Abstract A greenhouse experiment was conducted under simulated field conditions using large‐capacity plastic pots, filled each one with 25 kg of air‐dried calcareous soil. Besides the control, four treatments were prepared by applying separately two rates (20 and 80 Mg ha‐1) of municipal solid waste (MSW) compost, and co‐composted municipal solid waste and sewage sludge (MSW‐SS). Lettuce was planted and harvested 2.5 months later. The application of composted urban wastes tended to increase Cu concentration in lettuce with respect to the control, but it was only significant when the higher rate of MSW compost was applied. The control showed values of Zn concentration in plant within a deficient range. In general, composted urban wastes treatments had increased Zn concentration values, which were within the sufficiency range. Both treatments with MSW compost increased Cu and Zn uptake in comparison with MSW‐SS co‐compost treatments. At the postharvest, all composted urban wastes treatments increased significantly DTPA‐extractable Cu content in soil with respect to the control; it was also significant the increase in AAAc‐EDTA‐extractable Cu in soil produced by the addition of the higher rate of MSW compost. The application of composted urban wastes increased significantly DTPA‐extractable and AAAc‐EDTA‐extractable Zn contents in soil versus the control, except for the lower rate of MSW‐SS co‐compost. The values of DTPA‐extractable/total ratio for Cu and Zn were under 10%, except for the treatment applying the higher rate of MSW compost which promoted higher values. The values of AAAc‐EDTA‐extractable/total ratio for Cu were above 10% in all treatments including the control. This tendency was also observed in AAAc‐EDTA‐extractable/total ratio for Zn when applying both rates of MSW compost or the higher rate of MSW‐SS co‐compost. 相似文献
The purpose of this study was to evaluate photodegradabilities of the following new low-nitrogen chelating agents: N-bis[(carboxymethoxy)ethyl]glycine (compound 1), N-bis[(1,2-dicarboxyethoxy)ethyl]glycine (compound 2) and N-bis[(1,2-dicarboxyethoxy)ethyl]aspartic acid (compound 3). At first photodegradation of these chelating agents as uncomplexed Na-compound 1–3 and Cu(II) complexes were tested, both in lake and distilled water, by exposing them to near-UV region radiation at the range of 315–400 nm. Uncomplexed Na-compounds 2 and 3 were selected to sunlight exposure experiments carried out in lake and distilled water. Compound 3 was also tested in sunlight as Cu and Ca complexes in both solutions. Photodegradation of Na6-compound 3 in distilled water was studied by exposing it to radiation at the wavelength of 253.7 nm. Photodegradation products were analysed by means of GC-MS (gas chromatography with mass selective detector).
The results demonstrated that compound 1 was quite photostable even as Cu complex while compounds 2 and 3 were found to be photodegradable. Over 90% reduction of compound 3 was achieved during one week and 80% reduction of compound 2 in two weeks' time when they were added as Na salt to lake water and exposed to sunlight. Compound 3 as Cu complex degraded totally in the sunlight in less than one week. In the case of compound 3, the degradation rate decreased depending on the counter cation in the order Cu > Na Ca. The study demonstrated that photodegradation of Na6-compound 3 does not result in total mineralization of the compound. A photodegradation pathway for Na6-compound 3 is proposed. 相似文献
The photosensitizing perylenequinone toxin elsinochrome A (EA) is produced in culture by the bindweed biocontrol fungus Stagonospora convolvuli LA39 where it apparently plays a pathogenicity related role. We investigated the fate of EA with reference to its stability
under different temperature and light conditions. EA remained stable when boiled in water at 100∘C for 2 h. Similarly, exposing EA to 3–27∘C in the dark for up to 16 weeks did not affect its stability either in dry or in aqueous form. However, results from irradiation
experiments indicate that direct photolysis may be a significant degradation pathway for EA in the environment. EA either
in dry form or dissolved in water was degraded by different irradiation wavelengths and intensities, with degradation plots
fitting a first order rate kinetics. EA degraded faster if exposed in aqueous form, and at higher quantum flux density (μmol
s−1 m−2). Sunlight was more effective in degrading EA than artificial white light and ultraviolet radiations (UV-A or UV-B). Exposing
EA to natural sunlight, particularly, during the intense sunshine (1,420– 1,640 μmol s−1 m−2) days of 30 July to 5 August 2004 in Zurich caused the substance to degrade rapidly with half-life under such condition only
14 h. This implies that should EA gets into the environment, particularly on exposed environmental niches, such as on plant
surfaces through biocontrol product spray, or released from shed diseased leaves, it may have no chance of accumulating to
‘level of concern’. Furthermore, a toxicity assay using Trichoderma atroviride P1 as biosensor showed that photo-degraded EA was not toxic, indicating that no stable toxic by-products were left. 相似文献
Manufacturing composites with polymers and natural fibers has traditionally been performed using chopped fibers or a non-woven mat for reinforcement. Fibers from flax (Linum usitatissimum L.) are stiff and strong and can be processed into a yarn and then manufactured into a fabric for composite formation. Fabric directly impacts the composite because it contains various fiber types via fiber or yarn blending, fiber length is often longer due to requirements in yarn formation, and it controls the fiber alignment via weaving. Composites created with cotton and flax-containing commercial fabrics and recycled high-density polyethylene (HDPE) were evaluated for physical and mechanical properties. Flax fiber/recycled HDPE composites were easily prepared through compression molding using a textile preform. This method takes advantage of maintaining cotton and flax fiber lengths that are formed into a yarn (a continuous package of short fibers) and oriented in a bidirectional woven fabric. Fabrics were treated with maleic anhydride, silane, enzyme, or adding maleic anhydride grafted polyethylene (MAA-PE; MDEX 102-1, Exxelor® VA 1840) to promote interactions between polymer and fibers. Straight and strong flax fibers present problems because they are not bound as tightly within yarns producing weaker and less elastic yarns that contain larger diameter variations. As the blend percentage and mass of flax fibers increases the fabric strength, and elongation generally decrease in value. Compared to recycled HDPE, mechanical properties of composite materials (containing biodegradable and renewable resources) demonstrated significant increases in tensile strength (1.4–3.2 times stronger) and modulus of elasticity (1.4–2.3 times larger). Additional research is needed to improve composite binding characteristics by allowing the stronger flax fibers in fabric to carry the composites load. 相似文献
Recruiting intervention agents is a promising procedure to increase the reach of community-safety programs. Finding active and effective agents, however, has not always been a systematic process. One recent approach named Actively Caring (AC) hypothesizes that self-esteem, belongingness, empowerment, extroversion, and reactance constructs predict willingness to help others. This approach was tested as a mechanism for finding successful agents. Urban college students (N = 360) were asked to (a) complete a survey of AC measures and (b) volunteer to promote fire safety to others by distributing commitment cards requesting fire-safe behaviors. In all, participating volunteers (N = 107) motivated commitments from 278 households. These households represented many communities of the urban area, giving evidence that college students may be useful resources for promoting safe behaviors. However, the AC approach was not as effective as selected individual psychosocial and demographic variables in predicting active and effective agent behaviors. Implications for the AC approach, and other prosocial behavior models, for selecting intervention agents a priori are discussed. 相似文献