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1.
Reef‐fish management and conservation is hindered by a lack of information on fish populations prior to large‐scale contemporary human impacts. As a result, relatively pristine sites are often used as conservation baselines for populations near sites affected by humans. This space‐for‐time approach can only be validated by sampling assemblages through time. We used archaeological remains to evaluate whether the remote, uninhabited Northwestern Hawaiian Islands (NWHI) might provide a reasonable proxy for a lightly exploited baseline in the Main Hawaiian Islands (MHI). We used molecular and morphological techniques to describe the taxonomic and size composition of the scarine parrotfish catches present in 2 archaeological assemblages from the MHI, compared metrics of these catches with modern estimates of reproductive parameters to evaluate whether catches represented by the archaeological material were consistent with sustainable fishing, and evaluated overlap between size structures represented by the archaeological material and modern survey data from the MHI and the NWHI to assess whether a space‐for‐time substitution is reasonable. The parrotfish catches represented by archaeological remains were consistent with sustainable fishing because they were dominated by large, mature individuals whose average size remained stable from prehistoric (AD approximately 1400–1700) through historic (AD 1700–1960) periods. The ancient catches were unlike populations in the MHI today. Overlap between the size structure of ancient MHI catches and modern survey data from the NWHI or the MHI was an order of magnitude greater for the NWHI comparison, a result that supports the validity of using the NWHI parrotfish data as a proxy for the MHI before accelerated, heavy human impacts in modern times. Evidencia Arqueológica de la Validez de Poblaciones de Peces en Arrecifes Sin Explotar como Objetivos de Apoderamiento para Poblaciones Actuales  相似文献   
2.
Using a standard Hotelling model of resource exploitation, we determine the optimal energy consumption paths from three options: dirty coal, which is non-renewable and carbon-emitting; clean coal, which is also non-renewable but carbon-free thanks to carbon capture and storage (CCS); and solar energy, which is renewable and carbon-free. We assume that the atmospheric carbon stock cannot exceed an exogenously given ceiling. Taking into account learning-by-doing in CCS technology, we show the following results: (i) clean coal exploitation cannot begin before the outset of the carbon constrained phase and must stop strictly before the end of this phase; (ii) the energy price path can evolve non-monotonically over time; and (iii) when the solar cost is low enough, an unusual energy consumption sequence along with solar energy is interrupted for some time and replacement by clean coal may exist.  相似文献   
3.
文章通过对内蒙古中西部地区沙生灌木的成分分析,基于生命周期法(LCA),定量论证了沙生灌木直燃发电开发模式对环境的影响和推广的可行性,指出相比石油等传统能源,这种模式具有较大的潜在效益,对于我国发展绿色替代能源,促进西部地区生态环境和经济协调发展具有一定的战略意义。  相似文献   
4.
The amount of electrical and electronic products is increasing rapidly, and this inevitably leads to the generation of large quantities of waste from these goods. Some of the generated e‐waste ends up in regions with sub‐standard recycling systems and may be processed under poor conditions. During uncontrolled incineration, halogenated dioxins and furans can be generated from brominated and chlorinated compounds in the products. In order to reduce the health and environmental risks involved in the recycling stage of the life cycle of electronics, an effective design‐for‐environment process must be established during the product development phase. Knowledge of the chemical substances in the product is crucial to being able to make informed decisions. Through full knowledge of the material content of procured components, phase‐outs of unwanted substances, such as halogenated substances, can be performed in an effective manner. Therefore, information is the key to success in phasing‐out substances; facilitating compliance of legal provisions for manufacturers of electrical and electronic devices; and improving the environmental footprint of products as they reach the end of the life cycle. After an introduction to the challenges of electronics waste management, this paper describes supply chain information systems and how they are used to facilitate substance phase‐outs in the electronics industry. Sony Ericsson has been working with phase‐outs of unwanted substances since it was founded in 2001. Through the introduction of a material declaration system that keeps track of all substances in the components used in the company's products, Sony Ericsson has been able to replace unwanted substances to improve environmental impacts at the recycling stage of a product.  相似文献   
5.
This paper shows the strong relation between the factors that lead to the resource curse (RC) and factors that lead to a decline of genuine savings (GS). There is substantial empirical evidence that economies that rely predominantly on their natural resources are also characterized by slower economic growth. This so‐called RC is commonly traced back to the fact that natural resources' generate rents that are independent of a country's economic performance, which can lead to suboptimal reinvestments of this consumed natural capital. We argue that the factors responsible for the RC also have a negative effect on GS, a concept that measures “weak” sustainable development by considering reinvestment of natural capital rents in physical and human capital. We discuss whether the RC hampers possibilities for resource abundant countries to obtain sufficiently high rates of GS, and find indeed many reasons why resource‐dependent countries have problems achieving positive GS rates. We survey both areas of research, emphasizing the influence of the exogenous and endogenous determinants of economic growth, which are usually used to theoretically and empirically explain the RC on the three different forms of capital considered by GS. We specify why most countries suffering from the RC have negative GS rates and explain in detail where the linkages are. This overview could help with potential advancements in the explanation of GS through the inclusion of RC effects.  相似文献   
6.
基于四尾栅藻响应的有机磷农药生态风险评估   总被引:1,自引:0,他引:1       下载免费PDF全文
以系统评价有机磷农药在水域生态系统风险为目标,采用批次培养的方法研究了草甘膦和毒死蜱两种有机磷农药在高浓度下的毒性效应、低浓度下的刺激效应及微量条件下的无机磷替代效应.结果表明,草甘膦和毒死蜱对四尾栅藻(Scenedesmus quadricanda)的96h EC50值的分别为12.98,2.02μmol/L.低浓度草甘膦(0.014~1.35μmol/L)条件下细胞密度和最大光能转化效率表现出了显著的刺激作用,最大促进效应分别为13%和6.0%;草甘膦(0.40~0.67μmol/L)表现出显著的无机磷替代效应,而毒死蜱处理组未观察到刺激作用和替代效应.有机磷农药对微藻种群变化的作用方式以低浓度下的刺激作用为主,同时可以引发无机磷不足时某些可利用有机磷种类微藻的种群增长.  相似文献   
7.
控制农业温室气体排放(如N_2O)是减缓全球气候变暖的一个重要措施.本研究通过动态监测小麦-玉米轮作体系N_2O排放通量,探究不施任何肥料(对照,CK)、单施氮磷钾化肥(NPK)、75%NPK+25%(有机氮M)(25%M)、50%NPK+50%M(50%M)、25%NPK+75%M(75%M)以及100%M,即不同有机氮替代比例对陕西关中塿土冬小麦/夏玉米轮作体系N_2O排放及作物产量的影响.结果表明,各处理N_2O排放通量在施肥、降雨或灌水后出现排放峰值.在小麦季各处理变化幅度为-1.33~144.2μg·(m~2·h)~(-1),其中NPK处理峰值最高.玉米季各处理变化幅度为88.2~1 800.1μg·(m~2·h)~(-1),50%M处理峰值最高.小麦/玉米一个轮作年不同处理N_2O排放总量为429.8~2 632.1 g·hm~(-2),且50%M25%MNPK75%M100%MCK.无论小麦、玉米还是一个轮作年总产量,施肥处理产量均显著高于对照.小麦季,施用有机肥的处理小麦产量均显著高于单施化肥处理,增幅达26.1%~50.0%.玉米季,50%M和75%M处理产量与NPK相似,而25%M和100%M处理玉米产量显著低于NPK处理.小麦/玉米轮作总产量变幅为9 166~17 496 kg·hm~(-2),其中50%M和75%M处理显著高于NPK处理,25%M和100%M处理与NPK处理无显著差异.综合考虑塿土小麦/玉米轮作体系有机氮替代化肥氮75%最好,可以保证作物产量、实现N_2O减排.  相似文献   
8.
Ceria is widely used as a catalyst for soot combustion, but effects of Zr substitution on the reaction mechanism is ambiguous. The present work elucidates effects of Zr substitution on soot combustion over cubic fluorite-structured nanoceria. The nanostructured CeO2, Ce0.92Zr0.08O2, and Ce0.84Zr0.16O2 composed of 5–6 nm crystallites display Tm-CO2 (the temperature at maximum CO2 yield) at 383, 355, and 375°C under 10 vol.% O2/N2, respectively. The size of agglomerate decreases from 165.5 to 51.9–57.3 nm, which is beneficial for the soot-ceria contact. Moreover, Zr increases the amount of surface oxygen vacancies, generating more active oxygen (O2? and O?) for soot oxidation. Thus, the activities of Ce0.92Zr0.08O2 and Ce0.84Zr0.16O2 in soot combustion are better than that of CeO2. Although oxygen vacancies promote the migration of lattice O2?, the enriched surface Zr also inhibits the mobility of lattice O2?. Therefore, the Tm-CO2 of Ce0.84Zr0.16O2 is higher than that of Ce0.92Zr0.08O2. Based on reaction kinetic study, soot in direct contact with ceria preferentially decomposes with low activation energy, while the oxidation of isolated soot occurs through diffusion with high activation energy. The obtained findings provide new understanding on the soot combustion over nanoceria.  相似文献   
9.
This paper examines the energy and carbon balance of two residential house alternatives; a typical wood frame home using more conventional materials (brick cladding, vinyl windows, asphalt shingles, and fibreglass insulation) and a similar wood frame house that also maximizes wood use throughout (cedar shingles and siding, wood windows, and cellulose insulation) in place of the more typical materials used – a wood-intensive house. Carbon emission and fossil fuel consumption balances were established for the two homes based on the cumulative total of three subsystems: (1) forest harvesting and regeneration; (2) cradle-to-gate product manufacturing, construction, and replacement effects over a 100-year service life; and (3) end-of-life effects – landfilling with methane capture and combustion or recovery of biomass for energy production.The net carbon balance of the wood-intensive house showed a complete offset of the manufacturing emissions by the credit given to the system for forest re-growth. Including landfill methane emissions, the wood-intensive life cycle yielded 20 tons of CO2e emissions compared to 72 tons for the typical house. The wood-intensive home's life cycle also consumed only 45% of the fossil fuels used in the typical house.Diverting wood materials from the landfill at the end of life improved the life cycle balances of both the typical and wood-intensive houses. The carbon balance of the wood-intensive house was 5.2 tons of CO2e permanently removed from the atmosphere (a net carbon sink) as compared to 63.4 of total CO2e emissions for the typical house. Substitution of wood fuel for natural gas and coal in electricity production led to a net energy balance of the wood-intensive house that was nearly neutral, 87.1 GJ energy use, 88% lower than the scenario in which the materials were landfilled.Allocating biomass generation and carbon sequestration in the forest on an economic basis as opposed to a mass basis significantly improves the life cycle balances of both houses. Employing an economic allocation method to the forest leads to 3–5 times greater carbon sequestration and fossil fuel substitution attributable to the house, which is doubled in forestry regimes that remove stumps and slash as fuel. Thus, wood use has the potential to create a significantly negative carbon footprint for a house up to the point of occupancy and even offset a portion of heating and cooling energy use and carbon emissions; the wood-intensive house is energy and carbon neutral for 34–68 years in Ottawa and has the potential to be a net carbon sink and energy producer in a more temperate climate like San Francisco.  相似文献   
10.
研究了L-半胱氨酸与酰胺类除草剂的反应动力学、热力学及其机制.结果表明,L-半胱氨酸促进酰胺类除草剂的降解,该反应遵循二级动力学方程;除草剂降解速率同除草剂分子的亲电常数线性相关,降低顺序为甲草胺(kL-cysteine=7.65×10-3mol/(L×s))>乙草胺(kL-cysteine=7.23×10-3mol/(L×s))>丁草胺(kL-cysteine=6.01×10-3mol/(L×s))>S-异丙甲草胺(kL-cysteine=2.15×10-3mol/(L×s)),这与其土壤和高效菌降解速率顺序相一致;产物的质谱鉴定表明,L-半胱氨酸取代除草剂分子中氯原子.表明该反应为双分子亲核取代脱氯反应.热力学分析显示,该反应为焓控反应.除草剂间降解速率的差异性由熵变控制,且除草剂的降解速率与反应熵变(ΔS)具有良好的线性关系,ΔS数值越负,除草剂的降解速率越小.分子中N原子上的醚键取代基支链结构及链长度对反应速率影响较大,而芳环取代基结构没有明显影响.  相似文献   
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