提高农业种植体系有机物质中氮利用的可能性研究

土壤有机养分源中的氮释放受许多因子的影响,如土壤温度和水分、有机物质的化学组成.在某种程度上,控制有机物质的化学组成可以增加氮释放和植物需求的同步性,而气候因子是不能控制的,因此在计划管理措施时要考虑这些因素.本文通过调节新鲜或预处理过的植物材料和牲畜粪肥的化学组成、施用时间以及有意分配,来探讨影响氮释放的不同途径.最后阐述提高氮利用率需要实施的农场外的(off-farm)的选择,尤其是对氮过剩的农业体系.     

Possibilities for reducing nitrate leaching from agricultural land

Agricultural soil is a contributor of nitrate to natural waters. High nitrate levels in water leached from soils are related to high nitrate concentrations in drinking water, and excess levels change the ecological balance of rivers and lakes. In this paper, sound solutions to the major environmental issue of limiting nitrate leaching by modifying agricultural practices are discussed. The causes of nitrate leaching from agricultural land are briefly explained and existing measures for the reduction of nitrate losses are described, analyzed and evaluated. Reduction of nutrient leaching is not a question of organic or conventional farming, but rather of the introduction and use of appropriate countermeasures. We propose the following guiding principles to minimize leaching from agricultural soils. To some extent these principles require a new way of thinking: i) environmental indexing of fields and consideration of spatial variability within fields in relation to their contribution to leaching losses within a catchment; ii) reduction of nitrogen inputs to soil to levels slightly below those expected to give the optimum yield by applying less nitrogen fertilizer and by a further reduction in animal density; and iii) use of a range of counter-measures (catch crops, minimum tillage, control of biological processes, etc.) depending on how sensitive the farming system, soil and climate are to the risk of nitrate leaching.     

Toward chemical-free reclamation of biologically pretreated greywater: solar photocatalytic oxidation with powdered activated carbon

Heterogeneous photocatalytic oxidation is a water reclamation technology which avoids chemical consumption and can be powered by solar radiation. Because this generally sustainable process is of limited efficiency for the treatment of biologically pretreated greywater, it was combined with activated carbon adsorption. The effluent of a constructed wetland for treatment of separately collected greywater was subjected to photocatalytic oxidation using the photocatalyst titanium dioxide (TiO₂) “P25” in both the absence and the presence of powdered activated carbon (PAC). Photocatalytic oxidation alone with UV fluences of about 10 Wh L^?1 was not capable of reducing total organic carbon (TOC) from an initial concentration of 5.5 mg L^?1 safely below 2 mg L^?1 as a prerequisite for high-quality water reuse purposes. However, when PAC was added, TOC concentrations subsequent to photocatalytic oxidation were less than 2 mg L^?1 even after reusing the TiO₂/PAC mixture 10 times. PAC addition is estimated to reduce the insolation area necessary to achieve this target by solar photocatalytic oxidation of biologically treated greywater by a factor 7. This combination process represents an innovative chemical-free technology within wastewater reuse schemes.     

International Comparison of Occupational Safety and Health Research—A Review Based on Published Articles

A comparison of international literature in occupational safety and health (OSH) research over the years from 1980 to 1998 was conducted. The comparison is based on the different languages of the over 35,000 articles, which were collected from different databases. The distribution of languages in the analyzed data has to be considered carefully with respect to the original purpose of the data collection and the specific role of the international publication language, English. The comparison shows that in several aspects OSH research does not differ in different publication languages. In some methodological aspects, and in specific objects of research, differences between articles published in different languages can be found.     

Comparison Between the Strain Indicator HRV of a Head-Based Virtual Retinal Display and LC-Head Mounted Displays for Augmented Reality

Augmented Reality uses Head Mounted Displays (HMD) to overlay the real word with additional virtual information. Virtual Retinal Displays (VRD), a new display technology, no longer requires Liquid Crystal Displays (LCD). VRD technology addresses the retina directly with a single laser stream of pixels. There are no studies on the user’s informational strain in this new VRD technology. Various papers have shown that Heart Rate Variability (HRV) is a valid indicator for the user’s informational strain. An empirical test revealed no difference in the user’s HRV between VRD technology and LCD technology. Consequently, there seems to be a comparable user informational strain regarding the display types.     

Solidification with water as a treatment method for air pollution control residues

The process of solidification with water was studied on air pollution control (APC) residues from incineration of refuse-derived fuel (RDF) regarding mechanical strength and leaching behaviour of solidified material. Factorial design in two levels was applied to investigate the impact of water addition, time, and temperature to mechanical strength of solidified material. Factors time and temperature, as well as the interaction between the addition of water and time significantly (alpha=0.05) influenced the mechanical strength of solidified material. The diffusion-leaching test NEN 7345 was performed to investigate if the leaching behaviour of elements from solidified material was determined by diffusion. Since it was found that leaching is not diffusion controlled, the long-term leaching behaviour was not assessed. However, the investigation showed that some of the studied components (Al, Hg, Mn, Pb, Si, and Zn) could be considerably demobilised by solidification with water. Concentrations of As, Cd, Co, Cu, Fe, and Ni were either below or not quite above the detection limits to be included in the analysis of leaching behaviour. The elements least demobilised by solidification were Cl, Cr, K, and Na.     

Carbon turnover and ammonia emissions during composting of biowaste at different temperatures

The effects of different process temperatures (40, 55, and 67 degrees C) during composting of source-separated household waste were studied in a 200 L compost reactor at an oxygen concentration of 16%. The overall decomposition measured as carbon mineralization, decomposition of different carbon constituents, and the dynamics of nitrogen mineralization and the microbial community, are reported. Ammonia emissions at 67 degrees C were more than double those at lower temperatures, and they were lowest at 40 degrees C. The decomposition rate, measured as CO2 emission, was highest at 55 degrees C. Decomposition of crude fat was slower at 40 degrees C than at 55 and 67 degrees C. The peak in microbial biomass was largest in the run at 40 degrees C, where substantial differences were seen in the microbial community structure and succession compared to thermophilic temperatures. Biowaste composting can be optimized to obtain both a high decomposition rate and low ammonia emissions by controlling the process at about 55 degrees C in the initial, high-rate stage. To reduce ammonia emissions it seems worthwhile to reduce the temperature after an initial high-temperature stage.     

Soil compaction--indicators for the assessment of harmful changes to the soil in the context of the German Federal Soil Protection Act

Soil compaction in agriculture induced by large-scale equipment is of growing concern. Heavy wheel loads used in arable cropping have the potential to cause irreversible damage to the subsoil structure and may lead to harmful soil compaction. In order to sustain or improve soil health or fitness on a sustainable basis, indicators are needed to assess the changes in the soil structure and the respective soil functions. This requires an adequate verification of methods for distinguishing between the impairment of soil structure and the disruption of soil functions, and for the respective subject of protection. In this article the link between existing models of soil physical prognosis, practical guidelines, and criteria for the identification of affected soil structure is demonstrated, and a viable concept to distinguish harmful changes to the soil is presented. The concept consists of methods for soil physical analysis such as "pre-compression stress" and "loading ratio", practical recommendations for best management practice, and an indicator-based model for the identification of harmful subsoil compaction derived from a research project for the German Federal Environmental Agency, making it possible to determine for a respective location the required level of action far beyond the common practice of precautions against harmful soil compaction.     

Attitudes and perceptions of indigenous fishermen towards marine resource management in Kuna Yala,Panama

The Kuna are a strong and independent culture, however outside influences are imposing growing pressure on their people. Overpopulation and large-scale overfishing are among the most severe threats. The Kuna have developed their own management strategies to address these pressing issues. This study presents local perceptions and attitudes towards marine resource management of six indigenous fishing communities in Kuna Yala, Panama. Results highlight significant general and comparative differences in fishermen's attitudes and perceptions based on socio-cultural structures of communities, occupation and role in local decision-making. The level of cultural survival in communities was a strong indicator for different priorities and attitudes. Differences were also evident based on the level of marine resources used for income generation. Participation in local decision-making processes had positive impacts on levels of knowledge and information, and fostered critical thinking among participants. In addition, the results also denoted that conservation and development were more effective in the long term if the host population could develop strategies and plans for biodiversity conservation. Ownership and empowerment were strong indicators that influenced local livelihood to promote sustainable use of marine resources.     

Impact of pedological conditions on the distribution of Salicornia species (Southern North Sea coast)

The zonation of different Salicornia species within saltmarshes has been described controversially in prior publications. The aim of this study is to detect substantial relations between pedological conditions and the distribution of different Salicornia species (Salicornia stricta Dumort. 1868, Salicornia europaea L. 1753, and Salicornia procumbens Sm 1813). 37 sites were investigated regarding vegetation pattern, soil morphology and physicochemical and chemical soil properties. A multivariate approach indicate a clear differentiation of the sites dominated by different Salicornia species in respect to sand content, redox potential and water content. However, results of a detailed statistical assessment indicate that redox potential and salinity are the most relevant parameters. Salicornia stricta sites are characterized by a variety of grain sizes, reduced conditions in the rhizosphere, highest water contents (median: 71.5 Vol-%) and lowest Eh values (median: ?19.0 mV), indicating the best adaptation to anaerobic soil conditions. Salicornia procumbens occurs on aerated soils (median Eh: 455.6 mV) with high sand contents independent to position relative to mean high tide level. Exhibiting the lowest (11.5‰) and highest soil salinities (41.7‰), even developing in salt pans (136‰), Salicornia europaea feature a great ecological amplitude regarding temporal variations of salinity. These findings underline the ecotypic and phenotypic plasticity of Salicornia species and offer a promising approach for further experimental settings focussing on phenotypic adaptions and ecological amplitudes of Salicornia taxa and ecotypes.