Spatial and temporal variations in groundwater nitrate at an intensive dairy farm in south-east Ireland: Insights from stable isotope data

Achievement of at least “good ecological status” in all waterbodies under the EU Water Framework Directive by 2015 will in some cases be a challenge. The twin challenge is to manage expectations of policy makers for such waterbodies as to a realistic length of time required for improvement in water quality. Hence, understanding the source, transformation processes and residence time of nitrate in a hydrological system is an essential part of meeting such challenges. On a dairy farm with 24 shallow groundwater wells, the dual isotopic composition of nitrate (δ¹⁵N and δ¹⁸O) was used to clarify nitrate sources, to assess spatial and temporal variability in nitrate concentrations and to determine if and where denitrification was occurring. Vertical travel time was estimated to correlate nitrate concentrations with management practices. Organically derived nitrogen was the predominant source contributing to groundwater nitrate concentrations. Denitrification was identified as prevalent within specific regions of the study site. The distinct low temporal variability in the isotopic data suggests constancy among nitrate sources and processes over time across the study site. Vertical travel times of up to 3 years were estimated on site indicating the influence of recent management practices on nitrate concentrations. Very slow horizontal migration of groundwater (decades) indicates a legacy of older management practices. Stable isotope techniques, together with an understanding of time lag, provide an extra mechanism to test the efficacy of monitoring and mitigation programmes.     

An environmental impact assessment of quantum dot photovoltaics (QDPV) from raw material acquisition through use

Some emerging technologies are expected to be pivotal for solving many of the environmental challenges faced today, especially those related to energy. However, many of these technologies may incur significant environmental impacts over their life cycle, while having environmental benefits during their use. This paper presents results of a Life Cycle Assessment (LCA) of a proposed type of nanophotovoltaic, quantum dot photovoltaic (QDPV) module. The LCA is confined to the stages of raw materials acquisition, manufacturing, and use. The impacts of QDPV are compared with other types of PV modules and energy sources - both renewable and nonrenewable. To provide a comprehensive comparative assessment, QDPV modules were compared with mature as well as emerging PV types for which data are available. Comparative assessment with other types of energy sources includes coal, oil, lignite, natural gas, diesel, nuclear, wind, and hydropower.QDPV modules may have the potential to overcome two current barriers of solar technology: low efficiencies and high manufacturing costs. If higher efficiencies are realized, QDPV modules could pave the way to large scale implementation of solar energy, helping nations move toward greater energy independence. On the other hand, candidate materials as quantum dots for solar cell applications are mostly compound semiconductors such as cadmium selenide, cadmium telluride, and lead sulfide which may be toxic and for which renewable options are limited. Toxic effects of these materials may be exacerbated by their nanoscale features.The LCA was carried out using the software SimaPro, and the Ecoinvent Life Cycle Inventory (LCI) database supplemented with available literature and patent information. Our results indicate that while QDPV modules have shorter Energy PayBack Time (EPBT), lower Global Warming Potential (GWP), SO_x and NO_x emissions than other types of PV modules, they have higher heavy metal emissions, underscoring the need for investigation of emerging technologies, especially nano-based ones, from a life cycle perspective. QDPV modules are better in all impact categories assessed than carbon-based energy sources but they have longer EPBT than wind and hydropower and higher GWP.     

Ash deposition impact on the energy performance of photovoltaic generators

A little known side effect of the atmospheric air pollution is the degradation of photovoltaic (PV) cells’ performance due to the deposition of solid particles varying in composition, size and origin. In this context, an experimental-based investigation is conducted in order to compare the energy performance of two identical pairs of PV-panels; the first being clean and the second being artificially polluted with ash, i.e. a by-product of incomplete hydrocarbons’ combustion mainly originating from thermal power stations and vehicular exhausts. A series of systematic measurements of current intensity, voltage output and solar radiation are executed simultaneously for the clean and the polluted PV-panel, so that the effect of several mass depositions on the PVs’ power output, energy yield and conversion efficiency may be determined. According to the results, a considerable deterioration of the PV-panels’ performance is obtained, i.e. almost 30% energy reduction per hour or 1.5% efficiency decrease (in absolute terms) for ash accumulation on the panels’ surface reaching up to 0.4 mg/cm².     

Assessment of eco-labelling criteria development from a strategic sustainability perspective

To turn current patterns of consumption and production in a sustainable direction, solid and understandable market information on the socio-ecological performance of products is needed. Eco-labelling programmes have an important role in this communication. The aim of this study is to investigate what gaps there may be in the current criteria development processes in relation to a strategic sustainability perspective and develop recommendations on how such presumptive gaps could be bridged. First a previously published generic framework for strategic sustainable development is described and applied for the assessment of two eco-labelling programmes. Data for the assessment is collected from literature and in semi-structured interviews and discussions with eco-labelling experts.The assessment revealed that the programmes lack both an operational definition of sustainability, and a statement of objectives to direct and drive the criteria development processes. Consequently they also lack guidelines for how product category criteria might gradually develop in any direction. The selected criteria mainly reflect the current reality based on a selection of negative impacts in ecosystems, but how this selection, or prioritization, is made is not clearly presented. Finally, there are no guidelines to ensure that the criteria developers represent a broad enough competence to embrace all essential sustainability aspects.In conclusion the results point at deficiencies in theory, process and practice of eco-labelling, which hampers cohesiveness, transparency and comprehension. And it hampers predictability, as producers get no support in foreseeing how coming revisions of criteria will develop. This represents a lost opportunity for strategic sustainable development. It is suggested that these problems could be avoided by informing the criteria development process by a framework for strategic sustainable development, based on backcasting from basic sustainability principles.     

基于STIRPAT模型的能源消费碳足迹变化及影响因素——以江苏省苏锡常地区为例

定量研究经济社会发展对地区能源消费碳足迹的影响对区域实现低碳发展具有重要意义。论文计算了江苏省苏锡常地区1991-2008年能源消费碳足迹,采用岭回归函数对STIRPAT模型进行了拟合,采用脱钩指数分析了经济发展与能源消费碳足迹之间的关系。结果表明:①1991-2008年能源消费碳足迹平均增长速度为15.30%,能源消费碳足迹分配率以煤炭为主,石油所占比例呈波动下降趋势,天然气所占比例上升较快,能源消费碳足迹产值总体呈波动下降趋势;②经济增长是能源消费碳足迹的主要影响因素,两者关系模型拟合未出现环境库兹涅茨曲线;③经济增长与能源消费碳足迹之间处于相对脱钩与复钩的波动状态,从另一侧面验证了目前两者之间不存在库兹涅茨曲线假说的结论。     

崇明岛生态风险源分析及其防范对策研究

上海市城市总体规划（1999~2020年）中提出了要将崇明岛建成生态岛的发展目标,而保障崇明岛的生态安全,规避生态风险是实现这一目标以及实现经济可持续发展的重要内容。崇明岛地处长江的河口和经济最发达的长江三角洲,而且东邻东海,地理位置十分特殊,区域生态风险来源十分复杂。因此,深入分析崇明岛的生态风险源类型、来源和特征,是进一步开展生态风险评价和正确制定风险防范对策的基础。通过对崇明历史资料的分析和现状的评价,辨识出26种生态风险源,这些风险源按性质分可分为自然风险源和人为风险源两类,按来源分可分为来自流域、来自周边区域、来自海洋和来自岛屿内部4类;通过对风险源的发生概率、强度分析结果,结合各风险源的特点,筛选出咸水入侵、台风、暴雨、风暴潮、生物入侵为崇明岛的主要风险源,并分析了其对生态系统的干扰和危害。在上述分析的基础上,提出了具体的风险防范对策。     

碳源变化对降解2,4-D的好氧颗粒污泥性能及形态的影响

在长期运行的序批式生物反应器(SBR)中,考察了以葡萄糖和2,4-二氯苯氧乙酸(2,4-D)为混合碳源培养的好氧颗粒污泥在转换为2,4-D唯一碳源废水后,其形态、结构及对目标污染物去除功能的变化.结果表明,基质转换为2,4-D单一碳源后,好氧颗粒污泥仍保持了对目标污染物高效的去除能力.当进水2,4-D浓度为361～564mg/L,其去除率为99.2%～100%,COD平均去除率达到85.6%.混合碳源向2,4-D单一碳源转换对原好氧颗粒结构产生一定破坏作用,使其发生部分解体,粒径由513μm下降到302μm.但好氧颗粒污泥良好的耐负荷冲击使其保持了颗粒主体,通过一段时间适应调整后能够重新聚集生长,最终获得能够利用2,4-D为唯一碳源生长并具有良好沉降性(SVI20～40mL/g)的好氧颗粒污泥,粒径为489μm.扫描电子显微镜(SEM)观察结果表明,混合碳源转向单一碳源使好氧颗粒生物相丰富度降低.     

空调系统冷冻水循环水泵变频运行的变温差控制

在分析空调系统变流量运行调节的基础上,提出了变温差控制并给出了控制方案。变温差控制过程不仅具有负反馈,而且具有正反馈,能较好的适应空调负荷的变化。比较分析了变温差控制、定温差控制、定压差控制的节能性,变温差控制的节能潜力最大,是一种最佳控制方式。     

动力与热力抬升对烟气抬升高度的影响分析

通过模式选择和计算,得出烟气抬升高度的增加与动能和热能的关系,表明当烟囱出口处风速分别为3 m/s、2 m/s和1 m/s时欲增加同样大小的烟气抬升高度,需要的动能比热能要高,结论认为烟气的热力提升比动力提升的贡献大。