Analysis of annual fluctuations of C. nodosa in the Venice lagoon: Modeling approach

A simple simulation model was developed to describe the growth trends of Cymodocea nodosa (Ucria) Ascherson based on data sets from the Venice lagoon. The model reproduces the seasonal fluctuations in the above and belowground biomass and in shoot density. The modeling results are in good agreement with data on net production, growth rates and chemical–physical parameters of water. It was assumed that light and temperature are the most important factors controlling C. nodosa development, and that the growth was not limited by nutrient availability. The aim was to simulate biomass production as a function of external forcing variables (light, water temperature) and internal control (plant density). A series of simulation experiments were performed with the basic model showing that among the most important phenomena affecting C. nodosa growth are: (1) inhibition of production and recruitment of new shoots by high temperature and (2) light attenuation due to seasonal fluctuation.     

基于LCA的稻秸合成甲醇的环境-经济成本分析

以年产5万t甲醇的稻秸气化合成甲醇系统为研究对象,采用生命周期评价方法,对该系统进行了环境-经济成本分析.结果表明,稻秸合成甲醇系统的环境影响成本是284.99元/t(以甲醇计),且主要集中在生产转化过程和下游甲醇燃料消费2个单元阶段.在不同环境影响类型中,温室效应是生命周期最主要的环境影响因素,由于稻秸固碳作用产生的环境成本是-152.79元/t,生产上游温室效应影响负荷为负、总环境影响负荷为负.每t稻秸甲醇的真实成本比煤基甲醇低76.84元.     

纸塑铝复合包装处置方式的生命周期评价

采用生命周期评价(LCA)法研究了纸塑铝复合包装的全生命周期环境影响,并在处置阶段对不同处置方式的环境影响进行评价. 通过现场和资料调研的方式,获得所有生命周期阶段能量物质的输入/输出和环境外排数据. 结果表明:纸塑铝复合包装生命周期阶段中环境影响比重最大的是原料获取阶段,占75%以上. 纸塑铝复合包装的全生命周期环境影响主要集中在化石燃料、土地占用和无机物对人体损害3个方面,在矿产资源、气候变化、酸化富营养化和生态毒性方面影响稍小. 3种处置方式对环境影响由大到小依次为填埋＞焚烧＞再生,其中填埋和焚烧处置分别比纸塑铝复合包装处置阶段前的环境影响增加11%和7%,再生可降低23%,而进一步降低环境影响的方式为发展铝塑分离技术.      

Sensitivity of system stability to model structure

A community is stable, and resilient, if the levels of all community variables can return to the original steady state following a perturbation. The stability properties of a community depend on its structure, which is the network of direct effects (interactions) among the variables within the community. These direct effects form feedback cycles (loops) that determine community stability. Although feedback cycles have an intuitive interpretation, identifying how they form the feedback properties of a particular community can be intractable. Furthermore, determining the role that any specific direct effect plays in the stability of a system is even more daunting. Such information, however, would identify important direct effects for targeted experimental and management manipulation even in complex communities for which quantitative information is lacking. We therefore provide a method that determines the sensitivity of community stability to model structure, and identifies the relative role of particular direct effects, indirect effects, and feedback cycles in determining stability. Structural sensitivities summarize the degree to which each direct effect contributes to stabilizing feedback or destabilizing feedback or both. Structural sensitivities prove useful in identifying ecologically important feedback cycles within the community structure and for detecting direct effects that have strong, or weak, influences on community stability. The approach may guide the development of management intervention and research design. We demonstrate its value with two theoretical models and two empirical examples of different levels of complexity.     

Patchiness and bistability in the comprehensive cyanobacterial model (CCM)

We analyzed spatiotemporal dynamics of cyanobacteria using a four-component mathematical model with nutrients, unicellular algae, colonial algae and herbivorous zooplankton. One of the astonishing abilities of cyanobacteria is the morphological change from the unicellular type to the colonial or filamentous type in response to grazing activities of zooplankton, the phenomenon known as phenotypic plasticity. Our model, referred to as comprehensive cyanobacterial model (CCM), includes the effects of phenotypic plasticity. Depending on parameter values, CCM exhibits not only bistability but also limit cycle oscillations without showing the paradox of enrichment, which has been a controversy among mathematical ecologists. Further, CCM is modified to reaction–advection–diffusion equations, the simulation results of which indicate that the ratio of the lateral diffusivity to the turbulent velocity significantly affects the appearance of patchiness patterns.     

中国核电能源链的生命周期温室气体排放研究

应用全能源链分析(PCA)和生命周期分析(LCA)方法,采用第一手调查数据和一些新的参数,对我国核电能源链的生命周期温室气体排放进行评价计算.结果表明,现阶段我国核电能源链(包括核燃料循环前段、核电站)的实际温室气体排放量为6.2g CO2,eq/(k W·h),若考虑核燃料循环后段(乏燃料后处理与废物处置)则总的温室气体排放量为11.9g CO2,eq/(k W·h).核电是低碳能源,发展核电代替一定规模的煤电提供一次能源,每1k W·h电力生产能够减排大约1kg二氧化碳.推进核电产业链的技术升级和持续节能降耗,鼓励材料再循环再利用,核电能源链的温室气体排放仍有进一步降低的空间.     

应用煤制天然气防治大气污染合理性评估

以京津冀地区燃煤制天然气(SNG)锅炉为对象,基于生命周期角度对其大气污染物排放进行了分析.结果显示,燃SNG锅炉全生命周期排放少于燃煤锅炉,但存在着污染向SNG产地转移的效应.为进一步评估SNG防治大气污染的效果,对京津冀地区燃煤锅炉改造为燃SNG锅炉,以及燃煤锅炉末端排放治理2种方式在生命周期排放、资源消耗、经济性3方面进行了对比.结果显示,在全生命周期过程中,SNG锅炉相比末端处理方式有更多大气污染物排放,但若忽略污染转移现象而只考虑京津冀地区,则SNG锅炉相比末端处理排放更少;燃SNG锅炉相比末端处理会消耗更多的能源和水资源;SNG锅炉同时需要更高的投资和成本.以煤制天然气作为防治大气污染的选择需要谨慎考虑,不宜过度发展.     

乳化植物油强化地下水中Cr(VI)的生物地球化学还原研究

设计天然细砂模拟实验,利用乳化植物油作为电子供体,研究生物地球化学作用对Cr(VI)的还原过程和机理.结果表明,乳化油可以使地下水呈弱酸性,反应体系pH值最终为6.59;并长期维持还原环境,Eh最终降低至-158.6mV.乳化油可显著促进土著微生物的异化铁还原作用,将细砂介质中的Fe(III)还原成Fe(II)并耦合去除Cr(VI).当反应进行到14d时,Cr(VI)全部被去除,反应第28d总铬完全被去除.Fe(II)的累积对反应体系中的氧化还原环境有重要影响.当实验结束时,Fe(II)浓度为44.40mg/L,乳化油消耗了48.9%.XPS和XRD表征分析反应后的细砂,结果表明生成的Cr(III)最终以Fe-Cr无定型态沉淀存在.     

Analysis of blood chemistry and flow cytometry of gonadal cell cycle during reproductive cycle of Anabas testudineus

The population of climbing perch, Anabas testudineus, an important food fish in India, is presently under threat and has been declared endangered. A narrow range of environmental conditions for successful reproduction of the species was previously ascertained in breeding experiments. In this study, the role of physiological parameters including plasma glucose, total protein, cholesterol, and glycogen content in liver and ovary were determined with respect to the reproductive cycling stages. Flow cytometric analysis of cell cycle of ovary and testis in relation to reproductive cycle was also analyzed. In both the sexes, plasma glucose and plasma protein changed significantly during breeding cycle. Plasma cholesterol levels were reduced markedly during spawning. Liver and ovarian glycogen levels showed significant variation during reproductive cycling. Flow cytometric study revealed that the hypoploid and synthesis phase were altered significantly with breeding cycle in ovarian and testicular cells. Data indicate that the biochemical parameters indicative of the fish reproduction capacity are influenced by environmental conditions. Thus, climatic changes may therefore potentially induce biochemical alterations that may exert detrimental effects on fish reproduction and subsequent population decline.     

Alteration of photosystem II activity by atrazine on Chlamydomonas reinhardtii synchronized and asynchronized cell cycle cultures

Inhibition of photosystem II (PSII) activity by atrazine was investigated in the green alga Chlamydomonas reinhardtii during different states of the cell cycle. The algal cultures were maintained under continuous light or under light/dark cycle (16/8?h) to obtain homogenized cell cycle distribution. The cycle state of algal population was determined by the DNA content using flow cytometry and defined as newly divided cells before the initiation of DNA replication (G₀/G₁) and cells at the end of the replication cycle with fully duplicated DNA content (G₂/M). Under different synchronized states of the cell population, the photosynthetic activity was investigated after treatment at 10, 100, and 1000?µmol?L^?1 atrazine exposed for 24?h by using fluorescence parameters related to PSII activity measured with a plant efficiency analyzer and pulse-amplitude modulated methods. In this study, we found that the atrazine effect was different depending on cell cycle phases and the period of illumination. Algal cells under light–dark cycle showed inhibition of the PSII electron transport leading to an increase of heat energy dissipation by the PSII reaction center. Algal cells grown under continuous light was shown to be more resistant to atrazine than the cells grown under light–dark cycle.