2016—2018年北京城市湿地遥感监测分析

为全面了解北京城市湿地的现状及近年来的动态变化情况，利用高分辨率卫星遥感数据，综合运用GIS技术与景观生态学方法，定量分析了北京市6环内的湿地空间格局。结果表明，北京6环内城市湿地以河流湿地和湖库湿地为主；2016—2018年间湿地面积有所下降，2年间减少了126.58 hm²，主要转化为草地，少量转化为建设用地和林地；由于城市外围的开发建设强度较大，5-6环湿地被侵占面积相对较大，而4环内湿地面积的波动较小；2016—2018年，北京城市湿地的斑块密度增加，平均斑块面积有所减小，表明湿地斑块随时间变化呈破碎化的趋势，且从城市中心向城市边缘，湿地斑块的破碎化程度增强。     

初始温度和压力对排污空间甲烷-空气混合物爆燃特性影响的模拟研究

市政排污空间作为城市公共基础设施的重要组成部分，易积聚可燃气体形成爆炸性环境。结合排污空间的特殊环境条件，采用Fluidyn-MP多物理场数值模拟软件，建立了20 L球形爆炸罐分析模型，通过改变初始温度和初始压力，对排污空间甲烷-空气混合物爆燃特性及其变化规律进行模拟研究。结果表明:初始温度升高导致甲烷-空气混合物最大爆炸压力降低，缩短了到达最大爆炸压力的时间；初始压力增加导致最大爆炸压力急剧升高，并延长了到达最大爆炸压力的时间；最大爆炸压力对初始压力的敏感程度远大于初始温度的影响。此外，随着初始温度和初始压力的升高，爆炸火焰平均传播速度增加，而火焰传播速度对初始温度较敏感。     

Recent advances in the application of silica nanostructures for highly improved water treatment: a review

The demand for high-quality safe and clean water supply has revolutionized water treatment technologies and become a most focused subject of environmental science. Water contamination generally marks the presence of numerous toxic and harmful substances. These contaminants such as heavy metals, organic and inorganic pollutants, oil wastes, and chemical dyes are discharged from various industrial effluents and domestic wastes. Among several water treatment technologies, the utilization of silica nanostructures has received considerable attention due to their stability, sustainability, and cost-effective properties. As such, this review outlines the latest innovative approaches for synthesis and application of silica nanostructures in water treatment, apart from exploring the gaps that limit their large-scale industrial application. In addition, future challenges for improved water remediation and water quality technologies are keenly discussed.

     

Change in avian functional fingerprints of a Neotropical montane forest over 100 years as an indicator of ecosystem integrity

Ecologically relevant traits of organisms in an assemblage determine an ecosystem's functional fingerprint (i.e., the shape, size, and position of multidimensional trait space). Quantifying changes in functional fingerprints can therefore provide information about the effects of diversity loss or gain through time on ecosystem condition and is a promising approach to monitoring ecological integrity. This, however, is seldom possible owing to limitations in historical surveys and a lack of data on organismal traits, particularly in diverse tropical regions. Using data from detailed bird surveys from 4 periods across more than a century, and morphological and ecological traits of 233 species, we quantified changes in the avian functional fingerprint of a tropical montane forest in the Andes of Colombia. We found that 78% of the variation in functional space, regardless of period, was described by 3 major axes summarizing body size, dispersal ability (indexed by wing shape), and habitat breadth. Changes in species composition significantly altered the functional fingerprint of the assemblage and functional richness and dispersion decreased 35–60%. Owing to species extirpations and to novel additions to the assemblage, functional space decreased over time, but at least 11% of its volume in the 2010s extended to areas of functional space that were unoccupied in the 1910s. The assemblage now includes fewer large-sized species, more species with greater dispersal ability, and fewer habitat specialists. Extirpated species had high functional uniqueness and distinctiveness, resulting in large reductions in functional richness and dispersion after their loss, which implies important consequences for ecosystem integrity. Conservation efforts aimed at maintaining ecosystem function must move beyond seeking to sustain species numbers to designing complementary strategies for the maintenance of ecological function by identifying and conserving species with traits conferring high vulnerability such as large body size, poor dispersal ability, and greater habitat specialization. Article impact statement: Changes in functional fingerprints provide a means to quantify the integrity of ecological assemblages affected by diversity loss or gain.     

Sampling strategies in the assessment of long‐term exposures to toxic substances in air

The decision to mitigate exposures from vapor intrusion (VI) is typically based on limited data from 24‐hour air samples. It is well documented that these data do not accurately represent long‐term average exposures linked to adverse health effects. Limited decision guidance is currently available to determine the most appropriate sampling strategy, considering the cost of sampling alternatives along with the economic consequences of exposure‐related health effects. We present a decision model that introduces economic and statistical considerations in evaluating alternative VI sampling methods. The model characterizes the best sampling method by factoring economic and health consequences of exposure, the variability of exposure, the cost of sampling and mitigation, and the likelihood of false‐negatives and false‐positives. Decision‐makers can use results to select the sample size that maximizes net benefit. Conceptual and mathematical models are presented linking biological, statistical, and economic considerations to assess the cost and effectiveness of different sampling strategies. The model relates an average exposure concentration, determined statistically, to abatement costs and to the monetary value of health deterioration. The value of the information provided by different strategies is calculated and used to select the optimum sampling method. Simulations show that longer‐term sampling methods tend to be more accurate and cost‐effective than short‐term samples. The ideal sampling strategy shows significant seasonal variation (it is typically optimal to use longer samples in the winter) and also varies significantly with the stringency of regulatory standards. Longer‐term sample collection provides a more accurate representation of average VI exposure and reduces the likelihood of type I and type II errors. This reduces expected costs of mitigation and exposure (e.g., health consequences, legal and regulatory penalties), which in some cases can be quite significant. The model herein shows how these savings are balanced against the additional costs of longer‐term sampling.     

Adsorption/desorption of arsenite and arsenate on chitosan and nanochitosan

Equilibrium sorption studies of anionic species of arsenite, As(III) ions and arsenate As(V) ions onto two biosorbents, namely, chitosan and nanochitosan, have been investigated and compared. The results and trends in the sorption behavior are novel, and we have observed during the sorption process of the As(III) and As(V) on chitosan, a slow process of desorption occurred after an initial maximum adsorption capacity was achieved, before reaching a final but lower equilibrium adsorption capacity. The same desorption trend, however, is not observed on nanochitosan. The gradual desorption of As(III) and As(V) in the equilibrium sorption on chitosan is attributed to the different fractions of the dissociated forms of arsenic on the adsorbent surface and in solution and the extent of protonation of chitosan with the changing of solution pH during sorption. The change of solution pH during the sorption of arsenite ions on chitosan was also influenced by the interaction between the buffering effect of the arsenite species in the aqueous medium and the physical properties of chitosan. The final equilibrium adsorption capacity of chitosan for As(III) and As(V) was found to be around 500 and 8000 μg/g, respectively, whereas the capacities on nanochitosan are 6100 and 13,000 μg/g, respectively.

     

Overcoming barriers to sustainability by combining conceptual,visual, and networking systems

Sustainability challenges rarely align with the conventional boundaries of our disciplines, institutions and means of communication. To address these challenges amid real-world complexity, we need to think holistically and collaborate across disciplines. In this paper, we synthesise three themes: (1) more integrated conceptual frameworks; (2) digital visual communication which provides fluid expression of complex ideas and perceptions; and (3) online networks which can empower sustainability initiatives and communicate them across social and institutional barriers at a global scale. Each of these tools can help to overcome persistent barriers to sustainability. When used together, they provide a strategic basis for the design of digital collaboration platforms for addressing sustainability challenges. Using design thinking, we developed a Synergy Map which identifies relationships among a number of barriers to sustainability and conceptual and digital tools which help to address them. The Map identifies the potential for synthesising these tools into effective digital artefacts. We provide several examples and identify characteristics of particular value for overcoming barriers to sustainability. Combining new theoretical developments in sustainability sciences with recent advances in communication and networking technologies offers substantial potential for advancing sustainability on multiple fronts.     

循环载荷下煤裂隙演化试验研究

为了研究循环载荷下的煤体裂隙演化特征，在不同应力水平和不同频率条件下分别进行煤样破坏力学及声发射试验。结果表明:应力-应变曲线呈疏-密-疏的变化特征，对应的振铃数柱状图呈U型；上限应力点的应变值、累积能量、撞击计数均随循环次数增加而上升，曲线呈倒S型；煤裂隙演化经历了原始裂隙闭合、新生裂隙稳定发育和裂纹贯穿破坏等3个不同阶段；循环载荷的应力水平和加载频率对煤体疲劳寿命的影响具有差异性，对煤体裂隙演化和破坏模式均有明显影响。     

大肠杆菌吸附-化学还原法用废含金催化剂制备金纳米线

采用大肠杆菌吸附-化学还原法,以大肠杆菌(ECCs)为模板、十六烷基三甲基溴化铵为保护剂、抗坏血酸为还原剂,由废含金催化剂制备金纳米线(AuNWs)。采用XRD,SEM,TEM等技术对AuNWs进行表征。研究了AuNWs对罗丹明6G(R6G)和4-巯基苯甲酸(4-MBA)的拉曼散射信号的增强效果。实验结果表明:在制备过程中加入微生物ECCs,可使金回收率提高约20百分点;当溶液pH小于4时,反应2 h后,有大量呈线状的AuNWs聚集沉降,金回收率可达99%1以上。表征结果显示,AuNWs呈多晶结构,晶格间距为0.23 nm。表面增强拉曼散射分析表明,AuNWs对R6G和4-MBA具有良好的拉曼光谱增强性能。