propionate. Solvent entry into the heme crevice can enhance metHb formation and hemin loss, processes that accelerate lipid oxidation. Reduced pH also decreased the distance between Ile at E11 in one of the alpha chains and the ligand above the heme iron atom. This sterically displaces O₂ and protonated O₂ which increases metHb formation. These studies demonstrate that pH reduction causes structural changes in perch hemoglobin which increase oxidative degradation of the heme pigment.     

Relationship between greenhouse gas emissions and changes in soil gas diffusivity in a field experiment with biochar and lime

Reducing greenhouse gas emissions from arable soil while maintaining productivity is a major challenge for agriculture. Biochar is known to reduce N₂O emissions from soil, but the underlying mechanisms are unclear. This study examined the impact of green waste biochar (20 Mg ha^?1) and lime (CaCO₃; 2 Mg ha^?1) application on soil gas transport properties and related changes in these to soil N₂O and CO₂ emissions measured using automated chambers in a field experiment cropped with maize. In situ soil water content monitoring was combined with laboratory measurements of relative soil gas diffusion coefficient (D_p/D₀) at different matric potentials, to determine changes in D_p/D₀ over time. Cumulative N₂O emissions were similar in the control and lime treatment, but much lower in the biochar treatment. Cumulative CO₂ emissions decreased in the order: lime treatment > biochar treatment > control soil. When N₂O emissions were not driven by excess N supply shortly after fertilisation, they were associated with D_p/D₀ changes, whereby decreases in D_p/D₀ corresponded to N₂O emissions peaks. No distinct pattern was observed between CO₂ emissions and D_p/D₀. Cumulative N₂O emissions were positively related to number of days with D_p/D₀ < 0.02, a critical limit for soil aeration. These results indicate that improved soil gas diffusivity, and hence improved soil aeration, may explain the effect of biochar in reducing N₂O emissions. They also suggest that knowledge of D_p/D₀ changes may be key to explaining N₂O emissions.     

Organic Fertilization in Traditional Mediterranean Grapevine Orchards Mediates Changes in Soil Microbial Community Structure and Enhances Soil Fertility

Soil microbial populations and their functions related to nutrient cycling contribute substantially to the regulation of soil fertility and the sustainability of agroecosystems. A field experiment was performed to assess the medium‐term effect of a mineral fertilizer and two organic fertilization systems with different nitrogen sources on the soil microbial community biomass, structure, and composition (phospholipid fatty acids, pattern, and abundance), microbial activity (basal respiration, dehydrogenase, protease, urease, β‐glucosidase, and total amount of phosphomonoesterase activities), and physical (aggregate stability) and chemical (total organic C, total N, available P and water‐soluble carbohydrates) properties in a vineyard under semiarid Mediterranean conditions after a period of 10 years. The three fertilization systems assayed were as follows: inorganic fertilization, addition of grapevine pruning with sheep manure (OPM), and addition of grapevine pruning with a legume cover crop (OPL). Both treatments, OPM and OPL, produced higher contents of total organic carbon, total N, available P, water‐soluble carbohydrates, and stable aggregates. The organic fertilization systems increased microbial biomass, shifted the structure and composition of the soil microbial community, and stimulated microbial activity, when compared with inorganic fertilization. The abundances of fungi and G+ bacteria were increased by treatments OPM and OPL, without significant differences between them. Organic and inorganic fertilization produced similar grapevine yields. The ability of the organic fertilization systems for promoting the sustainability and soil biological and chemical fertility of an agroecosystem under semiarid conditions was dependent of the organic N source. Copyright © 2016 John Wiley & Sons, Ltd.     

Influence of redox conditions and rice straw incorporation on nitrogen availability in fertilized paddy soils

Biology and Fertility of Soils - Temporal nitrogen (N) availability in fertilized rice paddies is the result of a balance of processes, mainly the gross rates of N mineralization, microbial and...     

Supercritical CO2 extract of Cinnamomum zeylanicum: chemical characterization and antityrosinase activity

The volatile oil of the bark of Cinnamomum zeylanicum was extracted by means of supercritical CO2 fluid extraction in different conditions of pressure and temperature. Its chemical composition was characterized by GC-MS analysis. Nineteen compounds, which in the supercritical extract represented >95% of the oil, were identified. (E)-Cinnamaldehyde (77.1%), (E)-beta-caryophyllene (6.0%), alpha-terpineol (4.4%), and eugenol (3.0%) were found to be the major constituents. The SFE oil of cinnamon was screened for its biological activity about the formation of melanin in vitro. The extract showed antityrosinase activity and was able to reduce the formation of insoluble flakes of melanin from tyrosine. The oil also delayed the browning effect in apple homogenate. (E)-Cinnamaldehyde and eugenol were found to be mainly responsible of this inhibition effect.     

Hydroxytyrosol 4-beta-D-glucoside,an important phenolic compound in olive fruits and derived products

There is increasing interest in olive polyphenols because of their biological properties as well as their contribution to the color, taste, and shelf life of olive products. However, some of these compounds remain unidentified. It has been shown that hydroxytyrosol 4-beta-D-glucoside (4-beta-D-glucosyl-3-hydroxyphenylethanol) coeluted with hydroxytyrosol [(3,4-dihydroxyphenyl)ethanol] under reversed phase conditions in the phenolic chromatograms of olive pulp, vegetation water, and pomace of olive oil processing. A method to separate this compound from hydroxytyrosol by HPLC has been developed. The concentration of this glucoside increased in olive pulp with maturation and could be the main phenolic compound in mature olives. In contrast, the presence of this compound was not detected in olive oil by using HPLC-MS. The compound must be considered both in table olives and olive oil processing because of its glucose and hydroxytyrosol contribution to these products.